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

Abstract

Variable flux memory (VFM) permanent magnet (PM) machines exhibit an additional degree-of-freedom for control, i.e. PM magnetization state, and thus excellent flux controllability. Moreover, the hybrid PM topologies having variable PM (VPM) with low coercive force and constant PM (CPM) with high coercive force at the same time, are employed to improve the torque density and the flux controllability. The parallel and series connections between the two different kinds of PMs are both feasible. Based on equivalent magnetic circuits, two-dimensional (2-D) finite element (FE) analyses and experiments, the VFM machines with these two connection types are investigated and compared in this paper. The results reveal that the VPM with series connected CPM is beneficial for more stable working point and higher torque density. A pair of VFM prototypes with parallel and series hybrid PMs respectively are manufactured and tested to validate the analyses.

Multi-Objective Optimal Design and Analysis of Variable Leakage Flux Ipm Motors for Improve Flux-Weakening Ability

“…In Figure 5(a), it can be seen that the height H spm , length L pms , and width W pms of the PM and the long axis L es and short axis W es of the elliptic magnetic barrier have relatively great influence on the optimization objectives. In Figure 5(b), it can be observed that the In order to obtain the better performance of the two proposed motors, the boundary constraints are set as T r ≥ 60 Nm; T ripple ≤ 0.15; ΔΨ ≥ 0.25 (11) The MOGA is adopted for the two proposed motors to optimize variables. The optimization results of the two machines are shown in Figure 6, where the optimal point can be obtained efficiently based on the boundary constraints.…”

“…Hence, the wider speed range of the FI-IPM motor compared with some IPMSMs with the characteristic of L d > L q can be realized. In [11][12][13], variable flux memory motor (VFMM) has been proposed. Since s low coercive-force (LCF) PM is applied in VFMM, the LCF-PM magnetization strength can be controlled by injecting d-axis current pulses to remagnetize or demagnetize.…”

Swiveling Magnetization for Anisotropic Magnets for Variable Flux Spoke-Type Permanent Magnet Motor Applied to Electric Vehicles

“…For the parallel type of H-VFM [25], an active flux leakage bypass is established which is advantageous for flux regulation. Hua et al compared the series and parallel types of H-VFMs and revealed that the operating point of the LCF magnet in the parallel type is unstable [26]. To have a stable operation of the LCF magnet and excellent flux regulation ability, a variable-flux permanent-magnet synchronous machine with a quasi-series magnet configuration and passive flux barrier was proposed [27,28]; however, the problem of a large magnetizing current to switch from flux enhancing to weakening is yet to be resolved.…”

“…To simultaneously achieve the above-mentioned advantages, i.e., high torque density, excellent flux regulation ability, low demagnetization risk, low magnetizing impulse current demand, high efficiency at high speed, and expanded motor operating range, this paper proposes a novel VFS-PMSM topology combining HCF magnets and anisotropic LCF magnets, instead of the isotropic LCF magnet used in a previous study [32]. The method of swiveling the magnetic pole of the LCF magnet [32] is adopted, which differs from the previously mentioned methods that magnetize/demagnetize the magnets in the same axis [18][19][20][21][22][23][24][25][26][27][28][29][30][31]. It should be noted that there is a significant difference in flux generated and magnetizing field required between the easy and hard axes in the anisotropic magnets.…”

Comparative Study on Hybrid Excitation Flux Switching Motors without and with Variably Magnetizable Permanent Magnets for Electrified Vehicle Propulsion

“…As one of the possible solutions to mitigate the motor efficiency degradations mentioned above, a new HEFSM with variably magnetizable-permanent magnets (VM-PMs) replacing a part of the FECs was considered. This was because, based on the variable magnetization characteristic of VM-PM, which is well-known [10][11][12][13], the HEFSM with the VM-PMs would promise that the replacement of mmf of FECs with that of the VM-PMs made the motor efficiency better at both the lowand high-speed under the low-torque condition, that is, at both the urban driving and high-way cruising situation.…”