Need design Low pass filter for 20Khz to 50Hz for 300V 10A

[VijayVasant]

Hi guyz,
I'm designing a VFD for 300V 50Hz as single phase o/p but my drive generates o/p in 20Khz frequency so i want to design a low pass filter due to which the high frequecyies is removed and low frequency is passed... My PWM is 300V maximum current upto 10A in 20Khz frequency and want to reduce to 50Hz...
All your help is deeply appericiated...

Regards!

 

[4pyros]

Um?? You should already be able to control the frequency of your drive thats what it does.

 

[crutschow]

If the load is a motor, that will automatically filter out the high frequencies.

Otherwise you can use a series inductor. It's current rating must be 10A with inductance sufficient to reduce to high frequency ripple to a value you can tolerate, whatever that is.

 

[ronsimpson]

If I were building this filter:
Assume 300V in 150V out 50%.
Two pole filter.
First inductor: L= 300Volts 20khz 50% of the time. What inductance will give 1A ac?
The inductor needs to handle 10Adc + 1Aac + margin.

First Cap: V=500 2khz= 2 * 3.14 sqrt(C*L) set to resonate at 4khz.

Second inductor: current=10Adc very little ac current. (ac=20khz not 60hz)
Second cap= Set to resonate at 2khz.

This is a start.