A Study of Rotational Movement and Charging Torque of Reconfigured On-Board Charger

This article studies the rotational movement and charging torque in a new reconfigured on-board charger during the charging process. Recently, the reconfigured on-board charger becomes attractive because the propulsive units are engaged in the charging system to reduce the cost and volume. Since the unbalanced currents flow through the three-phase permanent-magnet synchronous machine, the rotational movement and charging torque are generated. The charging torque may be equal to the rated propulsive torque at some special rotor positions, which is unsafe and may lead to the rotational movement, extra noise, and motor wear. In order to reduce the influence of charging torque and rotational movement during the charging process, the charging torque is analyzed based on the magnetic coenergy. It is found that the charging torque is related to the unbalanced current, differential-mode current, and current ripple in motor windings. Thus, the mutual inductances of motor windings during the charging process are decoupled into the differential-mode and common-mode inductances. Furthermore, a solution is provided to significantly minimize the charging torque based on the control methods of the ac/dc side and dc/dc side. Finally, the experimental results are provided to verify the correctness of the suppression of rotational movement and the charging performance.