# Can not measure winding resistance of 3Ph Induction motor



## McClary’s Electrical (Feb 21, 2009)

sumet said:


> I measure winding resistance of motor by Ohm meter and micro-ohm meter,I found swing resistance. Who can explain me for this case and How to solve this problem?


 
You probably have bad motor windings, if I'm understanding what you're asking.


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## sumet (Dec 29, 2009)

I found this problem 3 month ago,and decide to rewinding. After rewinding I can read winding resistance and used it. Last week the motor overload trip and can't read winding resistance again (the resistance swing from 450-460 mohm and not stop)


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## Zog (Apr 15, 2009)

Your problem is simple, you are not using the right test equipment. You need to use a winding resistance test set. Neither an ohmeter or a microhmeter has a large enough power supply to charge the windings fully so you can get a stable and accurate winding resistance measurement. 

However, the actual value you that you get is nto all that important and should only be used for trending over time. What you are really looking for is that the 3 phases are close to each other (+/- 5%). There really is no winding resistance value (Besides an open winding) that would show a need for rewinding.


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## Mr.C (Dec 20, 2009)

What's the reason your checking this out so often,I am guessing your having problems with this motor that are similar to the original motor and your thinking maybe you should start looking in another direction. Also if your just PMing the motor and want to duplicate your original values at install, make sure your measuring at the pecker head. Allot of times when your having motor problems were your tripping ol's or ckt bkrs, and your sure the motor isnt going to ground you'll find a loose connection between a drive t-leads and the motor to be the caulprit, actually the loose connection could be before the drive on larger motors so check.


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## brownie (Jan 25, 2010)

250 hp synchronous motor failed to synchronize . Can this be troubleshooted and repaired.


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## brownie (Jan 25, 2010)

250 hp synchronous motor failed to synchronize . Can this be troubleshooted and repaired.


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## Mr.C (Dec 20, 2009)

Brownie could you give more info like did the drive tell you the motor failed to sync?


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## bobelectric (Feb 24, 2007)

How is your voltage/frequency reliability,over there?


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## piperunner (Aug 22, 2009)

sumet said:


> I measure winding resistance of motor by Ohm meter and micro-ohm meter,I found swing resistance. Who can explain me for this case and How to solve this problem?


You cant use a ohmmeter or a microhmmeter as other post has noted first its going to be real low and with inductance and such you need this 












1uohm to 20kohm 30 amps to 50 amps this will help you check your motor windings .


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## Bob Badger (Apr 19, 2009)

lemau said:


> hi...i usually check the motor winding condition before decide to re winding or not,im using Insulation tester meter


Pretty low class to dig up old threads just so you can post links.


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## McClary’s Electrical (Feb 21, 2009)

lemau said:


> hi...i usually check the motor winding condition before decide to re winding or not,im using Insulation tester meter


 

are you a person?


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