International Journal of Applied Electromagnetics and Mechanics - Volume Pre-press, issue Pre-press

Authors: Yan, Dong | Guo, Liyan | Shi, Tingna | Wang, Huimin | Yan, Yan | Xia, Changliang

Article Type: Research Article

Abstract: The split ratio is one of the most important design parameters of the machines and has a significant effect on the electromagnetic performance. Using the split ratio, this paper presents a performance analysis method for permanent magnet (PM)-assisted reluctance machine is presented. An accurate analytical model, which considers the saturation of outer iron ribs and the asymmetric saturation of rotor islands, is firstly proposed. In order to reduce the numbers of the adjustable structural parameters during the initial design process and ensure the independence among the parameters, a geometric structure corresponding to the split ratio is then established. The effectiveness …of the proposed analytical model based on the split ratio is verified by FEM, and applied to analyze the electromagnetic performance for the three-flux-barrier PM-assisted reluctance machines. On the basis of the analysis results, the design scheme corresponding to the optimal split ratio, which makes the machine obtain a higher efficiency and guarantees the PMs without irreversible demagnetization, is determined rapidly. Show more

Keywords: Permanent magnet (PM)-assisted reluctance machine, the gradient flux barrier, split ratio, analytical model

DOI: 10.3233/JAE-190104

Citation: International Journal of Applied Electromagnetics and Mechanics, vol. Pre-press, no. Pre-press, pp. 1-25, 2019

Authors: Yan, Xinxiao | Li, Yongjian | Cheng, Zhiguang | Zhang, Changgeng

Article Type: Research Article

Abstract: A 3-D coupled magneto-fluid-thermal model is established for temperature rise prediction in a ventilated dry-type transformer rated at 2500 kVA. In order to accurately estimate electromagnetic losses, a three-dimensional (3-D) transient finite element method considering the effect of eddy-current losses on the foil type windings is proposed. Besides, two orthogonal B -P loss curves are adopted to model the anisotropy of grain-oriented (GO) silicon steel. The non-uniform power losses of winding and core are mapped into the thermal field as heat sources. Moreover, the transformer structures such as the narrow struts, insulation barrier and clamps are considered to improve the …computational accuracy of air velocity and temperature distribution. At last, the test of temperature rise has been carried out to verify the proposed model. Show more

Keywords: Dry-type transformer, eddy currents, power losses, magnetic measurements

DOI: 10.3233/JAE-190054

Citation: International Journal of Applied Electromagnetics and Mechanics, vol. Pre-press, no. Pre-press, pp. 1-11, 2019

Authors: Sun, Hongyu | Wang, Shen | Huang, Songling | Wang, Qing | Zhao, Wei

Article Type: Research Article

Abstract: Electromagnetic ultrasonic testing, based on the propagation characteristics of the ultrasonic wave in the medium, is an effective technique for defect detection. The structural of the electromagnetic acoustic transducer (EMAT) determines the detection effect, which should be reasonably designed. We propose an improved unilateral point-focusing EMAT structure with curved coils in this manuscript. The 3D model of the designed EMAT is numerically simulated utilizing the finite element method, and the bilateral point-focusing EMAT is also studied for comparison. The simulation results of the magnetic field intensity and the distributions of the displacement are shown in the manuscript, which prove the …effectiveness of the improved unilateral point-focusing EMAT. Five impact parameters such as aperture angle, focal position, excitation current, lift-off distance, and coil winding number are investigated in detail. We verify the calculation results of the aperture angle and excitation current by the experiments. The conclusion shows that the focusing intensity of the improved unilateral point-focusing EMAT is relatively higher, and other factors also have a significant effect on the focal intensity. Show more

Keywords: Point focusing, electromagnetic acoustic transducer (EMAT), unilateral, bilateral, numerical simulation

DOI: 10.3233/JAE-190071

Citation: International Journal of Applied Electromagnetics and Mechanics, vol. Pre-press, no. Pre-press, pp. 1-18, 2019

