VFD intermittently trips breaker on bypass relay

[routercnc]

I've installed quite a few of these Huanyang VFDs on different machines in my workshop and all have worked for years except one a long time ago which went bang a few seconds after the first switch on. Luckily the seller replaced it. So like all things faulty units are possible.

In most inverter manuals they show a circuit breaker between the mains supply and the inverter but I've always connected them directly to the mains using the supplied plug. Industrially this would not be allowed as the inverter remains powered and should power down (after a delay) with the estop. Anyway the reason for me saying this is that when they switch on there is a short delay, maybe 1 or 2 seconds, before they actually come on and then there is a click from the relay inside the inverter. So I read your first post above and wanted to check if you meant the delayed click came from the VFD or the contactor. Pretty sure you meant from the inverter, and this normal. I've always assumed it is limiting current to the big capacitors inside.

So unless Muzzer has a different view on this I would try plugging the inverter in directly to eliminate the contactor (which has blown now anyway) and remove the EMI filter assuming it is just an external unit you wired in line (just for now). My inverters are not on special slow blow type C or D circuit breakers at the consumer unit so can't imagine they need anything special and they don't trip anything.

You mention running the water cooled spindle with no water, but no load for a bit of a test run at the beginning. I see absolutely no issue with that so I very much doubt that has done anything to the wiring etc. Extended running over 12000 rpm and under some load would get some heat into it, especially the bearings which is probably the bit the water is protecting the most but I don't think you went anywhere near that condition.

If all else fails these inverters are pretty cheap so maybe 'just' buy another one if you are not getting anywhere? Or is it new enough to ask the seller for a refund?