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DIY 6 kVA 48V inverter using low freq transformer

AntronX

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Oct 24, 2021
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South FL
Hi, I have big and heavy low frequency 27V > 120/240V toroidal transformer from parted out Xantrex 6048 inverter. I would like to make MOSFET H-bridge inverter and PWM controller to drive it. So far I found IPP016N08NF2S 80V 196A 1.6mOhm MOSFETs on mouser that look pretty good for low frequency commutation side at least. I may have to model their switching losses at PWM freq or look for other FETs with acceptable switching loss for high side of the H-bridge.

Has anyone here done this kind of project? Any pointers for controller software, gate driver and current protection? I would like this to be a pure sine wave inverter.

Thanks.
 
This is done all the time, and its fairly straightforward.
Suggest you do an internet search for "The Back Shed, Oz inverter". The Australians on The Back Shed Forum have built literally hundreds of these over the last few decades, and its all gradually matured into a very efficient and reliable design.

A couple of tips from an old hand...

I suggest you hook up your big transformer to the grid and measure the no load idling power. Some commercial transformers of that size can have a surprisingly high idling power, possibly well in excess of 100 VA. That transformer will work fine for you, but its probably going to chew through a lot of battery capacity at night with such a hungry greedy transformer.
The state of the art these days for a 6KVa inverter with home wound toroidal transformer would be a zero load idling power of around 25 to 35 Watts. If high idling power becomes an issue, a winding a more efficient transformer yourself, might be worth thinking about later on.

Second tip, those Mouser mosfets are nice at 1.5 milliohms, but I bet they are expensive.
I suggest you initially try some cheapy Chinese HY4008 mosfets. These are 2.9 milliohms and 80 volts, and will work fine for an initial prototype. If you blow up a few testing, its no great loss. Once all the Gremlins are finally sorted out, you can upgrade to the more expensive mosfets at a future date.
 
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