International Journal of Applied Electromagnetics and Mechanics - Volume 75, issue 3

Authors: Chen, Chen | Zhang, Wenfeng

Article Type: Research Article

Abstract: The optimized design of a new high-temperature superconducting rotating pole machine is presented. Its main structural feature is the use of a double stator core which separates the synchronous machine pole shoe from the pole body to rotate separately as the machine rotor, allowing the superconducting coil to operate in a stationary state. The inner stator core, the stationary dewar and the rotor core together form the excitation system of the machine. The excitation coil windings adopt a rectangular cross-section, with flux divertor strategically placed between the high-temperature superconducting coils. This configuration aims to modulate the background magnetic field, specifically …reducing the perpendicular magnetic field component. This mitigation minimizes the impact of ambient magnetic fields on the superconducting coil’s current carrying capacity, ensuring an optimized magnetic field environment for its operation. Through the integration of these modifications, the technical and economic parameters of the enhanced high-temperature superconducting machine have been significantly improved. The optimization of design, coupled with detailed calculations of the 3D electromagnetic field, was achieved utilizing the commercial software Ansys EM module. Show more

Keywords: YBCO high-temperature superconducting strips, critical current, superconducting rotating machine, optimized design, flux divertor

DOI: 10.3233/JAE-230085

Citation: International Journal of Applied Electromagnetics and Mechanics, vol. 75, no. 3, pp. 223-238, 2024

Authors: Wang, Huimin | Guan, Peijun | Xu, Jiacheng | Guo, Liyan

Article Type: Research Article

Abstract: Compared with double-winding bearingless permanent magnet synchronous motor, single-winding bearingless permanent magnet synchronous motor (SBPMSM) has the advantages of low copper loss and low failure rate. However, if the slot-pole combination of SBPMSM is not reasonably selected, the winding coefficient will be reduced, and even many advantages of the single-winding structure will be offset. In this paper, a single-winding design method based on magnetomotive force (MMF) star diagram is proposed, which can ensure high winding coefficient. The design process of the proposed single winding structure is introduced. This method can match the appropriate number of stator slots according to the …number of rotor poles, and the winding phase separation design can be realized by reversing the slot number transposition. The mathematical models of the suspension force and torque of the bearingless permanent magnet synchronous motor are derived considering the magnetic field harmonics, and the 6-slot/2-pole SBPMSM and 18-slot/8-pole SBPMSM are taken as examples to analyze the magnetic field. The finite element simulation models of 6-slot/2-pole SBPMSM and 18-slot/8-pole SBPMSM are built and analyzed. Through the analysis of electromagnetic torque, suspension force and air-gap magnetic field under different magnetic fields, the general rules of main torque fluctuation and suspension force fluctuation are summarized. Show more

Keywords: Single-winding bearingless permanent magnet synchronous motor (SBPMSM), harmonic analysis, torque fluctuation, suspension force fluctuation, finite element simulation

DOI: 10.3233/JAE-230045

Citation: International Journal of Applied Electromagnetics and Mechanics, vol. 75, no. 3, pp. 239-259, 2024

Authors: Lv, Pin | Wang, Kaixuan | Su, Xunwen | Zhai, Yuelin | Cheng, Lushuai | Wang, Haoming

Article Type: Research Article

Abstract: Because of the complex and frequent multi-operation conditions of pumped storage machine and the difficulty of its numerical analysis, an optimized network parameter method (ONPM) is given to identify the second harmonic electromagnetic torque of large salient-pole generators. Different from the former research which only considers the positive and negative sequence components, the second harmonic electromagnetic torque of pumped storage machine under power generation state is identified in neutral point grounded system, which are displayed by the lumped parameters. Then, in order to test the validity of the theoretical analysis among power generation salient-pole generators, the finite element model of …300 MVA pumped storage machine under power generation is established. Through the comparison and analysis of the finite element result data with the actual experimental data in the steady state of no-load test and short-circuit test, the correctness of the finite element model is completely verified. Finally, in the case of small current asymmetry and large current asymmetry, the second harmonic electromagnetic torques obtained by ONPM and finite element method (FEM) are found respectively, and their relative errors are elaborately displayed. The results display that ONPM can accurately identify the electromagnetic torque parameters which indicate the specific operation and fault state of pumped storage machine under power generation state. This fault parameter identification has practical significance for monitoring and improving the operation state and stability of large salient-pole generator. Show more

