The design of AC permanent magnet motors for electric vehicles: A computationally efficient model of the operational envelope

Salient brushless AC (BLAC) permanent magnet (PM) motors are a preferred topology in the rapidly growing area of electric vehicle traction due to their inherent high efficiencies and excellent power densities. In the design of these systems it is important to appraise the motor performance across the entire torque-speed envelope. This paper presents computationally efficient techniques that allow rapid and accurate modelling of the entire operational envelope of any BLAC PM motor, enabling the generation of torque/speed characteristics and loss maps that can be used in an iterative design process. The proposed techniques are validated against test data from an in-house 35kW interior PM motor design and a comparison between a measured and computed efficiency map for the 2004 Toyota Prius motor is undertaken.