Performance evaluation of straight-line magnetizing current trajectory for variable flux memory machine

The variable flux memory machine (VFMM) simultaneously achieves high torque density and regulable magnetization state (MS) property by applying a d-axis pulse current to the equipped low coercive force (LCF) permanent magnets (PMs). The working trajectories and stable working points of this type of machine switch back and forth at different MSs. Therefore, this paper proposes a straight-line magnetic current trajectory (SMCT) magnetization scheme, which is formed by applying a d-axis pulsed current while keeping the q-axis constant. Several optional magnetizing current waveforms with SMCT are investigated and the corresponding performance under no-load and load conditions are evaluated. The proposed method is relatively simple and exhibits an excellent ability to achieve magnetizing current control of multiple MSs. The effectiveness of the control scheme is validated by experimental results on a hybrid PM-VFMM prototype.