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.

 

... but now I'm only getting 130v when testing the socket any ...

I guess you were expecting 220V? Have you looked at the voltage when a small load is applied, like a 60W lightbulb?

Anyone that can help you is going to need a schematic and/or a photo and/or a model number.

 

I guess you were expecting 220V? Have you looked at the voltage when a small load is applied, like a 60W lightbulb?

Anyone that can help you is going to need a schematic and/or a photo and/or a model number.

Hi yeah looking for 240v I haven't measured voltage with a load I'll put it back together tomorrow and get a reading the make is dopower model number GYMS3KW.
You can see the resistors I have replaced in the pictures I ordered them online and when they came they were much bigger than I expected and help would be great

 

Hi,

What Make and model is the inverter, I may be able to help

 

Hi,

What Make and model is the inverter, I may be able to help

The make is dopower
model number is GYMS3KW. Any help would be great thanks

 

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

 

I am assuming that you connected the mains to the output of the inverter. (I suggest that you fit a suitable changeover switch so this cannot happen again.) I suspect that the 130 volts you have measured on the output could be the average of pulsed 330 volts. I think only one half of the H bridge is switching on. I suggest looking at the waveform with an oscilloscope. If you do not have an oscilloscope then test the output with your meter set to DC. If it is the correct waveform (AC) but low voltage then the meter should read zero.

Les.

 

I am assuming that you connected the mains to the output of the inverter. (I suggest that you fit a suitable changeover switch so this cannot happen again.) I suspect that the 130 volts you have measured on the output could be the average of pulsed 330 volts. I think only one half of the H bridge is switching on. I suggest looking at the waveform with an oscilloscope. If you do not have an oscilloscope then test the output with your meter set to DC. If it is the correct waveform (AC) but low voltage then the meter should read zero.

Les.

Thank you so much for your reply I'll get the meter out and test it. Could you suggest any changeover switches.

 

I am assuming that you connected the mains to the output of the inverter. (I suggest that you fit a suitable changeover switch so this cannot happen again.) I suspect that the 130 volts you have measured on the output could be the average of pulsed 330 volts. I think only one half of the H bridge is switching on. I suggest looking at the waveform with an oscilloscope. If you do not have an oscilloscope then test the output with your meter set to DC. If it is the correct waveform (AC) but low voltage then the meter should read zero.

Les.

I tested the inverter at the output and got a reading of -89v I check polarity and the leads were on the correct terminals. I went to get camera but when I reconnected the battery the whole inverter was dead no led screen,no output voltage. Any ideas

 

Quick update I've taken it out of its case and retested. the power is back on now but still only outputting 130v at socket even though the led screen says 240v

 

I have had this problem in the past

It usually one of the mosfets. I think it would be a good idea to replace all the irfp460 mosfet. Also look for dry joints on the mosfets and there resistors. They should be 47R0.25 Watt. Also check the diodes. I cant see them all in your photos but the ones near the mosfets.

 

I have had this problem in the past

It usually one of the mosfets. I think it would be a good idea to replace all the irfp460 mosfet. Also look for dry joints on the mosfets and there resistors. They should be 47R0.25 Watt. Also check the diodes. I cant see them all in your photos but the ones near the mosfets.

I have replaced 2 mosfets I'll go ahead and replace the rest should I replace all the ones on the board or just the side where the resistor have blown also I can't find irfp460 the shop I used sent me irfp460b will theses be ok

 

I have replaced 2 mosfets I'll go ahead and replace the rest should I replace all the ones on the board or just the side where the resistor have blown also I can't find irfp460 the shop I used sent me irfp460b will theses be ok

Ok I cant find a Data sheet for the irfp460b but if the supplier sent it to you they pretty good with knowing its ok. It may be a good idea to repace them all. But just start on the side they were burnt. Its probably good prcatice to test the mosfets rather than just replace them all. But I am not 100% sure how to test a mosfet.

Try this https://www.utm.edu/staff/leeb/mostest.htm

i have never done it myself

 

I guess you were expecting 220V? Have you looked at the voltage when a small load is applied, like a 60W lightbulb?

Anyone that can help you is going to need a schematic and/or a photo and/or a model number.

I tried it with a 13w pump plugged in but the voltage was still 130v

 

Ok I cant find a Data sheet for the irfp460b but if the supplier sent it to you they pretty good with knowing its ok. It may be a good idea to repace them all. But just start on the side they were burnt. Its probably good prcatice to test the mosfets rather than just replace them all. But I am not 100% sure how to test a mosfet.

Try this https://www.utm.edu/staff/leeb/mostest.htm

i have never done it myself

Thank you for your help I'll test them and replace if needed fingers crossed I find the fault

 

Right I've changed out the last mosfet on that bank and replaced the resistors with the same resistance but smaller physical size powered it up nothing went bang but still only getting 132v at the socket
There is still 3other banks of mosfets would it be worth taking them out the board and testing them

 

Did you find out if you were only getting the positive or negative half cycles out of the inverter ? It suggest tracing the schematic of the part after the 330 volt DC part so that the fault can be traced logicaly rather than just repacing parts. It could be the drive signals to the H bridge that is the problem.

Les.

 

Did you find out if you were only getting the positive or negative half cycles out of the inverter ? It suggest tracing the schematic of the part after the 330 volt DC part so that the fault can be traced logicaly rather than just repacing parts. It could be the drive signals to the H bridge that is the problem.

Les.

Hi les how do I go about find out if it's the positive or negative part of the cycle. I've emailed the company and asked for a schematic fingers crossed they get back to me also how would I test for a dive signal I'm sorry my knowledge of electronics is very basic. Thank you for you help

 

@James Harris 1
I have repaired a couple of inverters from low voltage to poor regulation.
I can help but my time is rather limited but I can point out what to look for.
I need voltage measurements at certain points but to point that out I need to see the PCB's properly.

Your pictures are not enough and of poor quality for me to tell you anything.
This does not mean I need big file size pictures. I need good quality pictures with good lighting and no glare.
Resize them and attach them. High resolution with small file size is OK for me as my bandwidth is limited.
Just attach them as you did before.

Then if time allowed I can guide you.
I may not reply promptly but I will reply.

PS. I need to see the whole PCB from both sides.

 

@James Harris 1
I have repaired a couple of inverters from low voltage to poor regulation.
I can help but my time is rather limited but I can point out what to look for.
I need voltage measurements at certain points but to point that out I need to see the PCB's properly.

Your pictures are not enough and of poor quality for me to tell you anything.
This does not mean I need big file size pictures. I need good quality pictures with good lighting and no glare.
Resize them and attach them. High resolution with small file size is OK for me as my bandwidth is limited.
Just attach them as you did before.

Then if time allowed I can guide you.
I may not reply promptly but I will reply.

PS. I need to see the whole PCB from both sides.

Hi R!f@@
Thank you for your reply I've attached some more pictures if these are still no good I'll take some on my camera and upload them.thank you for your help