Variable Magnetization Machine in Electrified Vehicle Application

This paper describes variable magnetization machines, which are capable of varying the magnetization state of permanent magnets during operation. A pulse current on the stator windings creates a magnetic field on the rotor; this can be used to manipulate the magnetization state of the rotor magnets. Regulating the magnetization state according to the machine operating condition can reduce machine losses. A proof-of-principle machine was designed and fabricated. A series of experiments was conducted to evaluate the torque-speed envelope and efficiency contours of the fabricated machine. A full-scale machine was then designed with a modified magnetic circuit for application to an electric vehicle and evaluated using finite element analysis. A control strategy for the magnetization state during machine operation is proposed, and the losses during a driving cycle with the strategy were evaluated.