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FAQ


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NEMA PREMIUM

1.1Are IE3 and NEMA Premium efficiency levels equivalent to each other?
1.2If 25HP 60Hz 8 POLE motor's calculated efficiency is 89%, this motor can be determined "Energy efficiency motor"? by the NEMA MG1 Table 12-11, 25HP 60Hz 8 POLE motor nominal efficiency is 89.5%, and minimum is 87.5%
1.3=1) I was under the impression NEMA was similar to UL and did not have direct government ties (unlike NFPA or OSHA). If a piece of equipment is not sold as being NEMA qualified, does it still need to use the NEMA Premium™ Efficiency motors? 2) Part 431 says it is mandated for certain commercial and industrial equipment. Does it matter what type of equipment the electric motor is installed on? 3) Does it matter what type of company the equipment the electric motor is installed on is being sent to (government vs private)? 4) Who is liable under the law (electric motor manufacturer, OEM, company equipment is installed in)? 5) When reading about this regulation online, it only states purchasing a NEMA Premium™ Efficiency motor gives companies a tax break. Why the tax break if it is mandatory under the law?
1.41) I am doing a project and working with many NEMA motors. I am looking for a catalogue or a chart in which I can see all the efficiencies for any size, class, speed motor, and for at least three load factors (100%, 75% and 50%), for NEMA Premium™ motors. After searching in many sites, I have only gotten to build charts for standard and high-efficiency motors, but it seems to be really difficult to find a chart with all the information I am requesting for NEMA Premium™ motors. I only find nominal efficiencies. 2) We are a contracting company located in Saudi Arabia, and we have a project located in Riyadh – Saudi Arabia (Olaya towers project), and for the Diesel Generator subject we have an issue in the definition of “compact package type generator”.
1.51) I am trying to find a data sheet that lists all the NEMA motor frame sizes. I have one that lists 42 and above, but leaves out 17, 23, 34, and maybe some others I do not know exist. Could you please direct me in the right direction for finding some official data sheet to find this information? 2) We are selling regenerative blowers in the U.S. I would like to know if our motors are not required to meet the NEMA Premium™ Efficiency standards due to the fact that they are not NEMA motors. The blower motor rotor is also the impeller shaft. We do not sell motors separately and they cannot be used for other applications.
1.61) In reviewing a submittal from a vertical turbine pump supplier, we made the following comment: "Provide NEMA Premium efficiency motors, as required by Section 26 05 12-2.05.A.3. The submitted motor data shows a nominal efficiency of 91.7% at full load, which does not meet the NEMA Premium™ requirements of 93.0% for 25HP, 6-pole enclosed motors." We received the following response: “Model XXX is a Premium Efficiency Design for a Vertical High Thrust Motor, 91.7% Nominal Efficiency at 100% load. NEMA Premium™ Efficiencies are not applicable for vertical high thrust motors as shown in NEMA MG 1 Part 12 Pages 6, as these are for horizontal motors." We can find no exclusion for NEMA Design B vertical high thrust motors from the NEMA Premium™ standard defined in NEMA MG 1. Can you please indicate whether the above statement from company XXX is correct? 2) Are premium efficient motors also inverter duty? What constitutes inverter duty?
1.7A customer that bought a motor from my company is claiming that they don't believe the motor is "high efficiency," as was specified before the purchase of the motor. What I would like to know is what standards does NEMA define for HVAC motor efficiencies? Is there a minimum efficiency? Are there levels like low, medium, high, and premium efficiency? I thought these questions might depend on the specific motor, so I've provided a pdf file with the motor and its specs. Any information you could provide would be very helpful.
1.8Are stainless steel, three-phase, T-frame motors currently EPAct? Do they need to be PE after Dec. 18, 2010?
1.9Can you answer me, please, what was the year the premium efficiency motors began to be manufactured in U.S.?
1.10Can you please clarify for me what are the "7 types of low voltage polyphase, integral-horsepower induction motors not currently covered under federal law"?
1.11Do you have any information regarding what type of motors are specifically not included in the NEMA Premium™ program? I’m mainly interested in explosion-proof motors, but would like a full list, if possible.
1.12Does NEMA certify or recognize Explosion Proof Motors with NEMA Premium™ Efficiencies?
1.13Generally speaking, motors in U.S. have to satisfy NEMA Premium™ standards; however, in case the motors are driven by inverters, it is out of regulation. The motor does not need to satisfy NEMA Premium™ standards. In case, may I ask how I can prove these motors are driven by inverter at U.S. Customs? Do I have to write any documents or have to do anything instead?
1.14I am helping my customer get a rebate for increasing energy efficiency at their metal shredding facility. The customer is using a 1000 HP, 8 pole, 4160 VAC wound rotor induction motor. The motor was built prior to 1998. I need to know what efficiency standards for large WRIM were prior to 1998. Would you have any information?
1.15I am in need of your assistance. I was wondering if the efficiency levels between NEMA and EPAct are the same for the following motor types (ODP), rpms, and Hp sizes listed below. They appear to have the same efficiency level for standard and high efficiency. Please apprise. ODP 1200 250 ODP 1200 300 ODP 1200 350 ODP 1200 400 ODP 1200 450 ODP 1200 500 ODP 3600 450 ODP 3600 500
1.16I am presently searching for a list of pre-1952 motor efficiencies from 1hp to 100hp. This will aid in assisting a customer garner the concept of savings when switching his old motors over to new premium efficient levels. Premium and EPAct levels are easy to find, however, any efficiency levels that were used prior to 1997 are obscure. Please assist in helping me find the industry standard efficiencies prior to 1997, and if possible, as far back as 1960/70. My customer has 40-year-old motors to replace. I thank you for your assistance.
1.17I am trying to clarify the dates when NEMA efficiency standards changed. I have reason to believe the changes occurred in 1980, 1985, and 2001, but I have not been able to find any source documents to support that belief and provide the efficiency standards established for motors manufactured in those years. Can you help?
1.18I am trying to find out the definition of "NEMA efficiency bands," which is an efficiency band above NEMA Premium™ motors. Would this be included in NEMA MG 1?
1.19I have a motor that is 7.5 Hp, open, 4-pole, with a FL Eff. of 91. Can I assume that this is a Premium Efficiency motor, or does the nameplate specifically have to say "Nominal Eff" of 91?
1.20I have a question whether or not all premium efficiency motors are inverter duty-rated. I do not see the standard refer to this phrase “inverter duty-rated”. Does the NEMA standard address this? I was thinking this was an IEEE test and not associated with premium efficiency ratings.
1.21I have been asked to find the correct documentation that legislates the efficiencies required for NEMA Premium™ standards and the deadlines to achieve this. I have been reading some of the documents available on the NEMA website indicating that integral gear motors do not need to meet these standards, however, we want to get ahead of the curve and place these types of motors on our gearboxes. Can you please help me locate this documentation?
1.22I have been doing research on electric motors in America, and I have found that the most common standards for efficiency apply only for 1-200 HP Motors. I am looking for any efficiency standards on 1 HP motors. I believe I read they are exempt from the NEMA Premium standards, and I cannot find any MG1 tables on efficiency standards for these either.
1.23I work for NYSERDA as a project manager dealing with incentivising energy efficiency projects in New York. We recently had an issue come up regarding electric motors on refrigerant compressors, and hoped someone at NEMA could answer it for us. In general, we require all electric motors to meet NEMA premium effieciency standards. However, do these standards also govern compressor, pump and fan motors where the motor is integrated into the assembly? The compressors for our refrigeration units do not have efficiencies labeled on them, and we are in the process of verifying the unit efficiencies.
1.24I would like to get more information about "NEMA Premium™ motors" and EISA 2007. Some motors are not covered by EISA in the exempt list, it is mentioned “Customized OEM mounting”. What does that mean? Could you please comment on the following example? If we sell a motorized-fan with an IE2 motor to a European OEM, can this OEM sell its final product including our motorized-fan in the USA? Shall we furnish motorized-fan with a NEMA Premium™ motor to this OEM?
1.25I would like to know what the differences are between “high efficiency” and “premium efficiency” motors, in terms of construction, pricing, efficiency, reliability, etc.
1.26In regard to premium efficiency 50 Hz motors, does a motor that meets the minimum efficiency, but not the nominal efficiency, still qualify as a premium efficiency motor? If not, would this qualify as an energy-efficient motor?The query is whether the rule is applied also for motors with a frequency of 50hz and if so, how could one document this information? As revising the standard, I see no way to evaluate the efficiency of the engine type A and B with 50 Hz. Although efficiently expressed tables by type, number of poles, and power, I do not clarify whether I can use the same efficiency requirements for a lower frequency.
1.27Is there a way to estimate efficiency of polyphase motors 30-50Hp before the NEMA standard of 1977? Can I assume ac motors from 1965-1975 were already close to the NEMA table?
1.28Must inverter-duty motors be NEMA Premium™?
1.29My company's focus is to be a service, repair, and parts supplier for textile equipment here in the US. All new equipment to the U.S. comes from Europe. I have informed our European counterparts of the new EISA standards (NEMA energy efficient to premium efficient) regarding the motors that will be supplied, with new equipment beginning on December 19. My counterparts have indicated that they are aware of new standards in Europe which will soon take place and be fully enacted for all motors by 2017. The first step in Europe will only affect low voltage motors which operate "across the line" and not the motors which operate with an inverter. The question they are asking is if the case will be the same for motors which will be supplied to the U.S. from Europe. Will there be a gradual evoking of the full "premium efficient" standard? “Efficient" standard?
1.30Question on whether dc motors also shall fulfill the requirements for NEMA Premium™. It's a problem since our units were specified (middle and late 2009) before the regulation were known, and then they were stored waiting to be exported to U.S. where the site is located. To change motors now will also have impact on other equipment due to different start current and so on. The new motors also differ in size compared to those with older standards, and that also has an impact on rebuilding different units also with ac motors. Is there any chance to avoid changing motors on units already specified/purchased/produced, but not exported before 19 December 2010?
1.31Table 12-12 is confusing. We have 125 Hp motors at 6-poles and 480 volts. Nameplate says "NEMA Nominal Eff. 94.1%". Table 12-12 indicates nominal of 95% and minimum of 94.1%. Is this considered premium efficiency motor or not? If not, why does Table 12-12, which is titled “Premium Efficiency Motors,” indicate a minimum efficiency of 94.1%? Would it be less confusing if the minimum efficiency figures were left off the table?
1.32The NEMA Premium™ Efficiency Tables list NEMA nominal efficiencies and minimum efficiencies for each motor type. It is my understanding that a motor nameplate that lists efficiency is generally the nominal efficiency. In short, the nameplate rating should conform to the NEMA tabulated nominal efficiency, not the tabulated minimum efficiency. Can you confirm this and advise as to the difference between the minimum and nominal tabulated efficiencies?
1.33There’s a lot of confusion and questions surrounding the EISA provisions. Some date back to the original EPAct legislation. I've been asked if special customer shaft extensions exempt motors from the efficiency requirements of NEMA MG 1, Tables 12-12 and 12-11.
1.34We are a manufacturer of industrial bulk material silo unloaders for the energy industry. We had a customer request Premium Efficiency motors that are to be used in a classified environment (Class 2, Division 2). We would typically use explosion proof motors in this classification; however, we did not find Premium Efficiency ratings for explosion proof motors. I do see them for TEFC and drip proof. Is there such a thing as Premium Efficiency Explosion proof motors? Maybe the need for explosion proof motors in Class 2, Division 2 environment should be revisited; TEFC may be sufficient.
1.35We have an engineer that is questioning that the "Nominal Efficiency" must meet or exceed 86.5% for 1.5HP motors to be considered NEMA Premium™ Motors under Tables 12-12 and 12-13 at 60hz. The EFF stamped on the motor in question is 84% and it is running at 208/3. We are under the impression that a 1-1/2hp motor rated in the range between 86.5%–84% would be considered NEMA Premium™ and meet all 2011 standards for motors. Would this be an accurate statement? Could you please inform me about NEMA rules when a motor is applied with VSD? Effectively, I would like to know if there are restrictions to use asynchronous motors with a special machine.
1.36We will deliver different units, for instance lube oil, control oil, etc., including motors. The units are included in total deliveries of steam turbines. Delivery time from Sweden is from now and some months further on. (Newer units are ordered with NEMA Premium™ motors.) Different organizations give different information about the motor requirements. I read in your NEMA summary and analysis of EISA of 2007, Appendix II, section 313, that motors manufactured after December 19, 2010, must fulfill the NEMA Premium™ requirements. That means that the motors on the units are OK if they are manufactured before the 19th of December 2010? This seems logical. Some other information, can't give a written example, says that it's not allowed to import motors to U.S. after the 19th of December 2010 if the motors are not NEMA Premium™. That information seems a little strange as it will give a lot of motors that have to be scrapped. Can you please send me a prompt answer, preferably today, to this question as we have to know? Can we deliver without any change of motors if they are manufactured 19th of December or earlier?
1.37Will the following motors need to meet NEMA Premium™ efficiency levels after December 19, 2010: Explosion-Proof Motors, Vertical Hollow Shaft Motors, Oil Well Pump Motors (Design D)?

Department of Energy (DOE)

2.1Are there any regulations that would prevent older standard efficiency motors from being brought in the states on an existing machine that is being relocated from overseas? If so could you point me to those standards?
2.2Might there be a standard efficiency for dc motors? (motors to turn screws/extruders for plastics reprocessing and/or plastic bag manufacturing lines) We have old dc motors, and looking to upgrade to new ac motors. There are rebates for the conversion (because the new motors are more efficient). We are trying to establish a baseline, either as the current motors we have now, or as a new dc motor (if there are new dc-standards or general industry standards for the motors, we can use that as a baseline to compare our choice of ac motors, which may be sufficiently more efficient for the purposes of this rebate program).
2.3=1) I was under the impression NEMA was similar to UL and did not have direct government ties (unlike NFPA or OSHA). If a piece of equipment is not sold as being NEMA qualified, does it still need to use the NEMA Premium™ Efficiency motors? 2) Part 431 says it is mandated for certain commercial and industrial equipment. Does it matter what type of equipment the electric motor is installed on? 3) Does it matter what type of company the equipment the electric motor is installed on is being sent to (government vs private)? 4) Who is liable under the law (electric motor manufacturer, OEM, company equipment is installed in)? 5) When reading about this regulation online, it only states purchasing a NEMA Premium™ Efficiency motor gives companies a tax break. Why the tax break if it is mandatory under the law?
2.41) Can I put the NEMA Premium™ Efficiency Logo on the nameplate when my base motor is NEMA Premium™?2) Also if I place the NEMA Premium™ Efficiency logo for the base motor, can I place a table for 5.5HP, 6HP and 6.5HP with specific efficiencies?3) What are the differences between MG 1 PART 16 circa 1987 and MG1 Part 33 circa 2011?
2.51) I am trying to find a data sheet that lists all the NEMA motor frame sizes. I have one that lists 42 and above, but leaves out 17, 23, 34, and maybe some others I do not know exist. Could you please direct me in the right direction for finding some official data sheet to find this information? 2) We are selling regenerative blowers in the U.S. I would like to know if our motors are not required to meet the NEMA Premium™ Efficiency standards due to the fact that they are not NEMA motors. The blower motor rotor is also the impeller shaft. We do not sell motors separately and they cannot be used for other applications.
2.61) I am trying to find a data sheet that lists all the NEMA motor frame sizes. I have one that lists 42 and above, but leaves out 17, 23, 34, and maybe some others I do not know exist. Could you please direct me in the right direction for finding some official data sheet to find this information? 2) We are selling regenerative blowers in the U.S. I would like to know if our motors are not required to meet the NEMA Premium™ Efficiency standards due to the fact that they are not NEMA motors. The blower motor rotor is also the impeller shaft. We do not sell motors separately and they cannot be used for other applications.
