How to power low resistance step up transformers?!

[delphino]

Hello everyone, so i'm trying to build a 12V to 240V power inverter with a 2 Transistors a tenter tapped step up Transformer and a Microcontroller (arduino) that makes a Modefied Sine wave right now for testing but i want to try to make a pure sine wave or as pure sine wave as possible
Anyhow, the problem is i have a 250 Watt step up Transformer witch i actually took from a broken Power inverter that i wanted to use for this project, it is pretty small for 250 Watt (in my opinion) but i figured it may have something to do with it have a very very low primary and secondary coil resistance, witch is my problem, wenn i tried to hook it up it made my cables melt in no time and then it burned the Transistors that came from the same power inverter where the Transformer came from, now i have new transistors and still would like to use that Transormer because it is (as i already mentioned) quite small and i don't have any other 24V to 240V tenter tapped Transformer that has right now, also i tried googling my problem, but all i found out is that low resistance tranformers (if that is how you call them) are more efficient witch makes sence to me, however i couldn't find anything about how you would power such a transformer.
I assumed you would some how have to limit the amount of current allowed into the primary coild dependant to the load connected to the secondary coil, but how would you do that without make the whole thing totally unpracticle and/or unefficient?

Thanks for your help in advance, hopefully someone here can help me...

Regards, Delphiño

P.S. Sorry for my bad explanation, i hope you can understand my problem more or less anyways..

 

[RobWansbeck]

It has nothing to do with the low resistance, the lower the better.
The current is limited by the primary inductance and the length of time each transistor is switched on. If you are burning things out you either have a short on the secondary or your circuit isn't switching correctly. You will also need to check if your microcontroller board has enough output to drive the transistors. Also if you have melted connecting wires you may have melted the insulation in the transformer so should test that.
Not wishing to sound harsh but in view of the fire and lethal shock hazards my best advice would be to try less dangerous projects until you have more experience and a better understanding of the circuit operation. The wrong switching waveform could lead to several thousand volts not 'just' 240.