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inverter repair help neede

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rory

New Member
I have a 3000W 2500w continuous inverter with 12V input. This is not functioning. I would like to repair it but have no circuit diagram, can anyone help?

Before all the usual Qualified persons only advice I would point out that I graduated in Electronic engineering in 1978 and have repaired inverters up to 1 Megawatt.

The product is I suspect Chinese made and of no recognisable Brand name. There are two circuit boards on with the control and two power stages and the other with 6 power stages. I suspect the master board may be able to work at reduced power without the extra stages.

There are no obvious signs of catastrophic failiure and all the 30A incoming fuses are intact.

The design clearly uses a high frequency as the trasformers are quite small. It would seem pointless for such a design to produce other than an aproximate sine wave by altering the mark space ratio of the higth frquency in a 50 Hz cycle.

One puzzling aspect of the design is no apparent path from the dc input to the control circuits other than via the power stages. This prompts me to think of the bootstap scenario. With no power how do the drive circuits drive the power devices and provide power to themseves?

Searching the web has been fuitless so far.

Rory
 
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Hero999

Banned
I've seen the inside of a similar inverter.

It used an isolated DC-DC converter to get the peak mains voltage and an h-bridge to create a modified sinewave.

I wouldn't know what's gone wrong with your inverter.

Please post some pictures of the board and I might be able to advise you.

Does each power stage have its own fuse? There's no way it's 30A for the whole thing. I'd expect the thing to use at least 275A assuming 90& efficiency.
 

rory

New Member
Thanks hero

Yes each DC-DC has two 30A fuses and there are 8 stages in Parallel. Total 16 fuses. Which ties in nicely with your figures.

Thank you for explaining how the thing works. I have also noticed a network style socket on the unit and I think this is used to connect a remote control switch.

Now that I know how it works I will ascertain if the DC-DC is working as a first step.

I will post pictures of the boards when time permits.

Thank you hero

rory
 
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