Analysis on Eddy Current Loss and Temperature Distribution for Ultra High Voltage Transformer in No-Load
North China Electric Power University, China
The presence of core joint increases the magnetizing current of the transformer, it is equivalent to an thin air gap in the FEM(finite element) model of this paper. Based on circuit-field coupling and magne-thermal coupling FEM model，the magnetic flux leakage, loss and temperature distribution characteristics of UHV main transformer under no-load operation are calculated and analyzed.
Multi-physics Field Coupled Analysis in Electromagnetic Rail Launcher With Different Shape Rails
1Xi’an Jiaotong University, China, People's Republic of; 2Naval University of Engineering, China, People's Republic of
This paper presents the coupling and application of a 3D multi-physics model of an electromagnetic rail launcher (ERL) modeling coupled thermal, mechanical, and electromagnetic diffusive field with moving armature. The ERL is a multi-physics field coupled system including electromagnetic, thermal, dynamic, and mechanical fields. The multi-physics field coupled characteristics in ERL with different shape rails are obtained. The coupled field relationship among displacement, temperature, and peak stress in ERL with different type rails are gained.
3-D Transient Magneto-Thermal Field Analysis Using Adaptive Degrees-of-Freedom Finite Element Method
1Department of Electrical Engineering, The Hong Kong Polytechnic University, Hong Kong S.A.R. (China); 2School of Electrical Engineering,Chongqing University, Chongqing, China
In this paper, an adaptive degrees-of-freedom finite element method is proposed for 3-dimensional (3-D) transient magneto-thermal field analysis. The coupling between the fields are implemented based on one set of mesh, hence obviating the usage of mapping algorithm for different meshes and the associated errors. Meanwhile, the degrees-of-freedom (DoFs) of each field are adjusted separately to meet the different requirements on discretization and improve the computational efficiency. Those dispensable DoFs are eliminated using the slave-master technique, and the elimination of DoFs has the same effect as mesh coarsening. Error estimators and mesh refinement algorithm for adaptive methods are also included. The effectiveness of the proposed method is showcased through the comparison with conventional methods.
Fast Analysis of Rotating Machine Using Simplified Model Order Reduction Based on POD
1Hokkaido University; 2MEIDENSHA CORPORATION
This paper proposes a simplified model order reduction for the fast dynamic simulation of electric motors. The magnetic fields are snapshotted for different input currents at a fixed mechanical angle to construct a data matrix. The basis vectors are then computed by the singular decomposition applied to the data matrix. Fast computation of the magnetic field for arbitrary input current and mechanical angle is performed through interpolation of the basis vectors in the space of input currents for the dynamic analysis of motors.
Multi-Physics Analysis of Surface Mounted Rotor with CFRP Sleeve for a High-Speed Permanent Magnet Synchronous Motor
1National Key Laboratory of Science and Technology on Vessel Integrated Power System; 2Wuhan Institute of Marine Electric Propulsion; 3Xi'an Kangben Material Co., Ltd.
A high-speed permanent magnet (PM) synchronous motor (HSPMSM) was designed, which employs carbon fiber-reinforced plastics (CFRP) protective sleeve in the surface mounted rotor. To structural design the surface mounted rotor, the multi-physics analysis of the rotor is presented, and the analysis process is summarized as follows. Firstly, the main parameters and loss of the HSPMSM were obtained respectively by means of finite element analysis (FEA) and theoretical calculation. Secondly, the temperature distribution of the motor was conducted by computational fluid dynamics method. The results show that the maximum temperature of the PMs and the CFRP sleeve are 115℃ and 113℃. Thirdly, the structural analysis and rotor dynamics analysis of the rotor were also discussed using FEA method. The results show that the critical speed exceeds the working speed by more than 20%, which avoids the resonance problem and satisfies the design requirements of the HSPMSM. Lastly, the CFRP sleeve was designed by structural design, sample fabrication, and water pressure test of the CFRP product. The results show that the structure of the CFRP sleeve meets the strengthen requirements of the HSPMSM.
The Thermal Field Analysis of Nanofluid-filled Power Transformers
1Hebei University of Technology, State Key Laboratory of Reliability and Intelligence of Electrical Equipment, Tianjin, China; 2The Hong Kong Polytechnic University, Hong Kong S.A.R. (China); 3Maintenance Branch, State Grid Jibei Electric Power Co. LTD, Beijing, China
To alleviate the adverse impact due to the deterioration of electrical insulation, this paper presents an electromagnetic-thermal-fluid analysis for the prediction of hot-spot temperature in transformers with pure oil or oil-based nano-fluids. The core loss and copper loss are taken as the heat sources for the temperature analysis using domain decomposition technology and Computational Fluid Dynamics (CFD). To strive for computing the hot-spot temperature accurately in the oil, an effective numerical method using finite volume method (FVM) is employed. Numerical simulation of the thermal performance of the nano-fluid with different volumetric fraction (0.001%, 0.002%, 0.004%, 0.01%, 0.02%, 0.04%, etc.) with Al2O3 nano-particles is compared with those using pure transformer oil in a 500 VA single-phase transformer. From the comparisons of the simulation results it is found that the volumetric fraction 0.01% is the optimum concentration in reducing the transformer size for the same power rating. The observation will serve as useful guidelines for the design of oil-based power transformers.
