To study the influence of complex impulse voltage parameters on the signal-to-noise ratio（SNR） of partial discharge inception voltage（PDIV） test under strong electromagnetic interference

based on the ultra-high frequency method

the insulation tests of inverter-fed motor under different rise time

frequency and duty cycle were performed

and the characteristics of PD signal in time domain and frequency domain were analyzed. The results show that the rise time has a significant effect on the high-frequency energy of discharge greater than 0.5 GHz. The high-frequency energy decreases gradually with the increase of rise time. The high-pass filter will weaken the discharge energy under different rise time

resulting in the decrease of the test SNR. The discharge amplitude decreases with the frequency increasing

and the discharge energy in high-frequency domain is weak. The discharge is more likely to be submerged in the residual interference. The discharge amplitude at the falling edge is small and the delay time is short under voltage of small duty cycle

such as 0.03% duty cycle. At this time

The SNR in PDIV test can be improved by detecting the partial discharge at the rising edge. The above results can provide a reference for the selection of repetitive square wave voltage parameters and the improvement of the SNR in the PDIV test

so as to improve the accuracy of insulation evaluation for inverter-fed motors.