LIke the other thread also discussing a similar inverter, I can tell you immediately that it will not deliver much power, based on the size of the switching device.
And I question the competence and ability of the producer of the video as they do not provide a circuit schematic, but only a POOR wiring diagram.

 

Consider that when one side of the transformer primary is pulled up to Vsupply, the other side is pulled down to Minus Vsupply. So the gate to drain voltage can be twice the supply voltage. My point being that voltages in an active circuit can be higher than the supply voltage.
Have you checked to see if the two transistors are damaged, or not? It seems that the 4017, being directly connected, might have been damaged.
Looking back at post #1, no hint as to where the spark happened, or any mention of any part looking damaged. The spark might even have been across the transformer secondary terminals.
We have no hint as to the actual construction of the circuit assembly. Is it a circuit board (PCB)?, or a white breadboard? Or just wires in air?? Are those transistors mounted on heat sinks?? A whole lot of variables that could assist answers.

One of the mosfet is damaged but the other is fine and the NE555IC is damaged. And yes the mosfet is attached to a heat sink

 

LIke the other thread also discussing a similar inverter, I can tell you immediately that it will not deliver much power, based on the size of the switching device.
And I question the competence and ability of the producer of the video as they do not provide a circuit schematic, but only a POOR wiring diagram.

It will be enough if I can get 100w from it

 

100 watts out will require more than 100 watts in. I recently checked two of my commercially made inverters powering a 100 watt incandescent light bulb, and for each case the input current was very close to ten amps, with 12.6 volts input. So all of your power components will need to be adequate, including the drive to the transistors.

 

100 watts out will require more than 100 watts in. I recently checked two of my commercially made inverters powering a 100 watt incandescent light bulb, and for each case the input current was very close to ten amps, with 12.6 volts input. So all of your power components will need to be adequate, including the drive to the transistors.

Is it worth giving a try to build it
I can add like 2 6A diodes in series to reduce the voltage

 

Is it worth giving a try to build it
I can add like 2 6A diodes in series to reduce the voltage

With my inverters and my power supply, which is regulated, as I reduce the voltage to the inverter the current increases, and the power out stays about the same. That is, if I just reduce the input voltage to 12 volts, or down to 11.5 volts. It is a much more complex inverter than your device, with a constant output function.
But the reality is that power in must be at least as much as power out, and is usually equal to power out PLUS power turned to heat produced. is how real world systems work.
That is an inescapable reality.

 

One thing that hasen't been mentioned yet is harmonics of the inverter out put. A square wave output(which this limited use inverter is) will have much more harmonis than a rael sine wave or even modified sine wave inverter. The harmonics may be very damaging to many AC devices like a TV or computer. Even electric motors don't like the harmonics.

 

Certainly this inverter circuit WILL deliver a very significant harmonics. That is what happens with the first effort at approximating a sine wave type of circuit. So if the inverter is used to power any sort of device that needs a clean sine wave supply, the results will less than good. An. y audio equipment will find a few of those harmonics in the signal path, and output. A switch-mode power supply might even have problems. Some induction motors may not be happy, either. But it will work very well for heater devices and incandescent lighting. A soldering iron will work very well, unless it has an electronic temperature control.

 

Is it worth giving a try to build it
I can add like 2 6A diodes in series to reduce the voltage

You probably won't want to reduce the voltage. The large magnetizing current in the driven windings will cause a significant IR drop, robbing you of your voltage amplitude. Yes, the low voltage winding was designed to supply the rated current, but it was designed to supply both the rated current to drive the load by means of the primary, but it was not designed to drive the rated load + the magnetizing current in the low voltage winding.

 

If you use a split bobbin transformer and put a capacitor across the 230V output, the capacitor forms a second order filter with the transformer leakage inductance which will significantly improve the waveform.