For example, the peak at 20 MHz in the spectrum is caused by the parasitic oscillation due to the output capacitance of the MOSFET and the leakage inductance of the transformer.
The peak value varies in different fault conditions and it can be used as a characteristic for diagnosing leakage fault of exhaust valve, the fault in initial stages can also be diagnosed.
The frequency response diagram under different leakage conditions are analysis. The influence of different leakage conditions on the peak value in frequent response diagram is summarized.