VFD intermittently trips breaker on bypass relay

[eci22]

Hi all,

I have a huayang YL-620L VFD with a 2.2Kw water cooled spindle, i am having issues with intermittent breaker trips and need to work out which component is to blame.

After powering the VFD via a contactor (ABB AF09) a few seconds later (~2-3) there is a 'click' sound, I believe this is the bypass relay kicking in. Sometimes this works fine and sometimes it trips my 20A breaker, not the RCD but the MCB. As far as I know this is not an inrush current issue, the point of the bypass relay kicking in there should be no noticeable current draw on a properly working unit. Is that correct ? The VFD is connected to the motor but at no point is the motor spinning when the breaker trips.

Here's the sequence of events from the other day, I wanted to check I could turn it on and off a few times without problems as i thought i had resolved the issue-
Turned on the VFD-> booted up fine. waited ~15 seconds turned it off.
Turned on the VFD->booted up fine. waited ~30 seconds (until the VFD fans stopped spinning), turned it off.
wanted to try one last time-
Turned on the VFD when the bypass relay kicks in i heard a pop sound and my contactor let out a puff of smoke. The A1 A2 coil is gone (it reads 15 mega ohms), this is the first time i've seen this and this time the breaker did not trip. This was quite a significant failure.


So it sounds like the VFD is not 'filling' up on the initial power on and the bypass relay is then creating a surge in current ?
At this point it could be a bad VFD unit, but is there a chance the spindle could be at fault or the EMI filter ?

When i first got everything hooked up, I successfully sent serial commands from linux cnc to the VFD to start and stop the motor, the motor was on for a few seconds only a few different times, but it didn't have water running through it, as there was no load on the spindle i thought this would be ok just to check it works. Could i have damaged the spindle and the actual VFD is not the issue ? Can the motor cause this issue even if it is not spinning ?

I'm in the process of moving to a 32 amp breaker but plan to put a 20 amp breaker in the cabinet to protect the house fusebox.

Any ideas or help would be very much appreciated.

Thanks

[Muzzer]

The MCB should never emit smoke or suffer a burnt out coil, no matter what load you present it. That suggests you either had a duff MCB or it was connected up incorrectly. Assuming this is a Type B (or Type C) breaker, you shouldn't need anything like a 20A or 32A rating just for a 2-3kW VFD.

If the inrush limiter / soft start relay is causing the problem upon closing, it suggests an intermittent fault in the VFD.

You mention an EMI filter. I wasn't aware these Huayang VFDs had any filtering. If you have fitted one yourself, that's A Good Thing but it shouldn't in any way cause the behaviour you are seeing.

[eci22]

The MCB didnt smoke, it was the contactor- A1-A2 coil.
The tricky thing is sometimes the VFD will start fine, to the point it will communicate with linuxCNC start the spindle over serial etc and sometimes the breaker trips but it always trips at the same point, not at power up but a few seconds in, when the click of the internal relay happens (I assume it's a relay making this sound). I', thinking if the wiring was faulty it would present this issue everytime, but that isn't the case. I added the EMI filter, it's not part of the VFD.