International Journal of Applied Electromagnetics and Mechanics - Volume 70, issue 1

Authors: Jin, Chaowu | Su, Hao | Dong, Yue | Zhou, Jin | Xu, Yuanping | Yan, Xu

Article Type: Research Article

Abstract: When the magnetic bearing rotor is working, the iron loss concentration phenomenon may occur on the rotor journal, which will cause the temperature gradient on the rotor journal and thermal unbalance. In order to study the iron loss concentration phenomenon, a multi-physics simulation method considering the magnetic-thermal coupling is proposed. Using ANSYS Maxwell for modeling and finite element analysis to obtain the causes of iron loss concentration in magnetic bearing and the influence of different parameters on the size and distribution of iron loss; using COMSOL for magnetic-thermal coupling in magnetic bearing to obtain the influence of iron loss concentration …on temperature distribution. The simulation results show that: because of the initial disturbance, the control effect of the magnetic bearing makes the magnetic field distribution on the circumference of the rotor journal uneven, resulting in the phenomenon of iron loss concentration; control current and bias current have significant influence on iron loss distribution, while bias current and speed have a significant influence on iron loss value; iron loss concentration will result in a temperature gradient on the rotor surface. The magnetic-thermal coupling finite element analysis is verified by the temperature rise detection experiment. It provides a theoretical basis and reference for the loss and thermal unbalance of magnetic bearing. Show more

Keywords: Iron loss, magnetic-thermal coupling, magnetic bearing, temperature gradient, thermal unbalance

DOI: 10.3233/JAE-220011

Citation: International Journal of Applied Electromagnetics and Mechanics, vol. 70, no. 1, pp. 1-20, 2022

Authors: Fejérvári, Lívia | Bilicz, Sándor | Gyimóthy, Szabolcs | Pávó, József | Varga, Gábor | Várallyay, Zoltán | Yamada, Yusuke | Shimura, Takahiro | Orito, Hiroshi | Azuma, Yoshifumi

Article Type: Research Article

Abstract: Litz wires consist of many individual, isolated conductor strands. Certain litz wires are fabricated by simply twisting the bundle of strands, hence a wire pitch is realized. In this paper, the ac resistance of coils made of such twisted litz wire are calculated by combining two-dimensional finite element simulation and circuit laws. In so doing, the inherently three-dimensional problem can be solved at much lower computational cost. Results are presented for the current distribution, and for the alternating current resistance of coils, validated against measured data.

Keywords: Litz wire, finite element, ac resistance, joule loss, skin effect, proximity effect

DOI: 10.3233/JAE-210205

Citation: International Journal of Applied Electromagnetics and Mechanics, vol. 70, no. 1, pp. 21-31, 2022

Authors: Lin, Qinghua

Article Type: Research Article

Abstract: The purpose of this study is to explore the causes leading to the rail gouging from the perspective of armature dynamics. The axial, lateral motion and rotation equations were derived, and a set of calculations according to the experimental conditions were conducted. The calculated in-bore processes of the armature exhibit apparent non-linear features. Especially with the contact interface of armature being worn rapidly, the armature gradually leans toward one side of the bore, and forms a trend of oblique impact to the rail that may lead to the gouging. This study offered an insight on the transient processes of armature …in bore, and helped to better understand the gouging failure mechanism. Show more

Keywords: Electromagnetic railgun, hypervelocity gouging, wear, nonlinear dynamics

DOI: 10.3233/JAE-210133

Citation: International Journal of Applied Electromagnetics and Mechanics, vol. 70, no. 1, pp. 33-54, 2022

Authors: Ai, Mengmeng | Shan, Yi

Article Type: Research Article

Abstract: With the rapid development of UHV power transmission and transformation project in our country, the gradually increasing electromagnetic capacity and electromagnetic loads of power transformers causes serious heating of the transformers. Therefore, it is particularly important to accurately calculate its temperature rise. Based on field-circuit coupling method, this paper took a 240000 KVA, 330 KV power transformer as the research object to calculate the whole temperature rise and heat transfer characteristics. Firstly, the average velocity of fluid was gotten by three-dimensional flow field of transformer which is calculated by establishing thermal network model of the transformer, phase winding and related structures. And …then substitute it into thermal network model. The whole average temperature and temperature rise was gotten by using first law of thermodinamics and after the iteration. And according to the temperature rise test, this paper comprised and analyzed the computed results of thermal network and numerical analysis. Results showed that the error of the thermal network model was within the scope of the permit, and it was simple and quick. The method can provide basis for the future heat transfer research and temperature rise prediction of transformer. Show more

Keywords: Oil-immersed transformer, field-circuit coupling, thermal networks, temperature rise prediction

DOI: 10.3233/JAE-210157

Citation: International Journal of Applied Electromagnetics and Mechanics, vol. 70, no. 1, pp. 55-72, 2022

Authors: Tekgun, Didem | Alan, Irfan

Article Type: Research Article

Abstract: In this paper, a 2 pole, 4 kW, 6 inches diameter line start synchronous reluctance machine (LS-SynRM) as a submersible water pump motor is designed and optimized with a new oval shaft structure. The aim is to improve the machine performance by widening the flux path on the rotor via narrowing down the shaft on the q -axis. This way a wider d -axis flux path is obtained, and accordingly, the d -axis inductance, the saliency ratio L d ∕L q , and the inductance difference L d –L q are increased. First, a set of …structural analyses is carried out on a 7-flux barrier rotor in 3 stages: modal, harmonic, and static structural analyses. According to analysis results, the safe limit for the shaft size reduction is determined as 8 mm to avoid excessive deformations and undesired vibrations due to resonance. Later, the machine is optimized using Multi-Objective Differential Evolution (MODE) algorithm with a narrower shaft. The quality of the Pareto front solutions shows that the oval shaft machine is superior to the circular shaft machine in terms of efficiency, motor mass, and torque ripple. The maximum recorded efficiency improvement for the same size LS-SynRM is 4 points and the same size commercial induction machine is around 20 points. Show more

Keywords: Synchronous reluctance machine, oval shaft, multi-objective optimization, line start

DOI: 10.3233/JAE-220026

Citation: International Journal of Applied Electromagnetics and Mechanics, vol. 70, no. 1, pp. 73-93, 2022

Authors: Tian, Lisi | Xu, Biyue | Yu, Qiang | Tang, Chaoquan

Article Type: Research Article

Abstract: This paper proposes a novel electromagnetic modelling method, with experimental study of the magnetic can-shield effect, based on a novel canned switched reluctance machine. Such model considers the characteristic electromagnetic coupling relation between magnetic flux and eddy current on cans, with harmonic analysis by analytical calculation in vector form. The model is structured with multiple concentrated layers in cylindrical coordinate and the main modeling process includes domain solution of the magnetic field, and an energy vector deduction for loss and energy. Comparative measurement with an indirect method demonstrates the electromagnetic features by the use of cans and meanwhile verifies the …analytical model. Show more

Keywords: Canned machine, can shields, switched reluctance machine, can loss, electromagnetic coupling

DOI: 10.3233/JAE-210143

Citation: International Journal of Applied Electromagnetics and Mechanics, vol. 70, no. 1, pp. 95-108, 2022