# Motor Test



## GEORGE D (Apr 2, 2009)

I know the answer to this probably exists somewhere on here but have a service call lined up today to test a motor, this is for a friend/electronics engineer who is replacing a 15 hp drive which had both input and output modules blow, and wants to be sure the motor wasn't the cause. Id be lying if I said that I was an ace with motors and such but did ask, on the phone, if there was a line-reactor for drive, and there isn't. He also asked me about surge protection which I instinctively suggested whole service protection. Back to my question, what is a safe 'pass' reading testing a 15 hp, 480 volt, 3-phase motor at 1,000 volts? I do know that there is much more than pass/fail when testing insulation as many variables affect the results, but was hoping for a confident answer to have ready, as I don't want to be the guy who says 'she's good' then have a very expensive drive blow-up again. Any help is appreciated as always.


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## JRaef (Mar 23, 2009)

GEORGE D said:


> I know the answer to this probably exists somewhere on here but have a service call lined up today to test a motor, this is for a friend/electronics engineer who is replacing a 15 hp drive which had both input and output modules blow, and wants to be sure the motor wasn't the cause. Id be lying if I said that I was an ace with motors and such but did ask, on the phone, if there was a line-reactor for drive, and there isn't. He also asked me about surge protection which I instinctively suggested whole service protection. Back to my question, what is a safe 'pass' reading testing a 15 hp, 480 volt, 3-phase motor at 1,000 volts? I do know that there is much more than pass/fail when testing insulation as many variables affect the results, but was hoping for a confident answer to have ready, as I don't want to be the guy who says 'she's good' then have a very expensive drive blow-up again. Any help is appreciated as always.


See Zog's post here:
http://www.electriciantalk.com/f28/insulation-resistance-tester-megger-6488/


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## John Valdes (May 17, 2007)

If this motor is a key piece in your process, you might want to let a motor shop take a look.
In addition to checking the windings, they will check the bearings and the tolerances for the end bells and shaft.
Something rarely mentioned is they can do whats called a core loss test.
Motors that have been previously rewound and not core tested could fail.

Loose lamination's cause heat. Heat leads to winding failure. 

If you are going to give this motor the seal of approval, you need a megger.
Zogs benchmarks posted above can be used to verify.

Motors connected to drives are protected by the drive itself and quite frankly the drive is very good at this.
It would be very unusual to have a drive run a motor that had issues. You can almost guarantee a defective motor will be exposed by the drive.


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## mutabi (Jun 2, 2009)

I agree, a drive does a very good job protecting the motor. I have frequently had motors that run all day long on a motor starter, but hook them to a drive and the drive says "hell no". 

A line reactor is a good thing to have. As for surge protection, a line reactor is a poor mans surge protection, but that is all we use at our plant. Meg it and see how it reads. Of course you can't be too careful so if this is critical, have a motor shop come out and check it. 

Was it possible that the load side of the drive was opened up while the motor was running? That can harm the IGBTs in the drive real quick.


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## GEORGE D (Apr 2, 2009)

Went there and motor megged 1 megohm at 1000 volt, thanks for input guys!


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