I need help to make a sine wave.
I have a full H-bridge connected to a transformer to get 230VAC 50Hz. PWM freq is 16KHz. The power of the inverter 300 watts.
I need an LC filter using the leakage inductance and a capacitor.
Can I measure the leakage inductance by short circuit?
How do I do the calculation? What else must I consider?
I have an full H bridge connected to the transformer to get 230 VAC 50Hz. PWM frequency is 16 KHz.
Your PWM frequency is 16 kHz and you want to have a fairly smooth 50 Hz sinewave output so, you need to choose a capacitor value that forms a low-pass filter with the leakage inductance as seen on the secondary side of the transformer.
To measure that leakage inductance (\$L_{LEAK}\$), short the primary and use an LCR bridge to measure the inductance on the secondary. There are other methods of course.
You should choose a resonant frequency that is in the middle ground between 50 Hz and 16 kHz. The normal starting approach is to choose the resonant frequency to be \$\sqrt{50\times 16000}\$ = 894 Hz.
Then you use this formula to calculate what C will be to get 894 Hz: -
$$894 = \dfrac{1}{2\pi\sqrt{L_{LEAK}\cdot C}}$$
But, be very careful about your PWM control; it mustn't have the ability to drop into a lower frequency of operation in case it hits the resonant frequency at 894 Hz. So, choose the lowest frequency at which PWM will operate and consider any hiccup or burst modes that may be used at light loads.
If the filtering you have added is not good-enough to achieve the sinewave quality you want, you can try lowering the resonant frequency towards 50 Hz but, be wary of making it any lower than 150 Hz without some careful considerations about the types of loads that might be connected (beyond the scope of this answer).
Make sure you choose capacitors rated for the output voltage and load surge currents by some margin. Polypropylene metallized film capacitors are likely to be the best even though they might be bulkier than what you expect to use.
And finally, I strongly suggest (nay urge) you to simulate your circuit before any electrons circuit are hurt!!
