Torque improvement in IPMSM for Electric vehicle application

摘要

The high power density, efficiency, and wide constant power operating region of an Interior Permanent Magnet Synchronous Motor (IPMSM) makes it the best choice for driving an Electric vehicle. But IPMSM has a pulsating torque which is inherent in its design. Fractional slot concentrated windings are used to reduce the cogging torque. But to have maximum use of the flux produced by the permanent magnets, a very small air gap is used. This introduces further ripples in torque. An IPMSM suitable for Electric vehicle application is designed in RMxprt. The effect of slot opening width on cogging torque is investigated in Maxwell 2D. The machine is coupled in Simplorer software to drive an Electric vehicle model. A rotor shaping technique with Inverse Cosine Shape (ICS) around each pole is used to modify the air gap flux density into sinusoidal shape and to reduce the cogging torque and torque ripple. Inverse cosine with third harmonic injected shape is used in rotor to enhance the average torque of ICS IPMSM. Electromagnetic performance, cogging torque, average torque, and torque ripple for conventional, ICS and ICS with third harmonic injected machines is investigated. The machine is further optimized using Genetic Algorithm.