Nana Duan

Hysteresis Modeling of High-Temperature Superconductor Using Simplified Preisach Model

This paper presents a hysteresis model for the high-temperature superconductor using a simplified Preisach model, in which the Preisach distribution function is determined only based on the M-H limiting loop. The results of simulation and experiment of accuracy of the simplified Preisach model are reported for the case of silver-sheathed Bi2223 superconducting tape samples with an external magnetic field perpendicular to the tape surface.

Initial Rotor Position and Magnetic Polarity Identification of PM Synchronous Machine Based on Nonlinear Machine Model and Finite Element Analysis

In this paper, a DC voltage pulse injection based method is proposed to detect the initial position and rotor polarity of permanent magnet synchronous motor (PMSM). The rotor angle vibration is expressed analytically as a function of the injected pulse. The nonlinear numerical simulation model of PMSM is employed, in which the saturation saliency is incorporated as well as the structural saliency. The proposed scheme is simulated and verified by using the nonlinear model and a 2-D finite element method (FEM) algorithm, respectively. The initial position detection is tested at different starting positions and the results show that the proposed scheme can be used to identify the PMSM initial rotor position.

An Improved XFEM With Multiple High-Order Enrichment Functions and Low-Order Meshing Elements for Field Analysis of Electromagnetic Devices With Multiple Nearby Geometrical Interfaces

This paper proposes an improved extended finite element method for modeling electromagnetic devices with multiple nearby geometrical interfaces. In regions near these interfaces, the magnetic vector potential approximation is enriched by incorporating multiple derivative discontinuous fields based on the partition of unity method such that the interfaces can be represented independent of the mesh. The support of a node or an element can be cut by several interfaces. This method results in the high accuracy in the approximation field and derivative field. Numerical examples applied to the iron core in 1-D eddy current field involving level set-based parts, error analysis, and electromagnetic field computations are provided to demonstrate the utility of the proposed approach.

A new Preisach type hysteresis model of high temperature superconductors

This paper presents a new Preisach type hysteresis model for the high temperature superconductor. This model requires only the limiting hysteresis loop as the input data, and for this model, the limiting hysteresis loop is first separated into two limiting M−H loops based on the mechanisms, which can then be modeled by two separate modified Preisach algorithms. The area integrations of the Preisach distribution functions are determined only based on the limiting M−H loops. The validity and accuracy of this model is confirmed by comparing the simulation and experiment results of Bi-2223 and YBa2Cu3Ox superconducting tapes with external magnetic fields.

Extended Finite-Element Method for Electric Field Analysis of Insulating Plate With Crack

In this paper, the extended finite-element method (XFEM) is employed to analyze electric field of insulating plate with crack. To begin with, both the approximation of XFEM and features of the enrichment functions for crack tip are presented. Then, XFEM is used to solve electric potential of an insulating plate with a middle crack, which proves the method can save computational time by comparison with classic finite-element method (CFEM) under the same computational accuracy. In addition, XFEM is also applied to calculate electrical field at crack tip of an insulating plate with an edge crack, which reveals that the relative error between XFEM and CFEM is small when the meshing size of CFEM around crack tip is smaller than that of XFEM. Therefore, electric field analysis of discontinuous and singular solutions can demonstrate the superior performance of XFEM.

Modeling and Measurement of Magnetic Hysteresis of Soft Magnetic Composite Materials Under Different Magnetizations

The soft magnetic composite (SMC) materials and their application in electromagnetic devices have undergone significant development due to their unique advantages, such as low eddy-current loss, quasi-isotropy of mechanical and magnetic properties, low cost, and low material consumption during the production process. However, the magnetic properties of the SMC materials are very different from that of the laminated SiFe materials, which are particularly challenging for the design and application of electrical machines. This paper presents the modeling and measurement of magnetic properties of the SMC materials under both alternating and rotational magnetic excitations. Based on the underlying magnetization mechanisms, a vectorial elemental operator with biaxial anisotropy is introduced, and the concept of distribution function is utilized to describe the density of operators in the specimen. To verify this proposed model, the magnetic hysteresis of the SMC material is simulated and compared with the experimental results obtained by the three-dimensional magnetic property measurement system. The good agreement shows the validity and practicability of this vectorial elemental operator.

Extended finite element method for electromagnetic fields

This paper presents the fundamental principle of the extended finite element method (XFEM) for electromagnetic field analysis. This method provides an accurate approximation for locally non-smooth features within finite elements, such as singularities, discontinuities, and high derivatives. An alternative enrichment function is introduced to improve the approximation space of the conventional finite element method (CFEM) such that non-smooth solutions are modeled independent of the mesh. The level set method is employed to describe the interfaces among different materials. To demonstrate the advantages, the XFEM is compared with CFEM by solving a 1D electrical field problem.

Extended Finite-Element Method for Weak Discontinuities in Electric Fields

In this paper, the extended finite-element method (XFEM) is used for modeling weak discontinuities in electric fields. For a weak discontinuous domain, the first-order derivative of the electric potential is discontinuous although the electric potential, degree of freedom, is continuous. In order to improve the approximation space of the conventional finite element method (CFEM), the enrichment function of the key of XFEM is used to model weak discontinuous solutions independent of the mesh. Interfaces among different materials can be described well by using the level set method. Numerical examples applied to the parallel plate electrodes in 1-D and the insulating oil with a bubble in 2-D static electric field involving error analysis, computational time, and electric field computations are provided to demonstrate the utility of XFEM in electric fields.

Current Distribution Calculation of Superconducting Layer in HTS Cable Considering Magnetic Hysteresis by Using XFEM

This paper presents a coupled field-circuit analysis method for the high-temperature superconducting (HTS) cable considering magnetic hysteresis by using the improved extended finite-element method (XFEM). The quasi-3-D cylindrical coordinate HTS cable model is first proposed based on the shell element theory. The quasi-3-D meshing elements are used instead of the traditional 3-D meshing elements to overcome the difficulties in meshing. A new Preisach type hysteresis model of HTS tapes is first combined with the improved XFEM to determine the magnetic hysteresis inductance. A magnetic field-circuit coupled program for current analysis of superconducting layers is coded. The numerical simulation results of this field-circuit coupled method are reported compared with the experimental test results for the case of an HTS cable with two layers.

A Temperature-Dependent Hysteresis Model for Soft Ferrites

This paper introduces a temperature-dependent hysteresis model based on a vectorial elemental operator with temperature-sensitive spontaneous magnetization and biaxial anisotropy for the soft ferrites. Detailed analysis of the temperature-dependent magnetic properties of one elemental operator has been presented thereafter. With the help of the proposed vector elemental operator and the 2-D Gaussian distribution function, the temperature-dependent magnetic hysteresis of soft ferrites can be simulated. This model is validated by the substantial agreement between the simulated and measured major hysteresis loops of a soft ferrite sample Siemens 4C65 at different temperatures with slight acceptable error.