2.71) In which ambient temperature range are motors covered by EISA? (Is it -15 to +40°C?) 2) Where can I find the best information for which motors are covered by EISA and which are not in scope? Good explanation of EISA and DOE regulations. 3) What happened when EISA covered motor have no CC-number from DOE and will be shipped in the USA? 4) Do you have some news about the rule for small motors (single- and polyphase)
2.81. In which ambient temperature range are motors covered by EISA? (Is it -15 to +40°C)? 2. Where can I become the best information which motors are covered by EISA and which are not in scope? Good explanation of EISA and DOE regulations. 3. What happened when EISA covered motor have no CC-number from DOE and will be shipped in the USA? 4. Do you have some news about the rule for small motors (single- and polyphase)?
2.9Are servo motors and stepper motors exempt from the Energy Independence and Security Act (EISA) because they are single speed? Also, are motors that are one or more frame sizes larger than that listed in the Frame Size Reference Tables for a given horsepower exempt from EISA?
2.10Are stainless steel, three-phase, T-frame motors currently EPAct? Do they need to be PE after Dec. 18, 2010?
2.11Can a manufacturer legitimately give us a design nameplate label efficiency of 93.0%, whereas the actual test result comes back as 92.8% and we still have a MG 1 Energy Efficient class motor, correct? They designed the motor to be EE, but the test came back 0.1% lower than nominal value.
2.12Can you verify if there is a minimum efficiency rating for standard efficiency vertical hollow shaft motors?
2.13Generally speaking, motors in U.S. have to satisfy NEMA Premium™ standards; however, in case the motors are driven by inverters, it is out of regulation. The motor does not need to satisfy NEMA Premium™ standards. In case, may I ask how I can prove these motors are driven by inverter at U.S. Customs? Do I have to write any documents or have to do anything instead?
2.14I am helping my customer get a rebate for increasing energy efficiency at their metal shredding facility. The customer is using a 1000 HP, 8 pole, 4160 VAC wound rotor induction motor. The motor was built prior to 1998. I need to know what efficiency standards for large WRIM were prior to 1998. Would you have any information?
2.15I have a copy of NEMA’s white paper on small motors and am hoping you may be able to provide some brief guidance on a related question. I realize that you can’t give official guidance / information, but I’d appreciate your feedback / insight on the following questions: Are all of the federal U.S. regulations concerning energy efficiency of motors found in 10 CFR 431 (i.e., there aren’t any other regulations regarding energy efficiency of motors somewhere that I’m missing)? Do you by chance know whether there are any similar (i.e., energy efficiency) regulations for fans, with the exception of ceiling fans (which are covered in 10 CFR 429.32)?
2.16I have been doing research on electric motors in America, and I have found that the most common standards for efficiency apply only for 1-200 HP Motors. I am looking for any efficiency standards on 1 HP motors. I believe I read they are exempt from the NEMA Premium standards, and I cannot find any MG1 tables on efficiency standards for these either.
2.17I was hoping to get some assistance in clarifying the types of motors that are regulated by Department of Energy for High efficiency. It relates to motors we supply integrated into our wire and cable making machines and accessories production lines and PART 431—ENERGY EFFICIENCY PROGRAM FOR CERTAIN COMMERCIAL AND INDUSTRIAL EQUIPMENT Up until May 2012, the U.S. Department of Energy’s regulations defined motors which are general purpose 3Ph ac single speed motors as the type being controlled. Development in the regulations for proposed rules looking forward from March 2011 can be found at http://www.regulations.gov/#!documentDetail;D=EERE-2010-BT-STD-0027-0017.In this document, Table 2 brings up the motors which were not currently controlled for efficiency ratings such as multi-speed, dc, electronically commutated, 1Phase, permanent magnet, inverter duty, and intermittent duty. It indicated the final date for proposing amendments to the regulation was December 19 2012. As of today, it seems further development of the U.S. code of federal regulations (paragraph 431.12) defines both general purpose and definite purpose motors. Paragraph 431.15 references test procedures (CSA, IEC,IEEE, NEMA & NFPA) for more motor types and incorporates (adds them) to the regulations. Paragraph 431.25 “Energy conservation standards and effective dates” specifies the efficiency ratings in Table 1—Nominal Full-Load Efficiencies of General Purpose Electric Motors (Subtype I), Except Fire Pump Electric Motors (Table 2) Table 3 & table 4. http://www.ecfr.gov/cgi-bin/retrieveECFR?gp=&SID=a48177fcfb7d122f513271ea54671c68&n=10y3.0.1.4.19.2&r=SUBPART&ty=HTML Other links for specific requirements for motor efficiency standards in U.S.: http://www1.eere.energy.gov/buildings/appliance_standards/product.aspx/productid/50 http://www1.eere.energy.gov/buildings/appliance_standards/product.aspx/productid/40 It would seems to me despite the title “Certain Commercial and Industrial Equipment” of section 431 of the federal regulation, that the purpose of the regulation is to cover all electric motors supplied alone or in a piece of equipment. Would that also be the general consensus of NEMA?
2.18I work for NYSERDA as a project manager dealing with incentivising energy efficiency projects in New York. We recently had an issue come up regarding electric motors on refrigerant compressors, and hoped someone at NEMA could answer it for us. In general, we require all electric motors to meet NEMA premium effieciency standards. However, do these standards also govern compressor, pump and fan motors where the motor is integrated into the assembly? The compressors for our refrigeration units do not have efficiencies labeled on them, and we are in the process of verifying the unit efficiencies.
2.19I would like to ask you information regarding the part of the EISA regulation related to the footless motor, where the act says that “motors footless must comply with the EPACT levels of efficiency as defined by NEMA MG1 table 12-11.” Do you know if this part is due to be changed and if so, in which way and is there already a dead line?
2.20I would like to get more information about "NEMA Premium™ motors" and EISA 2007. Some motors are not covered by EISA in the exempt list, it is mentioned “Customized OEM mounting”. What does that mean? Could you please comment on the following example? If we sell a motorized-fan with an IE2 motor to a European OEM, can this OEM sell its final product including our motorized-fan in the USA? Shall we furnish motorized-fan with a NEMA Premium™ motor to this OEM?
2.21In clause 31.4.4.2 (Voltage Spikes) from NEMA MG 1, two criteria are established for voltage peak limits at the inverter fed motor terminals. 1. For motors with Vrated up to 600 V, Vpeak should be less than or equal to 3.1*Vrated. 2. For motors with Vrated greater than 600 V, Vpeak should be less than or equal to 2.04*Vrated. The idea behind criteria 1 is clear. There is a physical meaning for it that is the total reflection of the voltage waveform at the motor terminals combined with an eventual variation of the input voltage of 10%. However, criteria 2 is not so clear for me. The number 2.04 results from the product between 2.5 and the ratio sqrt(2)/sqrt(3). What is the meaning of these terms? Is there any physical explanation for such consideration? I only understand the reason for the term sqrt(2), that is the consideration of the peak voltage, since Vrated is a rms value. But I cannot understand well the terms sqrt(3) and the 2.5 (is this empirical?). Could you please clarify it?For the vertical hollow shaft motors and oil well pump motors, do they need to be EPAct-rated after December 19, 2010?Where can I find efficiency table and related government regulations for the explosion-proof motors?
2.22My company's focus is to be a service, repair, and parts supplier for textile equipment here in the US. All new equipment to the U.S. comes from Europe. I have informed our European counterparts of the new EISA standards (NEMA energy efficient to premium efficient) regarding the motors that will be supplied, with new equipment beginning on December 19. My counterparts have indicated that they are aware of new standards in Europe which will soon take place and be fully enacted for all motors by 2017. The first step in Europe will only affect low voltage motors which operate "across the line" and not the motors which operate with an inverter. The question they are asking is if the case will be the same for motors which will be supplied to the U.S. from Europe. Will there be a gradual evoking of the full "premium efficient" standard? “Efficient" standard?
2.23There was confusion about the differences between the motors already covered in ASHRAE 90.1 (integral motors 1-500 Hp) and the motors covered under the recent DOE rules (0.25 to 3 Hp, polyphase, CSCR, and CSIR). Do you have some definitions or clarifications that you could send me to help avoid any confusion as to which efficiency table to use?
2.24There’s a lot of confusion and questions surrounding the EISA provisions. Some date back to the original EPAct legislation. I've been asked if special customer shaft extensions exempt motors from the efficiency requirements of NEMA MG 1, Tables 12-12 and 12-11.
2.25We are a manufacturer of ring compressors. These devices are manufactured at our facility in Taiwan. I have notified them of the motor efficiency requirements and we have a few questions. 1) If we meet the minimum efficiency requirement of the specification, can it be accepted by NEMA? 2) If our motor can meet NEMA’s request, what will we show to them? Does NEMA certify the motors? How should we mark the motors? 3) The motor’s Hp figure(X) of NEMA MG 1-2006 Table 12-12 as NEMA defined does mean not bigger than X? For example, the area of 1Hp means 1Hp >= X >=0Hp, 1.5Hp means 1.5Hp >= X >1Hp 4) What is NEMA’s standard to test the motor’s efficiency? 5) The motor’s efficiency in NEMA MG 1-2006 Table 12-12, does it include the 50 Hz also?
2.26We are a subsidiary of an industrial burner's manufacturer from Europe and we are aware that a new regulation regarding motor efficiency will be effective as soon as December 2010. As we utilized an electric motor on our product (flange mounted type IEC), we are wondering if you could confirm whether this type of motor IEC flange mounted electric motor with rating 1–200 Hp falls under Subtype I or Subtype II of the new EISA regulation. As additional information, please find below details regarding our electric motors: • Our motors are 3 phase TEFC • HP ranging from 1–60 Hp • Voltage 208–600V/ 3Ph/ 60Hz • Our motors are designed according to IEC specs (type N) however dimensions do not comply with IEC, since our motors have customized flange and shaft to fit into our burners Motors are single speed VFD compatible • 2 poles • Footless • Protection class IP56 designed for continuous operation S1 Based on the above, would you please help me classify whether our motors are subject to EISA 2007 and if so, please verify whether our motors fall into subtype I or subtype II of the regulation.
2.27We are manufacturer of dust collectors and screw conveyors. It’s my understanding of the new EISA regulation that footless motors need to meet the EPAct efficiency, while the foot mounted motors need to meet the Premium Efficiency. I would like to get a definition of a footless motor if it’s possible, because we actually import from Italy fans with IE2 (equivalent for values to the NEMA MG 1 Table 12-11) motors. These are footless IEC B5 2-poles, 3600 rpm, 230-460V at 60Hz with a power lower or equal to 11Kw. I would like to know if these motors that are in fact footless are considered also footless for the EISA purposes
2.28We have explosion-proof motors that meet minimum efficiency on the table attached, will have the nameplate marked "premium efficiency," and have the motor sold as premium efficiency motor. We understand that by December 19, 2010, all premium efficiency motors will need to meet the nominal efficiency. We are wondering whether we can still sell these motors that meet only minimum efficiency after December 18, 2010, as premium efficiency. Please advise us.
2.29We offer 2-speed, single winding motors that are primarily used in cooling tower application. They are 1800/900 rpm. Do these need to meet NEMA Premium™ on the 1800 rpm connection or are 2-speed motors not covered under EPAct / EISA?
2.30We will deliver different units, for instance lube oil, control oil, etc., including motors. The units are included in total deliveries of steam turbines. Delivery time from Sweden is from now and some months further on. (Newer units are ordered with NEMA Premium™ motors.) Different organizations give different information about the motor requirements. I read in your NEMA summary and analysis of EISA of 2007, Appendix II, section 313, that motors manufactured after December 19, 2010, must fulfill the NEMA Premium™ requirements. That means that the motors on the units are OK if they are manufactured before the 19th of December 2010? This seems logical. Some other information, can't give a written example, says that it's not allowed to import motors to U.S. after the 19th of December 2010 if the motors are not NEMA Premium™. That information seems a little strange as it will give a lot of motors that have to be scrapped. Can you please send me a prompt answer, preferably today, to this question as we have to know? Can we deliver without any change of motors if they are manufactured 19th of December or earlier?

MG1

3.1I am looking for standard for slip ring motor. But cannot find it in MG-1. So I am wondering I should look at which standard?
3.2I am searching for either a NEMA or IEEE standard for performing airborne sound level measurement of large motors (> 150 hp). Measurements are typically performed three feet from the machine either at no load or at rated load.
3.3Working on building and qualifying a 400Hz AC Motor. The customer drawing is specifying testing IAW MG 1 spec. MG 1 spec that we have, 2010, only makes reference to 50/60Hz machines. Do you cover the testing of 400Hz machine in any of the later or earlier revisions/editions?
3.4In regards to NEMA MG 1 10.37.2 Standard for Locked Rotor kVA per horsepower do you have a rough estimate of what HP size motors fall into each NEMA Code Letter category? Example: Code Letter H = 7.5 to 10 HP
3.5I am looking to run 2 motors at the maximum RPM the can safely be run at. The serial numbers of the motors are EV9105006001 and GW9117104001. I was wondering what is the maximum RPM the motors can run at, and what will be the side effects of running the motors at this speed continuously? The reasoning behind this is we are looking to get some rotaflex units to operate at higher speeds on the straight portion, so that when the corner speed is decreased to a safe operating speed we will still be able to reach our target strokes per minute.
3.6Does NEMA MG 1 cover ECM's?
3.7NEMA MG 1 Table 8 has values up to 250 HP motors. Can the table be extrapolated to large motors such as 1200 HP? If not, are there A, B and C values that can be used to determine the allowable number of starts and rest time?
3.8I am assisting with a large hydraulic forging press application. There has been some disagreement amongst the engineers involved in the project regarding how often the (15) 1200 HP, 4160V motors can be shut on/off per hour. Some of us are in the camp that these motors should not be shut off during production (1 minute of pressing time and 8 minutes of idle time), however we haven’t found a reference we can point to that spells out a motor of our size explicitly. We have referenced NEMA MG 10 as a source however we are looking for anything additional as to whether the on/off function is possible. Do you have such a source or could you offer your opinion on the applicability of using a soft start drive to turn off these motors during the idle portion of the cycle?
3.9Would a submersible motor (for sewer) be more heavy duty (better quality, longer service life) if it complies with NEMA MG 1, Part 31 vs one that does not not?
3.10I am in the process of ordering a new 3-phase 480volt 7.5hp motor for our ferry terminal (hoist application). I have requested the motor to be a NEMA design C, however the sales rep has told me that they no longer can make Design C because of new regulations. They recommended I upsize to a larger horsepower Design A motor however I am reluctant to do that since the hoist system was designed for 7.5hp. Is there anything else I can do to ensure this new motor will be able to handle the high initial torque of our hoist system?
3.11Is NEMA MG1, Part 31 applicable for dry installed motors only, and not submersible motors?
3.12I am a rod pump analysist and we are trying to set guidlines for our variable frequency drive units. All of these units have NEMA D motors and I'm trying to find the safe minimum and maximum hertz speed for these motors. Our motors are generally anywhere from 30-75 hp.
3.13I have some motors on some equipment which is from japan and the EX P. Degree is d2G4 is this equivalent to the USA STD of Class 1 Group C, D Division 1
3.14How might a soft start impact the number of starts and rest time for 1200 HP motors?
3.15Does NEMA MG 1-2011 contain specifics as to the clearance that should be maintained between the armature and magnet on a high speed DC motor? Does it also give specifics on the runout of both parts?
3.16I am hoping you can answer a question we have regarding Sound power levels – with respect to a Synchronous Generator. Our unit is 3,887 HP, it is self-excited, 277 rpm, salient pole. Looking at Table 9-1, for rpm’s less than 900, the rows showing maximum sound power levels stop having entries above 2250 HP. Is there a maximum sound power level for machines greater than 2250 hp (277 rpm) according to NEMA MG-1?
