Design of dual rotor — Axial gap PMVM for hybrid electric vehicle

We investigated the application of permanent magnet vernier machines (PMVMs) to electric vehicles and hybrid electric vehicles, because the low-speed, large-torque characteristics lead to an improvement in efficiency for low speed driving. However, in the case of a vernier machine, the magnetic flux density of the iron core is high and the linearity of the current-torque characteristics deteriorates significantly in the high torque range. As a result, larger machines are required to obtain the desired maximum torque. In order to overcome this problem, we investigated the use of a dual rotor axial gap structure in PMVMs. Through this investigation, a torque density equivalent to the traction machine of the third-generation Prius was achieved. Furthermore, the machine developed employed NdFeB bonded magnets containing no dysprosium (Dy) which is a heavy rare-earth material.