Electromagnetic Performance of Consequent Pole Permanent Magnet Machines, with Particular Reference to Analysis and Minimization of Torque Ripples

• Main Author: Qi, Ji
• Format: Thesis
• Language: English
• Published: 2022
• Subjects: South pole
• Online Access: https://etheses.whiterose.ac.uk/32600/; https://etheses.whiterose.ac.uk/32600/1/Thesis-Ji_Qi-23-3-16-v7.pdf

Consequent pole permanent magnet (CPPM) machines can save the amount of permanent magnet (PM) while produce comparable torque as conventional surface-mounted PM (SPM) machines. However, due to the unbalanced features between north and south poles, i.e. PM and iron poles, the presence of a large torque ripple can hinder their adoption in some applications. Unfortunately, the basic characteristics and generalized principles have not been fully established. This thesis investigates the electromagnetic performances of CPPM machines, with particular reference to the analysis and minimization of torque ripples. A general analytical model is developed for the first time to analyze the cogging torque accounting for unequal north and south pole widths as well as pole shifting. It can be applied to CPPM machines and other rotor PM machines. Based on the analytical expression, optimal design parameters for minimum cogging torque with/without pole shifting, including slot opening and pole-arc to pole-pitch ratio, are analytically derived and verified by finite element method (FEM). By selecting appropriate design parameters, the cogging torque and torque ripple under light load conditions can be suppressed effectively but little torque ripple reduction can be achieved at high currents. To solve this problem, symmetrical and asymmetric pole shaping methods with different PM and iron pole shapes are proposed. It is confirmed that the symmetrical pole shaping methods can only reduce the PM torque ripple while the asymmetric pole shaping method can minimize the overall torque ripple since it can adjust the amplitudes and phasors of torque ripple components, i.e. PM, reluctance, and cogging torques, to make them counteract each other. It is also the first time that the contribution of reluctance torque ripple is revealed and utilized to minimize the overall torque ripple in CPPM machines. However, the effect of proposed methods will be affected by different slot/pole number combinations and different load conditions. For CPPM ...