Authors: Jiang, Jinbo | Yang, Linsen | Yang, Wen | Su, Yi | Liu, Chang | Qiu, Li | Chen, Long | Yu, Kun

Article Type: Research Article

Abstract: Coil inductance calculation is one of the difficulties in Tesla transformer design. The estimation formulas of the conical winding Tesla transformers with different structures are derived by the simplified equivalent of magnetic circuits, and the estimation results are quite different and inaccuracy. This paper provides an energy method based on the FEM (finite element method) to calculate the coil inductance for a double-core conical winding Tesla transformer. A two-dimensional FEM simulation model is established, the magnetic flux density and flux lines distribution have been analysis. And the primary and secondary inductances of the transformer are calculated. Compared the estimation formula …results with the FEM results, the results show that the error difference calculated by the formula estimation is about 3.61%, and the FEM error difference is about 0.4%. The calculation results of FEM are more accurate and convenient, and this method can provide reference for the design of conical winding Tesla transformers. Show more

Keywords: Tesla transformer, conical winding, inductance calculation, magnetic field distribution

DOI: 10.3233/JAE-190089

Citation: International Journal of Applied Electromagnetics and Mechanics, vol. Pre-press, no. Pre-press, pp. 1-9, 2019

Authors: Park, Eui-Jong | Jung, Sang-Yong | Kim, Yong-Jae

Article Type: Research Article

Abstract: The magnetic gears which can replace the mechanical gear system are actively studied recently. Improving the power density is growing importance because the characteristics that as gear ratio grows so power density decreases were observed. This paper analyzes the various characteristics (power density, efficiency, torque ripple, loss, and so on) according to the gear ratio in detail, and proposes a concept that high gear ratio by combining two low gear ratio. A target gear ratio is 10 to 1 and application is 1 kW wind turbine. To obtain the optimal combination, 30 gear ratios were considered, and initial design process was …shown about this concept to propose the direction of improving the power density. All models were analyzed with 2D-FEM by numerical analysis. Show more

Keywords: Finite element analysis, magnetic gears, power density, high gear ratio

DOI: 10.3233/JAE-190097

Citation: International Journal of Applied Electromagnetics and Mechanics, vol. Pre-press, no. Pre-press, pp. 1-10, 2019

Authors: Toghraie, Davood

Article Type: Research Article

Abstract: Optimization of the cooling processes by fluids in many industries such as power generation, transportation, machining, and electronics is very important. Heat transfer equipment to achieve higher efficiency, need to downsizing of the equipment, and increase the heat transfer rate per unit of surface. The aim of this paper is to investigate the effect of MHD mixed convection flow of Cu-water nanofluid in a trapezoidal lid-driven cavity with different tilt angles in a range of 0° to 60°. The cavity consists of the non-uniformly heated bottom wall, insulated top wall, and isothermal sidewalls. The governing equations of the flow by …using the finite volume method and the SIMPLE algorithm have been numerically solved. The studies for the wide range of Richardson number (Ri) from 0.01 to 10, volume fraction of nanoparticles from 0.1% to 4% and Hartman number (Ha) from 0 to 40 in the steady-state have been done. Result in the form of streamline, vorticity and temperature contours for three geometry, local Nusselt number graphs for non-uniformly heated bottom surface and velocity profile on the vertical centerline of the cavity in different geometry have been investigated. The results show that the average Nusselt number on the non-uniformly heated bottom wall is dependent on dimensionless parameters and tilt angles. Also, applying a magnetic field, reduce the velocity profile changes, and using nanoparticles will cause increasing the Nusselt number. Show more

Keywords: Mixed convection, magneto-hydrodynamic, trapezoidal cavity, non-uniformly heated surface

DOI: 10.3233/JAE-190123

Citation: International Journal of Applied Electromagnetics and Mechanics, vol. Pre-press, no. Pre-press, pp. 1-28, 2019