low pass lc filter design

I dont have variable dc supply more than 32 volts.
But I have variable ac supply upto 260v . Can I simply rectify the supply using bridge rectifier and capacitor and use it as a dc bus in my hbridge.? Coz it will not be a pure dc.
One more thing I want to ask to fvm ."as u said that I should use a big value resistance than 1k at gate to source. Now I have decided to use 4.7k resistance .also I have calculated that using 4.7k resistance , will drop the voltage to 9.1v after 10ms. .
In all the circuits before, I was using 1k resitance , was the reason for damaging of mosfet was same that I was using 1k resistance between gate to source which was responsible for the voltage drop to 6.3v of my bootstrap capacitor (22ufd).

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I dont have variable dc supply more than 32 volts.
But I have variable ac supply upto 260v . Can I simply rectify the supply using bridge rectifier and capacitor and use it as a dc bus in my hbridge.? Coz it will not be a pure dc.
One more thing I want to ask to fvm ."as u said that I should use a big value resistance than 1k at gate to source. Now I have decided to use 4.7k resistance .also I have calculated that using 4.7k resistance , will drop the voltage to 9.1v after 10ms. .
In all the circuits before, I was using 1k resitance , was the reason for damaging of mosfet was same that I was using 1k resistance between gate to source which was responsible for the voltage drop to 6.3v of my bootstrap capacitor (22ufd).

As I already said, tripping of the bootstrap undervoltage-lockout should not cause transistor damage, at least I don't know why. But it' surely an unwanted effect.

FvM, is it necessary to use a damper resistor in the LC filter designed for the output of hbridge ?

FvM said:

As a rule of thumb, the filter inductor should be selected with a fundamental wave reactance of 1 .. 4 % of the characteristic inverter impedance Vrated/Irated

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which means that whether my carrier frequency is 16KHz or 40KHz, the size of the indctor is same .
in my latest design i have used UNIPOLAR SPWM of carrier 20KHz , so the output LC filter will see a frequency of 40KHz. so probably smaller inductor can be used as compared to my earlier design which was 5mH , but according to you ,if i use equation XL=2*pi*F*L, where XL in my design is 1.3 ohms , F= 50HZ,
now the L is not depending on carrier frequency ,however C has decreased drastically.
so my filter L is same while capacitor is very small , so how can we reduce the size of inductor?

please reply FvM

--BawA-- said:

Can we use electolytic capacitor to design a low pass lc filter for filtering spwm from h bridge ?

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i think most people use inductor and non polarized capacitor for their lc filter.the inductor design is the major headache for me.

You are right,the inductance can be reduced with higher carrier frequency. The 1 - 4 % rule is an estimation of maximum inductance related to the 50 Hz impedance and voltage drop. It applies if you want maximum filter effect with a second order filter. Other parameters that determine the design are acceptable reactive inverter load and intended carrier frequency suppression.