Comparison of electrically excited and interior permanent magnet machines for hybrid electric vehicle application

This paper comprehensively compares electrically excited (EE) and interior permanent magnet (IPM) machines for a hybrid electric vehicle application based on 2010 Toyota Prius system. An EE machine is globally optimized when it has the same machine size and total copper loss with the IPM machine. Efficiency maps of both machines are obtained and compared with iron losses calculated by finite element analyses. It shows that the EE machine can be a low cost alternative to the IPM machine with slightly lower efficiency and maximum torque. Due its adjustable excitation, the EE machine is able to achieve a wider constant power speed range than the IPM machine. However, the efficiency of the EE machine is not better than the IPM machine in the high speed region, since flux weakening control via armature windings is still necessary.