Current Coupling Based Parallel Operation of Multiple Electric Motors

We study parallel operation of electric motors that cooperatively drive a rotational load. In parallel operation, it is necessary to ensure speed regulation and load torque sharing characteristics. Further a fail-safe feature is desirable so that even if a single motor fails, the overall system can continue to operate. To achieve the three characteristics, we propose a parallel operation strategy in which electric motors share their torque current value through communication and adjust the reference input for their speed controller according to current value deviation. We show that the proposed method ensures speed regulation, load torque sharing, and fail-safe characteristics. Further we provide a design procedure for the proposed parallel operation system. We validate the proposed method based simulation and experiment.