FEA Analysis and Optimization of Rotor Models in Permanent-Magnet Synchronous Motors fitted with Bonded Rare-Earth Magnets

Abstract

The Toyota Prius MG2 electric motor and its upgrades, since its first appearance in 1997, are presented in this paper. This electric motor has an Interior Permanent Magnet (IPM) fitted with Rare Earth (RE) magnets, which presents clear advantages over the more widely used Induction Motors (IM). The principal advantage is its high power-density value that makes it a leader in the Electric Vehicles (EV) market. This technology, however, faces a problem, in so far as the global production of RE magnets is an exclusive monopoly of China, (motivating the United States and Japan, among others, to investigate alternative systems). In this paper, the proposal is to substitute the sintered magnet in current use by the bonded type of magnet. The use of bonded magnets permits curved geometric forms, reducing the use of dysprosium, one of the most controversial elements of sintered magnets. These materials are compared using Finite Element Analysis (FEA) in the design of various rotor models including the proposal of a model with bonded magnetic materials, with the advantages of curved magnets and a dual layer arrangement. The proposed rotor model yielded a considerably higher power density than the model developed by Toyota.

Less Rare-Earth Electromagnetic Design for a High-Performance Permanent Magnet Motor

“…Similarly, we can find few studies for banana-shaped Interior Permanent magnet Motors (IPM). These references [3][4][5][16][17][18] present studies that demonstrate an improvement in mean torque with this topology. Kim et al [3,16,17] studies show different performances are obtained by adjusting the radial direction, which they execute by changing the radius value of the center of magnetization in the molds used.…”

“…Hayakawa et al [4] compare the three-layer V-shaped structure with the three-layer arc-shaped structure, resulting in higher torque for the latter because of a better ratio of magnet and reluctance torque. Similarly, Abad et al [5] state that the double-layer arced structure required the least magnet material compared to the conventional block type structures to achieve the targeted performance. Their work [3][4][5] demonstrates that the arc-shaped structure provides the advantage of efficient use of the magnet material compared to the block type.…”

“…Similarly, Abad et al [5] state that the double-layer arced structure required the least magnet material compared to the conventional block type structures to achieve the targeted performance. Their work [3][4][5] demonstrates that the arc-shaped structure provides the advantage of efficient use of the magnet material compared to the block type. Therefore, opening the possibility of less rare-earth designs.…”

Optimal Design of a High-Speed Flux Reversal Motor with Bonded Rare-Earth Permanent Magnets

“…The optimization of motors with bonded magnets on the rotor is considered in [21][22][23]. An evolutionary approach is applied in [21].…”

“…A hand-made optimization is performed in [22]. A quasi-Newtonian technique is used in [23]. However, optimization of a singlephase FRM with bonded magnets has not been considered yet.…”