Harmonic Modeling and Ripple Suppression of Electromagnetic Torque in IPMSMs

Interior permanent magnet synchronous machines (IPMSMs) are extensively used in electric drives due to their high-power density and wide-speed operation capability. In order to improve the performance of the drive application, low torque ripple of the IPMSM is valuable and necessary. However, as far as the existing analytical models are concerned, it is difficult to establish a direct relationship between the structural parameters and the torque ripple law of IPMSMs due to the complexity of their flux circuits, and therefore, it is not easy to achieve a directional suppression of the torque ripple by means of design. With this in mind, this article establishes a general analytical model for electromagnetic torque and its ripples (including synchronous torque, reluctance torque, and cogging torque) based on the harmonic interaction effects. Thereby, a novel and simple design method to reduce torque ripple is proposed, and its principle is to change the rotor surface shape to artificially construct the specific number of reluctance harmonics. As a result, it is verified by finite element method and experiments that the proposed method can precisely eliminate the specific torque ripple and reduce the overall torque ripple.