Calculation of Core Loss under Harmonic Excitation for Laminated Steel Structure
Hebei University of Technology, China, People's Republic of
In this paper, a simple method of loss calculation which can effectively consider minor hysteresis loops is proposed. An improved 3-D finite element model for laminated steel structure is established by using the overall modeling based on homogenization method, this facilitates the meshing operations. The calculation results of both flux density and core loss are in good agreement with the measurement results, which verify the accuracy and feasibility of the proposed method.
Comparison of Electric Field Intensity between Conduction Model and BCT Model for XLPE insulation of HVDC Cable
Hanyang University, Korea, Republic of (South Korea)
Both conduction model and Bipolar Charge Transport (BCT) model are used to evaluate electric field distribution inside insulation material of hvdc cable. Calculation of the conduction model is based on Maxwell equations. On the other hand, Bipolar Charge Transport (BCT) model is numerical computation method that solves very complicated equations reflecting the space charge dynamics such as injection, conduction, recombination, trapping and de-trapping. Both models are very useful for insulation design of hvdc cable and estimation of its electrical characteristics. However, the conduction model and the BCT model produce quite different results. Furthermore, higher the ambient temperature, larger is the difference of maximum electric field strength. Therefore, in this paper, the electric field distribution and the space charge behavior computed from both models is compared. In the case of conduction model, electrical conductivity was experimentally measured to obtain a reliable value for electrical conductivity of XLPE (Cross-linked Polyethylene) insulation material. In case of the BCT model, the parameter sweep was applied. To perform a fair comparison between conduction model and BCT model the current density was kept equal in both under dc quasi-steady state. Thereafter, electrical breakdown tests were performed while maintaining uniform temperature throughout the specimen. We have concluded that, the conduction model shows uniform electrical field distribution, whereas BCT model shows an increased maximum electric field strength. Temperature increase results in significant decrease of electrical breakdown voltage.
Accurate inner hysteresis loops model based on the modified dynamic Jiles-Atherton model
North China Electric Power University, China, People's Republic of
The traditional dynamic Jiles-Atherton (J-A) hysteresis model is based on the Empirical Method of Loss Separation (EMLS) which lacks the physical basis and has low precision. Although the J-A hysteresis model is able to represent a wide range of major hysteresis loops, it can produces inaccurate inner hysteresis loops with its classical equations. In this paper, referring to the concept of_ magnetic field strength separation_, a* new dynamic J-A model *is proposed, which combines_ the Statistical Theory of Loss_ with traditional static J-A hysteresis model.
The static J-A hysteresis model is used to calculate the hysteresis magnetic field strength component, while the eddy field and excess field are calculated by the analytical formula derived based on the Statistical Theory of Loss. A modification is done in the proposed dynamic J-A hysteresis model in order to improve *the dynamic inner loops *representation. Finally, the simulation results are compared with the experimental results, which verifies the accuracy of the proposed model.
A Magnetic Hysteresis Model Based on the Minimization of Magnetic Domain Energy Under Harmonic Magnetic Field
1Shenyang University of Technology, Shenyang, Liaoning 110870 China; 2YingKou Institute of Technology, Yingkou, Liaoning 115014 China; 3College of Electrical and Computer Engineering, Florida International University, Miami, FL 33174 USA
The nonlinear loads connected to the power grid causes the presence of harmonics in magnetic field of transformer and motor cores, which will change the magnetic properties of electrical steel sheet and increase the loss and vibration of iron cores. In this paper, a hysteresis model based on the minimization of magnetic domain energy is established by combining the domain magnetization mechanism on a mesoscopic scale with the magnetic properties on a macroscopic scale. The hysteresis loop of electrical steel sheet under higher harmonic magnetic fields are measured and fitted into the hysteresis model. The model parameters are obtained by the gradient descent method. The model simulation results are compared with the experimental results under the same excitation conditions, and its effectiveness is verified.
Variable Coefficient Magnetic Energy Losses Calculation Model for Giant Magnetostrictive Materials
1State Key Laboratory of Reliability and Intelligence of Electrical Equipment, Hebei University of Technology; 2Key Laboratory of Electromagnetic Field and Electrical Apparatus Reliability of Hebei Province, School of Electrical Engineering, Hebei University of Technology
Testing and accurate calculation of magnetic energy losses for magnetostrictive material is a necessary step in designing high-power magnetostrictive transducer. In this paper, the values of magnetic energy losses are measured to investigate their variations at different frequencies and different magnetic flux densities of driving magnetic field. Based on the loss separation formula and measured data of Terfenol-D, the variation trends of the losses coefficients are investigated. An improved magnetic energy losses calculation method with variable coefficients is established and verified by experiments. This research can provide theoretical and experimental guidance for the higher frequency applications of magnetostrictive materials.
