My Axpert 3Kw inverter recently blew. AC IN and Battery terminals are now short circuited. I opened it up to take a look and it looks like a capacitor labelled MOV6 near the AC connectors has blown. I cannot see any other obvious damage, but have not stripped the unit completely.

For those with experience in repairing these things, do you think this is an easy fix to replace this one component, or is it likely to be a number of components that need to be replaced? Is it worth sending off for repair? Any recommendations?

Thanks!

Edited February 21, 20242 yr by Dylanjiva

@BritishRacingGreen can sort you out 

On 2024/02/21 at 4:48 PM, Dylanjiva said:

it looks like a capacitor labelled MOV6 near the AC connectors has blown.

Those are actually MOVISTORs, a non-linear resistor used to suppress transients. Basically, it's a very high resistance until a certain voltage is reached, at which point its resistance lowers dramatically to absorb the transient. Every time that they absorb energy, they degrade slightly, until they eventually fail.

On 2024/02/21 at 4:48 PM, Dylanjiva said:

AC IN and Battery terminals are now short circuited.

AC-in being shorted is likely because of the MOV. These are well known, fairly inexpensive, and replaceable.

The battery terminals being shorted is usually because the MOSFETs have failed shorted. These are much more expensive and difficult to replace, although any competent repair shop should be able to do it. When they fail, these often take out some gate driver components, which are much harder to track down. Sometimes it will also take out the IGBTs, and if so, some of their gate drive components. The MOSFETs are often lined up under the edge of a heatsink along one edge of the main board. It's hard to see them without removing the main board, though you might be able to see through some ventilation holes. Burned MOSFETs are usually very obvious: blackened parts, legs blown off, cracked or pitted epoxy.

There are some capacitors that should be replaced; these protect the MOSFETs from switching transients. These capacitors drying out may have caused most of the damage, although with the MOV failure, some sort of transient due to load shedding is more likely.

As for whether it is worth repairing, that's a harder call. If you can find the right repair person, it can well be.

Note that many repair facilities these days don't do component level repairs; they will replace the entire main board, which has about 75% of the complexity of the inverter, and hence a big chunk of the cost. If such a repair is the only option, then it becomes much more marginal.

Thanks Coulomb, for taking the time to answer my questions. The sharing of your knowledge and advice are appreciated. Sounds like it is not a simple fix and I think I will be going the replacement route.