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Godoh Guru Joined: 26/09/2020 Location: AustraliaPosts: 379
Posted: 04:01am 04 Nov 2021
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Godoh Guru Joined: 26/09/2020 Location: AustraliaPosts: 379
Posted: 04:08am 04 Nov 2021
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I have a few inverters, most now are junked powerjacks that have had 8010 based aliexpress boards fitted, using the transformer and cases of the powerjacks.
Yesterday a new 24 volt 5kva board arrived , i have fitted it to an 8kw powerjack transformer The powerjack transformer stated in a label that it is 18 volt primary 220 volt secondary. I was confused when I fitted it to the 8010 board as I could only get 212 volts out. Adjusting the voltage output would go down but no higher. I tried first adding a turn to the primary of the transformer that got me a max of 204 volts. So I took a turn off and now have 221 volts. I am hoping that someone here can tell me if I should
1 Take another turn off the primary or 2 use a resistor to trick the board into thinking the output voltage is lower than it is, in order to get it up to 230 volts at least.
The other boards I have used have easily adjusted to 240 volts, no problems, so I am wondering why this one is different. Unfortunately specs on these no name boards are hard to come by but one Sunyima board I read about suggested 12 to 14 volt primary for a 24 volt board. Hope someone here can explain it to me. Pete
Warpspeed Guru Joined: 09/08/2007 Location: AustraliaPosts: 4406
Posted: 07:16am 04 Nov 2021
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If primary is 18 volts rms, peak voltage at that will be 25.4v
You will need AT LEAST 25.4v dc to get 220v out of the beast the way it is, and probably more under any kind of reasonable load.
Usual ratio for a 24v sine wave inverter is about 16:1 step up. Yours is 220/18 or 12.2:1
I think you can safely remove some turns from the primary. That will increase primary current, but as the transformer is over rated anyway, that should not be a problem.Cheers, Tony.
Godoh Guru Joined: 26/09/2020 Location: AustraliaPosts: 379
Posted: 07:49am 04 Nov 2021
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Thanks for that info Tony, I will try removing one more turn. It would be good to get it up to 230 volts. Seems odd that none of the other powerjack transformers had to be changed. The other transformers were from an 8kw powerjack but it had two transformers. This one that I got the transformer out of only had one big trannie.
Seemed odd to me that when i measured the AC into the transformer when I was getting 212 volts out the board was pumping in 19 volts AC. Then when I took a turn off the voltage went up to 21 volts in the primary and 221 volts in the secondary.
My brain must be fuddled but I thought that I should have had to put more turns on the primary to increase the output voltage. Obviously something else is at play here. Thanks again Pete
Technophiliac Regular Member Joined: 18/12/2020 Location: New ZealandPosts: 89
Posted: 10:26am 04 Nov 2021
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Any chance of swapping some bits to see what's different?Davo, Wellington. You can have it perfect, on time, and at the best price. Choose any two.
Godoh Guru Joined: 26/09/2020 Location: AustraliaPosts: 379
Posted: 08:22pm 04 Nov 2021
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Hi Davo, I will open one of my other inverters and measure the voltages and see if they are similar.They have smaller transformers so it will be interesting to see what voltages they are feeding in. It may be something to do with having a much bigger transformer. I will also try undoing another turn on the big transformer and see what difference that makes. I know that powerjack over rate their inverters quite a lot, so I am only hoping to get about 3kw out of this one, any more is too much drag on the batteries in my way fo seeing things. My batteries are 24 volt 660 amp hour VRLA, so I try not to pull much more than 100 amps for long. Thanks Pete
Warpspeed Guru Joined: 09/08/2007 Location: AustraliaPosts: 4406
Posted: 09:30pm 04 Nov 2021
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If it says 18v/220v on the transformer, I don't think you need to look any further for the problem.
That transformer is more like something you might expect to see in a 12v battery charger, not a 24v inverter.
I would anticipate something more like 15v/240v which is 16:1 15v rms has a peak of 21.2v. At full flat out power, the minimum dc input voltage might need to be be a couple of volts more than that to allow for voltage drops that occur right around the whole system at full load.
A 24 lead acid battery would be pretty much done at 23.2v, but at least the inverter output voltage should still be voltage regulated down to that voltage.Cheers, Tony.
Godoh Guru Joined: 26/09/2020 Location: AustraliaPosts: 379
Posted: 10:33pm 04 Nov 2021
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Thanks Tony and Dave. I checked the other inverter that has the 8010 chip and the smaller powerjack transformer and it was feeding 15 volts into the transformer for a 240 volt output.
So I took Tony's advice and unwound another turn from the big transformer and all is good, I can wind it up to 240 volt output no problems now. So the end result was removing two turns from the primary sorted the problem out. The no load current is 0.8amps, I am pretty happy with that. The Powerjack was quite a bit higher than that and also much noisier. The PowerJack also kept on blowing up. So now all I need to do is tidy up the transformer winding excess leads and it is a going concern.
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