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Session Overview
PA-A2: Multi-Physics and Coupled Problems
Tuesday, 16/Jul/2019:
2:20pm - 4:10pm

Session Chair: Xavier Mininger
Session Chair: Yanhui Gao
Location: Patio 44-55

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Numerical Code for Modelling Electro-thermal Effects of Lightning Strike on Anisotropic Composites

Diego Audifredd1, Lucas Travassos1, Talita Possamai1, Nathan Ida2

1Universidade Federal de Santa Catarina, Brazil; 2The University of Akron

The present paper aims to model some of the effects of lightning strikes on a composite material modeled through numerical simulation. The simulation is based on the finite-difference time-domain (FDTD) method which allows the analysis of the electromagnetic and thermal effects related to the problem. The thermal distribution is evaluated based on results obtained from the electromagnetic simulation. Results show the current density distribution on a CFRP plate varying with the anisotropy characteristics of the material. From the thermal simulation it is shown that the lightning strike can cause a rise in the composite temperature over 900° with only 1 μs of interaction with the material for a current of 200kA.

Analysis of DC Bias Effects on Core Vibration of UHV Transformer Based on SRVCM

Bing Li, Mingyang Li, Ke Liu, Zezhong Wang

NCEPU, People's Republic of China

This paper analyzes the relationship between vibration characteristics of ultra-high voltage (UHV) transformer and DC bias current. The main source of UHV transformer’s no-load vibration is the magneto-strictive vibration of the magnetic core. However, unlike the small power transformer, the characteristic of large inductance to small resistance of UHV transformer which can easily lead to not only a long transient process but also the inundation of the small DC voltage relative to the 1000 kV AC voltage during the iterative calculation. Thereby, a fast solution called series resistance and voltage compensation method (SRVCM) is utilized to make the simulation reach the steady state quickly. The correctness of the method is verified by comparing the value of DC bias current and DC component of excitation current. By means of SRVCM, the vibration displacement, acceleration and its harmonics under different DC bias are calculated by a weak magneto-mechanical coupling model.

A Novel Approach to Investigate the Vibration and Noise in Power Transformers

Bo Zhang, Ning Yan, Shaohua Ma

Shenyang University of Technology, China, People's Republic of

The noise problem caused by electromagnetic vibration is the hot spot of transformer electromagnetic research. In the three-phase dry type transformer, the core and several windings produce electromagnetic vibration simultaneously. The sound field distribution of the transformer is changed. This paper presents a novel method of electromagnetic - structure - acoustic field coupling analysis of transformer. A coupled acoustic radiation calculation model is established, which considers the vibration-acoustic coupling of multiple structures. According to the electromagnetic vibration characteristics of transformer, the acoustic radiation and scattering wave equation of transformer is established. The analytic function of sound pressure is given. Finite element calculation of an amorphous alloy transformer is carried out. The natural vibration characteristics of the winding under coupling action and the acoustic pressure of the far field and the radiative sound pressure at different frequencies are compared.

Vibration Characteristic Analysis of Laminated Core under DC Bias by Using Coupled Magneto-Mechanical Model in Frequency Domain

Xiaojun Zhao1, Yutong Du1, Zhenbin Du2, Junwei Lu3, Zhiguang Cheng2

1North China Electric Power University, China, People's Republic of; 2Institute of Power Transmission and Transformation Technology, China, People's Republic of; 3Griffith University, Australia

In order to investigate the influence of Maxwell force and magnetostrictive effect on the vibration characteristic of iron core under DC bias, a coupled magneto-mechanical model is established. The harmonic balance finite element method is used to calculate the magnetic and mechanical field, and the magnetic vector potential and displacements are solved in the frequency domain. Experiment is carried out on twin laminated core models to measure the magnetic field and vibration under different magnetizations. The proposed method is verified by comparing the computational results with the measured ones based on the two different model.

A Study on EV Drive Efficiency of Traction Motor Considering Welding Effect on Laminated Magnetic Core

Hokyung Shim

POSCO (Pohang Steel Company), Korea, Republic of (South Korea)

This paper presents a study on drive efficiency of an electric vehicle (EV) powered by a traction motor considering tungsten inert gas (TIG) welding effect on laminated magnetic core as a fastening process. An equivalent circuit was derived to take magnetic properties (polarization, additional core loss) due to welding into account for motor performance based on finite element analysis. An In-house software was developed to predict the driving performance of the EV. It shows the driving mileage per battery charge, the required power of the traction motor, and the operation points on a torque-speed map when drive cycles are given. The driving performance is calculated from the battery capacity, vehicle specification, and efficiency map of the traction motor computed in advance. As a result, the 8 passes welded on laminated stator core is able to weaken the drive efficiency by 1.13-1.78 km. It shows that motor engineers need to optimize the core fastening technologies on the lamination & stacking process since additional adoption of battery package to extend 2km costs 60~70 USD.

