Conference Agenda

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Session Overview
PC-M3: Multi-Physics and Coupled Problems
Thursday, 18/Jul/2019:
10:50am - 12:40pm

Session Chair: Stephan Russenschuck
Session Chair: Sheppard Salon
Location: Patio 44-55

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Calculation Method of Electric Field in Oil-paper Insulation Considering Space Charge

Yu Tian, Zhiye Du, Jiaxin Yuan, Zhifei Yang, Yiming Xie, Jiangjun Ruan

Wuhan University, School of Electrical Engineering and Automation, Wuhan, China

Based on the multi-physics field coupling calculation of electric field and fluid field, considering the influence of parameters such as diffusion coefficient, carrier mobility, trap capture coefficient and carrier recombination coefficient, a method for calculating the electric field in oil-paper insulation considering space charge is presented. Meanwhile, an oil-paper insulation interface charge measurement test platform was built, and the parameters in the simulation would be determined based on the test results. Finally, through the analysis of the simulation results, the distribution characteristics of the internal charge and electric field of the oil-paper insulation medium are obtained. It has certain guiding significance for the engineering preparation of the oil-paper insulation material and the optimization design of the insulation structure in the converter transformer.

Modeling of SiC MOSFET Behavior in Short-circuit Transient Considering Gate Leakage Current

Jingcun Liu, Guogang Zhang, Bixuan Wang, Wanping Li, Jianhua Wang

State Key Lab of Electrical Insulation and Power Equipment, Xi'an Jiaotong University

A set of physics-based semiconductor equations, considering the drift-diffusion model and self-heating effect, have been proposed and solved to study the transient behaviors of SiC MOSFETs under extreme conditions, including short-circuit and avalanche, by using the finite element method. Results from the electro-thermal numerical simulations shed light on the physics of failure by revealing current and temperature trajectories, hotspot location, and practical issues between two unmatched cells. Furthermore, this modeling method could also be applied to structure optimization to enhance the ruggedness of SiC MOSFETs.

Study on the relationship between contact resistance and sliding speed in DRM test of circuit breaker based on deformation simulation

Yakui Liu, Guogang Zhang, Hao Qin, Weipeng Liu, Jianhua Wang

State Key Lab of Electrical Insulation and Power Equipment, Xi'an Jiaotong University

Contact sets are the key components of the high voltage circuit breaker, however, the condition of contact sets is hard to measure because of the sealing of arc extinguishing chamber. By the help of flexible body model and deformation simulation, the contact vibration and transient deformation of a 252kV SF6 circuit breaker during DRM test can be simulated. In order to validate the simulation model, dynamic contact resistance has been measured under different speeds. Then the comparison shows how the contact force and deformation affect the contact resistance. Finally, It was verified that the contact deformation has important influence on dynamic contact resistance, and a mathematical model between deformation and resistance has been built.

Surrogate-based Acoustic Noise Prediction of Electric Motors

Issah Ibrahim, Rodrigo Silva, Hossain Mohammadi, Vahid Ghorbanian, David Lowther

McGill University, Canada

Acoustic behavior is a crucial performance index in the design and optimization of any electrical machine. However, due to the multiphysical nature of how noise is generated and emitted, its evaluation by finite-element means can be CPU-intensive, especially when ancillary components such as the housing, installation fixtures etc. are included in the computational model. Where the computational budget is limited, replacing FEA simulations with models that can produce estimates very quickly can be extremely helpful. This paper attempts to use surrogate models to reduce the computational burden in the prediction of acoustic noise. The procedure involves data acquisition and training. A data-driven FEA is initiated to explore the design space of the prototype model to generate samples for training the surrogate. Once the inner physics of the high-fidelity finite-element model is understood by the surrogate, it will be able to predict the sound pressure levels for varying inputs, i.e. design variables, operating conditions etc., with less computational power.

A Novel Promising Signal Prediction Method using Frequency Summation Strategy for Eddy Current Pulsed Thermography

Zongfei Tong1, Shejuan Xie1, Jie Han2, Pan Qi2, Houxiu Gao2, Cuixiang Pei1, Zhenmao Chen1

1State Key Laboratory for Strength and Vibration of Mechanical Structures, Shaanxi Engineering Research Center of Nondestructive Testing and Structural Integrity Evaluation, Xi'an Jiaotong University, Xi'an 710049, China; 2China Nuclear Power Operation Technology Co., Ltd., Wuhan, 430223, China

The numerical simulation of eddy current pulsed thermography (ECPT) signals can be divided into two parts, the computation of electromagnetic field and the simulation of thermal field. However, the high frequency (typically 50 – 500 kHz) and short excitation time of excitation current make it difficult to simulate ECPT signals through conventional time iteration method. In this paper, the frequency summation method based on the Fourier series method is proposed to simulate the process of ECPT. For the process of computation of electromagnetic field, the excitation current can be decomposed into a series harmonic sinusoidal waves of different frequencies according to fast Fourier transforms. The electromagnetic response signals, i.e., the thermal source of temperature field, could be solved by first calculating the response signals of multiple single-frequency sinusoidal excitation currents using reduced magnetic potential method (Ar method) and then superimposing them. The temperature field signals of ECPT can be also simulated using frequency summation method as a result of that the time evolution of the thermal source at all nodes is the same. Preliminary results using the novel proposed methods show that the frequency summation method can simulate ECPT signals accurately and efficiently.

