State-of-art of research and development of vehicle motors

This paper overviews recent trend of research and development of main traction motors for automotive application in Japan. The main traction motors must be with high torque and power densities, wider torque-speed operating range and high efficiency under frequent operating conditions. As high performance motor candidates, novel ones with variable machine constant employing a change of a number of turns and remnant of permanent magnet are proposed by many researchers. In other circumferences, many researchers also pay attentions to developments of non- or less-permanent magnet machines because of risks of cost-up and undersupply of rare-earth materials.