This paper investigates the demagnetization characteristic and permanent-magnet (PM) minimization of the less-rare-earth interior PM synchronous machines (LRE-IPMSMs) used for the electric vehicles, which are featured with high power density, high efficiency, and low cost. First, the equivalent magnet circuit (EMC) of the investigated LRE-IPMSM in demagnetization case is established. Then, the effects of the PM width and the thickness on the machine demagnetization characteristic are investigated. After that, the no-load EMC of the investigated LRE-IPMSM is established. Finally, an analytical method is proposed to obtain the minimum PM volume scheme on the premise of providing the targeted no-load flux and taking the machine anti-demagnetization ability into consideration simultaneously.

The reverse-salient permanent magnet synchronous motors (RSPMSMs) exhibit remarkable potential for multi-mode applications owing to their wide constant-power speed range. Currently, the design of RSPMSMs predominantly relies on conventional methods, which necessitate extensive engineering expertise and consume substantial time. To address this problem, this paper proposes a novel rapid optimization design method for RSPMSMs. Initially, this paper establishes the correlation between design indexes and electromagnetic parameters. Subsequently, the relationship between structural dimensions and rotor radius is derived from electromagnetic and structural parameters. Finally, a comprehensive design method is formulated, encompassing the progression from design indexes to electromagnetic parameters and ultimately to structural parameters. To verify its effectiveness, the RSPMSMs are designed using both the proposed design method and the multi-objective optimization design method. A prototype is manufactured and tested. Simulation and experimental results show that the method can be engineered for rapid and precise optimization design. Moreover, the method can be extended to the design of permanent magnet synchronous motors (PMSMs) under complex operating conditions.

The less-rare-earth interior permanent-magnet synchronous machines (LRE-IPMSMs), which have the advantages of high power density, high efficiency, and low cost, are promising candidates for electric vehicles (EVs). In this paper, the equivalent magnetic circuit (EMC) of LRE-IPMSM is established and analyzed to investigate the machine design principles, and then the performance of an optimized machine is analyzed. Firstly, the equivalent magnetic circuits of the LRE-IPMSM are established by taking the saturation effect into consideration. Secondly, the effects of geometric parameters, such as the permanent-magnet (PM) width, the PM thickness, the flux barrier thickness, the flux barrier span angle, and the bridge width, on no-load flux, q-axis flux, and d-axis flux are investigated, respectively. The results calculated by the EMC method and finite-element analysis (FEA) are analyzed and compared, which proves the effectiveness of the EMC method. Finally, an optimized design of LRE-IPMSM obtained by the magnetic circuit analyses is proposed. The electromagnetic performances and mechanical strength of the optimized LRE-IPMSM are analyzed and verified, respectively.

This paper investigates the performance analysis and mathematical modeling of a staggered-tooth transverse-flux permanent magnet linear synchronous machine (STTF-PMLSM), which is characterized by simple structure and low flux leakage. Firstly, the structure advantages and operation principle of the STTF-PMLSM are introduced, and a simplified one phase model is established to investigate the performance of the machine in order to save the computation time. Then, the electromagnetic characteristics, including no-load flux linkage, electromotive force (EMF), inductance, detent force and thrust force, are simulated and analyzed in detail. After that, the theoretical analysis of the detent force, thrust force, and power factor are carried out. And the theoretical analysis results are validated with 3-D finite-element method (FEM). Finally, an improved mathematical model of the machine based on d-q rotating coordinate system is proposed, in which inductance harmonics and coupling between d- and q-axis inductance is considered. The results from the proposed mathematical model are in accordance with the results from 3-D FEM, which proves the validity and effectiveness of the proposed mathematical model. This provides a powerful foundation for the control of the machine.

This paper proposes a novel asymmetric permanent magnet assisted synchronous reluctance motor (APMA‐SynRM) used for electric vehicles (EVs), which adopts the magnetic isolation flux barrier to enhance the effect of magnetic field shifting. Firstly, the magnetic field shifting principle and magnetic circuit model of APMA‐SynRM are analysed. Then, a new design method of APMA‐SynRM that makes the reluctance torque and permanent magnet (PM) torque reach the peak value at same current angle is proposed. According to the design method's analysis, the condition that the structural and magnetic property parameters of APMA‐SynRM should meet is obtained, which provides significant reference for the APMA‐SynRM's design. After that, an APMA‐SynRM scheme is designed to verify the design method's accuracy and effectiveness. Finally, the electromagnetic and mechanical strength performances of APMA‐SynRM and corresponding permanent magnet assisted synchronous reluctance motor (PMA‐SynRM) are studied, which demonstrates the feasibility of APMA‐SynRM's application in EVs.

Multi-layer flux-barrier combined-pole permanent-magnet synchronous machines (MLFB-CP-PMSMs) are especially suitable for machines used in electrical vehicles (EVs), as they represent a tradeoff between electromagnetic performance and the consumption of high-priced rare-earth permanent magnets (PM). In this paper, magnetic pole equivalence and performance analyses of the MLFB-CP-PMSM are investigated. Firstly, three types of PM arrangements of combined poles are introduced, namely, parallel, series and series–parallel. Then, the magnetic circuit model and magnetic pole equivalence principle of MLFB-CP-PMSMs with different PM arrangements are analyzed. After that, the accuracy of the equivalence method is studied by comparing the machine electromagnetic performance before and after equivalence. Finally, the MLFB-CP-PMSM’s performance, including the loss, efficiency and electromagnetic torque, is analyzed. The results prove that the MLFB-CP-PMSM has the advantage of high efficiency, and the equivalence method can retain precision when the MLFB-CP-PMSM armature reaction degree varies.