Performance Improvement for Interior Permanent Magnet Machines by Winding Reconfiguration

Interior permanent magnet (IPM) machines have been widely employed in traction applications because of their significant advantages in power density and efficiency. In traction applications, it is essential to achieve speeds above nominal speed and operate in the flux-weakening region. In this paper, the winding reconfiguration method is proposed to improve the flux-weakening performance characteristics of IPM machines. An IPM machine, having the 2010 Toyota Prius IPM Machine's specifications, is designed to have two separate winding sets as “main” and “auxiliary” windings. Hence, it has become feasible to switch between different winding characteristics using power switches. The turns-changing method is employed to decrease the winding inductance by reducing coil turns, and the parallel branch method is employed to reduce the winding resistance. In this way, a high-torque at constant power region or high efficiency at constant torque region can be achieved. The influence of different operation modes, obtained by arranging the switching between windings, on the flux-weakening characteristics, including torque/speed, power/speed, and efficiency maps, has been investigated. The flux-weakening performance characteristics of the IPM machine with reconfigurable windings are calculated using a hybrid calculation method that combines finite-element analysis (FEA) with MATLAB. The flux-weakening performance characteristics of the IPM machine have been significantly enhanced thanks to the proposed winding changeover approach.