Hi Mr.Wendel,Hi Prithvi10

Below is a mathcad display showing the calculations for any Ott filter , but of course the example is for the filter

you need to transform a square wave of 400 hertz into a fairly cleans sinusoid with less than 4% total harmonic

distortion. The equations are algebraic and can be executed with just about any program.

View attachment 207948

Below is the Ltspice program that used the numbers above to calculate the filter performance:

View attachment 207949

And below is the performance calculated using the LTspice program:

The red plot is the square wave into the OTT filter. The Green plot is the sinusoidal waveform across the load

resistor at a power level of 20kw. Total harmonic distortion is 3.54 percent as noted above on the schematic.

Note that with a driving waveform duty cycle of 33.34% the total harmonic distortion would drop to below

1% and that is how I have driven the OTT filter in the past using a phase shift power stage.

View attachment 207950

The current through the each inductor is a quasi-resonant shape with few harmonics so copper wire losses will

be at the fundamental frequency of 400 hz for all practical purposes. What I usually do is measure the flux

density of each coil for 100 turns and 1cm squared core area. Then scale both of those values to design the

real hardware. I did not do it here though. Due to the inductance values being in the microhenrys, perhaps

ferrite material could be used for the inductor cores. By comparison, steel is very expensive.

I hope this material will help. The I will try to post the LTspice program itself in this communication.

Best regards, keep well away from the Corona virus.

Wendell Boucher

I tried the filter design you gave me, I simulated my design in Simulink and the waveform is not exactly clean.

and the THD is also quite high with 9%. I am sorry that I didn't tell you that I am using a Sine PWM inverter with a Switching frequency of 10000kHz.