3-Phase Motor Testing

[Darrensparky]

Hi I'm Darren and I work as a apprentice for a manufacturing company.

I was testing a 3kw 3-phase motor as it blew a fuse and when doing my IR test down to earth I got a reading of around 11Gohms. I was under the impression that the reading had to be above 1Mohm which this is as far as I am aware but I was advised by my colleague that this is a bad reading and the motor is no good. Can someone confirm for me if I am right or wrong and why


Thanks

 

[telectrix]

that is an extremely high reading. as 1 Gig is 1000 Meg. most IR testers won't read that high. if it blew a fuse, i'd be inclined to IR measure between each winding and also a resistance test of each winding. if good, then fire it up with new fuse and measure currents.

 

[LeeH]

As tel said, you have you ohms mixed up somehow.

Test all phases to ground again and between them @500v. Then check all the windings are balanced (the same).

Does the motor run freely?
Clamp on your ammeter and see what the FLC is.

 

[Pete999]

What the last two said, Tel and LeeH

 

[telectrix]

or it could just be a tired fuse.

 

[Marvo]

I usually take a hammer to the blown fuse and post mortem it to see if it went with a proper bang or whether it was just a lazy blow.

11Gohms is an enormously high IR reading, not sure why your colleague would be unhappy with it......

 

[HandySparks]

... to see if it went with a proper bang or whether it was just a lazy blow.

Cracking turn of phrase. I'll have to use it sometime.

 

[LeeH]

Yeah, lazy blows are no good. I like a little vigour.

 

[Marvo]

Cracking turn of phrase. I'll have to use it sometime.

Yeah, some things lose (or gain) a little in translation
Could have probably phrased that better.

 

[LeeH]

IR of a motor to blow jobs in 6 posts.

Awesome.