Keywords: Electromagnetic torque, fault parameter identification, finite element method (FEM), neutral point grounded system, optimized network parameter method (ONPM), pumped storage machine under power generation state

DOI: 10.3233/JAE-220267

Citation: International Journal of Applied Electromagnetics and Mechanics, vol. 75, no. 3, pp. 261-273, 2024

Authors: Zhu, Zichong | Ge, Wenjie | Deng, Jun | Dong, Jianning

Article Type: Research Article

Abstract: The slender shape of the driving machine leads to a low rigidity and large axial thermal elongation of the motorized spindle, which deteriorates the machining precision. To solve these problems and pursue a more compact size, this paper investigates the feasibility of using a tooth-coil permanent magnet synchronous machine in a high-speed spindle, replacing the original motor that has the conventional distributed winding. Comprehensive performance and behavior of machines with distributed and tooth-coil windings are comparatively analyzed, in terms of the essential torque ripples, winding inductances, electromagnetic losses, rotor integrity, and heat dissipation of the spindle. Thorough numerical simulation results …indicate that the newly designed tooth-coil winding solution shows significant advantages over the original design, regarding high rotor rigidity, low torque ripples, reduced electromagnetic losses, and reduced shaft thermal elongation. Prototypes and test setups for the high-speed tooth-coil machine are built, where preliminary measurements are carried out to validate the analysis results and system design. Show more

Keywords: Motorized spindle, electromagnetic loss, tooth-coil winding, permanent magnet synchronous machine, thermal elongation

DOI: 10.3233/JAE-230006

Citation: International Journal of Applied Electromagnetics and Mechanics, vol. 75, no. 3, pp. 275-295, 2024

Authors: Bao, Guangqing | Chang, Yong | Zhang, Anan

Article Type: Research Article

Abstract: This work aims to provide a unique analytical model designed for calculating the magnetic field of a surface-mounted permanent magnet Vernier motor (SPMVM). The model is created utilizing the separation variable method to solve Laplace or Poisson equations of the vector magnetic potential in a quasi-Cartesian coordinate system subdomain model. The theoretical justifications for the final analytical equations of electromagnetic torque, no-load back-EMF, stator inductance, and magnetic flux density distribution are given in detail. Then the solution of the equation is expressed in the form of a hyperbolic function. Furthermore, the improved analytical method in the study is generic and …can be applied to estimating the parameters of machines with different design concepts. Finally, FEM is employed as the reference for comparison between other models. Compared to the original subdomain model, the calculation results of the improved analytical model are more time-efficient and closer to those of FEM. In addition, the improved analytical method can reduce the dimension of the coefficient matrix and improve the calculation speed. The SPMVM prototype is then built to demonstrate the validity and feasibility of the improved subdomain method and serves as a guide for future SPMVM development. Show more

Keywords: Surface-mounted permanent magnet Vernier motor, magnetic vector potential, subdomain analytical model, hyperbolic function, quasi-Cartesian coordinate system

DOI: 10.3233/JAE-230062

Citation: International Journal of Applied Electromagnetics and Mechanics, vol. 75, no. 3, pp. 297-317, 2024

Authors: Chen, Tianyuan | Zhao, Zhigang | Ming, Lei | Zhang, Shi | Ge, Yajie | Wang, Huai

Article Type: Review Article

Abstract: Accurate calculation of power losses has always been important for the design and optimization of magnetic components consisting of windings and magnetic cores, such as inductors and transformers. Focusing on windings, litz wire outperforms its counterparts in terms of eddy current losses, making it particularly suitable for high-frequency (HF) applications. The power loss calculation of litz wire is however challenging due to its complex structure of thin strands twisted in multiple levels. This article therefore aims to review various kinds of litz wire power loss calculation methods from analytical methods, numerical methods to coupling ones. In addition to, the principles …and applications of each method, their inherent correlation and differences are also highlighted in this article. On this basis, a comprehensive review and comparison of different calculation methods of litz-wire power loss are provided. Finally, future challenges and directions are then summarized, whose ultimate goal is to calculate the power loss of litz wire accurately and efficiently. Show more

Keywords: Calculation methods, eddy current losses, high frequency, litz wires, overview

DOI: 10.3233/JAE-230171

Citation: International Journal of Applied Electromagnetics and Mechanics, vol. 75, no. 3, pp. 319-354, 2024