Magnet Weight Minimization of Electric Traction Interior Permanent Magnet Motor Over Multiple Operating Points

To satisfy the vehicle emission reduction mandates around the world such as China for 2020 and 2030 and for Europe centered around 2030, the focus is more and more on electric motors to power the vehicle traction either in addition to the internal combustion engine such as hybrid electric vehicles (HEVs) or only electric power train with battery, with the later technology becoming more and more preponderant. The electric motors used in the hybrid or electric powertrain are generally synchronous permanent magnet motors, synchronous wound field, induction, synchronous reluctance or switched reluctance motors. The synchronous permanent magnet motor, especially with the interior permanent magnet (IPM) rotor, is the preferred design choice for electric vehicle traction powertrain due to its specific advantages such as high efficiency, wide constant torque speed range, high torque density, and sensorless rotor position detection capability due to rotor saliency. However, the drawbacks would be the motor costs mainly due to the use of expensive high energy rare earth magnets such as NdFeB or SmCo. In the last few years, the volatile supply chain and the perspective of limited availability of rare earth materials have driven up the cost of rare earth magnets significantly and have pushed motor design engineers into efficiently using of these materials in the synchronous permanent magnet motor design. This paper describes the process of using Altair tools such as Flux for synchronous permanent magnet motor EM FEA analysis and HyperStudy to minimize the weight of the NdFeB magnets of a typical IPM motor for electric traction application such as the IPM motor of the Toyota Prius 2010.