3.17I am looking for information on NEMA Class B and Class F motor winding standards. Specifically, I would like to ask when or in what situations would a Class B winding be used? Is it obsolete? Or is it used only in special circumstances? Why would a Class B standard be requested or required? What is the most common standard for an elevator MRL machine?
3.18Might there be a standard efficiency for dc motors? (motors to turn screws/extruders for plastics reprocessing and/or plastic bag manufacturing lines) We have old dc motors, and looking to upgrade to new ac motors. There are rebates for the conversion (because the new motors are more efficient). We are trying to establish a baseline, either as the current motors we have now, or as a new dc motor (if there are new dc-standards or general industry standards for the motors, we can use that as a baseline to compare our choice of ac motors, which may be sufficiently more efficient for the purposes of this rebate program).
3.19We are looking to interpolate efficiency say, between the 50% and 75% load points, or below 50% given in a typical motor spec. Is there an equation to do that? A typical curve?
3.20What is the motor code for a 3 phase 600 Hp motor with an inrush of 700%?
3.21Will a NEMA 215TC frame brake motor match with a 210TC or 250UC worm gear reducer? Or, where can I be directed to figure this out?
3.221) . NEMA MG-1 12.44.1a defines voltage tolerances for alternating voltage motors under running conditions at rated load as +/- 10% of rated voltage. Does 12.44.1d apply to variable frequency motors and universal motors or to all motors? 12.44.1d applies to alternating-current motors connected directly to the sinusoidal power supply. This does not include variable frequency motors when connected to a variable voltage/variable frequency source of power. Specific operating conditions for universal motors are stated in 12.44.1d. 2) When running a medium (300 HP) fan motor at the nameplate rating, frequency will not be changing so does a. apply or does d. apply ? Both a. and d. apply. The frequency referred to is the frequency of the alternating-current power system to which the motor is connected. If the frequency of the power supply does not change then d. is the same as a. 3) to us, there appears to be a conflict between voltage tolerances in C84.1 and NEMA MG-1, i.e, +/-5% vs +/-10% respectively. We want to say the fan motor is able to operate from 432-528 volts (480V +/- 10%) are we correct on that? Standard motor voltage ratings in Part 12 for small and medium motors correspond to the utilization voltage in C84.1 which is derived from the nominal system voltage. For example, the standard voltage rating for a motor used on a power system with a nominal system voltage of 480 volts is equal to the utilization voltage of 460 volts. The voltage tolerances for Range B in C84.1 apply to the utilization voltage, not to the nominal system voltage. For a nominal system voltage of 480 volts and utilization voltage of 460 volts the limits in C84.1 for motors are a maximum of 508 volts and minimum of 416 volts. These values do not correspond to +/-5% as stated in the original question. The +/-10% variation on motor voltage in 12.44.1d corresponds to these maximum and minimum limits on the utilization voltage in C84.1 applicable to motors. There is no conflict between the two standards. For a nominal system voltage of 480 volts and utilization voltage of 460 volts, the limits in C84.1 for motors are a maximum of 508 volts and minimum of 416 volts. These values do not correspond to +/-5% as stated in the original question. The +/-10% variation on motor voltage in 12.44.1d corresponds to these maximum and minimum limits on the utilization voltage in C84.1 applicable to motors. (I got lost here - nominal utilization voltage is 460 volts.) 460 + 46 = 506 480 + 48 = 508 460 - 46 = 414 480 - 48 = 432 I can’t seem to come up with 416 volts as 10% less than 460 or 480 volts. What am I doing wrong?
3.231) Can I put the NEMA Premium™ Efficiency Logo on the nameplate when my base motor is NEMA Premium™?2) Also if I place the NEMA Premium™ Efficiency logo for the base motor, can I place a table for 5.5HP, 6HP and 6.5HP with specific efficiencies?3) What are the differences between MG 1 PART 16 circa 1987 and MG1 Part 33 circa 2011?
3.241) I am doing a project and working with many NEMA motors. I am looking for a catalogue or a chart in which I can see all the efficiencies for any size, class, speed motor, and for at least three load factors (100%, 75% and 50%), for NEMA Premium™ motors. After searching in many sites, I have only gotten to build charts for standard and high-efficiency motors, but it seems to be really difficult to find a chart with all the information I am requesting for NEMA Premium™ motors. I only find nominal efficiencies. 2) We are a contracting company located in Saudi Arabia, and we have a project located in Riyadh – Saudi Arabia (Olaya towers project), and for the Diesel Generator subject we have an issue in the definition of “compact package type generator”.
3.251) I am trying to find a data sheet that lists all the NEMA motor frame sizes. I have one that lists 42 and above, but leaves out 17, 23, 34, and maybe some others I do not know exist. Could you please direct me in the right direction for finding some official data sheet to find this information? 2) We are selling regenerative blowers in the U.S. I would like to know if our motors are not required to meet the NEMA Premium™ Efficiency standards due to the fact that they are not NEMA motors. The blower motor rotor is also the impeller shaft. We do not sell motors separately and they cannot be used for other applications.
3.261) I am working for Quebec government that takes care of health and safety for workers. We would like to know if there is any requirement (standard) concerning the maximum ventilation openings dimensions on a TEFC motor? Depending on holes dimensions, the fan could be accessible by a worker finger. 2) In MG 1, Table 12-8, the temperature values for a medium motor far exceed the values that would be obtained by applying clause 12.43. This appears to be a discrepancy. Please explain via email how to interpret Table 12-8 and clause 1.43 such that they are consistent with each other.
3.271) I received the following feedback from our Plant Engineers that the new premium efficiency motors are too flexible. This is the feedback that they have given me: “The NEMA frame 284TS 25 HP motor is a federally mandated Premium Efficiency Motor design which has reduced metal mass to improve electrical running efficiency. The problem is that the motor frame is so flexible that after it is fully aligned, and torqued down, it is possible to cause the alignment to fluctuate by +/- .020” just by leaning against the motor. The result is that when the motor is put in service, the resulting torque causes the motor frame to distort, causing high vibrations indicative of misalignment. Because the flow on the pump changes, based on tank level, the torque on the motor changes constantly in operation. As a result, the motor alignment can not be pre-adjusted to compensate for a running position that constantly varies. The new motor is not able to meet the required running conditions in service. We are not able to achieve an alignment that results in low vibrations when the motor is placed in operation. The running vibration levels of the motor, when aligned by our procedures to the correct alignment, exceed our criteria for removing the motor from service. This problem is generic in nature and applies to all NEMA Frame motors 300 or less, that fall under the new federal Premium Efficiency Guideline.” Your feedback on this issue would be greatly appreciated. Are there any motors available that would be the same fit, form and function without the reduced metal mass similar to the sturdier, older style motors? 2) We have a plastic vane per Mil P 8059 and NEMA-AA #3 and would like to know what NEMA AA #3 means? 3) I am working with a team of engineers on the design and development of a high performance, high efficiency generator. Single and Three phase, 15kW to 100kW. My question is which specification(s) do I reference for info on grid tie performance or stand-alone performance? I am trying to understand the power factors we have to meet, harmonic distortion / waveform quality, and surge requirements.
3.281) In order to understand more clearly about machine enclosure type, I would like to have your answer for my question below. According to your previous response, a TEFC machine may have an open drain hole based on common practice in the U.S. so that it would not meet the requirements of IP5X. Hence, if TEFC motors which were or will be provided by U.S. manufacturers do not have an open drain hole, should all of these motors be classified as IP5X? I have this question because I found many manufacturers specify in their catalogue that their TEFC motors are classified as IP4X; however, their motors don't have any open drain hole. 2) I am working on electric motor replacement policy for government buildings. Do you recommend premium efficiency motors in VFD applications? My research indicates mixed opinions.
3.291) In reviewing a submittal from a vertical turbine pump supplier, we made the following comment: "Provide NEMA Premium efficiency motors, as required by Section 26 05 12-2.05.A.3. The submitted motor data shows a nominal efficiency of 91.7% at full load, which does not meet the NEMA Premium™ requirements of 93.0% for 25HP, 6-pole enclosed motors." We received the following response: “Model XXX is a Premium Efficiency Design for a Vertical High Thrust Motor, 91.7% Nominal Efficiency at 100% load. NEMA Premium™ Efficiencies are not applicable for vertical high thrust motors as shown in NEMA MG 1 Part 12 Pages 6, as these are for horizontal motors." We can find no exclusion for NEMA Design B vertical high thrust motors from the NEMA Premium™ standard defined in NEMA MG 1. Can you please indicate whether the above statement from company XXX is correct? 2) Are premium efficient motors also inverter duty? What constitutes inverter duty?
3.301) Is there a standard for motor manufacturer to follow in regards to shaft voltage/current? 2) What are the upper/lower limits for shaft of voltage/current? > 3) I have read where 4160V motors "typically" include one insulated bearing in the motor to protect against shaft voltage/current.
3.311) Need clarification on MG1 31-31.4.2.1. • At what frequency does breakaway torque occur? • Is there a method for how to conduct the test? 2) • Is a foot-motor always part of NEMA premium level (NEMA MG-1, table 12-12)? • What about a footless, C-face mounted motor. Is it NEMA premium or EPACT (Table 12-11)? • Are totally enclosed, not ventilated motors like TENV, TEBC or TEAO always Standard Efficiency?
3.321. We are designers and manufacturers of agitation equipment which use electric motors. We are experiencing no load amperage on fractional horsepower motors that is higher than the full load amps on the NEMA nameplate provided by the manufacturer. When we questioned the manufacturer on this, we were told "It is normal for small motors to have relatively high no-load current, especially if the line voltage is above nominal." Is this correct? 2. It seems to us that some motor manufacturers are gaming the NEMA standards when it comes to the horsepower and service factor specification. We are finding examples of motors spec'd as 3/4 HP with a 1.8 SF. Of course they are running at 1HP or greater, but take advantage of the ignorance of the buying public to extrapolate that fact. Would NEMA have anything to say about that or is it perfectly legit?
3.33A. Customer has a group of pumps driven by 50Hp, 1800 RPM, open drip-proof, premium efficiency motors. One of the pumps on the order was factory-certified tested with a calibrated drive motor. The test verified the pump performance in that the maximum load that the pump could produce at any point in its operation parameters was 48.9 BHP. B. The motors are operating on a PWM variable speed assembly with by-pass contactor that enables them to operate on commercial power in the event of the VFD failure. C. When the pumps are operated at design conditions which are 48 BHP, the current on the motors either on PWM system or on the commercial power by-pass system is approximately 10% over the nameplate full load amperage. D. The input power is balanced within 2 volts and is 498 - 500 - 498. We have operated the motors on the VFD at 460, 470, 480, 490, and 500 volts without any appreciable change in motor full load amperage. E. The motors are rated 94.5% efficiency, 57 full load amps. Unfortunately, it would appear that they are operating at a lower efficiency, and at 62, 63, and 65 amps. The motor manufacturer indicates that the published data in his design information is a "nominal" rating and that the motors on this particular order may vary a significant amount from the published data. F. The overcurrent problem is identical on all of the pumps and motors on this particular order, so it just isn't that one motor may be an anomaly. Our questions are as follows: 1. What is the definition of "nominal" efficiencies? 2. Is there a range of efficiency values for this motor Hp/Speed that the production motors must meet in order to comply with NEMA standards? 3. Is there a "minimum" efficiency that these motors "must" meet to comply with these standards? 4. Does NEMA actually require that individual manufacturers test their motors to comply with NEMA standards, and does NEMA actually review or witness these tests to ensure compliance? 5. Does NEMA visit motor manufacturers and randomly test a motor now and then to ensure that the motors that are being produced meet NEMA specifications?
3.34About 10 years ago we purchased the MG 1 Motors and Generators, but not ALL sub sections were included. We need the subsection 20.54, dynamic balancing. Please let me know how I can obtain this for Las Vegas Water.
3.35Are stainless steel, three-phase, T-frame motors currently EPAct? Do they need to be PE after Dec. 18, 2010?
3.36Are the following (ODP, TEFC, TENV, TEAO) motor codes or motor designations?
3.37Are there any guidelines related to motor power factor? I have a 200Hp, 460VAC, TEFC motor that was recently installed that has a 95% power factor, which meets the NEMA guidelines for energy efficiency. However, the power factor is .81. This seems really low compared to some other motors I've researched. I would expect it to be in the .85 to .88 range. This low power factor will cause the motor to draw more current. Although this does not increase my KW, it does increase my KVA, which will require the utility to provide more power. I thought the reason the energy efficiency guidelines’ were to reduce overall power consumption. Shouldn't the motor power factor be a consideration or am I missing something?
3.38At some point of time in the past NEMA changed the values of Locked Rotor Code (kVA) of the motors. I am told Code " F" is really equal to new "E". At what time in the past year was this change was made? And is there a table available where I can compare the codes (old Vs New). I am currently looking at a plant which contain some old induction motors stamped with the older letter code. I need to calculate the inrush current but I am told Code letters are not the same we see in literature today. This induction motor was manufactured back in 90's.
3.39Attached is the 1998 NEMA Table 12-11 and on it we have highlighted two motors and hand written in what the efficiency value was from the factory testing. The value recorded when factory-tested is higher than the minimum efficiency value, but lower than the nominal value. The customer is contending that the factory efficiency testing must meet or exceed the nominal value in order to meet the NEMA standard. The article below leads me to believe otherwise and that the efficiency only needs to be at or above the minimum efficiency value. What is your or NEMA’s take on this?
3.40Can a manufacturer legitimately give us a design nameplate label efficiency of 93.0%, whereas the actual test result comes back as 92.8% and we still have a MG 1 Energy Efficient class motor, correct? They designed the motor to be EE, but the test came back 0.1% lower than nominal value.
3.41Can NEMA Nominal efficiency levels be met at either full load or 3/4 load, or just at full load? I have been involved in previous programs that accepted either.
3.42Can you answer me, please, what was the year the premium efficiency motors began to be manufactured in U.S.?
3.43Can you confirm that the NEMA Table 12-14 efficiency values match the values for IE3 50Hz exactly (for the equivalent rating)? I may have outdated information, but there were a few ratings that did not match—88.4% vs 88.6%, etc.
3.44Can you help me out? My copy of the NEMA MG 1 does not appear to have a Part 11, but one of our engineers has a customer that is referencing Part 11.08. Can you tell me what this part is or if it even exists?
3.45Can you inform that which code is provide the fulfill information regarding the recommended practice for requirement of Resistance temperature detector(RTD’S) in AC generators.
3.46Can you please elaborate on NEMA MG 1-2011: Section 12.68? I don't understand how the dc voltage is up to 110% of rated voltage while the ac voltage to the rectifier should be rated for plus or minus 10%.
3.47Concerning "NEMA Standards Publication MG 1-2006 Revision 1", part 12.54.1. One of the given conditions is "Two starts in succession (coasting to rest between starts) with the motor initially at the ambient temperature or one start with the motor initially at a temperature not exceeding its rated load operating temperature.” I have been told that this means 2 cold (or 1 hot) starts "per hour," but I don't see the "per hour" in the specification. How should I interpret this?
3.48Could you please help me understand the differences between the Traditional NEMA Design Letters A, B, C, & D, and the Modified NEMA design letters with respect to torque speed characteristics. Note that our Design Criteria requires Design B motors; however, I was told the modified A has the same characteristics.