Application of the Fast Micromagnetic Simulation to Thin Spintronic devices

Tadashi Ataka1, Akihiro Ida2, Atsushi Furuya1, Koichi Shimizu1, Jun Fujisaki1, Tomohiro Tanaka1, Hirotaka Oshima3

1Fujitsu Limited, Kawasaki, Kanagawa, Japan; 2Information technology center, The University of Tokyo, Bunkyo-ku, Tokyo, Japan; 3Fujitsu Laboratories Limited, Atsugi, Kanagawa, Japan

This paper examines the fast method of micromagnetic simulation used to analyze thin spintronic devices. Micromagnetic simulation takes significant memory and time to calculate the dipole interaction that is considered to design devices. To overcome this hindrance, we apply hierarchical-matrices (H-matrices) to the calculation of the dipole interaction. There are several methods for calculating the dipole interaction. We focus on the method that directly calculates magnetic charge. Although this method costs squared-order calculation cost, most time-consuming part is matrix-vector product. This is the advantage of applying H-matrices. Finally, by performing numerical experiments, we demonstrate the advantages of our proposed method.

Vibration Analysis of Switched Reluctance Motor Considering Magnetostriction

Rongge Yan1,2, Xiaojie Zhang1,2, Junjie Chen1,2, Wenmei Huang1,2

1State Key Laboratory of Reliability and Intelligence of Electrical Equipment, Hebei University of Technology, Tianjin 300130, China; 2Key Laboratory of Electromagnetic Field and Electrical Apparatus Reliability of Hebei Province, Hebei University of Technology, Tianjin 300130, China

The vibration of switched reluctance motor (SRM) has been a key factor on its wide application. In order to study the vibration of SRM more accurately, the finite element model considering the actual working conditions is established in this paper. The magnetostrictive and magnetization properties of the non-oriented silicon steel sheet are measured at first. Then the magneto-mechanical coupled model considering magnetostriction for SRM vibration is established. From computation results, it can be seen that the vibration amplitude of SRM considering the magnetostrictive effect is higher than that without considering the magnetostrictive effect. Finally, the correctness of the numerical method is verified by experiments. The calculated vibration characteristics of SRM considering the magnetostrictive effect are more accurately compared with that without considering the magnetostrictive effect, which provides a theoretical basis for the study of vibration reduction of SRM.

An Improved Magnetic Equivalent Circuit Method for Dynamic Characteristics Calculation of Relay Considering Temperature

Wenying Yang, Jiuwei Guo, Yang Liu, Guofu Zhai

School of Electrial Engineering and Automation,Harbin Institute of Technology, China, People's Republic of

The analysis of dynamic characteristics is very significant for the design of a relay. Temperature is an important influencing the dynamic characteristics of a relay. To ensure the simulation efficiency and precision, and the influence of the temperature should be considered at the same time. An improved Magnetic Equivalent Circuit method considering temperature was proposed. Novel method combines on efficient Magnetic Equivalent Circuit (MEC) method and Finite Element (FE) method to establish a quick calculation model. In the method, a three dimensional compensation matrix was established to take into account the influence of the temperature on the coil resistance and soft magnetic material. The compensation matrix corrects the error due to leakage and saturation of MEC method under different temperature. And the building principle of the matrix was described in the paper. The dynamic characteristics of a typical DC high-power relay were simulated under different environment temperature to verify the correctness and efficiency of the method.

Calculation and Analysis of Temperature Rise for High Speed Amorphous Metal Interior Permanent-magnet Synchronous Motor Using Electromagnetic-thermal Bi-directional Coupling

Wenming Tong, Ruolan Sun, Shengnan Wu, Wenjie Li

Shenyang University of Technology, China, People's Republic of

In order to consider the influence of temperature-dependent characteristics of motor components on its loss in the calculation of temperature rise, this paper uses the calculation method of bi-directional coupling between electromagnetic field and temperature field to realize the feedback of the two fields information and carries out an iterative heat calculation. The 3-D transient finite-element method is used to investigate the electromagnetic loss of the motor. The calculated electromagnetic power loss is loaded into the temperature field and the materials property is in turn updated according to the temperature distribution. Taking a 15kW high speed amorphous alloy interior permanent-magnet synchronous motor as an example, the temperature rise of the motor is calculated by using the method with regard to the assembling gap. Finally, the temperature rise test of the motor was conducted. Compared with the calculation results of a one-way coupling method, the temperature rise results of bi-directional coupling field are more consistent with experiment, which verifies the effectiveness of the analyzing method proposed in improving the calculation accuracy of the motor temperature rise.

