Powerflex 4 F5 on start

Hello,

Long story short replacing the motor resolved the issue. It was working then next time just would not start.

My issue is more on the why (explanation) Why would it start getting an overvoltage error only when the motor is started on the drive?

Everything I read has to do with braking and deceleration. But I was not lucky enough to find good reasoning why this would happen on acceleration.

My mind is driving me crazy, please someone enlighten me.

Thank you in advanced!!

Welcome to the forum!

I had a situation very similar to this and it drove me bonkers for weeks before I finally twigged.

In my case it was a Powerflex 525, controlled via Ethernet, running a large fan. I saw the same thing - every so often, I'd get a DC bus overvoltage fault, and after adding some diagnostic code to the system, I could see that it was always happening shortly after the drive started. I had the fan on a 60 second ramp up/down (it was a large fan with a lot of intertia), so I always knew that the fan was fully stopped before trying to restart.

Turns out that the wire loop between the +24VDC and the DI1 terminal was loose. DI1 on all powerflex drives is a stop input, and with my particular drive configuration, this input would trigger a coast stop. So, every so often, the wire would vibrate loose for a second, and the drive would immediately coast to a stop. Half a second later, the wire would vibrate back into place, and the PLC would command the fan to restart via ethernet. Of course, when it did, the fan was still spinning at the equivalent of almost 50Hz, having only been released from the VSD half a second ago - but I'm now telling it to ramp up from zero speed over the course of 60 seconds. So the drive attempts to slow the fan down from 50Hz to 2-3Hz almost instantaneously. The regenerated energy from the fan feeds straight into the DC bus, and hey presto, DC bus overvoltage.

Your situation isn't likely to be exactly the same, but given my experience, I would be looking very carefully to see if the motor may have been still spinning when commanded to start. Whether that's because it's still freewheeling after being stopped previously, or because it's being externally driven (e.g. a fan being driven by the wind, or a pump being driven by water pressure/gravity).

Thanks for the reply. The motor was off and would not spin at all