Damage caused to VSD from insulation tester voltage

[Munkey]

I'm lucky in that I think the process will allow the use of the drive in SCALAR. I'm just concerned that there may be an underlying issue that could cause further problems down the line.

 

[Wazzajnr]

I've just remembered having exactly the same issue with a siemens drive a couple of years back. Turned out the electrician had wired the motor in delta instead of star (or vice versa, can't remember which now)
The drive has motor models for running in sensorless vector which from memory is same as DTC mode. With the wiring incorrect it can run to a fashion but i was getting overload trips and DC bus O/V on that one.
Maybe if they've disconnected to do the tests they didn't connect it back up correctly??

 

[Darkwood]

What does the machine do, is it possible as a cheaper route to fit an encoder and use feedback loop to control motor speed thus eliminating need for torque option, but still need to establish what issue is to see if it is going to come back and cause problems.

 

[Munkey]

From what I've been told, the problems arose because they did not disconnect the drive prior to testing.

I would have expected the IGBT modules to take the brunt of whatever damage the test had done, and this would have materialised in a short circuit fault, not overcurrent.

 

[Munkey]

The machine is a centrifuge. A large barrel shaped hollow bowl that spins at speeds up to 1200 rpm with a screw conveyor inside that turns at a differential speed to the bowl. All run from variable speed drives. The drive that is faulty is the bowl drive. This normally stays at a single speed the screw conveyor drive normally does a lot of speed changes due to fluctuations in torque. It is a large density separator, solids from fluid basically. Bowl weighs around 8 tonnes!

 

[vaughant]

You could try opening the torque limits up a bit on the run settings,even if they are the same as when run otherwise.
Has your man in the field checked that the bowl is turning freely?
Not meaning to sound derogatory but if it's tripping on o/c immediately my guess is something's pretty tight to cause that or as you thought a drive issue.
Have to be honest until very recently I never bothered to remove tails to test which I know is wrong but I've never suffered a drive issue from it.
Good luck and keep us posted how you got on.
Ps,is there another drive nearby that you could swap just to prove it out?particularly as it's such a simple set up?
I'd also be tempted to bell out the motor again on continuity first just to check nothing silly happened when putting covers back etc as it's often easy to go off down certain routes just because it's the obvious,we've all done it.