electronpusher wrote: It may be repairable yet.
True. But unfortunately after a massive transient like that, blowing some parts to soot, it's likely that there is damage to other parts of the circuit.
As with the soot, I guess it could be HV discharge, but the only thing it would have discharge to was the relay next to is, as there is not burn marks anywhere else.
I don't think it was flash-over; it seems more like a massive overload.
I mean to say that the discolouration on the relay might be from internal arcing of the contacts, rather than external deposition from the blown components. When you get to it again, it would be good to distinguish between those two.
If the relay opened under load, which could happen if it lost power, then there is significant current in the Power Factor Correction inductor. This is also seen if you disconnect power to an Elcon charger when they are charging at full output. Inductors don't like to have their current changed instantly, like from 14 A RMS (so around 20 A peak) to zero. If you try, then they develop high voltage (of the order of kilovolts) to try and keep the current flowing. This is likely to take out the X and Y capacitors we've been talking about, but unfortunately also the bridge rectifier, the PFC MOSFETs (they could be IGBTs), and some snubber components.
Oh, duh. I've just realised that the input relay likely has the same function as on the Elcon EV chargers: to short out the pre-charge resistor. One of the large white vertical power resistors could be the pre-charge resistor. Though it is on the wrong side of the common mode choke. I'm thinking now that on some models, the pre-charge resistor is a through-hole component under the potting mix, and on others like electronpusher's, it's an array of larger surface mount resistors on a small daughter board. So the soot may have come from resistors after all. It's quite common (perhaps 30-50% of cases) for the pre-charge resistors on an Elcon charger to be burned up or high or low (!) resistance. Any time that the input relay opens under load, if it has the pre-charge resistors across its contacts, the pre-charge resistors will attempt to take full load current, possibly full mains voltage if there is a short circuit or near short further down. They often fail in spectacular fashion. Perhaps electronpusher's Y capacitors are smaller, kiev's capacitors have longer pigtails, so the tops of these capacitors isn't visible above the potting.
Then there is the reason that the input relay opened under load. If you don't recall switching off the charger at the mains (as opposed to getting the car to switch off charging digitally), then it could be another fault elsewhere that knocked out the power to the input relay. On Elcon chargers, the common failure mode is an electrolytic capacitor going high internal resistance from age, and it's protecting the main MOSFETs from switching transients. One MOSFET pair shoots through, shorting the DC bus, which causes an overload and also knocks out the power supplies, so the input relay opens. On a 2 kW Elcon, the parts to fix all this comes to well under AU$100. It might me a little more for a 3.3 kW iMiev charger, but still way less than AU$4000. Unfortunately, it takes hours of labour to do all this, and this is with a
schematic diagram of the charger, and a
web page with repair tips.
But maybe the iMiev chargers are better protected, and it's mostly the pre-charge resistors that blew. We just won't know until further investigation.
I'm a total iMiev noob, so I have no idea what the availability of schematic diagrams for things like the charger/DC-DC module. Are they available?
