VFD Capacitor Reforming Using The DC Bus From Another VFD

[EJSControls]

Hey guys,
I know this is not PLC related but many of you are pretty crafty.


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

 

[James Mcquade]

welcome to the forum.


I have no experience with that, but may I make a suggestion.
we send our parts to TEAM SESCO in Greensboro, NC for repairs.
plc's, I/o cards, drives....
1-800-487-3726. my contact is Mike Thompson. they can give you a free repair quote. they are reasonably priced, give great service, and stand behind their work. I have had no complaints is the 3 years I have dealt with them.


james

 

[jraef]

You could definitely do that, Just make sure you have a current limiting resistor in the circuit at all times; you don't want to end up with two dead drives...
The amount of current needed for this is very low, so I do it by using a 480-120V control transformer in reverse, then run the 480V single phase through a bridge rectifier; it doesn't need to be filtered for this. Then if you have a little 120V Variac (variable transformer), you can bring the 120V input up slowly in stages.

 

[TheWaterboy]

You could consider using a megger if the controls were sufficiently variable and could be incremented slowly.

 

[EJSControls]

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.