Design, analysis and implementation of a spoke-type motor with high-performance ferrite magnets for electric vehicle applications
Over the past decades, rare-earth permanent magnet motors have been widely used in high-power applications such as electric vehicle propulsion motors due to their high energy density and efficiency. However, the high cost, unstable supply, and small reserves of rare-earth materials make the continued use of rare-earth motors expensive, risky, and unreliable. Therefore, finding alternative solutions for permanent magnet motors with less or no rare-earth materials has become a new research hotspot. With the significant improvement in the performance of ferrite magnets, permanent magnet motors with ferrite magnets instead of rare-earth magnets are becoming possible candidates for high-power applications and are receiving increasing attention. This thesis aims to design a synchronous motor with high-performance ferrite magnets to investigate the feasibility of using such as high-performance ferrite magnets as alternatives to the current mainstream rare-earth permanent magnets in electric vehicle traction applications. First, a comparison between motor layouts with conventional and high-performance ferrite magnets is made to investigate the influence of ferrite-magnet upgrading on motor performance. Then, a comparison between spoke-type IPMSM using high-performance ferrite magnets and V-shape IPMSM using rare-earth magnets is made to investigate the cost difference between two motors for the same torque and power output. Finally, different rotor layouts of spoke-type synchronous motors are compared regarding electromagnetic performance and mechanical reliability. The electromagnetic properties of all mentioned motor designs in terms of mechanical, anti-demagnetization, torque, and core losses are simulated by ANSYS finite element software. A prototype with a peak power of 50 kW is finally designed and manufactured. The mechanical and electromagnetic analysis of the final design is carried out. The selection and design of components such as shafts, connecting keys, and rotor position sensors are also introduced. Test benches are established for prototype testing. No-load, load, and short-circuit tests are performed, and the measurement results are used for validation of the simulations in this thesis.
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