PIER C | PIER Journals

2026-05-06

PIER C

Vol. 170, 49-56, 2026

doi:10.2528/PIERC26032105

download: 11

Analysis and Optimal Design of a Novel Permanent Magnet Fault-Tolerant Vernier Rim-Driven Motor with Inclined Modulation Tooth

Defeng Zhao, Jingwei Zhu, Yaqian Cai and Anni Wang

To address the trade-off between torque density and power factor in conventional permanent magnet vernier rim-driven motors under material cost constraints, this study proposes a novel permanent magnet fault-tolerant vernier rim-driven motor with an inclined modulation tooth (PMFTVRDM-IMT). Unlike the conventional straight-tooth configuration, the proposed design introduces an inclination angle to the modulation teeth, thereby altering the air-gap permeance distribution pathway while preserving both the permanent magnet volume and overall motor envelope. Through magnetic field harmonic analysis, the underlying mechanism for the synchronous improvement in the torque and power factor was revealed: the inclined modulation tooth structure enhances the effective working harmonics while suppressing the ineffective harmonic components. To further optimize the motor performance, a combined approach of single-parameter scanning and multi-objective optimization was adopted, and the resulting performance metrics, such as the output torque and power factor, were systematically validated using the finite element analysis (FEA). The results indicate that, with modifications only to the modulation tooth structure, the proposed motor design achieves an approximately 15% improvement in the power factor and a 2.5% increase in the torque density, thereby substantiating the feasibility and engineering value of the inclined modulation-tooth topology in mitigating the low power factor issue inherent to vernier machines.

Analysis and Optimal Design of a Novel Permanent Magnet Fault-Tolerant Vernier Rim-Driven Motor with Inclined Modulation Tooth

2026-05-05

PIER C

Vol. 170, 38-48, 2026

doi:10.2528/PIERC25123005

download: 56

A High-Power, Low-Loss Single-Channel X-Band Waveguide Rotary Joint for Radar Systems with Ultra-Low Amplitude and Phase Variation

İsmail Şişman, Emin Polat and Tugba Haykir Ergin

In this study, a high-performance wideband I-type rectangular waveguide rotary joint (RJ) has been meticulously designed, simulated, and experimentally verified for deployment in X-band radar systems operating within the 9-10 GHz frequency range. The proposed RJ achieves superior radio frequency (RF) characteristics, including an insertion loss of less than 0.1 dB and a return loss exceeding -30 dB, making it highly suitable for critical applications that require minimal signal degradation. Unlike conventional rigid waveguide systems that restrict mechanical movement, the developed RJ enables full 360° rotation with negligible variation in both amplitude and phase, thereby ensuring continuous, stable operation in dynamic environments such as mechanically rotating radar platforms. Notably, the design achieves an amplitude and phase wobble (WoW) of only 0.005 dB and a phase fluctuation within ±3.2°, meeting the stringent performance requirements of modern radar and satellite tracking systems. In addition to RF characterization, the rotary joint has been subjected to high-power RF breakdown analysis using particle-in-cell (PIC) simulations to evaluate its resilience under extreme operational stress. High-power robustness was numerically assessed using PIC simulations, indicating stable operation up to 2 kW CW and 30 kW pulsed under the simulated conditions, without breakdown signatures. This performance is further supported by optimized choke structures that minimize discontinuity-related mismatch at the mechanical interface between stationary and rotating sections. The results confirm that the developed rotary joint is not only electrically efficient and mechanically reliable but also capable of sustaining stable RF performance under high-power and rotational conditions, making it a promising candidate for next-generation radar front-ends and high-power satellite communication terminals.

A High-Power, Low-Loss Single-Channel X-Band Waveguide Rotary Joint for Radar Systems with Ultra-Low Amplitude and Phase Variation