The Dynamic Electrochemical Behavior Prediction of Metal Components in HVDC Water Cooling System

Bing Gao1, Fan Yang1, Tingting He1, Tao Wu1, Chao Liu2, Sheng Han1

1State Key Laboratory of Power Transmission Equipment & System Security and New Technology, School of Electrical Engineering, Chongqing University, Chongqing, 400044, China; 2College of power engineering, Chongqing University, Chongqing, 400044, China

Due to the voltage level difference among metal components in water cooling system of high voltage direct current (HVDC) system, the platinum electrodes are widely installed at the distributary pipes. However, over 66% faults of cooling system is contributed by sediment deposition on grading electrode. This paper proposed a method to predict the dynamic deposition behavior through the built electro-mass transfer-velocity coupling model. Additionally, the deformation feedback effect of sediment growth is also included. An experimental water-cooling setup was established, and simulated operation experiments were conducted to explore the deposition mechanism, then the mathematical coupling model is proposed to describe the corrosion and deposition characteristic. In addition, the arbitrary Lagrangian–Eulerian (ALE) deformation method is adopted to count the feedback effect of deposition product formation process on multiple physical field model. Results show that the proposed method can do well with the dynamic sediment deposition and radiator corrosion problem together.

Finite Element Analysis of Pulsed High-field Magnets with Precise Thermal and Structural Calculation

Siyuan Chen, Yiliang Lv, Tao Peng, Xiaoxiang Li, Liang Li

Wuhan National High Magnetic Field Center, Huazhong University of Science and Technology, Wuhan, 430074, China

The design of high performance pulsed magnets largely depends on the accurate thermal and structural analysis. This paper presents a 2-D simulation method of the multi-physics in pulsed high-field magnets on the basis of ANSYS. The magneto-resistance (MR) and the eddy-current are both considered in this method. The induced voltage is calculated separately by the magnetic penetration method to realize the coupling between the transient field in a coil and circuits, while the effect of MR are treated as an extra equivalent heat source. This method also has a great convergence when dealing with the contact problem in magnets. The model is verified by a 65 Tesla mono-coil magnet designed by Wuhan National High Field Center (WHMFC). The simulated waveform at the center has a good agreement with the experimental result. Simulations also show that considering the MR and the eddy-current, the max temperature rises about 75K at the end of an 80 milliseconds pulse. The results in different rise time and the axial compression which could only be calculated through this 2-D simulation method are discussed at last.

Multiphysics analysis to limit the frequency detuning of an RF cavity due to deviation in fabrication and coolant temperature variation

Gowrishankar Thalagavadi Hallilingaiah1, André Arnold2, Peter Michel1,2, Ursula van Rienen1,3

1University of Rostock, Rostock, Germany; 2Helmholtz-Zentrum, Dresden-Rossendorf, Dresden, Germany; 3Department of Life, Light & Matter, University of Rostock, Rostock, Germany

Multiphysics analysis of a radio frequency (RF) cavity is an essential step preceding to the cavity fabrication. An electro-thermo-mechanical analysis of the cavity is performed to aid the cavity fabrication and confirm the cooling mechanism. Critical cavity surfaces and dimensions affecting the resonant frequency are identified from the eigenmode sensitivity analysis. Further, a parametric study was carried out to find the frequency drift for different cavity thickness. Subsequently, temperature variation and frequency shift for various coolant temperature were computed through multiphysics simulations. Results from the present study contributed in classifying sensitive surfaces and dimensions which need higher dimensional tolerances during fabrication and also the ideal copper cavity thickness was determined to resist the frequency drift. Furthermore, the results confirmed the adequacy of the cooling mechanism being employed to remove the RF surface power loss.

Research on Fault Currents of Amorphous Alloy Transformer under Reclosing Conditions

Ning Yan, Wei Li, Zhiyuan Cai, Bo Zhang

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

Amorphous alloy (AA) transformer is widely used. It is very important to calculate the fault current of AA transformer for safe power supply. Under reclosing condition, temperature and saturation magnetization of AA transformers make a complicated change in fault currents on windings. A new method to analyze the fault current of AA transformer is presented in this paper. By introducing the hysteresis model with thermal correction, the reclosing current of AA transformer is calculated. To verify the feasibility and applicability of the proposed method, a destructive test on AA transformer is carried out and the process of fault impact is simulated.

