Does anyone on here repair faulty inverter boards - shorted fets on Sunny Island

[rogerdw]

I just acquired a US Sunny Boy -41 series which did nothing with PV applied.
Opened it up and found liquid splattered and burst caps.

It has 3 PV inputs A, B, C. A and B read near zero ohms, C shows as correct capacitance.
I've pulled the PCB, plan to wash it with IPA, then try operating with input C powered.
Don't know if electronics survived however much over-voltage was applied, but if it does I'll replace caps on the other inputs.

I like jobs like that. Best of both worlds. Effectively three identical circuits with one still working. ... and all in the same box.

Well worth trying what you suggested. I'm always surprised at how often just a couple parts cause all the grief, though of course there are always exceptions. Good luck.

 

[rogerdw]

Is that a 48V inverter? Those IRF2907Z are 75V MOSFETs. Interesting that 1st tier brand would leave so little voltage headroom.

Yes, 48V ... and agreed ... and I was surprised at the physical size of them. Was expecting much bigger or a huge IGBT module.

My first thoughts were to look for a higher rated device to replace them ... but I'm not keen to risk introducing other issues. And then I remind myself that there are thousands/hundreds of thousands of these working perfectly around the world with those exact same mosfets ... so I'll stick with them.

As above, I will be looking for any additional component that has been in the line of fire and that may have been blown or weakened by the blowup. And even to the point of replacing components that may be perfectly okay ... but just see it as insurance in case.

600V caps (550V @ 105C) for 600V Sunny Boy.
Of course should only see max 600V cold, like 0C or below.

Transistors of course have a different set of issues.
Don't know if like an op-amp, where breakdown voltage varied with temperature.

In my work I rarely see electros blown (as in bulged and their guts spewed out) but it does happen, though is difficult to know just how much higher the voltage got before they failed. With smps it's common to see bulged mains capacitors when the equipment is run on a generator. One slight over-rev or surge can be all that it takes. To be clear I see plenty of failed electros ... just not from over voltage.

With semiconductors my belief is that it is usually voltage spikes or transient rubbish for any of a million reasons, that causes them to fail. Of course I'd expect voltage that is constantly over their rating to kill them as well.