Rotor design considerations for a variable-flux flux-intensifying interior permanent magnet machine with improved torque quality and reduced magnetization current

Comparative Study on Variable Flux Memory Machines With Parallel or Series Hybrid Magnets

“…1(a), two pieces of CPMs are located on each rotor pole and they are adjacent to the d-axis position, meanwhile, another two pieces of VPMs are placed at the side of the CPMs, and they are close to the qaxis position. A large number of flux barriers are applied on the rotor to alleviate the cross-coupling and help to maintain the working point of VPMs [6]- [11], [13]- [15]. In fact, these flux barriers are generally necessary in the sole VPM or parallel hybrid VFM machines for resisting the unintentional demagnetization.…”

“…According to (9) and (11), it is clear that the resultant PM flux can be regulated in the parallel and series hybrid VFM machines, by changing the VPM magnetization state, i.e. adjusting k m .…”

“…Consequently, the positive reluctance torque is obtained with +I d whilst the VPM magnetization state is stabilized simultaneously. Moreover, the spoke-type IPM rotor can be employed to boost the PM usage volume and hence the torque output [9]- [11]. In addition, the VFM concept can also be applied to the stator-PM machines, in which the VPMs are allocated on the stators to obtain a robust rotor topology [12], [13].…”

Permanent Magnets Aging in Variable Flux Permanent Magnet Synchronous Machines

“…VF-PMSMs can be equipped with different magnet types, including low coercivity magnets (low-Hc) like AlNiCo [6], [7] or SmCo [8], or a combination of low-and high-Hc magnets [3], [8]- [10].…”

“…VF-PMSMs equipping AlNiCo magnets require relatively small magnetic fields to change the MS [4], [6], [7]; this limits machine torque capability as the magnetic field produced by the q-axis current could demagnetize the PMs [8], [10]. VF-PMSMs combining low-and high-Hc magnets reduce the risk of undesired demagnetization due to q-axis current.…”