3.49Does NEMA have a modified Design Letter Standards for Premium efficiency Motors? If so, could you please share where I can find documentation on the theory?Please note – one of the books I used in my Graduate Studies “Electric Machines by Dino Zorbas” – page 231-- fig 3-17 (pic attached), illustrates the speed torque characteristics of the NEMA Design Letters A, B, C, & D Motors. I observed the speed of Design A motor drops between 10 – 20 % at starting of the synchronous speed; therefore, it draws very high current for that duration. Our Design Criteria constraints us to Design “B” motors. Question: One of our Design Vendors used the term “Modified Design A” to describe a NEMA Design Letter for a Premium Efficiency motor. Some of the research I did indicates the cooling fans design was modified from standard motor construction, this modification is considered premium efficiency since the new fan design allows more cooling. Was the Speed/Torque characteristics modified in the premium efficiency motors?
3.50First, we seem to be having some difficulty securing 200v premium efficiency motors (PEMs) for HVAC and Plumbing applications (air handlers, pumps, etc.). Most are double windings of 230/460v being run at 208v. The latest installation of this I saw indicated the motor could be run as a 200v motor with a SF of 1.0. It was a 230–460v motor. There is a plethora of data that yields recommendations of running 200v motors with 208v power for reasons of efficiency, heat generated, starting amps, etc. We generally ask our consultants to specify 200v motors where used in a 208v service. Additionally, it is our policy to specify PEMs, which NEMA has been instrumental in creating universally-accepted standards for. Obviously, most HVAC and plumbing applications utilize smaller horsepower motors, in the range of say 1–40hp. However, given the run time of these motors, the motor efficiency can yield significant energy savings. Can you advise as to manufacturers that provide 200v PEMs in this horse power range, preferably with a service factor of 1.2 or greater?Second, I understand from a brief chat with the CDA that an update to the PME definition and or new ultra efficient standard. We would be interested in a draft copy of the document after it is completed.
3.51How are current pulsations defined in NEMA MG 1 (in regard to an induction motor driving a reciprocating compressor)?
3.52I am a specifying engineer and would like to improve our specifications with regards to inverter duty-rated motors. I see NEMA has a standard, MG Part 31, that explains how to build a NEMA-rated motor. We can specify that the motors need to meet this standard, but what about proof? Does this standard also require that the motor come with a nameplate that states it was constructed to meet this standard? We have some suppliers that are giving us a verbal confirmation that their motors are inverter duty-rated, but this does not fly in our business. Perhaps you have a written standard specification to obtain an inverter duty-rated motor?
3.53I am a vibration analyst working in Michigan. I have a client that wants to know what a good vibration level is. I am quoting your MG 1 mechanical vibration standard. I would like to know if the values given in the table are "filter-in" or "filter-out". I do not have the whole standard, just the page with the table that was faxed to me by a motor repair shop.
3.54I am currently conducting HIPOT testing on an electric vehicle motor. I was writing to request some clarification based on the HIPOT sections of the NEMA MG 1 standards. The specific motor that I am testing has three ac phase cables connected to the windings. While reading through MG 1-3.01.7 and 3.01.8, I am a little confused if I should be including these in the NEMA HIPOT test, or if these cables count as an accessory or component that should be tested separately.
3.55I am helping my customer get a rebate for increasing energy efficiency at their metal shredding facility. The customer is using a 1000 HP, 8 pole, 4160 VAC wound rotor induction motor. The motor was built prior to 1998. I need to know what efficiency standards for large WRIM were prior to 1998. Would you have any information?
3.56I am looking for a NEMA standard that describes the criterion for material selection for low voltage motor frames. We have to decide whether to go for a motor with steel frame or a cast iron frame. Motors are 315 KW.
3.57I am looking for information pertaining to electrical motor efficiency, specifically historical efficiencies. I am doing a comparison of typical ventilation motors for a shopping center. The existing motors are from 1984 to 1988. Only general information is required. Motors range in size from 2Hp to 5Hp. Any feedback is appreciated as I am aware this is probably an abnormal request.
3.58I am seeking the standard for the permutations of the three phases in an L21-20 plug or receptacle. There are two possible permutations of the three phases, and using the wrong one causes motors to run in reverse, which would be detrimental. I am familiar with a labeling of the 4-poles as W for system ground, and X,Y,Z as the three phases of 120V with respect to W. Is the standard to have X leading Y, Y leading Z (each by a third of a cycle) or to have X leading Z, Z leading Y (each by a third of a cycle)?
3.59I am trying to clarify the dates when NEMA efficiency standards changed. I have reason to believe the changes occurred in 1980, 1985, and 2001, but I have not been able to find any source documents to support that belief and provide the efficiency standards established for motors manufactured in those years. Can you help?
3.60I am trying to find out the definition of "NEMA efficiency bands," which is an efficiency band above NEMA Premium™ motors. Would this be included in NEMA MG 1?
3.61I am trying to locate a copy of the 1972 version of MG 1, or at least verify that the 1972 version contains the same verbiage concerning "VARIATION FROM RATED VOLTAGE AND RATED FREQUENCY" with a +/- 10% voltage variation design requirement.
3.62I am trying to locate guidelines or other information for electric motor shaft requirements such as diameter, geometry, strength, etc. I was told that guidelines are possibly in the NEMA motors and generators standards. What is the current revision and what document/revision would have been applicable in the mid to late 1970s (1977 or 1978)? Are the documents available for purchase and at what price? My question really relates to the shaft dimension, particularly the shaft diameter. I am trying to find out whether a step-down shaft for a 215 frame is within the guidelines of NEMA MG 1, or whether that is something that the manufacturer would decide acceptability? I have an application for a 215 frame, but instead of the shaft being 1.375” diameter, it would step down to 1.125” diameter, and the frame is designated a 215Z. What would be the difference between a 215Z and a 215TZ frame? I am trying to get a better understanding of what I have and whether they meet the NEMA guidelines that would have been in place in the late 1970s.
3.63I am trying to verify the NEMA MG 1 requirements in-place at the time of motor purchase. Our motors were purchased in the 1967 to 1972 timeframe. Specifically, I am trying to determine when exactly Section MG 1-20.42 “Load for WK2” and revision to Section MG 1-20.45 “Subpart A and B” for motor became in effect. I have found a copy of the 1964 and 1974 version. The 1964 version does not provide Section MG 1-20.42; it is provided in the 1974 version. I was hoping you could provide any historical information on this section and when the Section MG 1-20.42 and Section MG 1-20.45 “Subpart A and B” revision came into the MG 1 standard?
3.64I am writing training material for a client regarding NEMA and the design codes for ac induction motors. I have looked through your website and have been unsuccessful in finding information regarding codes A, B, C, and D. Can you please send me some basic information regarding these codes? Do the motors look different across the codes? If the motors look different, can you please send me pictures of each motor and their respective code?
3.65I cannot locate what the difference is between motor frame C56C and 56C. There is no evidence of C56C frame; however, it is used as the NEMA frame number. Can you help?
3.66I do find it a bit hard to understand how progressive run out is acceptable to NEMA. But of course, I didn’t write the spec. You mention longer shafts have more runout tolerance. Can you advise what the allowable runout would be on longer shafts, say 10” long or the longest noted?
3.67I found a misuse in NEMA MG 1-2009, Revision 1-2010. Please check the following sentence: "The addition of letters and/or numbers to the auxiliart symbol shall wherever possible, be based on the rules given in 2.67.1" It is located in 2.67.2. I think that "2.2" is correct instead of "2.67.1".
3.68I got a request for a NEMA 320TSC adapter. What is the meaning of each letter (TSC) on the description?
3.69I have a big debate with contractor on pump motor, which is specified in our specs (NEMA MG 1 design B), while the contractor is proposing an IEC standard and insisting that it is the same as NEMA MG 1. Please advise me the difference between where the deviation occurs.
3.70I have a general question concerning the service factor for standard and non-standard NEMA motors. Is it true that NEMA MG 1 prescribes a service factor of 1.15 for every motor or is this up to the manufacturer?
3.71I have a motor that is 7.5 Hp, open, 4-pole, with a FL Eff. of 91. Can I assume that this is a Premium Efficiency motor, or does the nameplate specifically have to say "Nominal Eff" of 91?
3.72I have a question about the Locked-Rotor Torque, Breakdown Torque, and the Pull-Up Torque Tables found in Part 12, page 10 of the 1998 rev. 2 MG-1 standards. My question is: Are these tables the same tables that where used in 1976?
3.73I have a question regarding the motor frame dimensions given in Part 4 of the NEMA MG 1 standard. There are several dimensions that are defined graphically (Figures 4-1 and 4-2 of Part 4), however no quantitative information is supplied for the dimensions. For example, Dimension O: ‘Top of horizontal machine to bottom of feet’; Dimension P: ‘Maximum width of machine excluding terminal housing’; and Dimension AB: ‘Centerline of shaft to outside of terminal housing’. It appears that these dimensions are manufacturer-specific, however, there are documents labeled “NEMA” floating around the internet that supply values for the O, P, and AB motor dimensions, usually with the footnote that the dimensions may vary by manufacturer. Does NEMA impose any specific limits on the O, P, and AB motor dimensions for compliance with a given NEMA frame designation? Or are there industry best-practice standards that influence or control these dimensions?
3.74I have a question whether or not all premium efficiency motors are inverter duty-rated. I do not see the standard refer to this phrase “inverter duty-rated”. Does the NEMA standard address this? I was thinking this was an IEEE test and not associated with premium efficiency ratings.
3.75I have attached a tech sheet for some submersible pumps that appear to meet the NEMA Premium™ Efficiency standards. As you can see, these motor Hp’s don’t line up exactly with the NEMA min eff charts, so how do you determine if this will qualify for the NEMA rating? Does the Hp get rounded up or down to the next tier? Or is there another Premium Efficiency Chart that has more increments?
3.76I have been doing research on electric motors in America, and I have found that the most common standards for efficiency apply only for 1-200 HP Motors. I am looking for any efficiency standards on 1 HP motors. I believe I read they are exempt from the NEMA Premium standards, and I cannot find any MG1 tables on efficiency standards for these either.
3.77I have come across an issue with the BA dimension (C-Flange face to the center of the front foot mounting hole) being different between motor manufactures. The Company A catalog has a BA dimension for a 182-4TC frame motor to be 3.50". Company B motors have some that are 3.50" and some that are 2.75". Can you advise if NEMA standards control this value? Also can you advise the NEMA standard that covers this issue? Thank you for your time and I look forward to your response.
3.78I have general questions about NEMA motor nameplates. The NEC 2011 Chapter 430.32 is writing about a "temperature rise of 40°C" in case of overload protection. A continuous-duty motor with a marked service factor of 1.15 or greater or with a marked temperature rise of 40°C or less can carry a 25% overload for an extended period without damage to the motor. What is the meaning of "temperature rise"? Where I can find it on the NEMA motor nameplate? Is this maybe the AMB? What is the difference of "FL AMPS" and "SF AMPS" I found on a motor nameplate? I think SF_Amps = SF * FL_Amps
3.79I have ran into a major induced-shaft common mode voltage issue on a motor supplied with an air handling unit fan for commercial office building application. The VFD supplier has taken the stance that NEMA Part 31 motors should be able to handle 20 volts or more of induced shaft common mode voltage without electrical damage to the bearings. I can't find anything definitive in the standard to agree with the VFD supplier. It appears that NEMA 31 really doesn't address induced shaft common mode voltage at all. However, the motor manufacturers do not warrant against electrical damage due to induced shaft voltage and current (due to fluting or frosting in the raceway). Can you shed some insight?
3.80I have seen on the internet many NEMA MG 1 motors, and they are identical in respect to the mounting and shaft dimensions for a given frame size and variant. The one motor I am having real difficulty in understanding is the foot measurements. My hunch is that this motor is not in accordance with NEMA MG 1 and that the manufacturer may be using an IEC motor body that can be adapted to NEMA sizes, but I am not certain of that as like your NEMA specifications, I also don't have any detailed IEC specifications. The only point I can really see, and/or make judgment on, would be to ask if this motor would be interchangeable with a proper NEMA MG 1 dimensioned motor of the same frame, i.e. 449T. The application also calls for it to conform to IEEE 841 and it is on an inverter drive in a Class 1 Division 2 Groups B,C,,D, T3 Hazlok. As you can see, it is fitted with a "sparking device" and that is not allowed in this Hazlok, and it only has one insulated bearing. I also understand from what I can glean from NEMA MG 1 that it should have winding PTCs or RTD, but this has thermostats. The motor power and speed is another puzzler as we need 250 Hp and the voltage is 575 at 60 cycles, so on a 4-pole we will get 1800 rpm max. The speed range required is 1750 to 300 and max absorbed power is 140 kW at 1430 rpm.
3.81I have several new vertical solid shaft motors that have progressive run out from the motor base to the end of the shaft, starting at .0005" at the base and increasing to .002" at the end of the motor shaft. This will continue to increase the farther I get from the motor and as such, my rigid coupling will have excessive runout which will not be acceptable to the sealing device mounted on the pump. (The Pump AWWA Std for lineshafts is .005" per foot, which is much tighter than what the motors have been machined to.) The manufacturer is refusing to help me as they say the runout of .002" is within NEMA tolerances. I can live with .002" of runout if it is parallel to the centerline of the motor, not progressive. I am looking for clarification on the specification and whether NEMA addresses progressive runout, as it is generally not an acceptable machining practice.
3.82I have the MG 1 standard and my customer wants a 0.4 Hp Design B type motor, but it runs at 400 Hz. Everything I see in NEMA MG 1 is for 50/60 Hz. Please advise if there is another specification I am missing.
3.83I need to know the difference between a 254TC frame and 256TC NEMA frame. Also, if I could get a catalogue or brochure pertaining to NEMA ratings I would greatly appreciate it.
3.84I need to know what "Type 2 thermal protection" is per NEMA MG 1-12.53.2? Our submittal was rejected when we tried to use thermostats on the motor and I cannot find any information for Type 2 thermal protection.
3.85I need to know what parts of the motor and generator standard regulate the horsepower rating of electric motors. I am trying to explain in a civil manner to some members on a forum that the horsepower ratings of electric motors from the motor manufacturer itself are NOT inflated values as that could get them in hot water big time with you guys. I try to explain to them that companies that buy the electric motors are allowed to inflate the value, NOT the manufacturer of the motor. Unfortunately, the only way to make reason with them is to show direct proof from you guys what guidelines electric motor manufacturers most follow when rating horsepower of their motors.
3.86I refer to three-phase squirrel cage asynchronous motors. Until now, we ordered LV motors rated up to 200 kW. Bigger motors were ordered for HV. I would like to know if this limit for LV motors is according to NEMA MG 1 standard or is it possible to order LV motors until 375 kW (Energy Premium Motors)?
3.87I was on the phone this morning with a German-based client who had received a 100Hp North American-style motor for his machinery assembly. The motor was equipped with a metal terminal housing chamber, but inside, the motor lead wires were supplied loose, and only equipped with compression type lugs. He was asking me if that was typical in North America to provide motors with loose leads like that and how these leads are best secured. He was telling me that in the IEC world, it’s normal to provide motor terminal housings, but the motor leads inside are always secured, and the user just makes the connection to a lug or landing pad that is connected to the motor leads. I would appreciate if you would have any input on that from the motor folks in the U.S., i.e. if this is typical, or maybe just an unusual case.
3.88I was reading through NEMA MG 10 and noticed an error on Table 7. Under 2-Pole, column C, at 100 Hp, the table says the minimum off time between starts is 110 seconds. This should probably be 220 seconds. 110 seconds is for a 4-pole motor.
3.89I was trying to locate where and what NEMA Class 1-2-3-4 Stator rewind materials are defined as.
3.90I work for NYSERDA as a project manager dealing with incentivising energy efficiency projects in New York. We recently had an issue come up regarding electric motors on refrigerant compressors, and hoped someone at NEMA could answer it for us. In general, we require all electric motors to meet NEMA premium effieciency standards. However, do these standards also govern compressor, pump and fan motors where the motor is integrated into the assembly? The compressors for our refrigeration units do not have efficiencies labeled on them, and we are in the process of verifying the unit efficiencies.
