Failure phenomenon: The inverter power level is damaged by a pair of amplifier transistors. After replacing the same type of crystal tube, it runs out for a while.
From the phenomenon judgment, the cause of the fault is that the current is too large, and the cause of excessive current is:
1) Overcurrent protection failure. When the inverter output is over -current, the overcurrent protection circuit does not work.
2) Pulse width modulation (PWM) component fault, the two complementary waveforms output are asymmetric, one is long, and the other is short, which makes the two arms work unbalanced. Tube is damaged.
3) The power tube parameters are large. At this time, even if the input is symmetrically waveform, the output will be asymmetric. The waveforms pass through the transformer, which causes polarizing, that is, unbalanced magnetic flux, which causes the transformer saturation and the current increases sharply. The power tube, and one burned, and the other burned.