Analysis and Suppression of Bearing Electric Erosion in the Metro Traction Motors

摘要

The pulse-width modulation (PWM) inverter variable voltage variable frequency speed control systems are widely applied to the modern subway vehicles. The bearing electrical corrosion problems due to the variable frequency power supply have caused serious dangers to the subway operation. In this paper, the bearing current problem of Beijing Metro Line 10 traction motors was analyzed. The common mode equivalent circuit of the motor bearing current was established, and the influence of the ground resistance on bearing current was analyzed. The simulation results showed that the poor earthen condition of motor frame is the reason for the bearing electric erosion. Finally, the new bearing current suppression method was proposed. The appropriate stator ground resistance of the traction motor was determined by the shaft ground resistance and the motor stray capacitances, which could eliminate the bearing current.