3.91I would like to ask you information regarding the part of the EISA regulation related to the footless motor, where the act says that “motors footless must comply with the EPACT levels of efficiency as defined by NEMA MG1 table 12-11.” Do you know if this part is due to be changed and if so, in which way and is there already a dead line?
3.92I would like to clarify locked rotor current between NEMA MG.1 para code letter 10.37.2 and NEMA 12.35.1 design code. 1. which is order to priority to apply LRC in both code ? 2. Can we using this motor, if when actual test LRC is more higher than NEMA 12.35.1 design code even though motor was designed by NEMA MG.1 para 10.37.22 code letter G. 3. Could you kindly provide the reference or relevant doc about these issue.
3.93I would like to know if or when the last time NEMA has updated/expanded upon the standard for minimum recommended sheave diameters for electric motors. We are currently using data in our catalog from standard MG 1-3.16 and MG 1-3.16A. The Hp is from .50-30.00 and the motor rpm is from 575 to 3540.
3.94I’m working on a project and the noise level is critical issue for the surrounding area. Our sound consultant is referring to the power level (Lw) less than 85dBA instead of the sound pressure Lp less than 85 dBA at a distance of 3.3 feet (1 meter). The actual case and the consultant analogy from Reference to MG 1, Section 1 art. 9.7: Lp=Lwa – 10 x log (2π x rd square/ So) it gives: Lwa = Lp + 10 x log (2π x rd square/ So) The installation is: 125 HP motor (Noise level sound pressure 81 dBA at 3.3 feet (1 meter) From the Motor Data sheet: Lp = 81 dBA Rd = 1.0m + 0.5 x (1.1 m) = 1.56m; 1.1m is the linear dimension of the motor So = 1 Lwa = 81 + 10 = 91 dBA, which is higher than 85 dBA and noise mitigation is required by the sound consultant!!!!!!! I don’t agree since I refer to Lp = 81 dBA and less than 85 dBA required at 1 meter away (3.3 feet) which is achieved. I would like to clarify that Lwa (Sound Power) considered by the consultant is calculated as below: Lwa = 81 + 10 = 91 dBA Is it correct to consider his analogy from the formula? I do understand the decibel of the power isn't the same as the decibel of the pressure!
3.95If a motor complies with NEMA MG 1, Part 31.4.4.2, does that mean it is compatible with 'V/f' type variable frequency drives only, or “vector” type variable frequency drives only, or both?
3.96I'm wondering the difference between a 256TY NEMA frame and a 256TC NEMA frame.
3.97In NEMA MG-1, Table 4.4.4 for Type-C Face Mounting A/C Motors, shows 2 different dimensions in column "BB Min": a 0.16 and 0.25 dimension. The 0.16 dimensions reference a footnote showing a tolerance of "+0.00 inch, -0.06 inch." To me, that makes the 0.16 dimension a maximum and makes this table unclear. What is the tolerance for the 0.25 dimension in "BB Min" column? Is there a UOS tolerance for dimensions in this standard that I have not discovered?
3.98In reading both the 2003 and 2006 versions, Section 12.41 "Breakdown Torque of Polyphase Wound-Rotor Medium Motors with Continuous Ratings" has an error in the table. The table shows the synchronous speed of the 50 Hz machine as 100 RPM and it should be 1000 RPM.
3.99In regard to premium efficiency 50 Hz motors, does a motor that meets the minimum efficiency, but not the nominal efficiency, still qualify as a premium efficiency motor? If not, would this qualify as an energy-efficient motor?The query is whether the rule is applied also for motors with a frequency of 50hz and if so, how could one document this information? As revising the standard, I see no way to evaluate the efficiency of the engine type A and B with 50 Hz. Although efficiently expressed tables by type, number of poles, and power, I do not clarify whether I can use the same efficiency requirements for a lower frequency.
3.100In Section 32.13 of NEMA MG 1, it says that "a synchronous generator shall be capable of withstanding, without damage, a 30 seconds, three-phase short circuit at it terminals when operating at rated kVA and power factor, at 5-percent over-voltage with fixed excitation," but in Section 9.9 of IEC 60034-1, it says that the short circuit shall be maintained for 3s. Please help me to know why the requirements of the two standards have such a wide difference.
3.101In your MG 1 documentation, section 12.38.1, Table 12-2 (Locked Rotor Torque for Design A & B), why doesn't the table show any information below 1/2 Hp and what does the value '...' in the table mean?
3.102Is it true that starting torque of high voltage motors is lower than the full load torque?
3.103Is there a chart made that shows runout tolerances set by speed? We are in need of a guideline for acceptance criteria. Any help would be much appreciated.
3.104Is there a maximum number of electrical motor starts (up to full speed) within an hour that is not recommended by NEMA to exceed? It is my understanding that the intent of a maximum number is to avoid damage to the motor due to excessive heat from the start load. Motor specifications include: 150 Hp, 900 rpm
3.105Looking at an electric motor NEMA rating is a NEMA L can you tell me what L means?
3.106My company's focus is to be a service, repair, and parts supplier for textile equipment here in the US. All new equipment to the U.S. comes from Europe. I have informed our European counterparts of the new EISA standards (NEMA energy efficient to premium efficient) regarding the motors that will be supplied, with new equipment beginning on December 19. My counterparts have indicated that they are aware of new standards in Europe which will soon take place and be fully enacted for all motors by 2017. The first step in Europe will only affect low voltage motors which operate "across the line" and not the motors which operate with an inverter. The question they are asking is if the case will be the same for motors which will be supplied to the U.S. from Europe. Will there be a gradual evoking of the full "premium efficient" standard? “Efficient" standard?
3.107On page 29, Table 11, there are "typical" characteristics, etc. This typically does not mean “mandatory” right? I have a question about motor Design D. On the table, the locked rotor current is 600-700, while at NEMA MG 10-2001 it is 600-800? The same for slip; on this document it is 5-8% while at NEMA MG 10-2001 it is greater than 5%.
3.108On Table 7 titled, "ALLOWABLE NUMBER OF STARTS AND MINIMUM TIME BETWEEN STARTS FOR DESIGN A AND DESIGN B MOTORS": What Hp does this table use? Is it electrical Hp? Or Brake Hp? Or is there some other way to determine the Hp rating of a motor independent of where it’s being run at? How do you determine the Hp rating of a motor?
3.109One of our vendors sells a NEMA 3.5 Hp motor. Can a NEMA motor be made that doesn't have a standard Hp size?
3.110Our client is insisting that NEMA MG 1-1998 efficiency requirements in Table 12.11 apply to 50 Hz motors. Would it be possible to get a letter from NEMA stating that NEMA MG 1-1998 Table 12.11 only applies to 60Hz motors and does not apply to 50 Hz motors?
3.111Our company is a motor manufacturer in Korea. The standard of our motor is NEMA. There is a technical data sheet (MG 1-1993, Part 12, page 21, section 2) about tests and performance of ac motors. In this table, NEMA suggests the data to keep the value of efficiency. I wonder that when our company makes a pole change motor, the value of efficiency is really difficult to follow the NEMA standard in case of high efficiency motor. The data is only for a one-pole motor, not for a pole change motor. I need a document that this table is the standard of one-pole motor and pole change motor is not adapted as our customer wants an official document from NEMA.
3.112Our company supplies and installs diesel generator sets in the range of 2.5-2,000 kVA. We have a request to supply a diesel generator set for a public tender in Greece. The tender states that the generator of the diesel generator set should comply with standard NEMA MG 1 Part 22, among other standards (IEC, CSA etc.). I can't find any references to MG 1-22 in the free, condensed version, nor is it in the contents table of MG 1-2011. After some internet research, I have found a citation stating that MG 1-22 referred to synchronous generators. As far as I understand, it was part of previous editions of NEMA MG 1 and at some point it has been repealed and replaced by NEMA MG 1 Part 32 and ANSI standards C50.12, C50.13, and C50.14. Did I understand this correctly?
3.113Please confirm a couple final clarifications: 1) YES or NO: “There is a NEMA MG 1 rated motor with full load efficiency table having nominal values LOWER than ‘Energy Efficient’”?2) YES or NO: “Can the motor manufacturer (with full integrity) give us a nameplate of 93.0% efficiency on two identical motors, when their one test sample result was calculated at 92.9% efficient”? (We are actually held to the old NEMA MG 1 1998 version on this contract when there was no separate 50Hz efficiency table.)
3.114Question on whether dc motors also shall fulfill the requirements for NEMA Premium™. It's a problem since our units were specified (middle and late 2009) before the regulation were known, and then they were stored waiting to be exported to U.S. where the site is located. To change motors now will also have impact on other equipment due to different start current and so on. The new motors also differ in size compared to those with older standards, and that also has an impact on rebuilding different units also with ac motors. Is there any chance to avoid changing motors on units already specified/purchased/produced, but not exported before 19 December 2010?
3.115Recently we had a 350 Hp electric motor 440V/3Ph/60 Hz burned in 3 phases. Motor has only 22,000 hours operating directly connected to a centrifugal compressor. Company hired to do the repair job says that the source of the problem is that this motor has no code to operate with a solid-state starter. We asked the motor manufacturer and they answered that there is no such a thing, but repair shop insist in their diagnosis and said that it is in the NEMA MG 1 standard. We can’t find where in this standard is such requirement.
3.116Regarding polyphase AC motors, is there a standard or guideline for current balance between the 3 phases?
3.117Section MG 1-20.45 did not point to the table in MG 1-20.42. We recovered the 1964 version and it does provide those values that we are looking for. We did have one question. The 1974 version removed some values from this table as compared to the 1964 version, specifically the values for 250 Hp–500 Hp for rpm at a range of 1800–3600. Additionally, the note “This formula may not be applicable to the ratings not included in the above table. Consult the manufacturer for the ratings which are not shown.”
3.118Sir, I would like to know the minimum resistance and reactance value of a motor and useful calculation formulas.
3.119The efficiency levels are provided with nominal and minimum efficiency values. I am correct when I say that a motor rating must meet both of these criteria and not just one or the other, right?
3.120The explanation for sealed windings is very clear. We would also like to ask if there is a standard and definite definition of “sealed motor” in the motor industry according to NEMA the standard.
3.121The NEMA MG1 standard states a “shaft parallel to foot plan” of 0.015”, but that incongruent since parallel requires an angle not an offset. Could you provide some guidance on how the parallel tolerance is measured?
3.122The question is in regards to Table 32-3 and the 5 degree C delta when comparing Rise-by-Resistance to Embedded Detector temperature rise. This maximum delta requirement seems to be a recent addition as it was not present in the 1993 version of MG-1. In discussion with generator manufacturers, I am told that this delta maximum is not achievable unless the embedded detectors are located in stator winding spots that are not hot spots. As a customer of generators, we would prefer that embedded detectors were in the hot spots. In hot spots, the delta rise tends to be 25-30 degrees C.
3.123The temperature rise limits in 12.43 are based on a maximum ambient of 40 degrees C, as stated in the clause. Both 12.43 and Table 12-8 are based on winding rise by resistance. The highest temperature rise values in 12.43 are 70 degrees C for Class A, 90 degrees C for Class B, 115 degrees C for Class F, and 130 degrees C for Class H. Adding ambient to highest rise results in maximum temperature limits of 110 C, 130 C, 155 C, and 170 C for Classes A, B, F and H, respectively. As I interpret it, a motor complying with the limits in Table 12-8 of 12.56.1.1 would be in excess of the limits of 12.43 by at least 30 degrees C for Class A, 35 degrees C for Class B, 35 degrees C for Class F, and 45 degrees C for Class H. Both clauses apply to medium motors, thus my perception is that the motor configurations are, or could be, the same. What am I missing?
3.124The user would like clarification on whether or not compliance of a motor to Part 31 would/could also cover or partially cover its compliance to Part 30 of the MG-1.
3.125There was confusion about the differences between the motors already covered in ASHRAE 90.1 (integral motors 1-500 Hp) and the motors covered under the recent DOE rules (0.25 to 3 Hp, polyphase, CSCR, and CSIR). Do you have some definitions or clarifications that you could send me to help avoid any confusion as to which efficiency table to use?
3.126There’s a lot of confusion and questions surrounding the EISA provisions. Some date back to the original EPAct legislation. I've been asked if special customer shaft extensions exempt motors from the efficiency requirements of NEMA MG 1, Tables 12-12 and 12-11.
3.127This question is in regard to the nameplate on single phase electric motors. Salesman 1 tells me that a voltage rating of 230V means that the motor will operate between a range of 207V to 253V (+ or - 10%). Salesman 2 tells me that a voltage rating of 208V-230V means that the motor will operate between the voltages of 187V to 253V (208 less 10% and 230 + 10%). Salesman 3 tells me that a voltage rating of 208V-230V means the same thing as 230V and will operate safely between 207V and 230V, and there is no (affordable) motor that will operate between 187V and 253V. What does NEMA say? Why the confusion? We have a situation where we need to make the best choice on motors for mobile equipment on our farm where we can plug the equipment into a building with a 208V service one day and move the same equipment to a building with a 230V service. I am looking for full-load efficiencies of "premium efficiency" 480V, 8-pole motors, but noted that Table 12-12 in NEMA MG 1-2006 Revision does not include them. Is this full table available? In accordance with subclause 31.4.4.2 (Voltage Spikes) from Nema MG1, stator winding insulation systems of definite purpose inverter fed motors shall be designed to withstand the following limits at the motor terminals: 1. For motors with Vrated £ 600 V, Vpeak should be less than or equal to 3.1*Vrated (where 3.1 = 1.1 * 2 * sqrt(2) ). 2. For motors with Vrated > 600 V, Vpeak should be less than or equal to 2.04*Vrated (where 2.04 = 2.5 * sqrt(2) / sqrt(3) ). We were wondering why this difference exists. Why is there not a single criterion that is valid for every base rating voltage? Now looking a little more deeply into the equations of the two criteria, one can notice that the criterion valid for motors with Vrated £ 600 V does not take into account the term sqrt(3). Does it mean that this criterion is valid for delta-connected motors only? That is, if the motor is star-connected, should the criterion 1 be divided by sqrt(3) to be correctly considered? On the other hand, the criterion valid for motors with Vrated > 600 V takes into account the term sqrt(3) and this may lead to the conclusion that it is valid for star-connected motors only. Is this the case? Or can the criterion 2 be literally applied to delta-connected motors too? In other words, does the term Vpeak of these criteria refer to phase voltage (line-to-neutral voltage) or line voltage (line-to-line voltage)?
3.128Was there an efficiency rating for NEMA D motors installed during the 1970-1980?
3.129We are a manufacturer of ring compressors. These devices are manufactured at our facility in Taiwan. I have notified them of the motor efficiency requirements and we have a few questions. 1) If we meet the minimum efficiency requirement of the specification, can it be accepted by NEMA? 2) If our motor can meet NEMA’s request, what will we show to them? Does NEMA certify the motors? How should we mark the motors? 3) The motor’s Hp figure(X) of NEMA MG 1-2006 Table 12-12 as NEMA defined does mean not bigger than X? For example, the area of 1Hp means 1Hp >= X >=0Hp, 1.5Hp means 1.5Hp >= X >1Hp 4) What is NEMA’s standard to test the motor’s efficiency? 5) The motor’s efficiency in NEMA MG 1-2006 Table 12-12, does it include the 50 Hz also?
3.130We are a producer of turbo generators. On a new project (32MW generator for 50Hz and 60Hz market), the customer requires NEMA approval certification. How can that be achieved? Is it via a notified body? Is it just by following design guidelines according to NEMA? Or any other way? Please advise, and respectively assign a contact for further clarification!
