The reverse-salient permanent magnet synchronous motors (RSPMSMs) have attracted considerable attention in electric vehicles due to their wide constant-power speed range. However, the dq -axis current distribution laws of the RSPMSM are absent, and the relationships between motor parameters and the constant-power speed range are still unclear. First, the flux-intensifying effects and dq -axis current distribution laws of the RSPMSM are investigated. Second, the relationships between motor parameters and the constant-power speed range are summarized. Then, an RSPMSM with a wide constant-power speed range is proposed. The electromagnetic performance of the proposed RSPMSM is investigated by finite element method simulations and is compared with a conventional interior permanent magnet synchronous motor. Finally, an RSPMSM prototype is manufactured and tested. The results show that the RSPMSM exhibits favorable characteristics such as a wide constant-power speed range, weak flux-weakening current, high permanent magnet operating point, strong short-circuit current suppression capability, and high efficiency at a high speed. The constant-power speed range tested by the experiment reaches 5.5:1. Thus, the dq -axis current distribution laws, the relationships between motor parameters and the constant-power speed range are of great significance to the design of the RSPMSM.

Permanent magnet synchronous motors (PMSMs) provide many attractive electromagnetic performances such as high torque density, high efficiency and simple structure, which make them more competitive in electric vehicles (EVs). However, designing a PMSM with a wide constant-power speed range and high power factor at high speeds is still full of challenges and requires further effort. In this paper, the performance of vehicle motors considering their operating conditions is analyzed. The design rules of the reverse-salient permanent magnet synchronous motor (RSPMSM) are summarized, and an RSPMSM is proposed. The principle of the RSPMSM with high torque especially in the flux-weakening states is studied by analyzing the variable flux leakage and variable saliency ratio in detail. The electromagnetic performance of the proposed RSPMSM is investigated using the finite element method (FEM), and its prototype is manufactured and tested. The experimental results show that the constant-power speed range is 5.5:1, and the power factor is close to 1 at high speed. Thus, the RSPMSM proposed in this paper is a favorable candidate for EVs.

The stator coreless axial flux permanent magnet (AFPM) motor with a compact structure, low torque ripple, and high efficiency is particularly suitable as a motor for electric propulsion systems. However, it still requires great effort to design an AFPM motor with higher torque density and lower torque ripple. In this paper, a stator coreless multidisc AFPM (SCM-AFPM) motor with a three-rotor and two-stator topology is proposed. To reduce rotor mass and increase torque density, the proposed SCM-AFPM motor adopts the hybrid permanent magnets (PMs) array with Halbach PMs in the two-terminal rotor and the conventional PMs array in the middle rotor. In addition, a multi-objective optimization model combining response surface method (RSM) and genetic algorithm (GA) is proposed and applied to the proposed SCM-AFPM motor. With the help of the three-dimensional finite-element analysis (3-D FEA), it is found that the torque ripple of the optimized SCM-AFPM motor is 4.73%, while it is 6.21% for the initial motor. Its torque ripple is reduced by 23.8%. Therefore, the proposed multi-objective optimization design method can quickly and reliably obtain the optimal design of the SCM-AFPM motor.

The reverse-salient permanent magnet synchronous motor (RSPMSM) is a competitive candidate for electric vehicles due to its high torque density and high efficiency. This paper proposes an optimized RSPMSM by adopting a segmented permanent magnet structure. First, the structure, electromagnetic torque, and current control laws of the RSPMSM are introduced in detail. Second, the optimization design method of the RSPMSM is proposed by taking the torque and constant-power speed range as optimized objectives, with the saliency ratio as a constraint. The optimized model of the RSPMSM is determined using the genetic algorithm (GA). Further performance analysis and comparisons are made between the initial motor and the optimized motor. Finally, a prototype is manufactured, and the performance of the RSPMSM is verified through the finite element method (FEM) and experiments.

The Ld of a negative-salient permanent magnet synchronous motor (NSPMSM) is greater than Lq. When a NSPMSM is operating at or below the rated speed, the id is flux-intensifying current, which can improve the flux density of permanent magnets (PM). First, a NSPMSM is proposed and compared with a positive-salient permanent magnet synchronous motor (PSPMSM). The d-axis and q-axis equivalent magnet circuits of the NSPMSM are then established. According to the limitation of the equivalent magnet circuit, the PM dimensions formula and optimization of the finite element method (FEM), PM dimensions are determined, and the constant power speed ranges of the two motors are calculated. Second, the influence of the saliency ratio on the internal power factor angle and the average flux density of PM at different internal power factor angles are calculated. Third, the flux density of PM in two motors are calculated when the windings are short-circuited. Finally, the bypass function of the NSPMSM magnetic bridges during the flux-weakening state is analyzed. The results show that the flux-weakening magneto motive force (MMF) of the NSPMSM is smaller at high speed, the short-circuit current (SCC) is smaller when the windings are short-circuited, and the magnetic bridges protect the PM in the flux-weakening state, so the flux density of PM is larger.

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.