I was just wondering if anyone knows where I can get a list or info about the lowest / safest meg reading for 480 volt motors? I made a couple of calls where the motors were taken out of service because my 1587 came up .7 megs and the voltage would not reach 1000s. My boss asked me what the lowest reading should be and I told him 1 meg. not sure about that . 40 hp.

thanks for any help

I think anything below 500k ohms raises eyebrows.
But you should always follow the manafactures specs.

You should read up on IR testing some more. If you had a 480V motor at 700K, I would of replaced it as well.

Search "insulation testing" on this forum or Google it. Read up and get back to us,..........

The old handbook which is a bit outdated, some say, "A Stitch in Time" Megger/Biddle states the following.

Insulation resistance should be approximately one megohm for each 1,000
volts of operating voltage, with a minimum value of one megohm

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Bill

Yeah, I remember this coming up before......I dont think there is any black&white numbers out there however Bill is right only because it seems to be the one that everyone know, it the lowest is 1M ohm

__________________
MIKE
SHAKE THE TREE

I think that there are specs out there for cables but not much for motors.

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Bill