3.131We are having a difference of opinion on the interpretation of the NEMA motor standard regarding permissible runout on the shafts of JM frame motors. Can NEMA clarify to resolve the dispute? We interpret the max runout to be .002 for shafts for 143JM - 256JM, .003 for 284JM - 326JM frames, (per Section II, Part 18, Page 86). My motor supplier is saying that because JM shafts are an extended length, there is a caveat in the standard that allows max runout of .004 T.I.R. We can only find that this applies to extended length shafts on C-face motors in the standard.
3.132We are seeing a reference to NEMA MG 1-22-61 in ac generator specifications. I am not sure what or where this reference comes from. I am looking in my copy of MG 1-2003, rev 1-2004 and do not find a 22-61.
3.133We are the earliest and largest company of China producing large wind turbines. When we learned of NEMA MG 1-2006 Revision 1 Motors and Generators, chapter 20.18, we had some doubts about following: 1. What's a non-ionic wetting agent? Is it like a pesticide spray application? Is it harmful to the insulation system? 2. What's the purpose to do high-potential test when the motor is submerged?
3.134We have a little (big) problem concerning the dimensions of a type C flange (the motor frame is 182 TC). On page 59 of NEMA standards publication, it is not clear which plane the dimension AH is referred to (I suppose that AN means AH, in the upper drawing). Could you be so kind to send me a drawing with the real dimensions for a motor frame 182 TC?
3.135We have a question on Design C motors to consult with you. We understand that a Design C motor must meet the requirements of NEMA MG 1, at least conform to this standard on locked-rotor torque, pull-up torque, breakdown torque, locked-rotor current, slip, and etc. Do these requirements have an allowance (tolerance)? As you know, the Design C motor is designed as per NEMA MG 1, the average performance specification can meet or exceed NEMA requirement, but a small part of these motors may have a deviation, for example, some 25 Hp, 4-pole motors have a locked-rotor torque, 198 percent of full-load torque, but NEMA requires 200 percent. Are these 25 Hp, 4-pole motors with deviation belong to Design C motor? For another example, NEMA MG 1 requires 10 Hp Design C motors have a locked-rotor current not exceeding 162A at 230V 60 Hz, but some motors with deviation has an 8 percent higher than the standard current 162A. Can these motors be regarded as Design C motors? Do these Design C motors have to be re-designed to assure each motor meets all the NEMA requirements without any percent allowance? 2. You mention "resistance" test method when determining the insulation life of a motor. Where can I get information on the resistance method? 3. Does this standard include the small motor dimension standard for NEMA 8, 11, 14, 17, 23, and 34? Those are the primary sizes for this gear reducer family that I am working on. I looked in the MG 1 condensed version and it has the type of information I am looking for, but the smallest I found was the NEMA 42.
3.136We have an engineer that is questioning that the "Nominal Efficiency" must meet or exceed 86.5% for 1.5HP motors to be considered NEMA Premium™ Motors under Tables 12-12 and 12-13 at 60hz. The EFF stamped on the motor in question is 84% and it is running at 208/3. We are under the impression that a 1-1/2hp motor rated in the range between 86.5%–84% would be considered NEMA Premium™ and meet all 2011 standards for motors. Would this be an accurate statement? Could you please inform me about NEMA rules when a motor is applied with VSD? Effectively, I would like to know if there are restrictions to use asynchronous motors with a special machine.
3.137We have heard rumors that NEMA changed their Class B temp rise from 80 degrees C to 85 degrees C for electric motors. Is this correct? When did this happen? I cannot find any documentation online to support the rumor, but it came from some electric motor manufacturing engineers.
3.138We have recently noticed an apparent change in the NEMA specified hi-potential test voltages.The specific section in question is NEMA MG 1-2006, Part 12, Page 2, Paragraph B.2.A that specifies a test voltage of 1500V for motors rated 1/2horsepower and less and 250V or less.Previous versions of NEMA MG 1 specified a test voltage for these motors of 1000V. This results in a 50% increase in the test voltage. We are concerned that the increased test voltage may be overstressing the motor insulation, as our motors are typically hi-potential tested at least three times (the motor manufacturer, and our customers).Please confirm if the 1500V test voltage is indeed the current specified hi-potential test voltage for these motors. If it is correct, we would appreciate your comments regarding the reason for this change.
3.139We have to clarify a customer complaint and desperately need the tolerance classes for a NEMA flange 9”. Is it possible to get just a short overview?
3.140We manufacture ceiling lifts for hospital, which are used to lift and transfer patients. For lifting, we use a 24V permanent magnet dc motor. One of our customers has requested that we provide a NEMA Class A motor. We believe this class only describes ac motors. Are we correct in this belief?
3.141We manufacture electric motors in Guadalajara Mexico. so, I would like to know if exist the possibility to manufacture the conduit box housing in material poliamida reinforced with fiber Glass (30 %). (Nylon reinforced). The question is because, due the news developments material in resins reinforced have equivalents mechanical properties like the steel. Your reference 4.19.1 of the NEMA std manual
3.142We ordered 800 Hp, 6.6kV motors from a local electrical motors manufacturer. He was requested to perform the sealed windings test according to paragraph 20.18.2 of MG 1-2009, Revision 1-2010, Part 20, Page 13. According to this paragraph, Item A.: "The wetting agent shall be non-ionic and shall be added in a portion sufficient to reduce the surface tension of water to a value of 31 dyne/cm or less at 25 degrees Celsius." The manufacturer sent three samples to a laboratory and the results were 31.1, 31.1, and 31.2 dyne/cm. The measurements were done by Kruss Easy Dyne apparatus. Our chemical laboratory people are not pleased with these results. As I am an electrical engineer, it is very difficult for me to find a solution, therefore, I need your help. Can you inform me what is the standard or procedure the manufacturer has to use in order to achieve the required result? Your quick answer will be highly appreciated.
3.143We would like to ask if there is a standard and definite definition of “sealed motor” in the motor industry. According to the NEMA standards publication, there is a classification of motor by “machine with encapsulated or sealed windings”. Can we say that such a motor is an electrically-sealed motor?
3.144We would like to know what will be the code letter recommended for a tefc 5 hp / 600 volts / 60 hertz Are they all recommended?NEMA Code Letter kVA/HP with locked rotor Approximate Mid-Range Value A 0-3.14 1.6 B 3.15-3.55 3.3 C 3.55-3.99 3.8 D 4.0-4.49 4.3 E 4.5-4.99 4.7 F 5.0-5.59 5.3 G 5.6-6.29 5.9 H 6.3-7.09 6.7 J 7.1-7.99 7.5 K 8.0-8.99 8.5 L 9.0-9.99 9.5 M 10.0-11.19 10.6 N 11.2-12.49 11.8 P 12.5-13.99 13.2 R 14.0-15.99 15.0 S 16.0-17.99 T 18.0-19.99 U 20.0-22.39 V 22.4-and up
3.145What are NEMA's standard generator sizes? I am looking for sizes 1000 kW and larger.
3.146What does motor type 56 FR mean? Could you send me some information on this by email?
3.147What if the motor I am referring to is reduced voltage, soft-start with no VFD?
3.148What is the difference between an open dripproof and an open slotted motor?
3.149What is the difference between these two standards in general terms? Can a motor be both MG1 and MG2? If they are different, is there a document that compares the two?
3.150What is the equivalent Ingress Protection (IP) code of a Totally Enclosed Fan-Cooled (TEFC) Machine which is specified in clause 1.26.2 of NEMA MG 1? Is it IP 4X, IP 5X, or both ?
3.151What under voltage is allowed on 380/220-volt systems at 50 Hz? How low can it be set at for a transfer switch with a default setting at -15% dip?
3.152When going over the 2010 revision of NEMA MG 1, I noticed a section that does not make much sense when being read. Section 7.8.5.2 Filtered Vibration: The second paragraph states that if the level does NOT exceed 90% of the unfiltered limit then the machine has failed and corrective action is required. The third paragraph states what to do if it DOES exceed 90%. In regard to the second paragraph if you have vibration under a set value, you should find that acceptable rather than failing the machine.
3.153When NEMA specifies a bolt hole size for a motor foot, how much smaller in diameter can the hold down bolt be to allow for coupling alignment adjustments? Is there a chart based on hole size or a rule of thumb? Can the hole in the motor foot be enlarged if needed and if so how much and what roll does frame size in these questions? This question was brought to me from our millwrights and I don't know that I have ever seen an actual rule or chart.
3.154When NEMA specifies a bolt hole size for a motor foot, how much smaller in diameter can the hold down bolt be to allow for coupling alignment adjustments? Is there a chart based on hole size or a rule of thumb? Can the hole in the motor foot be enlarged if needed, and if so, how much and what roll does frame size in these questions? This question was brought to me from our millwrights and I don't know that I have ever seen an actual rule or chart.
3.155Would table 12-11 still apply to a custom built motor that is operated at 50Hz but on 460V?
3.156Would you please refer to the below question and explain in detail for our understanding. In NEMA MG 1, section 1.26 Totally enclosed machine, IEC Ingress Protection (IP) codes are defined for some totally enclosed machine type. However, IP code is not defined for the totally enclosed fan-cooled guarded (TEFC) machine in clause 1.26.3 (only the International Cooling (IC) code is defined). So, would you please tell me the equivalent IP code of a TEFC machine?

Miscellaneous

4.1While checking NEMA MG 10-2017, we noticed that you list all the different options for horsepower on the left column, however I just wanted to know the values for A, B, and C for values larger than 250 HP if it´s possible. Is there a table with larger intervals, or should I look somewhere else? Or is this information undiscovered/irrelevant?
4.2A motor is running at about 140 degrees and the center of the housing is 170. Is that normal?
4.3i found some literature on forums suggesting the existence of a NEMA MG 7 standard, including a description of an inertial measurement technique. I would like to confirm this technique exists and purchase the standard if so.
4.4Does NEMA MG 1-2011 contain specifics as to the clearance that should be maintained between the armature and magnet on a high speed DC motor? Does it also give specifics on the runout of both parts?
4.5I am an instructor in electrical technology at the Northern Alberta Institute of Technology, in Edmonton Alberta, Canada. In my classes, I cover topics relating to electric motors, including the "locked-rotor KVA code letters" (NEMA MG-1, 2011, section 10.37). I am wondering, why has NEMA chosen to report locked rotor currents using such codes? Why not simply report locked rotor currents as a fraction of rated motor current? Is there an application note or an explanation of how locked-rotor KVA codes should be determined? Any information that you could provide me in this regard would be appreciated.
4.6I am hoping you can answer a question we have regarding Sound power levels – with respect to a Synchronous Generator. Our unit is 3,887 HP, it is self-excited, 277 rpm, salient pole. Looking at Table 9-1, for rpm’s less than 900, the rows showing maximum sound power levels stop having entries above 2250 HP. Is there a maximum sound power level for machines greater than 2250 hp (277 rpm) according to NEMA MG-1?
4.7I am looking for information on NEMA Class B and Class F motor winding standards. Specifically, I would like to ask when or in what situations would a Class B winding be used? Is it obsolete? Or is it used only in special circumstances? Why would a Class B standard be requested or required? What is the most common standard for an elevator MRL machine?
4.8If you could respond to a few questions about Class F adhesives in regards to Rotor's being refurbished I would appreciate it. I have a customer who refurbishes Rotors and they want to use an adhesive that is a class F adhesive that is rated by NEMA as such. My question is does NEMA rate adhesives or certify an adhesive to be a Class F adhesive? Second, are there guide lines for companies to follow who want a Class F rating on their refurbish rotors or motors in order to get them certified?
4.9Might there be a standard efficiency for dc motors? (motors to turn screws/extruders for plastics reprocessing and/or plastic bag manufacturing lines) We have old dc motors, and looking to upgrade to new ac motors. There are rebates for the conversion (because the new motors are more efficient). We are trying to establish a baseline, either as the current motors we have now, or as a new dc motor (if there are new dc-standards or general industry standards for the motors, we can use that as a baseline to compare our choice of ac motors, which may be sufficiently more efficient for the purposes of this rebate program).
4.10We are looking to interpolate efficiency say, between the 50% and 75% load points, or below 50% given in a typical motor spec. Is there an equation to do that? A typical curve?
4.11What is the motor code for a 3 phase 600 Hp motor with an inrush of 700%?
4.12Will a NEMA 215TC frame brake motor match with a 210TC or 250UC worm gear reducer? Or, where can I be directed to figure this out?
4.131) . NEMA MG-1 12.44.1a defines voltage tolerances for alternating voltage motors under running conditions at rated load as +/- 10% of rated voltage. Does 12.44.1d apply to variable frequency motors and universal motors or to all motors? 12.44.1d applies to alternating-current motors connected directly to the sinusoidal power supply. This does not include variable frequency motors when connected to a variable voltage/variable frequency source of power. Specific operating conditions for universal motors are stated in 12.44.1d. 2) When running a medium (300 HP) fan motor at the nameplate rating, frequency will not be changing so does a. apply or does d. apply ? Both a. and d. apply. The frequency referred to is the frequency of the alternating-current power system to which the motor is connected. If the frequency of the power supply does not change then d. is the same as a. 3) to us, there appears to be a conflict between voltage tolerances in C84.1 and NEMA MG-1, i.e, +/-5% vs +/-10% respectively. We want to say the fan motor is able to operate from 432-528 volts (480V +/- 10%) are we correct on that? Standard motor voltage ratings in Part 12 for small and medium motors correspond to the utilization voltage in C84.1 which is derived from the nominal system voltage. For example, the standard voltage rating for a motor used on a power system with a nominal system voltage of 480 volts is equal to the utilization voltage of 460 volts. The voltage tolerances for Range B in C84.1 apply to the utilization voltage, not to the nominal system voltage. For a nominal system voltage of 480 volts and utilization voltage of 460 volts the limits in C84.1 for motors are a maximum of 508 volts and minimum of 416 volts. These values do not correspond to +/-5% as stated in the original question. The +/-10% variation on motor voltage in 12.44.1d corresponds to these maximum and minimum limits on the utilization voltage in C84.1 applicable to motors. There is no conflict between the two standards. For a nominal system voltage of 480 volts and utilization voltage of 460 volts, the limits in C84.1 for motors are a maximum of 508 volts and minimum of 416 volts. These values do not correspond to +/-5% as stated in the original question. The +/-10% variation on motor voltage in 12.44.1d corresponds to these maximum and minimum limits on the utilization voltage in C84.1 applicable to motors. (I got lost here - nominal utilization voltage is 460 volts.) 460 + 46 = 506 480 + 48 = 508 460 - 46 = 414 480 - 48 = 432 I can’t seem to come up with 416 volts as 10% less than 460 or 480 volts. What am I doing wrong?
4.141) I am trying to find a data sheet that lists all the NEMA motor frame sizes. I have one that lists 42 and above, but leaves out 17, 23, 34, and maybe some others I do not know exist. Could you please direct me in the right direction for finding some official data sheet to find this information? 2) We are selling regenerative blowers in the U.S. I would like to know if our motors are not required to meet the NEMA Premium™ Efficiency standards due to the fact that they are not NEMA motors. The blower motor rotor is also the impeller shaft. We do not sell motors separately and they cannot be used for other applications.
