An Enhanced Axial-flux Magnetic-geared Machine with Dual-winding Design for Electric Vehicle Applications

Axial-flux magnetic-geared machine(MGM) is a promising solution for electric vehicle applications for combining the virtues of both axial-flux electric machine and magnetic gear. However, generalized MGMs are limited by the torque density issue, accordingly inapplicable to industrial applications. To solve the abovementioned issue, an improved axial-flux magnetic-geared machine with a dual-winding design is proposed. The key merit of the proposed design is to achieve enhanced torque performance and space utilization with the proposed design, which installs a set of auxiliary winding between modulation rings. With the proposed design, overload protection capability, and fault-tolerant capability can be also achieved, for the proposed machine can work with either the excitation of armature windings or auxiliary windings. The pole-pair, slot combination, and parametric design is studied and optimized by the 3d finite-element method and designed C++ optimization software. Electromagnetic analysis and performance comparison indicate that the proposed machine can achieve a torque enhancement of 68.6% compared to the comparison machine.

Message from Editors

THE rapid growth of new energy vehicles is accelerating the low-carbon transition in the global transportation sector. According to the international energy agency report, more than 10 million electric vehicles(EVs) including pure electric and hybrid models were sold worldwide in 2022, which means that the global share of electric vehicles in the overall automotive market has risen from less than 5% in 2020 to 14% in 2022.

Design and Comparison of Electrically Excited Double Rotor Flux Switching Motor Drive Systems for Automotive Applications

This paper presents a cost-effective driving system for automotive applications based on a double rotor electrically excited flux switching machine(FSM).Benefiting from a double rotor topology,this FSM can realize a drum winding design and thus winding ends are effectively shorten and the copper loss is mitigated.The machine structure,operation principle and design consideration are studied and further verified by time-stepping finite element method.Moreover,three topologies of drive circuit for the proposed FSM are introduced.By using electromagnetic-circuit coupling simulation,a comparison between three different three drive systems are performed,with focus on the system cost and overall electromagnetic performance,especially the effect of current control and torque ripple.A prototype is established and tested.Relevant experimental results verify the effectiveness of the proposed new FSM drive system.

Pole-wrapped Negative Equivalent Magnetic Reluctance Structure-based Transformer for Line-frequency Isolation-dependent Applications

Isolation-dependent applications require a transformer with high efficiency,low magnetizing current,and anti-DC bias capability.The kilohertz planar negative magnetic reluctance structure is used to achieve this target with its magnetic-frequency variation property,which reduces the magnetic reluctance of the fundamental component.However,this design cannot be applied to low-frequency transformers owing to the high loss caused by its limited self-inductance and quality factor.To solve this problem,a pole-wrapped negative equivalent magnetic reluctance(PNEMR)structure is presented.The proposed design employed a copper-based PNEMR structure wrapped around the magnetic poles to enhance the fundamental flux and suppress the DC component of flux.Accordingly,the magnetizing current is reduced,and the isolation transformer is less susceptible to the DC bias.The proposed design can simultaneously improve the anti-DC magnetic bias capability,efficiency,and power factor of the transformers.To verify the effectiveness of the proposed design,a 10 kW C-core PNEMR structure-based transformer for isolation-dependent applications was constructed and compared to the generalized structures and transformers with planar negative magnetic reluctance structures.Results indicate that the PNEMR-based transformer can enhance the efficiency and power factor from 96.1%and 0.87 to 96.6%and 0.93,respectively,under full load conditions.

Design and Optimization of a Slot-PM-assisted Doubly-salient Machine Based on Saturation Assuaging

In this study,a novel slot PM-assisted doubly-salient machine(SPMA-DSM)is proposed based on saturation assuaging.In this machine,DC current is adopted as the excitation source.The permanent magnets assembled in slots are used to realize saturation assuaging,which can offer higher torque density and improved overload capability.Additionally,the torque density can be extended to wider scale before saturation.Multi-objective optimization based on differential evolution(DE)coupled with finite element method(FEM)is conducted to further improve the performance of the proposed machine.When compared to traditional flux-controllable machine,the PMAHEM exhibits the merits of:①higher torque density per PM volume,②lower torque ripple,and③wider flux controllable range.The simulation results indicate that the electromagnetic torque increases by more than 20%after the saturation assuaging design and optimization.

A Novel Stator and Rotor Dual PM Flux Modulated Machine

A novel structure of Veriner permanent magnet(VPM)machine is presented as an effective option for high torque density direct-driven applications.The key is to locate PMs on both sides of rotor and stator,and design the stator PMs as a cylinder shape,the rotation of which can be controlled by an external driven system.With this design,magnetic field in the airgap can be directly regulated by the rotation of stator PMs.The structure and operation principle are introduced and the performance is analyzed with time-stepping finite element method(FEM).Analysis results show that the novel structure has really high torque density and good field weakening performance.