Cow
Senior Member
- Location
- Eastern Oregon
- Occupation
- Electrician
Had a tough one(for me) today. I have an ABB ACS800 150HP drive running a wellmotor that keeps tripping on a "short circuit" fault, anything from just a few mins. to a few hours apart. Drive manual says the cause can be a cable/motor problem or a faulty output converter in the drive. Simple things first, so I start with busting the T leads loose in the drive, megging the cables off the drive right on through to the motor and figure I'll find the problem lickity split. I should also mention this drive has a reactor between it and the motor, but nothing on the line side of the drive.
It megged fine, 700 megaohms at 1000v(phases-ground) and still climbing when I decide to quit testing. Look in the reactor, open the p-head, everything looks clean and tight, conduit to the motor is in good shape as well. Decide to do a resistance test, with the alligator clips clipped to each other I get .2 ohms. I get the same thing when I clip them to the T leads??? So the resistance is 0 ohms for the motor? Is that right?
I decide to call the local motor rewind shop to cover my bases, see if there is anything else I can check without sending it in for a rewind and he tells me the motor either works or it doesn't. Simple as that.
I then call ABB to see if there is anything that I can check in the drive without sending it in to have the "output converter" looked at. Nope.
I decide to put everything back together(with the reactor bypassed) and then fire the drive/motor back up just to see if it'll run. It does just fine for 4 mins. and then drops out on a "short circuit" fault.
How can I test in the future to know if it's the drive or motor in this instance? Usually it'll meg bad or have something obvious that jumps out at you. But not this one...
The customer wants this well running so they're taking a chance and having a drive expedited out here, I believe. It just kills me I can't narrow this down any better, I hate the guess and replace method, and I definitely don't like the customer spending money this way.
Thanks for the help!
It megged fine, 700 megaohms at 1000v(phases-ground) and still climbing when I decide to quit testing. Look in the reactor, open the p-head, everything looks clean and tight, conduit to the motor is in good shape as well. Decide to do a resistance test, with the alligator clips clipped to each other I get .2 ohms. I get the same thing when I clip them to the T leads??? So the resistance is 0 ohms for the motor? Is that right?
I decide to call the local motor rewind shop to cover my bases, see if there is anything else I can check without sending it in for a rewind and he tells me the motor either works or it doesn't. Simple as that.
I then call ABB to see if there is anything that I can check in the drive without sending it in to have the "output converter" looked at. Nope.
I decide to put everything back together(with the reactor bypassed) and then fire the drive/motor back up just to see if it'll run. It does just fine for 4 mins. and then drops out on a "short circuit" fault.
How can I test in the future to know if it's the drive or motor in this instance? Usually it'll meg bad or have something obvious that jumps out at you. But not this one...
The customer wants this well running so they're taking a chance and having a drive expedited out here, I believe. It just kills me I can't narrow this down any better, I hate the guess and replace method, and I definitely don't like the customer spending money this way.
Thanks for the help!