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Unread December 2nd, 2019, 01:54 PM   #1
Leukic
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ABB ACS550 Earth Fault

I just replaced this drive as the old one went out when the plant had a power surge/flicker.

1-Installed the drive
2-Powered up
3- Got an immediate EARTH FAULT, so I check the manual and it talks about wires being grounded.
4- Disconnected wires from the motor and ohm out the wires to ground( CHECKS GOOD)
5-So I ohmed out the motor and I was getting 40-50 ohms when tested to ground.

6-I have not powered up the drive with out the wires disconnected. I will try that next to confirm my thoughts that the motor windings are starting to go bad and current is leaking out.

Bad motor?
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Unread December 2nd, 2019, 02:06 PM   #2
OkiePC
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Quote:
Originally Posted by Leukic View Post
5-So I ohmed out the motor and I was getting 40-50 ohms when tested to ground.

Bad motor?
Yes. Less than 10kohms is failing. Some drives require much more than that to overcome a ground fault.
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Unread December 2nd, 2019, 02:49 PM   #3
Leukic
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Seperated motor from power booted drive up and no fault. looks like im searching for a motor. Thanks OkiePc
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Unread December 2nd, 2019, 08:38 PM   #4
jraef
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VFDs are better at finding faults than a lot of other things that are supposed to...
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Unread December 3rd, 2019, 08:02 AM   #5
OkiePC
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Quote:
Originally Posted by OkiePC View Post
Yes. Less than 10kohms is failing. Some drives require much more than that to overcome a ground fault.

That should read 10 megohms. I have seen motors on starters work as low as 2 Mohm. I once replaced an obsolete 1336 VFD with a Toshiba G7 and it wouldn't run. The motor megger test showed 80 Megohms to ground... The 1336 was fine with it, the G7 said nope.
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