need help for inverter

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i m working on inverter.
my load is a heating coil that can resist up 1000kW. my source is a 18Ah AGM battery.
i followed the circuit below.




i build a circuit accordingly. but when i conencted it to the transformer, it will bcome short circuit. the transformer i used is also centre tapped transformer, 12-0-12 (60KVA) to 240V. it is ok when i tested with each transistor separately.
the circuit must be tested with load, m i rite? i used a light bulb as my temporary load.
i use power supply as my temporary source, which adjust to 12VDC.
can someone help me? thank you
 

The battery you are using 18AH AGM would have to supply about 100Amps if you connect 1KW load (assuming around 80% efficiency - but it will actually be more like 60-70%). I wouldn't push n AGM that hard. But lets leave that behind.

When you use transistors in parallel, you have to have a small value resistor in series with each transistor. This will balance for any change in the output current among the transistors. This is explained in a lot more detain here : https://www.electro-tech-online.com/general-electronics-chat/25500-transistors-parallel.html

Read that thread.

Another thing is, how do you know you have a short? Explain the situation please..
 

Hi,
You have a 60kVA transformer and 1000kW load, and you're using 6 TIPs in parallel?

First of all, I don't think the TIPs will take the load.
You don't have anti-parallel diodes across the transistors.
Your transformer is A VERY POWERFUL one, which has very low inductance. This, without full or near that much load, will be dangerous and may draw immense current.
I think you should load it with something more powerful and see what happens. Before that, you need to add MORE transistors.

You'd be better off using MOSFETs and appropriate drivers.

Hope this helps.
Tahmid.
 

firstly i wan to thx u 2 for the help. i might not use that for tat big amount of power. most probably arnd 100W will do for my project.

eXnol,
i try my circuit use power supply. the power supply shows me tat short circuit.

tahmid,
i tried adding anti parallel diode for transistor, it stil give me short circuit shown on the power supply. i tried wif a 5A, 12-0-12 to 240 V transformer. it stil gv me shortcircuit even the power generate is low
 

while starting the inverter takes more power, if the power supply is not capable that much of current if will show short circuit or reduce voltage (current limit )
 

Hi,
I think the problem is the transformer. Since, it's a 60kVA transformer, it has a very low inductance, and at 100W load, the efficiency is VERY low (which starts getting higher with increasing load). Your power supply may not have enough capability to supply the load, as efficiency is very low and a lot of current is required. I think this is the scenario.

Try using a 100-200W transformer and you won't be seeing that problem.

Hope this helps.
Tahmid.
 

If you have a scope (CRO/DSO) try checking whether the transistors are properly driven and is oscillator is working properly. Also, check whether only one set of the driving transistors get hot. (If yes, then its not switching.
 

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