OK, so no one has a circuit diagram, was worth a shot.
I have attached a couple of photos of the affected area.
Left to right is diode (HFA15TB60) transistor (11N60C3) diode then transistor, diode, diode.
As you can see, the left hand diode left leg arc'd across to the surrounding copper track. Since the board is multilayerd and there is some scorching of the PCB it's hard to track down what is exactly conneted to the leg. The IGBT's (I think?) behind the diode normally have a heatsink on top and they are fed from the large inductors on the right (as far as I can tell), so would the diode be protecting the IGBT from voltage spike from the inductor?
Does that mean there wouldn't be anything else connected to it?
Whats strange is I can't find anything connected to the the left hand leg (cathode I think) on the far right diode, as I was trying to analyse that side to work out how the damaged side should be.
Any suggestions on where I should be looking or testing would be greatly appreciated, its a 10KVA UPS and wasn't cheap, so really want to fix it...