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Experimental Validation and Performance Analysis of a Dual-Airgap Permanent Magnet Vernier Machine with Yokeless Rotor for High-Speed Operation
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Keywords
Permanent Magnet
Vernier Machine
Dual-Airgap Machine
Yokeless Rotor
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Abstract
This study presents the experimental validation and performance analysis of a dual-airgap permanent magnet Vernier machine (PMVM) with a yokeless rotor, designed for high-speed applications. The proposed machine architecture integrates a dual-airgap configuration with a yokeless rotor to enhance torque density, reduce cogging torque, and achieve smooth high-speed operation. The theoretical framework underlying the design is grounded in the Vernier magnetic gearing principle, which enables high torque amplification from relatively low-speed rotating magnetic fields. A comprehensive methodology combining analytical modeling, finite element analysis (FEA), and experimental testing was employed to evaluate key performance indicators, including torque, back-EMF, efficiency, power factor, and harmonic behavior.
Experimental results demonstrate that the machine achieves a peak torque of 11.2 Nm at 1000 rpm, maintaining high torque consistency across an extended speed range up to 4500 rpm, while torque ripple remains below 5%. Back-EMF measurements reveal highly sinusoidal waveforms with a total harmonic distortion (THD) of less than 3.5%, indicating excellent voltage quality suitable for precision drives. The dual-airgap design, combined with fractional-slot concentrated windings, enables effective flux weakening, allowing high-speed operation without compromising torque output or efficiency. The yokeless rotor further reduces cogging and mechanical inertia, enhancing dynamic response and operational smoothness. Peak efficiency reaches 93.6% at 2500 rpm, and the power factor remains consistently above 0.92, confirming the machine’s suitability for industrial applications such as electric vehicle propulsion and wind energy conversion.
Critical analysis of the results highlights the advantages of the proposed topology compared to conventional single-airgap PMVMs and dual-stator Vernier machines. The findings indicate that the integration of dual-airgap architecture and yokeless rotor not only optimizes electromagnetic performance but also minimizes harmonic losses and mechanical stresses. Moreover, the experimental validation confirms close alignment between FEA predictions and measured performance, reinforcing the reliability of the proposed design methodology. The study provides a robust framework for high-speed, high-torque density PMVM development, offering practical insights into the implementation of advanced Vernier machines for industrial-scale applications.
In summary, the dual-airgap yokeless PMVM demonstrates a significant improvement in torque density, efficiency, and operational stability over conventional designs, establishing a foundation for future research in high-performance, variable-speed permanent magnet machines. The integration of advanced flux weakening strategies and dual-airgap configurations positions this machine as a highly viable candidate for next-generation high-speed electrical drives.
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References
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