There's pretty easy to make square wave inverter circuit in the internet. But to run most load like fan, TV, etc you need to have a sine wave inverter.

Making sinewave or near-sinewave inverter is more complex and costly. But we can also convert square wave inverters to sinewave inverters.

A LRC resonant circuit is needed for this. The values determine the output frequency and waveform.

For a 50Hz 150V square wave output to become 230V 50Hz sine-wave, you need the above circuit connected to the output of the inverter.

Parts list:

- 100mH (0.1H) inductor, make sure you get high amperes rating ones.
- 27Ohm resistor, get atleast 50Watts resistor for a 250Watts inverter.
- 100uF nopolar capacitor. Get 450V ones.

Assemble the whole kit like the diagram above and connect the output of the inverter to the input of this circuit.

Lawrence Igenewari says

(1)What will be the values if I want to convert 50Hz 220V input square wave to 220V 50Hz output Sinewave?

(2)May I also know the mathematical calculations to arrive at values

Turgut Kalfaoglu says

If it's so easy to create true sine waves, why don't the makers of inverters include these components?