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Thread: electric motor classification

  1. #1
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    Default electric motor classification

    Do terms like "pump duty", "compressor duty" or "farm duty" have any basis as a standard? Are these defined terms according to motor manufacturers or rating agencies or electrical standards certifiers? I imagine that the intent is to give some indication of durability. Or ...? Practically, for home shop (intermittent vs an 8-hour work day) would any of these ratings matter? Would they give any indication of bearing quality, windings, etc?

    If yes, then where would the standards be found for - for example - a "mill motor" or "metal lathe motor"?

  2. #2
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    Default A bit more

    Thanks Dunc.

    I'd like to expand it as little if I may to include the mounting base details and what machines they are typical for - and how they are identified - in typical HSM machines - say mills (all types), lathes (all types), grinders etc. - including country/area/zone of origin (USA, UK, Europe, Asia (Japan, China, Taiwan etc.).

    I'd guess that many of us have hit quite a problem in identifying these details - including those required in the original post.

  3. #3
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    Default

    I'd not pay any attention to that nonsense, since they are not "real" specs, just "suggestions".

    Service factor is what you want, that and duty percent if listed. Service factor tells you whether it can be overloaded, etc.

  4. #4
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    Default

    Continuous Duty / Intermittent Duty are for service sizing information

  5. #5
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    Default

    I have been told that "Farm Duty" means that it can be used outside and left out side. I have an old GE "Farm Duty" motor on my LeBlond lathe. It does not have the HP listed anywhere on it. Gary P. Hansen

  6. #6
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    Default

    Avoid pump or compressor duty motors,they are built to the razor thin edge of perforamce-vs-cost. Most times they will have little or no protection against dust and in the case of pump motors oddball shaft configs.

    Farm duty and general purpose motors are decent for the average home shop.Me I generally look for TEFC(Totally Enclosed Fan Cooled) motors with at least a 1.15 service factor.

    Like this-

    http://web3.automationdirect.com/adc.../MTR-P33-1AB18
    Last edited by wierdscience; 09-22-2008 at 11:58 PM.
    I just need one more tool,just one!

  7. #7
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    Default

    I was of the opinion that farm duty meant that they could be washed down safely. This probably means totally enclosed, but doesn't necessarily mean fan cooled. Pump duty meant that it doesn't necessarily have a high starting torque, while compresor duty meant that it did have high starting torque. Lathe motor may have meant that it was a slow speed, like 1100 rpm. So I have been led to believe. Some of that makes sense to me, but it's certainly a crap shoot these days.

    Oh, and motor rated ball bearings are among the lowest quality ball bearings made, not including rolled steel strip races.

  8. #8
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    Default More info

    I decided to go looking for myself and to see what I could find as regards electric motor classifications and details of motor mountings.

    I really don't know how far I got or whether or not it is relevant - but here goes:

    NEMS frames and mountings:
    http://www.motorsanddrives.com/cower...ms2_chart.html

    Motors generally:
    http://www.sawdustmaking.com/ELECTRI...ricmotors.html

    Circuit diagram software (free):
    http://www.smartdraw.com/specials/co...FQkiagodD0Zlfg

    Maintenance and trouble-shooting:
    http://www.reliance.com/prodserv/motgen/h7000.htm

    Google:
    http://www.google.com.au/search?hl=e...e+Search&meta=

    Now, what I'd like to know is whether the typical Chinese motors as face-mounted etc. on mills, lathes and drills etc. complies with the NEMA standards.

    I think I know of at least three Electrical Engineers, Contractors and others who will have detailed knowledge in/of such things as I'd appreciate their advice both to the OP's questions and my own.

    So let's hear it please.

  9. #9
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    Default

    Farm duty motors are totally enclosed to guard against dust and ambient moisture, such as rain. They might have additional sealing to protect the bearings from moisture, but they are not washdown duty.

    Farm duty, compressor and pump duty are not industry classifications, but are manufacturer's descriptions and can vary from manufacturer to manufacturer.

    NEMA standards are US industry standards that are the same among all manufacturers. European motors are made to ISO/DIN standards that are the same among manufacturers using that system. Both of these standards relate to the physical dimensions of the motors and their mounts.

    I would guess that the Chinese would be using something that represents the DIN standard, but that does not rule out the use of proprietary mounts for specific machines.
    Jim H.

  10. #10
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    Default Motor details

    This is a glossary of terms for electric motors (USA) that might assist.

    http://www.reliance.com/prodserv/mot...2new/b9652.htm

    Quote Originally Posted by JCHannum
    NEMA standards are US industry standards that are the same among all manufacturers. European motors are made to ISO/DIN standards that are the same among manufacturers using that system. Both of these standards relate to the physical dimensions of the motors and their mounts.

    I would guess that the Chinese would be using something that represents the DIN standard, but that does not rule out the use of proprietary mounts for specific machines
    Thanks JC.

    I rather suspect, although I can't prove it - that many of the ISO/DIN standards are in fact "hard-converted" (ie inch to mm) US standards, as are the milling machine tapers, Morse tapers, 1/4" (6.35mm), 3/8" (9.525mm), 1/2" (12.70mm) etc. squares on ratchet spanners, socket spanners etc.

    I'd also be surprised if the ISO/DIN did not also have full (separate) metric standards as well.

    I'd expect that many of the motor frames and mounts (including end-mounts/faces) were actually the US NEMA standards hard-converted to metric.

    I just haven't been able to confirm it so far.

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