I was cutting this morning and all of a sudden there was a large blue flash from the connector into the top of the spindle, and the RCD tripped on the consumer unit.

The connector is the standard 3 pin type for chinese wc spindles. Looking inside the female part of the connector (from the VFD) showed a burn mark around the clear plastic sleeve. I checked the resistance between each socket and earth, checked the spindle pins for resistance (about 2.2ohms so ok there) and resistance to earth. All fine.

I then noticed that the pins which stick up inside the spindle connector are split down the middle to provide some spring loading and make good connection. 2 of them had a gap between, but the third one was fairly close together. This meant that when the connector was applied, the pin wasn't making a great contact.

I think this was enough to momentarily break the circuit to the spindle (while it was cutting!). Part of the reason for this is probably because (like many DIY machines I suspect) the cable from the VFD goes into the spindle and any movement of the machine during cutting continually strains the cable. I've been running like this for about 4 years, and kept meaning to make a strain relief arm, but never have done.

Knocked one up in about 30 minutes after the problem, but it's too late now.

Now I can't start the VFD. It keeps telling me there is a fault (E14 - UVW to earth fault). It does this without the spindle connected, plus without the VFD cable connected. There is a reset procedure which involves briefly connecting a terminal mark P24 (24v?) to pin 5, which make symbols on the display goes round in little circles. But the error remains.

I've tried switching on and off many times, held the reset for a long time, nothing. Wondering about if there is a factory reset option. Also wondering if I've damage the VFD. It is a Moeller DV51.

Any ideas?

Thanks

p.s. Start making up strain relief arms for your spindle cable - you have been warned!