4.151) I received the following feedback from our Plant Engineers that the new premium efficiency motors are too flexible. This is the feedback that they have given me: “The NEMA frame 284TS 25 HP motor is a federally mandated Premium Efficiency Motor design which has reduced metal mass to improve electrical running efficiency. The problem is that the motor frame is so flexible that after it is fully aligned, and torqued down, it is possible to cause the alignment to fluctuate by +/- .020” just by leaning against the motor. The result is that when the motor is put in service, the resulting torque causes the motor frame to distort, causing high vibrations indicative of misalignment. Because the flow on the pump changes, based on tank level, the torque on the motor changes constantly in operation. As a result, the motor alignment can not be pre-adjusted to compensate for a running position that constantly varies. The new motor is not able to meet the required running conditions in service. We are not able to achieve an alignment that results in low vibrations when the motor is placed in operation. The running vibration levels of the motor, when aligned by our procedures to the correct alignment, exceed our criteria for removing the motor from service. This problem is generic in nature and applies to all NEMA Frame motors 300 or less, that fall under the new federal Premium Efficiency Guideline.” Your feedback on this issue would be greatly appreciated. Are there any motors available that would be the same fit, form and function without the reduced metal mass similar to the sturdier, older style motors? 2) We have a plastic vane per Mil P 8059 and NEMA-AA #3 and would like to know what NEMA AA #3 means? 3) I am working with a team of engineers on the design and development of a high performance, high efficiency generator. Single and Three phase, 15kW to 100kW. My question is which specification(s) do I reference for info on grid tie performance or stand-alone performance? I am trying to understand the power factors we have to meet, harmonic distortion / waveform quality, and surge requirements.
4.161) In order to understand more clearly about machine enclosure type, I would like to have your answer for my question below. According to your previous response, a TEFC machine may have an open drain hole based on common practice in the U.S. so that it would not meet the requirements of IP5X. Hence, if TEFC motors which were or will be provided by U.S. manufacturers do not have an open drain hole, should all of these motors be classified as IP5X? I have this question because I found many manufacturers specify in their catalogue that their TEFC motors are classified as IP4X; however, their motors don't have any open drain hole. 2) I am working on electric motor replacement policy for government buildings. Do you recommend premium efficiency motors in VFD applications? My research indicates mixed opinions.
4.171) In which ambient temperature range are motors covered by EISA? (Is it -15 to +40°C?) 2) Where can I find the best information for which motors are covered by EISA and which are not in scope? Good explanation of EISA and DOE regulations. 3) What happened when EISA covered motor have no CC-number from DOE and will be shipped in the USA? 4) Do you have some news about the rule for small motors (single- and polyphase)
4.181) Need clarification on MG1 31-31.4.2.1. • At what frequency does breakaway torque occur? • Is there a method for how to conduct the test? 2) • Is a foot-motor always part of NEMA premium level (NEMA MG-1, table 12-12)? • What about a footless, C-face mounted motor. Is it NEMA premium or EPACT (Table 12-11)? • Are totally enclosed, not ventilated motors like TENV, TEBC or TEAO always Standard Efficiency?
4.191. In which ambient temperature range are motors covered by EISA? (Is it -15 to +40°C)? 2. Where can I become the best information which motors are covered by EISA and which are not in scope? Good explanation of EISA and DOE regulations. 3. What happened when EISA covered motor have no CC-number from DOE and will be shipped in the USA? 4. Do you have some news about the rule for small motors (single- and polyphase)?
4.20About 10 years ago we purchased the MG 1 Motors and Generators, but not ALL sub sections were included. We need the subsection 20.54, dynamic balancing. Please let me know how I can obtain this for Las Vegas Water.
4.21Are stainless steel, three-phase, T-frame motors currently EPAct? Do they need to be PE after Dec. 18, 2010?
4.22Are there further regulations which need to be met for supplying electric motors in the U.S.?
4.23Article 310.6 of the 2005 NEC appears to require the use of shielded cable as the supply conductors for motors rated above 2400VAC. How is this handled in a standard motor lead termination box? Does the customer have to order the motor with an oversized connection box or install one in the field that will accommodate the stress cone terminations? Is there a shielded cable made that meets 310.6 and does not require stress cones? Has this issue been addressed by NEMA and or any of the motor manufacturers?
4.24Basically, we need to know the proper test procedure/requirements for hi-pot testing a motor. The motors we are trying to test are all ac permanent magnet motors. The voltage range is: 145 – 350 VAC The HP range is: 6.7 - 44.9 HP The current range is: 13.5 - 66.7 A We are looking for the procedure/requirements for the 1 sec, as well as the 60 sec hi-pot test.
4.25Can you give me the definitions of “random” and “form” wound motors?
4.26Can you help me out? My copy of the NEMA MG 1 does not appear to have a Part 11, but one of our engineers has a customer that is referencing Part 11.08. Can you tell me what this part is or if it even exists?
4.27Can you tell me difference between letter temperature classes and numbered classes? Are letters still in use? Are letter-only in NEMA classification? Temp class F is class 155. In some new datasheets, I can't find classification by letter (like L or H), only with number for IEC 60317-51 (like 180, 155) and NEMA MW82, MW79 marking.
4.28Do all motors that are used in the U.S. need to be manufactured according to NEMA MG 1 or can motors according to IEC 60034 also be accepted?
4.29Do motors that are manufactured according to NEMA MG 1 require an approval according to UL or is an UL-approval only necessary in particular cases?
4.30Does MG 1 have a table with typical FLA similar to NEC table 430.250?
4.31First, we seem to be having some difficulty securing 200v premium efficiency motors (PEMs) for HVAC and Plumbing applications (air handlers, pumps, etc.). Most are double windings of 230/460v being run at 208v. The latest installation of this I saw indicated the motor could be run as a 200v motor with a SF of 1.0. It was a 230–460v motor. There is a plethora of data that yields recommendations of running 200v motors with 208v power for reasons of efficiency, heat generated, starting amps, etc. We generally ask our consultants to specify 200v motors where used in a 208v service. Additionally, it is our policy to specify PEMs, which NEMA has been instrumental in creating universally-accepted standards for. Obviously, most HVAC and plumbing applications utilize smaller horsepower motors, in the range of say 1–40hp. However, given the run time of these motors, the motor efficiency can yield significant energy savings. Can you advise as to manufacturers that provide 200v PEMs in this horse power range, preferably with a service factor of 1.2 or greater?Second, I understand from a brief chat with the CDA that an update to the PME definition and or new ultra efficient standard. We would be interested in a draft copy of the document after it is completed.
4.32For one of our projects, we need an electric motor (which can work as a generator too) with a power capability of 25kW peak, and a speed of about 6000 rpm max.
4.33I am attempting to create a drive design manual for couplings, and want to reference the standard NEMA ratings for different frame size motors and ensure the coupling sizing is correct. One of our European manuals for the same style of product lists the standard nominal, peak, and alternating torques for various sizes of European motors, such as a D80 frame. (The listed D80 frame values are 18Nm, 30Nm, and 4Nm respectively.) Is this information (nominal, peak, and alternating torque) listed in NEMA MG 1 for nominal NEMA standard motors, for example, a 143T frame (Design Type B) motor? If this is not listed in MG 1, which standard would it be listed in? I know that the nominal torque information for standard size motors is widely available, but I am significantly interested in the peak and alternating torque values.
4.34I am field testing some European motors which are reading meggering at 30MΩ when meggered. Normally I would consider this as failure; I know that NFPA 79:18.3 allows an insulation reading of just 1MΩ. Normally when I megger a motor I get a reading of .999MΩ. What would be your opinions on this?
4.35I am involved in a project whereby to replace a self-contained diesel firewater pump with a 500 Hp, 4160 volt, 3-phase electric-driven firewater pump-wound squirrel-cage induction motor. Our project specification is based on API 541. I am currently evaluating a quote from a motor manufacturer whereby their wound squirrel-cage induction motor will be designed, built, and tested per NEMA MG 1. They will make an exception to API 541 motor as we requested. My question is that on which areas (design, construction, testing, environment, etc...) of API 541 are more stringent as compared with NEMA MG 1?
4.36I am looking for codes and standards for motor overload reset and its location, and if it shall be able to reset the overload from outside of the enclosure.
4.37I am looking for information pertaining to electrical motor efficiency, specifically historical efficiencies. I am doing a comparison of typical ventilation motors for a shopping center. The existing motors are from 1984 to 1988. Only general information is required. Motors range in size from 2Hp to 5Hp. Any feedback is appreciated as I am aware this is probably an abnormal request.
4.38I am reviewing efficiency of our compressed air plant. One of the machines we have is a 1952 800 Hp synchronous motor reciprocating air compressor. The owner’s manual says that at no-load capacity the machine will draw 3 to 5% of indicated Hp. Is this theoretical or actual? Will a synchronous motor go down to 5% load at a no-load condition? What about a standard squirrel cage induction motor at no-load condition?
4.39I am trying to clarify the dates when NEMA efficiency standards changed. I have reason to believe the changes occurred in 1980, 1985, and 2001, but I have not been able to find any source documents to support that belief and provide the efficiency standards established for motors manufactured in those years. Can you help?
4.40I am trying to locate a copy of the 1972 version of MG 1, or at least verify that the 1972 version contains the same verbiage concerning "VARIATION FROM RATED VOLTAGE AND RATED FREQUENCY" with a +/- 10% voltage variation design requirement.
4.41I am trying to locate guidelines or other information for electric motor shaft requirements such as diameter, geometry, strength, etc. I was told that guidelines are possibly in the NEMA motors and generators standards. What is the current revision and what document/revision would have been applicable in the mid to late 1970s (1977 or 1978)? Are the documents available for purchase and at what price? My question really relates to the shaft dimension, particularly the shaft diameter. I am trying to find out whether a step-down shaft for a 215 frame is within the guidelines of NEMA MG 1, or whether that is something that the manufacturer would decide acceptability? I have an application for a 215 frame, but instead of the shaft being 1.375” diameter, it would step down to 1.125” diameter, and the frame is designated a 215Z. What would be the difference between a 215Z and a 215TZ frame? I am trying to get a better understanding of what I have and whether they meet the NEMA guidelines that would have been in place in the late 1970s.
4.42I am wondering which section or standard contains the NEMA 23 and NEMA 34 motor mounting standards. Please get back to me on which standard I need to purchase.
4.43I am writing training material for a client regarding NEMA and the design codes for ac induction motors. I have looked through your website and have been unsuccessful in finding information regarding codes A, B, C, and D. Can you please send me some basic information regarding these codes? Do the motors look different across the codes? If the motors look different, can you please send me pictures of each motor and their respective code?
4.44I encountered a problem with my supplier's 12VDC 15W brushed motor with high noise level (dB). This vibration noise is not spelled out in the manufacturer product specification. The supplier is measuring the noise as per following methodology. 1. Motor is placed on high density foam 2. Input voltage, 12Vdc 3. dB meter place at 100mm directly on top of the test motor 4. Measurement duration 10mins, by taking the average across the 10mins, we can derived the noise figure 5. Noise Level up to 80dB is consider normal (subject to ambient noise level) I need the advice on the following: 1. Is this an acceptable industrial standard? 2. What is an acceptable noise (dB) for 12VDC 15W? 3. What is approved test method for checking motor noise?
4.45I found a misuse in NEMA MG 1-2009, Revision 1-2010. Please check the following sentence: "The addition of letters and/or numbers to the auxiliart symbol shall wherever possible, be based on the rules given in 2.67.1" It is located in 2.67.2. I think that "2.2" is correct instead of "2.67.1".
4.46I get a feeling that the ratio of maximum torque to full torque is decided arbitrarily. I am in the process of working out a mathematical relationship between these parameters. Please inform me if such relationship already exists to save my unnecessary efforts.
4.47I had a Colorado electrical inspector send me a note over the weekend to draw attention to this proposed legislation in Colorado. Apparently, the hearing is scheduled for Tuesday, February 4, 2014. Would the members have anything to say about the use of their equipment in this manner? HB14-1030 CONCERNING THE ESTABLISHMENT OF INCENTIVES FOR THE DEVELOPMENT OF HYDROELECTRIC ENERGY SYSTEMS. (formerly designated interim committee Bill A) Water Resources Review Committee. As introduced: In order to promote the construction and operation of hydroelectric energy facilities in Colorado, the bill provides the following incentives: * Section 1 of the bill requires the state electrical board to approve the installation of a motor as a generator for a hydroelectric energy facility if the installation would be approved but for the fact that the motor is not being used in a manner commensurate with its nameplate; * Section 2 authorizes the department of natural resources to serve as the coordinating state agency for obtaining and compiling state agency comments about an application for a license or license exemption from the federal energy regulatory commission; and * Section 3 incorporates community hydroelectric energy facilities into the community solar garden statute, so that a group of community members may jointly subscribe to and receive electricity from a small hydroelectric energy facility located in or near the community.
4.48I have an old FHP repulsion-start, single-phase 1750-RPM electric motor that is frame size M5. When did NEMA change the electric motor frame size designation, and how do I compare old and new frame sizes for FHP motors?
4.49I have been very confused with measuring some motors and finding huge differences in the efficiency. IE: A - 95, B - 88 C - 50. Why is C so low?Based on a local electrician's description, open delta power could be the cause. My layman’s description would be 2 phase power delivered semi 3 phase. Utility company is only using 2 transformers, thus the power is unbalanced. Could you explain why one phase of power is being so out of whack? Does that make sense? Or is there another reason? Motors have one/two legs that are efficient and one leg not at all.
4.50I have ran into a major induced-shaft common mode voltage issue on a motor supplied with an air handling unit fan for commercial office building application. The VFD supplier has taken the stance that NEMA Part 31 motors should be able to handle 20 volts or more of induced shaft common mode voltage without electrical damage to the bearings. I can't find anything definitive in the standard to agree with the VFD supplier. It appears that NEMA 31 really doesn't address induced shaft common mode voltage at all. However, the motor manufacturers do not warrant against electrical damage due to induced shaft voltage and current (due to fluting or frosting in the raceway). Can you shed some insight?
4.51I have seen on the internet many NEMA MG 1 motors, and they are identical in respect to the mounting and shaft dimensions for a given frame size and variant. The one motor I am having real difficulty in understanding is the foot measurements. My hunch is that this motor is not in accordance with NEMA MG 1 and that the manufacturer may be using an IEC motor body that can be adapted to NEMA sizes, but I am not certain of that as like your NEMA specifications, I also don't have any detailed IEC specifications. The only point I can really see, and/or make judgment on, would be to ask if this motor would be interchangeable with a proper NEMA MG 1 dimensioned motor of the same frame, i.e. 449T. The application also calls for it to conform to IEEE 841 and it is on an inverter drive in a Class 1 Division 2 Groups B,C,,D, T3 Hazlok. As you can see, it is fitted with a "sparking device" and that is not allowed in this Hazlok, and it only has one insulated bearing. I also understand from what I can glean from NEMA MG 1 that it should have winding PTCs or RTD, but this has thermostats. The motor power and speed is another puzzler as we need 250 Hp and the voltage is 575 at 60 cycles, so on a 4-pole we will get 1800 rpm max. The speed range required is 1750 to 300 and max absorbed power is 140 kW at 1430 rpm.
4.52I inspected a motor with a temperature code of T3C. My inspection criteria said that the temperature code is to be T2D. I was told by another inspector that T3C was better and would supersede a code of T2D, but everything that I look at in my opinion based on the temperature rating a T2D motor can't be superseded by a T3C. Please email me a response.
4.53I need to know what "Type 2 thermal protection" is per NEMA MG 1-12.53.2? Our submittal was rejected when we tried to use thermostats on the motor and I cannot find any information for Type 2 thermal protection.
4.54I want to know whether a 75 Hp electrical motor built to NEMA standards can be used in the Philippines.
4.55I was on the phone this morning with a German-based client who had received a 100Hp North American-style motor for his machinery assembly. The motor was equipped with a metal terminal housing chamber, but inside, the motor lead wires were supplied loose, and only equipped with compression type lugs. He was asking me if that was typical in North America to provide motors with loose leads like that and how these leads are best secured. He was telling me that in the IEC world, it’s normal to provide motor terminal housings, but the motor leads inside are always secured, and the user just makes the connection to a lug or landing pad that is connected to the motor leads. I would appreciate if you would have any input on that from the motor folks in the U.S., i.e. if this is typical, or maybe just an unusual case.
