Oh boy, new VFD trips breaker on initial power up.

JL Sargent · Apr 1, 2017

I bought a new KBAC 29 single phase input VFD off Ebay and on initial power up the breaker trips. VFD not switched to run mind you. I check my wiring and try again and breaker trips immediately. I never even got to hit the start button? VFD has a bad smell to it. Something just crapped out? Anybody got a clue why this would happen? It's a 230v single phase input, 3 phase output unit rated for 3hp.

JST · Apr 1, 2017

It's certainly a bad sign.... as in very bad. But, in many cases when it needs repair, that is better than a more subtle failure.

First: Can it be returned? If so do that. In that case you don't care "why" it does not work, it's a case of "Ugh... no workee" and you return for refund.

Are you sure the unit is 230 only? Might there be a 115/230 jumper? It would be "J1" right behind the AC input connections. If so, is it set for 230V?

JL Sargent · Apr 1, 2017

Yeah, it's a 230v only drive which I guess is really 240v in the US? Anyway, not a 115/120v unit at all. Hate that it didn't work.

I wonder what % of new drives just fail right out of the box? Old RPCs I made years ago still working fine........

JST · Apr 1, 2017

If it is oldish "new old stock", the capacitors may be the problem.

If you cannot return it, you might be able to identify the problem at least, and it is possible it is fixable. We've discussed "re-forming" capacitors here, and if that unit was many years old, even though unused, he capacitors might have failed when voltage was applied.

The symptom does indicate a probable short on the high voltage bus, which could be rectifier, capacitors or IGBTs as the main likely causes. The first two are reasonably repairable. Bad IGBTS usually have other problems extending into the electronics.

JL Sargent · Apr 1, 2017

Thanks, It is only 10 days old for me so I will return it for another drive or a refund.

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Oh boy, new VFD trips breaker on initial power up.

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