Asymmetry of Windings Inductance in High-torque Low-speed Multi-unit Permanent Magnet Synchronous Motor

摘要

The high-torque low-speed PMSM directly driving the load without speed reducer can be widely used in electric propulsion fields. It is necessary to employed for the superpower drivers (i.e. higher level power device) which can support the large current. However, it would increase the cost of the PMSM drivers extremely. In order to solve the contradiction between the power output of the PMSM and the limitation of single driver output of power, the multi-unit winding topology with five units including five independent three-phase star-connected windings is proposed aiming to develop the PMSM with high-torque low-speed performance and high reliability. The unit motor can be operated independently or jointly. During normal operation, the multi-unit PMSM is similar to the conventional three-phase PMSM. However, it is no longer regarded as a conventional three-phase PMSM when part of the units motor is in operation or the some of the units are in fault condition. The mathematical model of the multi-unit PMSM is established. The mutual inductance and eletromagnetical torque under various of operation are derived by analysis method. Meanwhile, the expression of torque ripple are obtained under normal and faulty operation. On the other hand, the asymmetric mutual inductances is computed by using 2D Finite Element Method (FEM). The harmonic components of torque ripple is computed with different currents of phase winding. The validity of analysis method can be verified by 2-D FEM.