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Hi guys,

I need to replace 2 capacitors from my immersun solar PV, an IGBT has blown and took 2 of the caps with it. I'm just not sure which voltage rating to get as they're on the emitter side and it's max output is 600v. Struggling to get hold of 1kv capacitors so I'm wondering if I can get away with 250v instead. I've already replaced the IGBT and repaired the traces

Here's some pictures:



Thanks

Welcome aboard Cpt.
I found this video on youtube but it does not go as far as the caps. Still, it will be of interest to others regarding the main culprits.

Thanks for the welcome, I saw that video, my problem is unfortunately on the opposite end up of the board. The max voltage for the 10uf smd multilayer capacitors seems to be 100v anyway though so it can't possibly need a 1kv

I need 2 different caps, on my testers they're coming up as 50nf and 11.x uf, so I'm guessing they will be 47nf and 10uf as those other values aren't available and it's within 10%
I can find 1kv 47nf's but the max 10uf's I can get is 100v, I couldn't get hold of those so have got 50v 10ufs instead. Fingers crossed its enough

Those caps should only see the gate drive supply voltage: 15v but obviously can be subject the the full mains voltage if the IGBT fails.

Have you verified/replaced the driver chip U1 and Q7, Q8 dual mosfets? I'd expect them to fail if the caps have been blown up. And there's the bridge rectifier and zenner on the 15v gate supply. Do you know what caused the failure?

I did do a brief write up of a similar repair on the 'old forum' but would have to dig out the info now - which might take me a few days.

Thanks for your reply Marcus, I did check Q7 and Q8 they are both reading the same as the Q12, Q11 etc. They're not shorted and there's no psyical damage. I think the traces blew out before it caused any other damage from the look of it.

The capacitors didnt blow, they were singed from the heat of the traces and IGBT blowing. They're actually testing ok but I thought it best to replace as they didn't look to healthy. I have some better pictures of the damage before I removed the parts here:

I can't seem to find a bridge rectifier anywhere, do you know its location?

If you know the title to the old post I should be able to find it using the Wayback Machine

There should be two 15v supplies 'above' the heatsink (from memory), one for the high side pair of IGBTs and one for the low side. Each has a bridge rectifier, zenner and a cap or two; they are supplied from one or two 0.5va transformers adjacent to the top of the heatsink.

IIRC the post(s) were called something like 'immersun went bang - fixed' , but there were two:- the first was a failure of one of the big 5uF a.c. caps leading to the overvoltage varistor going bang, and the other was a failure of the IGBTs caused (speculatively) by the failure of the insulation between the 2ndaries of the 0.5va transformer.

If you can't find them I'll dig out my notes - eventually.

Don't know how I missed those, I saw them too but thought they were part of the 5v circuit that runs underneath them. They're all testing fine thankfully

I've seen a few posts about those varistors going bang, seems like the most common problem with these. Everything is testing good on this board now though so it'll hopefully be fine now.

The wayback machine only goes back to 2021 for camelot-forum.co.uk

Really appreciate the help buddy

CptChronic wrote: ↑Wed Jun 01, 2022 1:46 pm I've seen a few posts about those varistors going bang, seems like the most common problem with these.

And the two piece green mains connectors which eventually melt, but are easily upgraded to single piece ones.

Got some of those here ready to swap, that's the next job

CptChronic wrote: ↑Wed Jun 01, 2022 1:46 pm
The wayback machine only goes back to 2021 for camelot-forum.co.uk

Don't know about the wayback machine, but the posts were not on this forum but its predecessor which was closed down and who's name we don't mention - whispers navitron.co.uk.

Edit: it doesn't allow me to say the name even - gets changed to elsewhere