Electrohydrodynamic Analysis for Active Dielectrophoretic Nano-patterning Considering Particle-particle Interactions

MinHee Kim, Su-Hun Kim, Se-Hee Lee

Kyungpook national university, Korea, Republic of (South Korea)

The properties of nanoparticles depend on the size of particles, and studies have continued to use the unique properties of nanoparticles by mixing with composite materials for the development of new materials. For manipulating the motion of nanoparticles in the composite material, some techniques have been studied to locate the nanoparticles in the desired pattern. We, here, numerically analyzed the motion of nanoparticle in a channel with ring electrodes for designing the active nanoparticle patterning system adopting the dielectrophoresis (DEP) force. Ring electrodes are widely used to trap particles at desired locations. We derived the analytic solution of electric field and DEP force by revising the previous analytical solution, and compared with those from the numerical analysis. Especially, the DEP force derived from the analytical solution was compared with that obtained from the integrated value of the Maxwell stress tensor. The motion of the particles was analyzed by using the fully-coupled Finite Element Method considering the particle-particle interactions. These numerical results were affected by the size of the particles, applied voltage, and the velocity of injecting fluid. Our numerical model was verified successfully with the previous experimental results, and provides a fundamental understanding of particle trapping mechanism as well as a set of design rules for nanoparticle patterning system with the wide range of variables.

Energy-Based Modelling of Coupled Magneto-Thermal Transients in Superconducting Magnets

Michał Maciejewski1,2, Bernhard Auchmann1,3, Herbert De Gersem4

1CERN, Geneva, Switzerland; 2Łódź University of Technology, Łódź, Poland; 3PSI, Villigen, Switzerland, CERN, Geneva, Switzerland; 4Institut für Teilchenbeschleunigung und Elektromagnetische Felder (TEMF), TU Darmstadt

High-field superconducting accelerator magnets store several orders of MJ of energy in their magnetic field. This stored energy poses a risk in case the superconductor is locally heated above its phase transition to the normal-conducting state, i.e., in case of a quench. It is important to study the laws governing local and global variations to the energy state of a magnet in the electromagnetic and thermal domains. In this paper we present results of energy-based modeling by means of bond graphs and the theory of port-Hamiltonians in an effort to derive a full and consistent formulation of the quench problem in superconducting magnets. The model accounts for the loss of the superconducting state, eddy currents, persistent magnetization as well as the heat balance equation along with the magneto-caloric effect. This approach allows studying the inter-domain coupling, lumped and distributed ports as well as the computational causality.

Investigation of Electromagnetic Sources on Noise in a Permanent Magnet Synchronous Motor by Multi-Physical Analysis

Changhwan Kim1, Hongsik Hwang1, Jeonghyun Cho1, Yongha Choo1, Jungmyung Kim1, J.Y. Choi2, Cheewoo Lee1

1Pusan National University, Korea, Republic of (South Korea); 2Kyungsung University, Korea, Republic of (South Korea)

This paper analyzes and compares radial force and sound pressure level (SPL) by two key parameters, a frequency of inverter switching and applying of slits on a rotor. Switching frequency is varied from 2 kHz up to 6 kHz at the intervals of 1 kHz and the result of variation is not critical in terms of noise. The slit changes the radial force by influencing the harmonic component of the back electromotive force. However, the change does not always have a proportional relationship with SPL. Therefore, for the accurate noise analysis in the motor design process, the proposed multi-physical investigation between electrical and mechanical perspectives is required.

A Numerical Approach Including the Winding Impact for Electrical Machine Vibration Analysis

Limin Huang, Nicolas Galopin, Olivier Chadebec, Gerard Meunier, Bertrand Bannwarth

Université Grenoble-Alpes, France

A numerical approach for electrical machine vibration analysis is presented to study the winding influence on the vibration problem of electrical machines. A multiscale homogenization method is developed to model the mechanical response of the winding structure, which is hard to be finely modeled. Associated to a magneto-mechanical formulation, this approach permits to analyze the deformation and vibration of electrical devices. The computational approach has been applied to the magneto-mechanical analysis of a switched reluctance machine.

Identification of nonlinear magnetic damping in vibrating coupled structures

Elvio Bonisoli1, Cristiana Delprete1, Fabio Freschi2, Domenico Lisitano1, Maurizio Repetto2

1DIMEAS, Politecnico di Torino, Italy; 2DENERG, Politecnico di Torino, Italy

Magnetic damped vibrations are obtained by coupling a conductive structure with a magnetic field. The induced damping force characteristic depends upon displacement and velocity. When the magnetic field is generated by permanent magnets, a good model of the damping characteristic requires the estimation of the eddy currents induced in the conductive parts and subsequently of the resulting Lorentz force acting on them. This force is unfortunately nonlinear as its magnitude depends both on frequency and amplitude of oscillations. Considering by hypothesis a harmonic motion of the system, a simulation of the magneto-dynamic phenomenon is performed by means of a partial element equivalent circuit of the conductive parts. The force characteristic is then used to fit a quadratic dependence of damping coefficient on the oscillation amplitude values. Results obtained by simulations are validated versus experimental measurements on a three degrees of freedom structure.

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