Design and Analysis of an Asymmetric Spoke and Delta-Shape Interior Permanent Magnet Synchronous Machine

Abstract

This paper proposes a design of an asymmetric spoke and delta-shape interior permanent magnet (AIPM-P) synchronous machine for electric vehicles that use the magnetic-field-shifting (MFS) technique to improve the average torque and reduce torque ripples. The asymmetry of the AIPM-P is due to the asymmetric rotor structure, asymmetric permanent magnet (PM) placement, and asymmetric flux barriers (AFB). Due to this asymmetry, the MFS is utilized, which decreases the current angle difference between the peak PM torque ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$T_{PM}$ </tex-math></inline-formula> ) and reluctance torque ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$T_{r}$ </tex-math></inline-formula> ) components. In the delta-shape, the bar magnet helps reduce the d-axis inductance, which helps in increasing the reluctance torque, ultimately increasing synthetic torque. Furthermore, the combination of delta-shape and spoke shape PM makes the novel hybrid layer structure that improves the average torque. The proposed AIPM-P is then compared with the conventional designs in the literature having the same stator and rotor radius, with a 4-pole and 24-slot combination. The open circuit, on-load characteristics, efficiency, copper, and iron loss maps of the proposed and conventional designs are investigated and compared. Compared to the conventional designs, the proposed AIPM-P synchronous machine has high efficiency and a good torque profile, which is suitable for EV applications.