Common-Mode Voltage-Reduction Method of 7-Phase BLDC Motor Control System

Abstract

This paper describes a method for reducing the common-mode voltage in a seven-phase brushless DC motor (BLDC) drive. The conventional interleaved method used in the three-phase inverter system is extended and applied. The proposed phase-phase interleaved method is studied to apply the six-phase excitation method for controlling the seven-phase BLDC. The six-phase switching functions related with modulation index (MI) and interleaved angle are obtained, and the average of the common-mode voltage is derived mathematically. The proposed control method reduces the common-mode voltage generation by applying the optimal interleaved angle according to MI. The proposed method is verified by experimental results.

Keywords

• BLDC motor
• common-mode voltage
• conducted EMI
• interleaving PWM
• seven-phase motor
• switching frequency