Inverter Output Transformer Saturation

Discussion in 'General Electronics Discussion' started by franticEP, Apr 1, 2017.

1. franticEP

4
0
Apr 15, 2015
Hi,
i'm testing an inverter with these features:
Fswitching=220KHz
Fout=3KHz-10Khz
Vout=150Vac
Pout=150W
Current feedback.
Sinusoidal output is obtained with transformer leakage inductor+output capacitor.
In the figure below there is the schematic.

The problem is that a little DC component (about 100mA) put transformer into saturation and the output waveform has a distorsion as in figure

I don't understand from where it can come this DC component. Could you help me?

A capacitor could solve my problem? what features should have this capacitor? Ceramic or film cap? I had thought of [email protected] as the voltage across it should never be too high.

Let me know.

2. duke37

5,364
772
Jan 9, 2011
What has temperature (K) to do with it?
The H bridge needs two n channel fets and two p channel fets and a level shifter to drive the p channel fets.
The four transistors will need to be matched to get an average zero transformer current.
Passing high voltage, high current AC through a low voltage electrolytic capacitor is likely to lead to tears.

3. (*steve*)¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥdModerator

25,500
2,840
Jan 21, 2010
If the total time your H bridge remains in one state does not equal the total time in the other state over some large number of cycles, then there will be a net DC voltage across the transformer and a net DC current.

Yes, a cap would improve things, but the voltage rating would be significantly larger than you imagine.

25,500
2,840
Jan 21, 2010

5. franticEP

4
0
Apr 15, 2015
Why? Could you explain me better?

6. (*steve*)¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥdModerator

25,500
2,840
Jan 21, 2010
It's quite possible for it to have -70V on one side and +70 on the other.

7. franticEP

4
0
Apr 15, 2015
In case of failure i'm thinkin of protecting device with transzorb across capacitor

8. (*steve*)¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥdModerator

25,500
2,840
Jan 21, 2010
You should possibly study the voltages in series resonant circuits.

You may want to stay away from resonance, but even still, there will be effects.