4.56I was trying to locate where and what NEMA Class 1-2-3-4 Stator rewind materials are defined as.
4.57I work for an association of approximately 1,000 manufacturers and 200 related companies in Northern Illinois and would appreciate your help on determining if there is any possible value to an “energy savings device” that we are being asked to look at for possibly promoting to our members or if it is possibly a scam. Years ago, when I had my own company, I heard that putting capacitors on electric motors can save energy and once tried a little to find out more about it as I had a lot of motors in my plant. I was told by someone that it was expensive and was unable to find anybody that would give me a proposal at that time. One of our instructors ran across a company that has apparently developed and patented systems for industrial and residential use. She thought that this might be of interest to our members. (She has also somehow gotten involved with them, probably in some sort of training capacity.) Nevertheless, a couple of the principles in the company are in Chicago and have offered to make a short presentation to us to see if we would like to offer the information about them to our members. What I remember from one of my electronics classes has something to do with three-phase current and with the sinewaves and power curves being affected and changed with capacitors. One thing that I am wondering about is if it’s just some way to trick an electric meter or if there is some actual energy savings potential. They have more information and a video are available on their website. http://www.cenergy-tech.com/ . The video is at: http://www.cenergy-tech.com/video/ . Can you tell me if this might be for real or if it is just some sort of scam? Any suggestions along this line would be greatly appreciated! Thanks for any insight that you might be able to offer!
4.58I would like to ask you information regarding the part of the EISA regulation related to the footless motor, where the act says that “motors footless must comply with the EPACT levels of efficiency as defined by NEMA MG1 table 12-11.” Do you know if this part is due to be changed and if so, in which way and is there already a dead line?
4.59I would like to know if or when the last time NEMA has updated/expanded upon the standard for minimum recommended sheave diameters for electric motors. We are currently using data in our catalog from standard MG 1-3.16 and MG 1-3.16A. The Hp is from .50-30.00 and the motor rpm is from 575 to 3540.
4.60I’m working on a project and the noise level is critical issue for the surrounding area. Our sound consultant is referring to the power level (Lw) less than 85dBA instead of the sound pressure Lp less than 85 dBA at a distance of 3.3 feet (1 meter). The actual case and the consultant analogy from Reference to MG 1, Section 1 art. 9.7: Lp=Lwa – 10 x log (2π x rd square/ So) it gives: Lwa = Lp + 10 x log (2π x rd square/ So) The installation is: 125 HP motor (Noise level sound pressure 81 dBA at 3.3 feet (1 meter) From the Motor Data sheet: Lp = 81 dBA Rd = 1.0m + 0.5 x (1.1 m) = 1.56m; 1.1m is the linear dimension of the motor So = 1 Lwa = 81 + 10 = 91 dBA, which is higher than 85 dBA and noise mitigation is required by the sound consultant!!!!!!! I don’t agree since I refer to Lp = 81 dBA and less than 85 dBA required at 1 meter away (3.3 feet) which is achieved. I would like to clarify that Lwa (Sound Power) considered by the consultant is calculated as below: Lwa = 81 + 10 = 91 dBA Is it correct to consider his analogy from the formula? I do understand the decibel of the power isn't the same as the decibel of the pressure!
4.61I'm interesting in a methodology of how to evaluate the point of performance of an electric motor (how to evaluate the efficiency of the electric motor).
4.62I'm trying to determine the output in kWh of a motor. Hp x 746W/hp x hr x a load factor. Using the NEMA information, would a good average load factor be 0.95 or higher 0.97?
4.63I'm trying to get information on coil-wound electronic motors. What has the industry growth been over multiple decades, what products still use this, is it at the risk of obsolescence, etc.?
4.64In NEMA MG-1, Table 4.4.4 for Type-C Face Mounting A/C Motors, shows 2 different dimensions in column "BB Min": a 0.16 and 0.25 dimension. The 0.16 dimensions reference a footnote showing a tolerance of "+0.00 inch, -0.06 inch." To me, that makes the 0.16 dimension a maximum and makes this table unclear. What is the tolerance for the 0.25 dimension in "BB Min" column? Is there a UOS tolerance for dimensions in this standard that I have not discovered?
4.65In Section 32.13 of NEMA MG 1, it says that "a synchronous generator shall be capable of withstanding, without damage, a 30 seconds, three-phase short circuit at it terminals when operating at rated kVA and power factor, at 5-percent over-voltage with fixed excitation," but in Section 9.9 of IEC 60034-1, it says that the short circuit shall be maintained for 3s. Please help me to know why the requirements of the two standards have such a wide difference.
4.66Is it true that starting torque of high voltage motors is lower than the full load torque?
4.67Is NEMA MG 1-2011 applicable to medium voltage 750Hp and 1500Hp motors? If not, which standard should I reference in my electrical equipment specification? I want to insure the motor manufacturer complies with industry-acceptable vibration limits.
4.68Is the following statement true? "All standard 3-phase motors will rotate in a clockwise direction (when viewed from the output shaft end of the motor) when the 3-phase supply has a clockwise (ABC) phase rotation connected to Line1/Line2/Line3 respectively." Is this covered in a national (NEMA) standard? I am trying to establish a phase rotation standard for pre-wired (pig-tailed) small motors in our plant that assures correct motor rotation when installed.
4.69Is there a maximum number of times a motor can or should be rewound and if so, how is this issue regulated?
4.70Is there a wind rating test associated with NEMA MG 1 enclosure, or is this like asking if a NEMA 3R weatherproof box is tested for wind load? I have a spec calling for 140 mph wind speed design and my generator is in an MG 1 housing, so just wondering if that implies anything about wind speed.
4.71Is there NEMA MG 1 premium efficiency certification for VFD's or inverters? Otherwise, do you have any certification about VFD's or inverter's?
4.72It is possible to know where to find the maximum value of the dimension in the MG1-2003 standard?
4.73New nanotechnology materials promise to improve the permeability of magnetic materials, the conductivity and weight of wiring for motors, and the strength of magnetic materials. Can you recommend / provide me with an estimate of the size and weight reductions such changes in conductivity, mass of wires, and magnetic strengths could make to electric motors? For instance, suppose conductors with the same current carrying capacity in motors could be reduced in size to 1/10th that of copper and the mass by 1/6th that of copper—how much would the weight of a 10 hp motor be reduced? Suppose the magnetic permeability of the core were increased by a factor of two—how much would the weight of a 10 hp motor be reduced? For a permanent magnet-based motor, if the magnetic strength of the magnets were increased by a factor of two (with approximately the same density), how much would the weight be reduced?
4.74On page 29, Table 11, there are "typical" characteristics, etc. This typically does not mean “mandatory” right? I have a question about motor Design D. On the table, the locked rotor current is 600-700, while at NEMA MG 10-2001 it is 600-800? The same for slip; on this document it is 5-8% while at NEMA MG 10-2001 it is greater than 5%.
4.75On Table 7 titled, "ALLOWABLE NUMBER OF STARTS AND MINIMUM TIME BETWEEN STARTS FOR DESIGN A AND DESIGN B MOTORS": What Hp does this table use? Is it electrical Hp? Or Brake Hp? Or is there some other way to determine the Hp rating of a motor independent of where it’s being run at? How do you determine the Hp rating of a motor?
4.76Please confirm a couple final clarifications: 1) YES or NO: “There is a NEMA MG 1 rated motor with full load efficiency table having nominal values LOWER than ‘Energy Efficient’”?2) YES or NO: “Can the motor manufacturer (with full integrity) give us a nameplate of 93.0% efficiency on two identical motors, when their one test sample result was calculated at 92.9% efficient”? (We are actually held to the old NEMA MG 1 1998 version on this contract when there was no separate 50Hz efficiency table.)
4.77Regarding the Keyseat width tolerances, NEMA MG.1 conflicts with USAS B17.1. Please let me know the reason and how to deal with this. NEMA MG.1 Clause 4.9.2 Keyseat Width indicates plus tolerances like +0.000~+0.002 for width of keyseat 0.188 to 0.750, incl. and +0.000~+0.003 for Over 0.750 to 1.500, incl. But, USAS B17.1 Table 6 Keyseat Tolerances for Electric Motor and Generator Shaft Extensions regulates minus tolerance like below. Keyseat width tolerance -0.001~+0.001 for width up to and include 1/4, -0.002~+0.000 for width Over 1/4 to 3/4(incl.), -0.003~+0.000 for width Over 3/4 to 1-1/4(incl.)
4.78The ANSI/NEMA C50.41-2000 standard states that a motor that is running will continue to run as long as its terminal voltage is 75% or higher. I am trying to see if this statement is made in another standard that would apply to motors not located in power generation stations. Specially, I am designing for an onshore gas plant, but I cannot find this statement in API 541, 547 or IEEE 841. All I can find are the requirements for starting a motor (80% terminal voltage).
4.79There was confusion about the differences between the motors already covered in ASHRAE 90.1 (integral motors 1-500 Hp) and the motors covered under the recent DOE rules (0.25 to 3 Hp, polyphase, CSCR, and CSIR). Do you have some definitions or clarifications that you could send me to help avoid any confusion as to which efficiency table to use?
4.80We are a lubes producing company looking for information on the insulation classification of electro motors and the relation to lubricating grease which can be advised, ref. example: product Esso Unirex N3, technical data mentions: ...is applicable for the lubrication of electro motors of insulation class H according NEMA (National Electric Manufacturer's Association) can you please advised relevant documents or test methods?
4.81We are looking for some information on motor greasing. I was wondering if you wouldn't happen to have some charts or any kind of information to help us determine the frequency and amount of grease that should be put in motors of different sizes.
4.82We are manufacturer of dust collectors and screw conveyors. It’s my understanding of the new EISA regulation that footless motors need to meet the EPAct efficiency, while the foot mounted motors need to meet the Premium Efficiency. I would like to get a definition of a footless motor if it’s possible, because we actually import from Italy fans with IE2 (equivalent for values to the NEMA MG 1 Table 12-11) motors. These are footless IEC B5 2-poles, 3600 rpm, 230-460V at 60Hz with a power lower or equal to 11Kw. I would like to know if these motors that are in fact footless are considered also footless for the EISA purposes
4.83We are the earliest and largest company of China producing large wind turbines. When we learned of NEMA MG 1-2006 Revision 1 Motors and Generators, chapter 20.18, we had some doubts about following: 1. What's a non-ionic wetting agent? Is it like a pesticide spray application? Is it harmful to the insulation system? 2. What's the purpose to do high-potential test when the motor is submerged?
4.84We have about 600 electric motors on site with about 80% being under 100 kW. We have some odd sizes, with a standard size of 250 kW and then an odd one at 260 kW. Is there a preferred kW rating that motors can be grouped into so that spare parts can be minimized and service schedules better planned?
4.85We have heard rumors that NEMA changed their Class B temp rise from 80 degrees C to 85 degrees C for electric motors. Is this correct? When did this happen? I cannot find any documentation online to support the rumor, but it came from some electric motor manufacturing engineers.
4.86We manufacture ceiling lifts for hospital, which are used to lift and transfer patients. For lifting, we use a 24V permanent magnet dc motor. One of our customers has requested that we provide a NEMA Class A motor. We believe this class only describes ac motors. Are we correct in this belief?
4.87We ordered 800 Hp, 6.6kV motors from a local electrical motors manufacturer. He was requested to perform the sealed windings test according to paragraph 20.18.2 of MG 1-2009, Revision 1-2010, Part 20, Page 13. According to this paragraph, Item A.: "The wetting agent shall be non-ionic and shall be added in a portion sufficient to reduce the surface tension of water to a value of 31 dyne/cm or less at 25 degrees Celsius." The manufacturer sent three samples to a laboratory and the results were 31.1, 31.1, and 31.2 dyne/cm. The measurements were done by Kruss Easy Dyne apparatus. Our chemical laboratory people are not pleased with these results. As I am an electrical engineer, it is very difficult for me to find a solution, therefore, I need your help. Can you inform me what is the standard or procedure the manufacturer has to use in order to achieve the required result? Your quick answer will be highly appreciated.
4.88We use electric motors in our products and are located more than 1500m above sea level. How does this affect our efficiency in our motors used? The current motors used are for 1000m above sea level and less, while their efficiency is 72% to 75%.
4.89We would like to know what will be the code letter recommended for a tefc 5 hp / 600 volts / 60 hertz Are they all recommended?NEMA Code Letter kVA/HP with locked rotor Approximate Mid-Range Value A 0-3.14 1.6 B 3.15-3.55 3.3 C 3.55-3.99 3.8 D 4.0-4.49 4.3 E 4.5-4.99 4.7 F 5.0-5.59 5.3 G 5.6-6.29 5.9 H 6.3-7.09 6.7 J 7.1-7.99 7.5 K 8.0-8.99 8.5 L 9.0-9.99 9.5 M 10.0-11.19 10.6 N 11.2-12.49 11.8 P 12.5-13.99 13.2 R 14.0-15.99 15.0 S 16.0-17.99 T 18.0-19.99 U 20.0-22.39 V 22.4-and up
4.90What are the skin surface temp limits of a T2A, T2B type motors?
4.91What I’m looking for is if there is a standard tolerance for the “AH” – shaft extension dimensions for c-face motors. The “AH” dimensions are listed for various frame sizes in tables: 4.4.4 & 4.4.6 for A/C machines and 4.5.4, 4.5.5, & 4.5.7 for D/C machines.
4.92What is the difference between an open dripproof and an open slotted motor?
4.93What is the equivalent Ingress Protection (IP) code of a Totally Enclosed Fan-Cooled (TEFC) Machine which is specified in clause 1.26.2 of NEMA MG 1? Is it IP 4X, IP 5X, or both ?
4.94What is the relationship between the torque and the rpm of a PMAC motor?
4.95When NEMA specifies a bolt hole size for a motor foot, how much smaller in diameter can the hold down bolt be to allow for coupling alignment adjustments? Is there a chart based on hole size or a rule of thumb? Can the hole in the motor foot be enlarged if needed and if so how much and what roll does frame size in these questions? This question was brought to me from our millwrights and I don't know that I have ever seen an actual rule or chart.
4.96When NEMA specifies a bolt hole size for a motor foot, how much smaller in diameter can the hold down bolt be to allow for coupling alignment adjustments? Is there a chart based on hole size or a rule of thumb? Can the hole in the motor foot be enlarged if needed, and if so, how much and what roll does frame size in these questions? This question was brought to me from our millwrights and I don't know that I have ever seen an actual rule or chart.
4.97Why are the voltage ratings on motors less than the line supply voltage? For example, the 3-phase motors that I chose for my design have a motor nameplate voltage of 200 volts. The line voltage supplying the motor is 208V. At first, I thought this 200V was perhaps chosen to accommodate an expected voltage drop, but since line voltage fluctuates over time, that would make no sense. The only information I could find on that matter was that the nameplate voltage was a utilization voltage. Can you explain why motors are designed for less voltage than supply line voltage?
4.98Would an ac induction motor with Class F insulation (115°C + 40°Camb = 155°C max. winding temperature) meet surface temperature t-code T3C (160°C max.)? In other words, is the maximum surface temperature of the motor dependent on the motor’s insulation class?
4.99Would you please refer to the below question and explain in detail for our understanding. In NEMA MG 1, section 1.26 Totally enclosed machine, IEC Ingress Protection (IP) codes are defined for some totally enclosed machine type. However, IP code is not defined for the totally enclosed fan-cooled guarded (TEFC) machine in clause 1.26.3 (only the International Cooling (IC) code is defined). So, would you please tell me the equivalent IP code of a TEFC machine?
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