2026-05-04

PIER C

Vol. 170, 28-37, 2026

doi:10.2528/PIERC26021205

download: 37

Design and Experiment of Compact Rotary MCR-WPT Coils at MHz Band

Kunming Chen, Yanhong Li, Caiyun Dai, Guo-Qiang Liu, Chao Zhang and Guanchen Li

Aiming to meet the contactless power supply requirements of rotary equipment, this study investigates the coil design and performance of a small resonator for magnetically coupled resonant wireless power transfer (MCR-WPT) systems operating in the MHz band. Based on the series-series (S-S) WPT circuit topology, the influence of coil inductance on the transmission characteristics of the system was analyzed. By combining the inductance calculation formula for planar spiral coils, the geometric parameters of the coil were designed with the objectives of load power (P_RL) > 40 W and transmission efficiency (η_T) > 90%. The rationality of the designed parameters was verified by field-circuit coupled simulation, and the influence laws of the driving frequency and transmission distance on transmission characteristics were also analyzed. The coils were wound according to the designed parameters, and both static and rotary dynamic power transfer experiments were conducted. The simulation results show that the designed coil achieves a transmission efficiency of 94.783% at a transmission distance of 50 mm in the 1 MHz, which meets the preset design objectives. The results of the static experiment and the dynamic rotation experiment show that the overall operating efficiency of the system (η_dc-dc) is 84%. This study demonstrates the feasibility of the proposed coil design method, and the designed small coil can realize high-efficiency and stable wireless power transfer under rotary working conditions. The research findings provide a reference for the coil design and engineering application of rotary MCR-WPT systems in the MHz band and possess practical value for the contactless power supply of sensors in rotary electrical equipment operating in confined spaces.

Design and Experiment of Compact Rotary MCR-WPT Coils at MHz Band

2026-05-04

PIER C

Vol. 170, 15-27, 2026

doi:10.2528/PIERC26030706

download: 21

A Deadbeat Fault-Tolerant Control Strategy for PMSM Demagnetization Faults Based on an Improved Flux Linkage Observer

Yang Zhang, Wancheng Xie, Yang Gao, Jiahao Zhang and Moutao Li

To address issues such as reduced motor output performance and diminished load capacity caused by permanent magnet demagnetization in Permanent Magnet Synchronous Motor (PMSM), a super-twisting algorithm-based fault-tolerant predictive control strategy for demagnetization faults in PMSM is proposed. First, the improved super-twisting non-singular fast terminal sliding mode observer (IST-NFTSMO) is constructed to accurately observe the flux linkage and predict the current at the next moment. Based on the observed values, a deadbeat fault-tolerant predictive control (DFTPC) algorithm is built to compensate for the torque loss due to permanent magnet demagnetization, thereby achieving fault-tolerant control of the system. Second, a sliding mode controller based on a novel reaching law is designed, thereby overcoming the shortcomings of traditional control strategies in PMSM vector control systems, such as poor anti-interference capability and slow response speed. Finally, experimental results demonstrate that after a demagnetization fault occurs in the PMSM, the proposed method effectively improves the fault tolerance capability of the PMSM system while ensuring the dynamic response speed of the control system, thereby endowing the system with enhanced stability and robustness.

A Deadbeat Fault-Tolerant Control Strategy for PMSM Demagnetization Faults Based on an Improved Flux Linkage Observer

2026-05-03

PIER C

Vol. 170, 1-14, 2026

doi:10.2528/PIERC25120601

download: 50

Design Optimization of a Permanent Magnet Biased Fault Current Limiter via Pattern Search for High Efficiency and Reduced Material Use

Tirtha Sankar Daphadar, Tapan Santra and Amalendu Bikash Choudhury

This paper presents a useful design optimization methodology for a permanent-magnet-biased fault current limiter (PMFCL), aiming to achieve good fault current limiting performance with small magnetic materials and their losses. A physics-based magnetic circuit modelling approach is developed to update the nonlinear core saturation and permanent magnet biasing, enabling fast and reliable analysis of candidate designs. Additionally, a weighted multi-objective formulation is adopted to balance fault current mitigation, material volume, and loss minimization. The resulting optimization problem is solved by means of a deterministic pattern search approach, which enables efficient design space exploration without access to gradient information. The optimized configurations are validated using the finite-element simulations, and the robustness of the configurations under practical operating conditions is analyzed. The obtained results show a significant reduction of the magnetic material volume with the optimized PMFCL without compromising and, in certain cases, with an improvement of the function of fault current limiting against a baseline design. The research identifies technical configurations of design that are practical for real-world deployment. The combination of reduced material usage, passive operation, and better energy efficiency means the proposed PMFCL represents a reliable and sustainable solution for better protection of modern power systems, especially in areas where power systems are cost-sensitive and infrastructure-limited.