Can someone please try to explain how I can re wire a microwave transformer (or any other Transformer) to be used in a custom inverter. The input is 12 volts and the output needs to be 120 volts. Pictures would be great, thanks in advance.

dave fitz7 years ago
Typical microwave transformers take half-wave 120v and turn it into ~4,000 vDC. Running them backwards can get you a decent stitch-arc welder at around 3V(presuming you respect load capacities) but it would be an enormous hassle to make them go from 12V to 120V.

If you have a transformer where one winding can be cut off, you might do this and rewind the winding with an appropriate number of turns. Unless you're desperate and/or know exactly what you're doing, I wouldn't recommend this- my experiments have been less than heartening.

Your absolute best option is look around for a car/truck battery charger used/thrown out, with a usable transformer. You'll probably have to adjust your inverter circuit to drive picky appliances (if you don't need portability, a heavy resonant circuit will work wonders here) and the charger transformer is actually wound closer to a 120V-14V ratio, but it's tons closer than most other options.

A final option- do you have access to electronic scrap? Many Uninterruptible Power Supplies are excellent inverters with a few fans added for cooling. They're often not very efficient because of all their extra line-matching circuitry, but you could always scrap the vast bulk of it and just reuse the transformer/power transistors.
Re-design7 years ago
You may have to rewire the transformer.

Wire 12 volts ac to the side of the transformer with the fewest turns.  Measure the ac on the other side of the transformer.  Be careful you are going to be measuring several hundred volts probably.

If you get 120 volts then you are very lucky.

If you got more then take off a few turns off the high side or add some the the low side.

If you got less than 120 volts ac then either take off some of the low side or add some on the high side.

It's not really an inverter though it's just a step up transformer.

Now if you are trying to do this with a 12 volt battery then you really do need an inverter like this one.

You can't use this for a computer of anything sensitive like that, but you could run lights off it.  It's not going to be frequency controlled and probably not true sine wave.
arenavles (author)  Re-design7 years ago
Sorry the link didnt add, here it is.www.sm0vpo.com/
There is the circuit.
arenavles (author)  Re-design7 years ago

Thank you for the answer, but I actually have a circuit for my inverter. The thing I cant get around for some reason is the transformer part.

Not my design but nice though. Anyways wanted to know if I can just re-wire a MOT to use in this circuit.