Asymmetric Pulse Width Modulation for Improving the Reliability of Motor Drive Inverters

In multi-chip power modules, each power device could have different thermal impedance due to an asymmetric internal layout of the power module. This may lead to different thermal loadings and thereby having lifetime difference of the power devices in practical applications. Both lifetime and power rating of motor drives are limited by the most stressed device. Therefore, the reliability of motor drive can be improved by increasing the lifetime of the most stressed device. In this paper, the asymmetric Pulse Width Modulation (PWM) method to increase the reliability of inverters in motor drive systems has been proposed. The effect of an asymmetric layout of IGBT modules on the reliability of motor drives is studied based on a 3-phase motor drive application. Then, an asymmetric PWM method is proposed. Finally, the lifetime of the IGBT is compared before and after the proposed method is applied.