Magnetization State Control of Variably Magnetizable Permanent Magnets Employed in HEFSM at Starting Up

This paper presents the magnetization state control of variably magnetizable-permanent magnets (VM-PM) - for a hybrid excitation flux switching motor (HEFSM) at the initial starting up. The HEFSM employing N-d-F-e-B type magnets with low coercive force as VM-PMs can achieve higher efficiency driving over the whole operating area compared with the conventional HEFSM without VM-PMs by appropriately adjusting the magnetization state according to a given operating condition. To put such the HEFSM into practical use for automotive traction applications, it is essential to be able to intentionally control the magnetization state by applying a pulsewise current to field excitation coil (FEC) during rotation as well as at starting up aiming at initialization of the magnetization state of VM-PMs. At first, a difference in the magnetization state controllability during middle-speed rotation and at a standstill and the angular dependence of the magnetizing magnetic field applied on VM-PM are investigated and discussed. Subsequently, the "quasi-impulse current train magnetization method" at starting up is proposed as a novel magnetization state control scheme. The effectiveness of the proposed control scheme is experimentally verified using a 60kW test motor. As a result, it is revealed that the magnetization control at the starting up can be achieved similar to that during the middle-speed rotation.