AV-07 Torque Improvement and Core Loss Reduction with Controllable Flux-Leakage Design in Spoke-Type Flux-Intensifying PM Motors
Creators: Min-Fu Hsieh
Anh Thanh Huynh
Duc-Kien Ngo and Minh-Hoc Duong Le
Publisher: name: IEEE
Year: 2025

I. Abstract This paper presents a novel approach for enhancing torque performance and reducing core loss in Spoke-type Flux-Intensifying Permanent Magnet (SFI-PM) motors using controllable magnetic flux leakage barriers. The SFI-PM motor design incorporates multiple flux barriers into a conventional Spoke-type Interior PM (SIPM) motor to increase d-axis inductance (Ld > Lq) and intensify magnetic flux density. However, this also reduces the output torque capacity compared to conventional SIPM motors. To mitigate this, magnetic flux leakage barriers are integrated into the q-axis of the SFI-PM motors, allowing control of the flux leakage bypass via the q-axis current. Then, under low-speed and heavy-load conditions, minimal leakage flux occurs within the rotor. Conversely, at high speed and light load, significant leakage flux reduces the flux-weakening current, enhancing output torque and efficiency across a wide speed range. To further optimize efficiency and torque, a multi-objective genetic algorithm (MOGA) is employed. The performance of the proposed Controllable Flux-Leakage SFI-PM (CFL-SFI-PM) motor is compared with conventional SIPM and SFI-PM motors and validated through Finite Element Analysis (FEA). II. Research Method and Analysis Results A 5kW CFL-SFI-PM motor model is developed from a conventional SIPM motor (Fig. 1). The rotor is enhanced with alternating flux barriers and magnetic flux leakage barriers in the q-axis to boost flux intensity and control leakage via q-axis current. The performance is compared with conventional SIPM (Fig. 1(a)) and SFI-PM motors in [1] (Fig. 1(c)). Efficiency and torque are further optimized using a MOGA method. Key specifications are provided in Table 1. The proposed model achieves an output torque of 23 Nm, slightly higher than the SFI-PM motor but lower than the SIPM motor. However, it boasts a better constant power speed range (CPSR) (Figs. 2(b) ) and reduced high-speed iron loss, as shown in Fig. 3. Consequently, the efficiency map of the CFL-SFI-PM motor is improved (Fig. 3(c)). Detailed Finite Element Analysis (FEA) analysis and experiment will be reported in the whole paper.References: [1] Min-Fu Hsieh, Anh Thanh Huynh, Viet-Vu Do, David Gerada, Chris Gerada, “Design Optimization of Spoke-type Flux-intensifying PM Motor with Asymmetric Rotor Configuration for Improved Performance,” IEEE Transactions on Magnetics, Early Access, July 2024. DOI: 10.1109/TMAG.2024.3428416
I. Abstract This paper presents a novel approach for enhancing torque performance and reducing core loss in Spoke-type Flux-Intensifying Permanent Magnet (SFI-PM) motors using controllable magnetic flux leakage barriers. The SFI-PM motor design incorporates multiple flux barriers into a conventional Spoke-type Interior PM (SIPM) motor to increase d-axis inductance (Ld > Lq) and intensify magnetic flux density. However, this also reduces the output torque capacity compared to conventional SIPM motors. To mitigate this, magnetic flux leakage barriers are integrated into the q-axis of the SFI-PM motors, allowing control of the flux leakage bypass via the q-axis current. Then, under low-speed and heavy-load conditions, minimal leakage flux occurs within the rotor. Conversely, at high speed and light load, significant leakage flux reduces the flux-weakening current, enhancing output torque and efficiency across a wide speed range. To further optimize efficiency and torque, a multi-objective genetic algorithm (MOGA) is employed. The performance of the proposed Controllable Flux-Leakage SFI-PM (CFL-SFI-PM) motor is compared with conventional SIPM and SFI-PM motors and validated through Finite Element Analysis (FEA). II. Research Method and Analysis Results A 5kW CFL-SFI-PM motor model is developed from a conventional SIPM motor (Fig. 1). The rotor is enhanced with alternating flux barriers and magnetic flux leakage barriers in the q-axis to boost flux intensity and control leakage via q-axis current. The performance is compared with conventional SIPM (Fig. 1(a)) and SFI-PM motors in [1] (Fig. 1(c)). Efficiency and torque are further optimized using a MOGA method. Key specifications are provided in Table 1. The proposed model achieves an output torque of 23 Nm, slightly higher than the SFI-PM motor but lower than the SIPM motor. However, it boasts a better constant power speed range (CPSR) (Figs. 2(b) ) and reduced high-speed iron loss, as shown in Fig. 3. Consequently, the efficiency map of the CFL-SFI-PM motor is improved (Fig. 3(c)). Detailed Finite Element Analysis (FEA) analysis and experiment will be reported in the whole paper.References: [1] Min-Fu Hsieh, Anh Thanh Huynh, Viet-Vu Do, David Gerada, Chris Gerada, “Design Optimization of Spoke-type Flux-intensifying PM Motor with Asymmetric Rotor Configuration for Improved Performance,” IEEE Transactions on Magnetics, Early Access, July 2024. DOI: 10.1109/TMAG.2024.3428416