Cut-off frequency of LC low-pass filter adjustment for 220V 50Hz.

Please let me know that how to set cutoff

frequency of LC low-pass frequency for

220V, 50hz sine wave inverter.

For 3-level pwm inverter.

Hi,

not much information....

For sure you did some search for LC low pass filter calculations in the internet. There are a lot of free online calculators.
If you did so, you surely found out, that you need a lot more informations than 220V, 50Hz and 3-level.

Without the informations it is not possible to do the calculations.

You should have a clue about overtones in your 3-level inverter. (Sometimes this is called "distortion"). You need to know the frequencies and their amplitudes.
Then you need to know what "distortion" you expect after the filter. Here also the frequencies and amplitudes.

With both informations you are able to calculate the filter characteristics. = how much attenuation you need for the frequencies.
Usually the overtones ner the 50Hz are the critical ones. So you can concentrate on them.

Then you need to know your max load current => lowest load impedance.

****

in short:
* the LPF needs to pass as much as possible at 50Hz --> this calls for a high cutoff frequency
* lhe LPF needs to attenuate at much as possible above 50Hz --> this calls for a low cutoff frequency
--> you need to find a compromise.


Klaus

Thank you,

Please let me know what information

do you want to know?

Hi,

As said: frequencies, amplitudes, load.

Klaus

In some respects your LC filter is like driving a woofer from a class D amplifier. Try the online calculators for this type of second order filter. Input your load impedance. For cutoff frequency choose 70-90 Hz, because if you choose 50 Hz it will attenuate your waveform and you don't want that.

In other respects your operation is similar to a buck converter, whose duty cycle varies so it makes the output voltage (a) go up, then down, in 1/100 sec, and (b) do the same in reverse direction for 1/100 sec. You should select LC values to suit. Consider the capacitor absorbs current spikes going back and forth through it, many times per second.

1)Carrier frequency 25khz is triangular wave

2)Amplitude of output is 311V or 220Vrms AC.

3)Load is varying but maximum load is 100 ohms.