Test of the energy-based vector hysteresis model on a transformer under different supply conditions
1Univ Lyon, ECLyon, Université Claude Bernard Lyon 1, INSA Lyon, CNRS, Ampère, F-69130, Ecully, France; 2Univ Lyon, Université Claude Bernard Lyon 1, INSA Lyon, ECLyon, CNRS, Ampère, F-69100, Villeurbanne, France; 3Institute Montefiore - ACE - Université de Liège, B-4000, Liège, Belgium
A test case for examining the energy-based model is presented. An experimental setup constituted of a three-limbed core transformer is built in order to study the vector hysteresis modelling in different configurations. Simulation results are compared to measurements made on a soft ferrite and discussed.
Pinning Field Modeling Using Stop Hysterons for Multi-domain Particle Model
1Kyoto University, Japan; 2Doshisha University
For an efficient stress-dependent magnetization analysis of silicon steel using the assembled domain structure model, its magnetostatic computation is simplified, where independent particle approximation is adopted. To represent its pinning field, stop hysterons are assembled. The distribution of stop hysterons is determined by the identification method of scalar and vector stop models. The stress-dependent loss property is successfully predicted through the energy-minimization process.
Modeling of Anisotropic Magnetostriction under DC Bias Based on an Optimized BP Neural Network
1Shenyang University of Technology, Shenyang, Liaoning 110870 China; 2Chungbuk National University, Cheongju, Chungbuk 360-764 KOREA; 3Florida International University, Miami, FL 33174 USA
The existence of direct current (dc) bias magnetic field will change the magnetostrictive properties of electrical steel sheets, which will intensify the vibration and noise of transformers. In this paper, the dynamic magnetostrictive property of electrical steel sheet under dc bias is measured and analyzed, and the anisotropic magnetostriction along different magnetized directions is also illustrated. An optimized back propagation neural network (BPNN) model is proposed to estimate the dynamic magnetostrictive curves under the dc bias. The uncertainty of neural network structure is improved by introducing genetic algorithm (GA). The particle swarm optimization (PSO) algorithm is employed to train BPNN network so as to fast the convergence speed and avoid the local optimal solution. Finally, the pro-posed model is verified by comparing the measured magnetostriction and computed one.
An Improved Dynamic Hysteresis Model Based on Anisotropic Vector Preisach Model for Iron Loss Calculation in Laminated Core
1Shanghai Maritime University, China, People's Republic of; 2Tongji University, China, People's Republic of; 3Aalborg Univeristy, Denmark; 4Dong-A University, Korea; 5Chungbuk National University, Korea
This paper proposes an improved dynamic hysteresis model which is based on vector Preisach model, and the proposed model can consider the anisotropic property of electrical steel sheet (ESS). In the Preisach model, the Everett function is identified by a set of symmetric minor hysteresis loops. The minor loops are measured by using one-dimensional (1D) single sheet tester (SST) with the frequency of 1Hz. Then the vector Preisach model which can consider the anisotropic property by using an anisotropic matrix. The identified vector Preisach model is applied to form a dynamic three-term vector hysteresis model to estimate iron loss of laminated core taking rotating magnetic fields into account. The dynamic hysteresis model consists of static hysteresis field, frequency-dependent eddy current field and excess field, and its parameters are inversely found by fitting the experimentally measured iron losses under various field conditions by using particle swarm optimization (PSO) method. The validity of the proposed hysteresis algorithm is investigated through comparisons with experimental results under various magnetic field conditions.
Numerical Analysis of Space Charge Behavior and Transient Electric Field under Polarity Reversal of HVDC Extruded Cable
Hanyang University, Korea, Republic of (South Korea)
Polarity reversal that occurs during the process of reversing power flow give a severe stress to cable insulation. Especially, in case of extruded polymer cable, the transient electric field generated by the space charge accumulated in the insulation under the polarity reversal condition is a vital threat to HVDC cable. Therefore, HVDC cable insulation must be designed considering the possibility of polarity reversal. Recognizing the stress associated with polarity reversal, test recommendations of the HVDC cable have established a process of polarity reversal test and experimental studies are actively being carried out. However, there are relatively few studies on numerical analysis of polarity reversal. In this paper, a Bipolar Charge Transport (BCT) model is applied to simulate space charge behavior and transient electric field for 1D cylindrical geometry. This model is designed to explain the transport of electrons and holes in insulation materials and the mechanism of space charge accumulation. The polarity reversal was performed after application of positive DC voltage and the temperature gradient was set differently in three loaded cases. The maximum transient electric field was compared for each of the temperature gradient and the analysis of significant underlying phenomenon was carried out through the space charge distribution. From simulation results, we confirmed that larger the temperature gradient, larger will be the transient electric field intensity after the polarity reversal. Furthermore, we have concluded that these results are in line with those obtained from conventional polarity reversal experiments.
