1000W homemade sine wave inverter help needed

Hello to all.

I am building a 1000w pure sine wave inverter.

It has a 12V to 320V converter made with an SG3525 controller and BD139/BD140 at the output as a driver, 2 ETD39 ferrite core, each of them driven by 4 IRF3205 fets.

The secundary winding of the transformers is in series ( they are supouse to be 160V each) so after this stage the output should be about 320V.

so, i have imput gates of the fets in parallel 4 and 4 for each half period, each of the transformers is suppozed to create a secondary tension of 160v and they are in series conected. The transformers output is rectified by a bridge and filtering capacitor.

The problem is that when i am testing the output of a single transformer on a 54.6ohm resistor my fets get worm wery fast. This happens with the output of a single transformer rectified, with both in series it worket for about 1minute and then it blow my fets and a rectifier at the output when i was testig with the same 54.6ohm resistor.

With both of the transformers in series i was not surprised that that it blew because the diodes are 6A/800v.

My problem is that i don't know what diodes to use.

Now i am using uf608, are these usabile in an inverter? they have a reverse recovery time of 75ns and a capacitance of 300pf.

i am thinking of using by500-800 because they have a reverse capacitance of only 28pf but the recovery time is 200ns.

Also i don't think that the fets should get worm in about 10 seconds because they are mounted on a heatsink.

The transformers have on primay side 2x3, with 6wires of 0,7mm and on the secundary side 58 with o.7mm wire.

The main reason of your problem is the output of the two transformers are not ok as a series connection should have. They are being connected with the same polarity. It will be good to find the error if you can show the circuit diagram. Anyway, you can test it yourself. Just keep the output of these transformers open. Then run the system. If FETs are not warm the it is ok. It will be good if you can keep an Ampere Meter in seriesed with Supply. If the system takes low current, it is ok. If not, then there is a fault in either your FET Driver or Duty cycle.

If the system runs good with transformer outputs open, then connect them changing the terminals I mean the polarity. Then test again.

I hope your problem will be solved. Then, to make AC/DC you can use HER308 Diodes. I used these Diodes for my case. And results is fine.

Let me know if you have any further trouble with SMPS.