# Motor testing



## John Valdes (May 17, 2007)

What type of testing equipment do you have?


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## dronai (Apr 11, 2011)

John Valdes said:


> What type of testing equipment do you have?


Tic tracer, why ?


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## Nissil07 (Oct 17, 2013)

Just a megger and ohm meter


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## Big John (May 23, 2010)

For large motors and generators, they get a PI, winding resistance, surge test, and vibration analysis.

You need a solid current source with good resolution to do accurate winding resistance, and you can't really do that with a standard ohmmeter. 

For small motors of just a couple dozen HP, literally all we'd bother with is a megger, just make sure you correct for temperature and humidity and watch your trend. I suppose if you were worried about it you could set up a dial indicator and look at shaft-runout and that would give you an idea of your bearing health. But you can often just plain hear that when it's online.


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## Chrisibew440 (Sep 13, 2013)

Big John said:


> For large motors and generators, they get a PI, winding resistance, surge test, and vibration analysis.
> 
> You need a solid current source with good resolution to do accurate winding resistance, and you can't really do that with a standard ohmmeter.
> 
> For small motors of just a couple dozen HP, literally all we'd bother with is a megger, just make sure you correct for temperature and humidity and watch your trend. I suppose if you were worried about it you could set up a dial indicator and look at shaft-runout and that would give you an idea of your bearing health. But you can often just plain hear that when it's online.


Nice answer. I've always megged on all size motors I've come across, seems to work out.


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## Chrisibew440 (Sep 13, 2013)

Nissil07 said:


> Hi just wondering if anyone could give me tips on testing electric motors eg:Star and delta IR test
> Ohm test
> Windings test
> Risk of blowing resistors and so on
> Any info would be apprecatied thanks guys


Look up winding schemes and energize those bad boys with a megger.


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## gnuuser (Jan 13, 2013)

having familiarity of three phase motors and wiring schemes helps a lot
depending on the manufacturer the winding leads in the peckerhead may be connected as delta at the factory or they may not be twisted together at all (small 3 phase)
but will be labeled on the side of the motor.
larger motors may be wired wye or delta at factory

an ohm meter can be used but its a ball park reading
again knowing what the reading should be helps a lot.
taking readings at installation time and recording them is a must if just using a multimeter.
while an infinite reading shows an open, a marked difference in a winding resistance is an indicator if a heat stressed winding.(unbalanced loading)
this motor may work but would not be very reliable


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## Burgoon (Nov 20, 2012)

A good megg goes a long way.


Current draw


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## wdestar (Jul 19, 2008)

Nissil07 said:


> Hi just wondering if anyone could give me tips on testing electric motors eg:Star and delta IR test
> Ohm test
> Windings test
> Risk of blowing resistors and so on
> Any info would be apprecatied thanks guys


I think you should be diligent and do your research as the instructor requested.:thumbsup:

Or did I guess this wrong?


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## Nissil07 (Oct 17, 2013)

What would be the process of doing a annual check on three phase motor from maintenance side of things eg meg test to earth and test between windings also temp conversion?


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## gnuuser (Jan 13, 2013)

Nissil07 said:


> What would be the process of doing a annual check on three phase motor from maintenance side of things eg meg test to earth and test between windings also temp conversion?


it in how you record the info and estimate wear and tear!

for instance log books ( motor number, type,resistance readings, current draw readings, running temp at each test. and visual inspection comments.
first info recorded from the motor tag and 
second after the motor has run under load for 5 minutes (these readings taken initially when a motor is installed)
and last after each cycle (week, month, year however you set up the cycle)

tracking these inspection results gives you a better idea whats going on in the motors world.
examine the windings in failed motors and note the leads they are connected to these will give you a very good indicator of loading and supply problems.
this chart may help.
http://www.castellanomotors.com/techinfo/windfail/3ph.htm

hope this helped:laughing:


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## Big John (May 23, 2010)

Nissil07 said:


> What would be the process of doing a annual check on three phase motor from maintenance side of things eg meg test to earth and test between windings also temp conversion?


 This is a good megger tutorial. 

http://www.biddlemegger.com/biddle/Stitch-new.pdf


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## Nissil07 (Oct 17, 2013)

What would be a acceptable M ohms reading for a two year motor?


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## Burgoon (Nov 20, 2012)

Nissil07 said:


> What would be a acceptable M ohms reading for a two year motor?


Phase to phase or to ground? Phase to phase very low,phase to ground as close to infinite as your meter can tell ya


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## nolabama (Oct 3, 2007)

Big John said:


> For large motors and generators, they get a PI, winding resistance, surge test, and vibration analysis.
> 
> You need a solid current source with good resolution to do accurate winding resistance, and you can't really do that with a standard ohmmeter.
> 
> For small motors of just a couple dozen HP, literally all we'd bother with is a megger, just make sure you correct for temperature and humidity and watch your trend. I suppose if you were worried about it you could set up a dial indicator and look at shaft-runout and that would give you an idea of your bearing health. But you can often just plain hear that when it's online.


If I saw someone pm'ing a motor with a dial indicator for bearing health I would make fun of them. I have use a dial indicator to set up bearings to increase life, but not on an electric motor. Seems silly.


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## Nissil07 (Oct 17, 2013)

That's what I thought ph 2 ph should be no lower than 1m as lowest and 100m on ph 2 earth


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## Burgoon (Nov 20, 2012)

Nissil07 said:


> That's what I thought ph 2 ph should be no lower than 1m as lowest and 100m on ph 2 earth


I wouldnt run a motor with phase to ground at 100Mohm. But I dunno if that's just me.


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## Zog (Apr 15, 2009)

Nissil07 said:


> That's what I thought ph 2 ph should be no lower than 1m as lowest and 100m on ph 2 earth


The phases are connected so a Megger is the wrong tool fo rthe job, you need a winding resistance test set to properly charge the windings and get an accurate reading. A typical ohmeter won't do it either. Depending on the motor size you should see a few ohms, the value does not really matter, the key is to compare each phase, they should be close but never >10% difference. 

To ground you use a Megger, the biggest mistake people make is testing a cool motor and not tempature correcting the readings, it makes a huge difference. IEEE/ANSI/NETA standards for minimum insulation resitance is:

IR test values corrected to 40 degrees Celsius

Minimum IR readings:
• IR 1 min = 100M> for DC armature and AC winding built after 1970
• IR 1 min = 5M>for most machines and random-wound stator coils and form wound coils rated below 1kV
• IR 1 min = kV+1 for machines made before 1970, all field windings, and others not listed above

Be sure to correct your readings to 40C, that makes a huge difference.


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## KennyW (Aug 31, 2013)

As a side note, I really want an impulse tester like a Baker tester. 

A neat toy, just hard to justify.


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## Zog (Apr 15, 2009)

KennyW said:


> As a side note, I really want an impulse tester like a Baker tester.
> 
> A neat toy, just hard to justify.


Just rent when you need it. I own most of our toys but still rent a few pieces, just signed rental renewal for one test set $22,000 for the year. Pays for itself though.


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## KennyW (Aug 31, 2013)

Most work I do where I'd need one is overseas, so renting isn't really practical.
Think large ports and mines in places like South America. 
I bury equipment costs into projects when I can. At some point I'll get an appropriate project where there's enough budget to cover 2/3 of the cost and I'll pull the trigger.


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## 360max (Jun 10, 2011)

dronai said:


> Tic tracer, why ?


:laughing::laughing::laughing:


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