Thermal-electric characteristics coupled with space charge of 2-D angle ring in ±500kV converter transformer

Cheng Chi1, Bing Gao1, Fan Yang1, Gang Liu2, Li Cheng1, Sheng Han1

1State Key Laboratory of Power Transmission Equipment & System Security and New Technology, Chongqing, China; 2Hebei Provincial Key Laboratory of Power Transmission Equipment Security Defense, North China Electric Power Uni-versity, Baoding, Hebei, China

This paper proposed a method to study electric field with space charge in angle ring, and the impacts of temperature and electric field are taken into consideration. The bipolar charge transportation and trap theory of space charge have been adopted to analyze space charge density. As angle ring at the end of winding stands higher temperature and stronger electric field, and thermal-electric coupling properties of space charge are obvious. Hence oil-paper insulation models are constructed to simulate the process of injection, migration and diffusion under non-uniform temperature and uneven electric filed. Results show that space charge has a significant effect in angle ring of converter transformer, which changes electric field distribution obviously, and the maximum field intensify can be up to 12.28kV/mm. Therefore, space charge with thermal-electric coupling properties should be considered in insulation design, or the distortion of electric filed would cause a serve operation hazard in insulation safety.

Vibration Analysis of Multi-stage Magnetic-valve Controlled Saturable Reactor

Rongge Yan1,2, Xiaojie Zhang1,2, Yuxiang Gao1,2, Jinlong An1,2, Zhiliang Qiu1,2, Shuai Zhang1,2

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 magnetic-valve controlled saturable reactor (MCSR) can smoothly adjust the reactive power based on the size of the power system, which has been widely used in power system and related industries. However, its DC and AC excitation working mode will lead to the magnetic saturation, which inevitably produces harmonics. Multi-stage MCSR (MMCSR) can effectively reduce the output harmonics, but no research on the vibration of MMCSR is done before. Based on the finite element method, this paper establishes an electromagnetic-mechanical coupled model considering the electromagnetic force and magnetostrictive effect of silicon steel to compute the vibration characteristics of MMCSR. The computation results show that the vibration stress and displacement increase obviously with the increase of magnetic-valve number and mainly concentrate in the magnetic-valve, the T-type contact surfaces, the lower iron yoke and saturation magnetic-valve on the side of the upper iron yoke. This paper provides a theoretical basis for the production of lower vibration MMCSR.

Electromagnetic Vibration Characteristic of High-Speed Permanent Magnet Synchronous Machines with Amorphous Metal Stator Cores

Shengnan Wu, Wenming Tong, Wenjie Li, Shenbo Yu, Renyuan Tang

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

This paper investigates the electromagnetic vibration characteristic of high-speed permanent magnet synchronous machines (HSPMSMs) with amorphous metal stator cores (AMSCs). An analytical model has been developed for analyzing the frequency spectrum of the radial force of HSPMSMs with sinusoidal supply and converter supply. The frequency spectrum of the radial force of a 15kW, 20000r/min HSPMSM with sinusoidal supply and converter supply is analyzed by the analytical model, and the results are compared with finite element analyses. The electromagnetic vibration of the HSPMSM with sinusoidal supply and converter supply is calculated, in which modified elasticity modulus parameters of AMSCs are used. At last, the vibration of the prototype under the no-load condition was tested.

An Efficient MPI-based Parallel Simulator for Streamer Discharges in 3-Dimensions Considering Photoionizations

Chijie Zhuang1, Bo Lin2, Rong Zeng1

1Tsinghua University, China, People's Republic of; 2National University of Singapore

We propose an efficient message passing interface (MPI) based parallel simulator for streamer discharges in three dimensions using the

fluid model considering the photoionization. A geometric multigrid preconditioned FGMRES solver is introduced to dramatically improve the efficiency of solving the Poisson equation and the photoionization terms. It is numerically shown that the proposed elliptic solver typically converges to a relative residual of $10^{-8}$ with only 2 to 4 iterations, and has a very good parallel efficiency. A double-headed streamer is studied considering the photoionization, using up to 2 billion mesh cells.

Computational and Experimental Study of a Novel Structure Reactor with Low Electromagnetic Vibration

Lihua Zhu1, Qianchao Wang1, Rui Sha1, Qingxin Yang1,2, Chang-seop Koh3

1Tianjin Polytechnic University, China, People's Republic of; 2Tianjin University of Technology, China, People's Republic of; 3Chungbuk National University, Cheongju, Korea

Magnetostriction effect is an inherent property of electrical steel sheet. Measurements showed that the direction magnetostriction of oriented and non-oriented electrical steels is mostly opposite. Therefore, a new structure to reduce the core vibration of the reactor is proposed and the method does not change the manufacturing process of the reactor. The new structure of reactor is implemented by alternating stacking of oriented and non-oriented cores. In order to verify the effect of the method on vibration reduction, the electromagnetic vibration, stress and displacement of the reactor are analyzed based on the magneto-elastic coupled analysis. The measured magnetization and magnetostriction data of the core were used during the numerical calculation. Prototypes of new and traditional structures with the same parameters were produced and related vibration were measured and analyzed. Both the calculation and experiment results showed that the vibration is weakened by the proposed structure. In a word, the new method proposed in this paper can reduce the vibration of split core reactor from the root source without changing the overall structure and process.

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