Inverter problems please help

[Lexm]

Hi all
I have a 3000w inverter in my camper but when I'm at home I plug the camper into the mains to run a battery charger and keep fridge and frezzer on. when I got home the other day I forgot to isolate the inverter and when I plugged the camper in and blow the inverter. Having been a electrician I figured I'd have a go at fixing it. I thought I'd tracked the problem do to a irfp460 mosfet when I changed it out the inverter was working fine (no buzzer going off) but when I put it under load it went bang. So taking apart again I found that it had blown 3 resistors so I replaced them but now I'm only getting 130v when testing the socket any help,idea would be great

Forgot to add if it's any relevance I'm getting 330v dc from the dc side of the board.

 

[shrtrnd]

What's the make and model number, it'll help us find a schematic and maybe help you out.

 

[Arouse1973]

Got any pictures of the inside of the unit?
Cheers
Adam

 

[Lexm]

What's the make and model number, it'll help us find a schematic and maybe help you out.

Hi thank you for your reply the make is DoPower model number GYMS3KW

 

[Lexm]

Got any pictures of the inside of the unit?
Cheers
Adam

 

[Lexm]

Got any pictures of the inside of the unit?
Cheers
Adam

Hi sorry was just going out before.I've now stripped the inverter down so you can get a good look at the boards. It's easy to see the resistors I've changed. I ordered them online and when they arrived they were much bigger than I was expecting

 

[Arouse1973]

Um can't see anything that stands out as damaged, we could really do with a circuit diagram. I'll see if I can find one.
Cheers
Adam

 

[Lexm]

Um can't see anything that stands out as damaged, we could really do with a circuit diagram. I'll see if I can find one.
Cheers
Adam

This is the inverter on amazon if it's any help
https://www.amazon.co.uk/d/i19/Gene...qid=1489222951&sr=8-6&keywords=3000w+inverter

 

[Arouse1973]

Ok thanks. So basically you put mains on to the output of the inverter whilst it was still connected to the appliances?
Thanks
Adam

 

[Lexm]

Ok thanks. So basically you put mains on to the output of the inverter whilst it was still connected to the appliances?
Thanks
Adam

Yeah I've got it setup so that the inverter runs though a switched fused spur then up to a fuse board then to the sockets but the fuse board is also connected to a 240v commando socket that gets plugged into the mains when at home I forgot to isolate the inverter via the switched fused spur. I'll add some pictures if it helps

 

[Arouse1973]

Yeah ok. Just re-read your thread and you say you have 330 Volts DC, it concerns me that this voltage is appearing on the DC rail. I would have expected 24 Volts. Or is this not on the power rail for the MOSFETS and somewhere else.
Thanks
Adam

 

[Lexm]

Yeah ok. Just re-read your thread and you say you have 330 Volts DC, it concerns me that this voltage is appearing on the DC rail. I would have expected 24 Volts. Or is this not on the power rail for the MOSFETS and somewhere else.
Thanks
Adam

Yeah it's on the power rail for the mosfets. on the other side of the mosfets it becomes 130v ac

 

[Lexm]

Yeah it's on the power rail for the mosfets. on the other side of the mosfets it becomes 130v ac

Don't know if it makes a difference or not but when I changed out the mosfet I couldn't get the irfp 460. The shop rs components sent me irfp 460B mosfets does that make any difference

 

[Lexm]

Yeah ok. Just re-read your thread and you say you have 330 Volts DC, it concerns me that this voltage is appearing on the DC rail. I would have expected 24 Volts. Or is this not on the power rail for the MOSFETS and somewhere else.
Thanks
Adam

I've uploaded a picture of the test in case I'm doing it wrong

 

[Arouse1973]

Don't know if it makes a difference or not but when I changed out the mosfet I couldn't get the irfp 460. The shop rs components sent me irfp 460B mosfets does that make any difference

The differences between the two shouldn't make any difference but it's always best to replace like for like. The non B version looks like it might be obsolete, the one from ST is.
Adam

 

[Arouse1973]

I've uploaded a picture of the test in case I'm doing it wrong

It difficult to tell where you are measuring without a circuit diagram. I have had a quick look at some circuits online and basically the MOSFETS drive a transformer. Here is an example. Not sure why you are seeing 222 V d.c

http://www.lz2gl.com/power-inverter-3kw/

I couldn't find one for go power. It might be worth emailing them for a circuit.

http://www.solar-knight.com/index.php/e-shop

Thanks
Adam

 

[Arouse1973]

Here's another circuit http://schematics.circuitdiagram.net/viewer.php?id=bwy1303597284b.gif
Thanks
Adam

 

[Lexm]

Here's another circuit http://schematics.circuitdiagram.net/viewer.php?id=bwy1303597284b.gif
Thanks
Adam

Hi Adam thank you for the links I've email them hopefully they come back with something. I've looked at the drawing you found but my electronic knowledge is extremely basic I can't read the to save my life.

 

[Arouse1973]

That's ok. If you look at the output and trace it back, you will hit a transformer, that's the thing that gives you your output. You fed mains into the output so the mains is going to get through to the other side because it's a transformer, although it will be a lower voltage because it will be acting as a step down in this case. What damage has it done.....? hard to say.

I don't like doing this (Blanket Change) but it might be worth changing all the MOSFETS otherwise you will have to take each one out and test them on load to see if they are naff.

Thanks
Adam

 

[Lexm]

That's ok. If you look at the output and trace it back, you will hit a transformer, that's the thing that gives you your output. You fed mains into the output so the mains is going to get through to the other side because it's a transformer, although it will be a lower voltage because it will be acting as a step down in this case. What damage has it done.....? hard to say.

I don't like doing this (Blanket Change) but it might be worth changing all the MOSFETS otherwise you will have to take each one out and test them on load to see if they are naff.

Thanks
Adam

Thanks Adam I'll start tracing it back and testing the mosfets over the weekend if I still can't figure it out I think changing them out could be a good solution or at least it would eliminate them as the problem thank you again I've been pulling my hair out over this.