Analytical Design of a V-type Consequent-Pole IPM Machine for PM Cost Reduction

Abstract

In this thesis, an analytical method (AM) for the V-type consequent-pole permanent magnet (V-CPM) machines is proposed to determine the permanent magnet (PM) volume quickly for improving the PM utilization and reducing the PM cost simultaneously. The V-type interior permanent magnet (V-IPM) machine is set as a comparison to design the V-CPM machine, while the performance of the V-IPM machine and V-CPM machine will be compared under the FEM. First, based on the background that the consequent-pole permanent magnet (CPM) topology is utilized to reduce the PM volume and V-IPM topology could enhance the torque density, the V-CPM machine is employed to replace the conventional V-IPM machine in various applications. The principle of the investigated V-CPM machine will be introduced in detail. Second, the analytical modeling of the slot-less air gap flux density distribution in the V-IPM machine and V-CPM machine is built considering the magnetic saturation. Due to CPM topologies, the analytical modeling consists of 4 asymmetric regions is adopted for the V-CPM machines. The accuracy of the analytical modeling is verified by the FEM. Then, the Fourier series expansion of the slot-less air gap flux density in the V-IPM and V-CPM machine is calculated and verified. Finally, to obtain the same output torque with the V-IPM machine, the fundamental air gap flux density of the V-CPM machine obtained by analytical modeling should be kept equal to that of the V-IPM machine. During the analytical design, the rotor size limitation is employed to avoid unnecessary saturation and the 9th harmonic minimum is considered to reduce the torque ripple. Thus, a V-CPM machine is designed by AM as an example. The performance including the open circuit air gap flux density, the back-EMF, the torque performance is investigated by FEM. Through a comparison with the V-IPM machine, the designed V-CPM machine could obtain the same average output torque, however the PM volume is decreased by 35.7%. The results indicate the V-CPM machine designed by AM could meet the requirements well, thereby demonstrating that the proposed AM is effective and fast.