Internal sparking from toroidal transformer

[malcs]

I've got a problem with my relatively new inverter. (Renogy 2000w 240v 12v)
I purchased it in UK and moved to Peru
Was pleased to get it set up and working, powering small appliances.
Then one morning I turned it on, and heard a crackling noise. I honestly thought an insect had got inside and was fried! It stopped after a few seconds and operated normally.
Then next day it did the same thing but continued to crackle, so turned off.
I wanted to see if there was an insect inside so took it apart. Nothing, clean and dry inside.
So I carefully started it up with cover plate off, and to my surprise saw arking coming from the toroidal transformer and an adjacent resistor.
I tried to isolate with plastic, which worked for a day, but now happens all the time.
If I was in the UK, I would have just returned under warranty. But being in a remote part of Peru, where the nearest city is 3 hours away, I was hoping to fix it.
Any thoughts on what has gone wrong? Do toroidal transformers fail that easily? Or was it the resistor? I can't see any burning on it.
The design doesn't look too good, as the toroidal transformer is really close to the resistor and other components.
I raised the issue with Renogy, but not heard back.

 

[v_green57]

Can you post a macro image of the ckt. board area you are speaking of? With the point of a pen (or something) pointing to the site of the arcing?

 

[malcs]

Can you post a macro image of the ckt. board area you are speaking of? With the point of a pen (or something) pointing to the site of the arcing?

2nd image shows location of arcing. I did a video here too: https://vm.tiktok.com/ZGJxnDKD7/

 

[malcs]

 

[v_green57]

Holy #&@+_!!!

That's not good...

If it were easier, I would make Renogy exchange it.

But given your remote situation:

Clean the area where the arc has been occuring with a cotton swab (Q-tip) and a minimal amt. of 100% isopropyl alcohol. This should get rid of (most of )the carbon tracking left by the arc.

Let the area dry.

Apply a generous blob of clear silicone to the area. Make sure it gets good adhesion to the ckt. board and affected components and isolates them from each other.

Let it cure overnight.

Give it the zap test.

Of course this will irrevocably null out your warranty, but I get the impression you're OK with that.

Even if stops after doing this, I would leave the cover off and pay close attention to the unit for a few weeks.

 

[malcs]

Thanks for the update. Yes I wouldn't normally attempt to work on something brand new, but I've had no update from Renogy, and chances are they will say send it back when you're in the UK. Branded products here in Peru are 50% more, but might be able to pick up a Chinese import nearer the original cost.
I've never worked on an inverter before, but did discharge it as much as I could and wore gloves.
I would like to know the cause, I.e. was it just a poor manufacturing defect, or a component failure, or could the design be improved to provide better isolation (track design)

 

[MisterSandals]

or a component failure,

That looks like a failed resistor. Probably received too much voltage or overheated. Definitely needs replacing but I have no idea if this was caused by a different component failure. I'd definitely stop using it to prevent widespread failures until you attempt some fix.

Conjuring an expert: @RCinFLA


Is this the resistor color decoded?

 

[v_green57]

"I would like to know the cause, I.e. was it just a poor manufacturing defect, or a component failure, or could the design be improved to provide better isolation"

Any or all of the above.

I agree with wanting to know what happened, but it sounds like you're in a remote place and need the unit to be operational. Any other failure analysis would very likely require tearing it apart. Which, of course, has the potential to make things worse.

If you can keep the arcing from occurring by introducing the silicone as dielectric, and the unit is operating normally after that, it's worth trying. Listen very carefully afterward to make sure the arcing is still not happening through the silicone. The noise produced will be very reduced and there may be no visible arc unless you check while in a darkened room.

Do you have a backup inverter you can use while you duke it out with Renogy? You didn't really say and that makes a difference in which road you travel.

 

[v_green57]

Okay, now at home where I can see things on a big display.

Dropped your landscape image into GIMP, cropped out the area of interest, Unsharp Masked it to see more clearly. See attachment.

I know it's hard to tell exactly, because the sparks blind your detail vision momentarily, but can you tell if the arc is actually between the enameled magnet wire on the toroid and the PCB land for the resistor on its right side? Or is it actually to the resistor body?

When I was hand-winding toroids for DC-DC converters, what I would usually do when I was done was paint them with fingernail polish (Flaming Red was my favorite). You can buy "special" electronic enamel for doing this, but as far as I could tell, it was the same damn thing but cost a lot more.

You could try that if you're pretty sure that one end of the arc is the windings. The means the enamel on the magnet wire has gotten scratched OR the connection to the PCB was over-soldered and the enamel burned off and some bare Cu is showing. The enamel on the wire itself is rated pretty high voltage-wise.

Fingernail polish has a nice little brush inside that makes applying it exactly where you want it to go easy. You can apply multiple layers as it dries quickly. Make sure you don't use the "metallic" kind that looks like it has micro-fine glitter in it ;-) .