Temperature rise calculation in dry-type transformers through 3-D coupled electromagnetic - thermal model and fluid-dynamical analysis
1State Key Lab of Reliability and Intelligence of Electrical Equipment, China, People's Republic of;; 2Key Lab of EFEAR of Hebei Province, Hebei University of Technology, Tianjin, 300130, China; 3Tianjin University of Technology, Tianjin, 300384, China
A 3-D coupled electromagnetic-thermal finite-element method (FEM) is proposed in this paper for temperature rise calculation in air-cooled transformers. 3-D eddy current field is established to copy with the non-uniformity density distribution of foil type windings induced by leakage flux, the Joule’s losses and core losses are applied as the heat source for thermal field analysis, which is deeply dependent on accurate convection heat transfer coefficient. Moreover, the influence of multi-channel structure of high-voltage winding on temperature rise and maximum air velocity is taken into account. The optimal position and thickness of insulation barriers between HV and LV windings are compared and analyzed. A 2500kVA/10kV transformer prototype is designed and carried out to verify the correctness of temperature rise calculation between the simulated and measured results .
Simulation of electrospray onset in conductive fluids
Technische Universität Darmstadt, Germany
The numerical simulation of electrohydrodynamic atomization of a conductive liquid in the cone-jet mode is considered. The numerical approach is based on the solution of the multiphase flow coupled with an electroquasistatic problem including capacitive, resistive and convection electric currents. The formulation allows for the simulation of charge relaxation effects in a liquid thread before its atomization in a number of microdroplets. Topology changes associated to this event are implicitly handled by the use of a diffuse interface model based on the Volume of Fluid method. Sufficient spatial resolution of the microdroplets is achieved by the means of adaptive mesh refinement in the vicinity of the fluid-fluid interface. The model thus defined is used to study the characteristics of electrospray onset, and in particular of the first atomized droplet.
Electromagnetic and Vibration Modelling of an Electric Powertrain for a Simulation-driven Fault Diagnosis System
University of Agder, Norway
In this study, finite element analysis (FEA) of an electric powertrain is used to generate simulated data for various faulty and healthy conditions of the powertrain. The electromagnetic forces and torque of the powertrain are modelled in a 2-D time-stepping FEA and mechanical forces of the powertrain are modelled in 3-D FEA. The electromagnetic forces and mechanical stresses are coupled so that electromagnetic forces and mechanical vibration on housing and gearbox affecting the air gap variation will reflect in stator currents. This coupled mechanical and electrical modelling generates both vibration and stator current data for fault diagnosis purpose. The collected data is used to train a data-driven fault diagnosis algorithm.
A Finite Element Study on the Distribution and Variation of the Eddy Current in Electromagnetic Sheet Free Bulging
Ximan University, China, People's Republic of
Electromagnetic forming (EMF) technology employs electromagnetic force to deform metal workpiece. It is a promising solution for the room temperature processing of lightweight alloy. EMF is a complicated process which is under the coupling effect of the multi-field. Many processing parameters will influence the forming result. Among those, the excitation frequency is one of the most important parameter. In order to clarify the effect of the discharge frequency on the forming performance, a simulation study on eddy current is conducted. The distribution of the induced current and the magnetic pressure in electromagnetic sheet free bulging is analyzed in detail. It is found that the distribution of eddy current is different from that in infinite plate when Sine uniform planar electromagnetic wave incidences. The movement and the thickness of the plate will influence the density and change of the eddy current. And this study is instructive to the design of the process parameters in EMF.
A Coupled 3D Finite Element-Distributed Circuit Model for Numerical Analysis of Small Time Scale Transients of Three-phase Inverter
1Zhejiang University, China, People's Republic of; 2Sorbonne University, France
In order to quantitatively analyze the voltage and current overshoots in the fast switching-on and -off transients of an inverter, a coupled 3D finite element-distributed circuit model is proposed and its solution methodology is introduced. Moreover, a model order reduction technique based on Krylov subspace is presented. The effects of the displacement and the thin skin depth of the electromagnetic phenomenon are properly modeled in the 3D finite element model. The comparisons between the simulated and tested results evidence the feasibilities and merits of the proposed work.
Functionalization of Electric Field Enhancement Factor in Evaluating Ion Flow Field Under HVDC One-Bipolar Configuration
Kyungpook National University, Korea, Republic of (South Korea)
This paper demonstrates a finite element analysis scheme for the calculation of corona current in the ion flow field under HVDC one-bipolar configuration consisting of 6-conductor bundles in a ± 800 kV transmission line network. The ground level electric field strength and the ion current density are calculated for the applied electric field enhancement factor as a function of various parameters related to the corona onset field such as the orientation of the sub-conductors within the bundles, the region of the corona-current-injection along the curved-surface of the individual conductors, and so forth. The effective values of the local electric field enhancement factor have been defined and calculated using the criterion of Peek’s law. From this study, it was uncovered that the effective electric field enhancement factor decreases with the increase in the applied electric field, provided the geometry is kept constant. Furthermore, a charge-injection-region on the outer surface of an individual sub-conductor within the conductor-bundle that surrounds the point where maximum electric field is observed is analyzed by employing various shape functions, which will eventually determine the electric field enhancement on the surface of the conductor.
3-D Coupled Magnetic-Fluid-Thermal Field Analysis of Single-phase Potential Transformer Under Overvoltage Condition
1Xi'an Jiaotong University, China, People's Republic of; 2State Grid Shaanxi Electric Power Company Construction Branch, Xi’an 710065, China
This paper presents the 3-D coupled magnetic-fluid-thermal field analysis of single-phase potential transformer under overvoltage condition. The distribution of magnetic field and excitation current are obtained by electromagnetic field simulation. To improve the accuracy of calculation results, the influence of temperature on the electric power losses is considered in this paper. Compared test results and simulation results, it is noted that temperature calculation results are highly consistent with test temperature results. Therefore, this coupling method is effective in the calculation of the thermal field of transformer-type equipment.