A New Segmented Rotor to Mitigate Torque Ripple and Electromagnetic Vibration of Interior Permanent Magnet Machine

Abstract

This article presents a new rotor configuration for V-shaped interior permanent magnet machine to reduce torque ripple and electromagnetic vibration. The proposed rotor structure consists of two segments staggered mechanically 180°. In each segment, the intersection angle between two magnets of one V-shaped pole is different to the others, resulting in a different pole arc to pole pitch ratio. The dimensions and total volumes of magnets keep unchanged. Benefitting from the two opposing segments, unbalanced magnetic pull can be offset. Machine performances in terms of back-EMF, <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">d</i> -& <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">q</i> -axis inductance, radial and axial force and instantaneous torque ripple are intensively compared and evaluated to the conventional machine with skewing slots, which is often used in mass production. Comprehensive models using coupled multiphysic fields are established and the comparative study of electromagnetic vibration aspects are done. Two machines, i.e., the proposed machine and the conventional machine with slot skewing are prototyped. Extensive experiments are carried out and compared in terms of back-EMF, current, modal frequency, static average torque, instantaneous torque, and efficiency.