Conference Agenda

The required magnetization current for variable flux memory machines (VFMMs) is typically several or even tens of times the load current, which severely limits their potential for high-speed efficiency improvement. To address this issue, this paper proposes a novel composite multi-magnetic circuit VFMM (CMMC-VFMM), where the maximum magnetization current is capped at the on-load current. By employing distinct series magnetic circuit arrangements on both dq-axes, the proposed machine ensures stable operation points of low coercive force (LCF) magnets. Additionally, the high coercive force (HCF) magnet on the d-axis and the LCF magnet on the q-axis can form two parallel magnetic circuits, thereby enhancing its flux-adjusting (FA) capability. Furthermore, the proposed machine not only inherits the advantages of various magnetic circuit configurations but also substantially reduces the magnetization current requirements by utilizing more magnetic circuits. The results indicate that the proposed CMMC-VFMM can achieve a wide FA range, which results in notable efficiency improvement at the high-speed region, even under the constraints of the low magnetization current.

The increasing demand for high-efficiency propulsion motors to enhance the energy efficiency of electric vehicles (EVs) necessitates accurate efficiency estimation during the design stage. When evaluating AC copper losses in propulsion motors, neglecting losses caused by PWM current-based calculations, particularly at high-speed and low-torque operating points, can result in an overestimation of motor efficiency. However, incorporating PWM currents into optimization for enhancing motor efficiency at the design stage is often impractical due to the significant computational time required. To address the challenge of accurately calculating AC copper losses in propulsion motors, this study proposes a method that combines analytical models and FEA. The method efficiently accounts for proximity and skin effects while incorporating PWM current harmonics alongside sinusoidal currents. This approach significantly reduces computation time, enabling the practical integration of PWM currents into motor design. Additionally, it provides a framework for significantly reducing the time required to construct motor efficiency maps.

Axial flux permanent magnet (AFPM) machines are well-suited for industrial manufacturing, electrical transport and a variety of direct drive and low speed applications, due to their advantages in high torque density, high power density, and axial compactness. Since cogging torque can exacerbate torque ripple, vibration, and noise in these applications, a dual air-gap phase shift scheme is proposed in this paper to minimize the cogging torque of dual-stator single-rotor (DSSR) AFPM machines based on the theoretical calculation and analysis. Three specific methods, permanent magnets (PMs) shift, stators shift, and tooth tips shift, are introduced and validated through finite element analysis (FEA), where significant cogging torque reduction is demonstrated.

Recently, studies on Brushless Direct Current (BLDC) motors have been conducted to address efficiency issues caused by mechanical friction in brushes. Simultaneously, Permanent Magnet Synchronous Motors (PMSM) have garnered significant attention. However, the rare-earth permanent magnets commonly used in PMSMs are highly dependent on imports from China, posing supply instability risks and potential price hikes due to Chinese policies. To mitigate these issues, research on motors utilizing ferrite permanent magnets as an alternative to rare-earth magnets has been actively pursued. Despite their advantages, ferrite permanent magnets have a lower residual flux density compared to rare-earth magnets. Consequently, Concentrated Flux-type Synchronous Motors (CFSM) have also emerged as a promising solution, as they can maintain performance levels and improve air-gap flux density. Especially Double-Spoke type Motor offer the potential to reduce reliance on rare-earth magnets and enhance air-gap flux density. However, due to structural limitations, a significant portion of the flux leaks axially from the rotor instead of linking with the stator through the air gap. This axial leakage flux reduces effective flux and can degrade motor performance. In this study, we propose an asymmetric rotor permanent magnet structure for the Double-Spoke type Motor while maintaining the total amount of magnet material. The proposed structure is compared with a conventional symmetric structure in terms of axial leakage flux for various designs. Furthermore, a magnetic equivalent circuit is constructed to determine the optimal design that minimizes axial leakage flux.

Axial flux permanent magnet (AFPM) motors have drawn significant attention due to their compact size, high torque density, and broad applicability. However, accurately designing an AFPM motor often requires computationally intensive three-dimensional finite element analysis (3D FEA). To alleviate this, a quasi-three-dimensional (quasi-3D) model can be employed, in which the AFPM motor’s geometry is represented in a flattened, two-dimensional equivalent form. The quasi-3D model offers an efficient alternative but typically fails to consider important factors such as radial flux leakage. This limitation can lead to predicted voltage and torque discrepancies compared to 3D FEA results. In this article, we improve the conventional quasi-3D model by calculating the radial leakage path’s permeance and incorporating it into the two-dimensional analysis. As a result, the improved quasi-3D model shows a better correlation with 3D FEA. The improved quasi-3D model significantly reduces computational cost with minimal sacrifice of precision compared to 3D FEA, enabling faster and more reliable design processes.