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Motor resistance

Discussion in 'Commercial' started by Texas-Tech, Jun 3, 2017.

  1. frozensolid

    frozensolid Psychologist's Dream

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    Hey TT spin the shaft while you keep the VOM probe on it. Does the resistance change? If so may be reading some kind of residual magnetic field. Also If you are getting more than, I think its 200mv at the shaft when it runs you may have a shaft voltage thing going on. more than that (200mv) and you would see some frosting of the balls in the bearings (not Ice you Jokers). The race would be very dull Not (polished shiney) if this happens too.

    Just a guess from an old guy. :) Or maybe your an old guy too and are just senile. :D
     
    Daryl_Dixon likes this.
  2. crackertech

    crackertech assholiness *

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  3. pecmsg

    pecmsg Junior my ASS

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    Mention Senile and look who shows up :dunno:
     
    HMD likes this.
  4. Y7turbo

    Y7turbo New Member

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    This may sound stupid, but Is it possible your fingers were touching the metal on your meter probes when testing resistance from the shaft to the windings? Sweaty fingers will have that amount of resistance.

    Its interesting a motor had that low of a resistance and still works fine. I believe Copeland said 1000 ohms per volt to ground is the minimum.
     
  5. Texas-Tech

    Texas-Tech Official Geezer*

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    duhh
    No fingers on the probe
     
  6. HMD

    HMD does it matter?

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    fingers on his johnson
     
    Texas-Tech likes this.
  7. Daryl_Dixon

    Daryl_Dixon New Member

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    I've had similar situations. Was helping a super-smart electrician troubleshoot a 60 hp 480-v 3-phase motor...took out a fuse. He condemned the motor because my Fieldpiece said something like 25 M-ohms to ground. I suggested we take a reading on the motor in the unit next to this one, nearly exact same reading.

    It was corrosion on L-2 contact of motor starter.

    Glad I'm not an electrician and diagnosed it properly.

    :eek:
     
  8. Joey791

    Joey791 New Member

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    Any chance the pump is on a vfd?
     
  9. otto

    otto Bakery Chef

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    I have seen compressors and motors with slight ground readings and even at times would look like I was reading a capacitor. Then after check again and the reading was gone. One of those things I never followed up on as to why.
     
  10. Texas-Tech

    Texas-Tech Official Geezer*

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    duhh
    Nope
     
  11. flange

    flange Act like you care and do SOMETHING!!

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    Have you determined that there is no aegis ring?