Various aspects of home brew inverters

Author	Message
Warpspeed Guru Joined: 09/08/2007 Location: Australia Posts: 4406	Posted: 08:15pm 23 Apr 2017       It looks like your 50uH series choke resonates about 80Khz when connected to the capacitive primary winding, which is excellent. At 20 Khz, the input side of the choke will look like a very efficient inductor (as it should). But the main transformer itself resonates at only around 4Khz, so without the series choke fitted, the input impedance across the primary is going to be predominantly capacitive, and extremely low at 20 Khz. That primary leakage inductance of 10uH is very good too, as its less than a thousandth of the unloaded 10.6mH primary inductance. Try measuring the secondary inductance directly (at 100 Hz) and then try shunting it with additional capacitance to bring the resonance point down from 4Khz to about roughly 75 Hz. That should further increase the 20Khz attenuation and improve the waveform at 50 Hz. Cheers,  Tony.