Using PowerFlex 700 VFD DC Bus to Reform Capacitors on Another VFD—Is It Safe?

Hey guys, Many of you are pretty crafty so here's a question for you.  I need to resurrect an old PowerFlex 700 VFD.  AB calls for reform through the DC bus terminals and not the supply inputs.  We don't have a lab power supply handy to reform the bus caps.  Have any of you ever tried using the DC bus from another drive to reform the caps on another bus?  My theory would be to regulate the current through some resistors and divide the voltage to bring it up in steps.  Any thoughts would be greatly appreciated.  Thanks

Hi Erich,
Having reformed the caps on quite a few drives over the years, I see no reason why your suggestion would not work. It's an interesting idea and not one that I have considered before. I'm assuming the drive you are reforming has an equal or lessor dc bus voltage than test voltage drive.I would be a bit concerned  damaging the drive used as the "power supply" so to speak, but as long as you were careful and can regulate voltage and current in some external manner then I see no reason why this would not work. I would only be concerned with shorting the Dc bus.Let us know how you get on with it, if you get a chance.Cheers
Alan

I got lucky.

There were a bunch of chunky power resistors in the parts room.

I made a voltage divider which limited the current and gave me the ability to adjust the voltage in steps.

I put a circuit breaker in line for safety.

There was no DC(-) terminal on my drive so I had to solder a wire onto the circuit board.

It seems to have worked well.

Glad to hear it worked well.