A Novel Magnetic Flux Weakening Method of Permanent Magnet Synchronous Motor for Electric Vehicles

In this paper, a novel field weakening control method for permanent magnet synchronous motor is proposed to improve maximum speed range and maximum power, which are important parameters for electric vehicle application. Unlike general field weakening control method in which current vector is used to decrease linkage magnetic flux, the proposed method can decrease linkage magnetic flux by creating a difference gap between a stator and a rotor in axial direction without moving the current vector. This method is effective in increasing the maximum speed and the output power of permanent magnet synchronous motor, including surface permanent magnet-type rotor and interior permanent magnet-type rotor. Three-dimensional finite element method is adopted for the analysis of the proposed method in order to calculate d-axis and q-axis inductances as well as linkage magnetic flux according to axial gap. Motor performances according to speed are also compared with one another.