Analysis of dead time influence on common mode volt-second and inductor saturation in three-phase dc-fed motor drive systems

This paper presents a systematical analysis to predict the volt-second on the inductors of EMI filters through analytical calculation and provides a detailed analysis about the impact of system dead time on inductor saturation for EMI filter design. The equivalent circuit for inductor volt-second prediction is presented. Based on the equivalent circuit, a prediction method is proposed to analytically calculate the voltsecond on the common mode (CM) inductors using double Fourier integral transformation (DFIT) method for noise source calculation. Moreover, the impact of dead time on the output voltage spectrum and inductor volt-second is discussed in detail. The results show that the volt-second on the inductors can be predicted through analytical calculation and the impact of dead time on inductor saturation is related with system modulation methods, dead time value and also the inductors´ and capacitors´ value selection of the EMI filters. The analysis is based on a dc-fed motor drive system with output EMI filter as an example and the verifications are carried out through both simulations and experiments on a 3 kW motor drive system.