Simplified Computation Model of Efficiency Map For Low-Speed and High-Torque PM Machines

This paper proposes a computation model for efficiency map in a low-speed and high-torque permanent-magnet synchronous machine without magnetic bridge. According to the magnetic field distribution, the whole machine topology is then divided into seven types of subdomains. By means of the magnetic field prediction and classic loss model, different losses and electromagnetic torques of motor under different working conditions are obtained, and finally the full analytical calculation of the motor efficiency in the all working domain is realized. The impact of rotor saturation is analyzed by establishing a local polar coordinate system. Then a program is used to build efficiency map. Results from Finite Elements Analysis (FEA) are used to verify the proposed method.