Analytical modelling of the magneto-elastic behaviour of Terfenol-D
GeePs | Group of electrical engineering - Paris, CNRS, CentraleSupélec, Univ. Paris-Sud, Université Paris-Saclay, Sorbonne Université, 3 & 11 rue Joliot-Curie, Plateau de Moulon 91192 Gif-sur-Yvette CEDEX, France
Giant Magnetostrictive Materials (GMM), such as Terfenol-D or Galfenol, are used to design actuators and sensors converting magnetic input into a mechanical response, or conversely, mechanical input into a magnetic signal. Under standard operating conditions, these materials are subjected to stress. It is therefore important to describe their magneto-mechanical behaviour under stress. In this paper, an analytical model for the stress-dependent magneto-elastic behaviour of ferromagnetic materials is proposed. This model is based on a simplification of energetic multiscale approaches for magneto-elastic behaviour. It is applied to Terfenol-D and compared to experimental results with very satisfactory agreement.
High Frequency Dynamic Hysteresis Model Considering Magnetic Field Distribution of Giant Magnetostrictive Material
1state Key Laboratory of Reliability and Intelligence of Electrical Equipment, Hebei University of Technology; 2Key Laboratory of Electromagnetic Field and Electrical Apparatus Reliability of Hebei Province, School of Electrical
Under high frequency exciting, the radial magnetic field distribution in the giant magnetostrictive materials is uneven and the inner temperature changing affects the precision of its output displacement. Based on the Jiles-Atherton model and the energy balance principle, this paper established a high frequency dynamic hysteresis model considering magnetic field distribution of the magnetostrictive material by using the Maxwell’s equation and the Bessel function. The effect of skin effect on the magnetic field distribution in a giant magnetostrictive rod is discussed. The model is calculated using the numerical algorithm. The effect of frequency and temperature on the hysteresis characteristics of the material is analyzed. The results indicate that the proposed multi-fields coupling dynamic hysteresis model considering the internal magnetic field distribution can well describe the actual working state of the giant magnetostrictive material. The model can provide a theoretical guidance for design and developing high frequency magnetostrictive transducers.
Thermo-Electro-Magnetic Convection in Electrically Conductive Ferrofluids
Technical University of Sofia, Bulgaria
This work examines the thermo-electro-magnetic convection effect in ferrofluid cooling in presence of alternating electric and magnetic fields. We develop a multiphysics field model for electrically conductive ferrofluid transport and heating calculations under outer electromagnetic and thermal field sources. The finite element method is used for 3D electromagnetic-fluid dynamics-thermal model of high reluctance circular coil. The thermo-electro-magnetic convection effect results are proved by direct measurements on a real device, where thermal field results are verified by infrared thermograph imaging.
Effect of Uniaxial Stress on Alternating Magnetic Properties of Silicon Steel Sheet
1Key Laboratory of Reliability and Intelligence of Electrical Equipment, Hebei University of Technology, Tianjin; 2School of Electrical and Information Engineering, University of Sydney, Sydney, NSW 2006, Australia
In electromagnetic devices, mechanical stress may influence the magnetic properties of the core materials. The performance of the devices should be therefore decreased by the stress effect. In this paper, an improved magnetic properties measurement system under stress based on large single sheet tester has been designed and developed. The influence of specimen shape on the uniformity of stress distribution is analyzed by numerical method. Also, the magnetic properties under uniaxial stress of non-oriented silicon steels 50JN470 are discussed in alternating magnetization along the rolling direction. Because the effect of uniaxial stress depends strongly on its orientation with respect to the magnetic field, the uniaxial stress applied along both transverse direction and rolling direction. Eventually, to investigate the dependence of hysteresis loss and excess loss on the stress, three loss components are separated from total loss.
Fractional derivatives: from magnetic spectroscopy to high amplitude dynamic hysteresis in soft ferromagnetism.
1LGEF INSA LYON, FRANCE; 2SHANDONG UNIVERSITY, CHINA; 3FACULTY OF ENGINEERING AND TECHNOLOGY OF THE UNIVERSITY OF BUEA, CAMEROON; 4ELYTMAX, TOHOKU UNIVERSITY, JAPAN
Considering harmonic evolution of the magnetic induction field, we establish a link between a time domain, high amplitude, fractional hysteresis model and the frequency domain, weak amplitude, fractional, ferromagnetic Cole-Cole model. A relation between α (the fractional order), τ (the relaxing time) and ρ (the dynamic constant) can be set. Experimental results performed on a typical soft ferromagnetic (Fe-Si) validate the theory. Correct comparison simulations/measures are observed for both situations (weak and high amplitude excitation) conserving the same set of parameters (α, τ, ρ). The dynamic behavior of a ferromagnetic sample can be set under weak amplitude excitation using simple impedance LCR meter characterization and conserved for the simulation of high amplitude dynamic hysteresis cycles.