Help Converting PWM with varying duty cycle to sine wave

[tdawg001]

Hi,

I am trying to convert a PWM signal into a sine wave. My PWM carrier frequency is 15kHz and I am trying to create a 400 volt, 50 Hz sine wave. I know that I need to use a low pass filter, however I am not sure what values of R and C, or L and C to use, cuttoff frequency, etc. I am new to low pass filters and need some help. Thank you in advanced.

 

[kabiru]

Use this formula to calculate your cut off frequency .F=1/2pisquare root LC.

 

[chuckey]

Classic filter design relies on the input and output impedances put on the filter. I suspect that you are building some sort of synthetic mains three phase generator. What sort of current will flow out of this 440V supply?. It has to flow through any series element, so that must be designed for that current flow. Also if any of the elements are resonant at 50 HZ or nX15KHz their current may increase beyond their ratings. Also if the load is removed the increased voltage due to resonance may burn them out. I think a series inductor with Xl = a few ohms at 50Hz, would be enough, as its Xl would be 300 times greater at you carrier frequency with a capacitor to ground which takes a current of Iout/10 at 50 HZ, hopefully they would not resonate anywhere near 50 or 15 KHz.
Frank