International Journal of Applied Electromagnetics and Mechanics - Volume 51, issue 4

Authors: Ma, Yao | Chen, Shu-Wen | Lu, Feng | Su, Li-Yuan | Duan, Yan-Tao

Article Type: Research Article

Abstract: This paper proposes the complex frequency shifted (CFS) perfectly matched layer (PML) of dispersive media for finite-difference time-domain (FDTD) method combined with weighted Laguerre polynomials (WLP). According to the property of Laguerre basis function, the relative dielectric constant ε _r (ω ) of dispersive media and complex frequency shifted (CFS) PML parameters, auxiliary differential equation (ADE) technique is introduced. Based on the ADE technique, the relationship between field components and auxiliary differential variables is derived in Laguerre domain. Using ADE scheme, the relationship between electric flux density D and electric field E is derived in Laguerre domain. …Substituting auxiliary differential variables into CPML absorbing boundary conditions, using auxiliary differential variables, electric flux density D of order q can be expressed directly by magnetic field H in Laguerre domain. Using the same procedure, magnetic field H of order q can be expressed directly by electric field E in Laguerre domain. Inserting H of order q$ into D , using the relationship between D and E , and using central difference scheme, the formulations for dispersive media are obtained. In order to validate the efficiency of the presented method, two numerical examples are simulated. Numerical results show that, compared with the Berenger PML (BPML) and nearly PML (NPML), the CFS-PML has about more than 24 dB improvement in terms of the maximum relative error and much lower reflection error for the late-time region. Show more

Keywords: Auxiliary differential equation (ADE), dispersive materials, finite-difference time-domain (FDTD)

DOI: 10.3233/JAE-150051

Citation: International Journal of Applied Electromagnetics and Mechanics, vol. 51, no. 4, pp. 349-361, 2016

Authors: Chen, Shu-Wen | Lu, Feng | Ma, Yao | Su, Li-Yuan

Article Type: Research Article

Abstract: A VIE-based domain decomposition method (DDM) is proposed for analyzing EM scattering from inhomogeneous electrically large dielectric objects. The volume integral equation (VIE) still uses tetrahedra to model the entire body and uses the SWG basis functions to expand the equivalent electric flux density. This new DDM is established by dividing the unknowns on the whole electrically large body into groups, serving as subdomains. Through necessary symmetry treatment of standard MoM impedance matrix, the DDM using subdomain-decoupling technology can be combined with the VIE model to reduce memory requirement. Actually, this is an algebraic DDM, not a geometric DDM. In …other words, it has no requirement of physical location of basis functions belonging to the same subdomain. This decoupling procedure is completely eliminating the coupling impact of the primary subdomain with the rest of the dielectric body, until every subdomain is independent with each other. In this work, when solving ultimate decoupled impedance subdomain matrix, the LU decomposition process for solving interpolating coefficients of multiple right sides is accelerated by GPU parallel technology to significantly decrease CPU time. In brief, this paper first time combines the algebraic DDM with the conventional VIE model (including both isotropy and anisotropy VIE model) to significantly decrease the requirement of memory. At last, a few representative numerical examples are provided to demonstrate validity, efficiency and stability of the new method. Show more

Keywords: MoM, domain decomposition, volume integral equation

DOI: 10.3233/JAE-150064

Citation: International Journal of Applied Electromagnetics and Mechanics, vol. 51, no. 4, pp. 363-373, 2016

Authors: Lv, Pin | Ge, Baojun | Tao, Dajun | Yin, Jiwei | Zhao, Hongsen

Article Type: Research Article

Abstract: With the forthcoming global energy crisis, the nuclear power has a broader range of the applications. At the same time, the safe operation of the nuclear turbo-generator, particularly the calculation of the rotor shaft vibration, becomes incredibly important. This paper takes a nuclear power turbo-generator as an example and the finite element calculation model has been built up. During the process of the analytic algorithm, the current vector caused by the rotating rotor is replaced by the three-phase current vector induced by the static rotor windings. When symmetrical component transform and dq0 transform employed, the impact of positive current vector …and negative current vector on the constant and second harmonic part of the electromagnetic torque has been discussed. Then a novel method for second harmonic electromagnetic torque calculation has been proposed. The data of the finite element algorithm is consistent with that of analytic algorithm, verifying the correctness of the method proposed by this paper. Show more

Keywords: Nuclear turbo-generator, rotor shaft vibration, analytic algorithm, finite element algorithm, second harmonic electromagnetic torque calculation

DOI: 10.3233/JAE-150151

Citation: International Journal of Applied Electromagnetics and Mechanics, vol. 51, no. 4, pp. 391-403, 2016

Authors: Yan, Chenguang | Hao, Zhiguo | Zhang, Song | Zhang, Baohui | Zheng, Tao | Li, Zhengyuan

Article Type: Research Article

Abstract: Being aware of the great hazard of transformer winding deformation and insulation damage under the impact of huge electromagnetic forces caused by short circuit faults, this paper presented an analysis method based on explicit dynamic 3-D finite element method, enabling detailed and representative investigations of the mechanical effects of external short circuit faults in power transformers. Considering the displacements and deformations of windings could change the leakage flux distribution and further influence the remaining computation, an electromagnetic-mechanical field coupling model was proposed. To accurately calculate the windings transient deformation, both the disks and spacers were considered as the elastic-plastic body. …Meanwhile, the high-voltage and low-voltage windings were modeled into 21 disks and 18 spacers are evenly arranged between the adjacent copper disks. For illustrating the effectiveness of the proposed method, a real full-scale 120 MVA/220 kV oil-immersed transformer model was built to suffer the serious three-phase short circuit fault as the case study. A comparison of the von-Mises stress distribution in healthy, pre-strain and dislocation windings under the same short circuit fault confirmed that the healthy winding can withstand the impact of short circuit fault without any unrecoverable deformation; insufficient mechanical strength, pre-strain and local dislocation are the key factors to winding deformation, rupture even collapse. Additionally, the theoretical model and simulation method can be used as a substitute for costly and cumbersome field tests in faults characteristics analysis of transformer windings. Show more

Keywords: Power transformer, short circuit fault, winding deformation, electromagnetic-mechanical field coupling, finite element method

DOI: 10.3233/JAE-150163

Citation: International Journal of Applied Electromagnetics and Mechanics, vol. 51, no. 4, pp. 405-418, 2016

Authors: Witczak, Pawel | Majer, Krzysztof

Article Type: Research Article

Abstract: The paper analyses the no-load vibration of a three-phase three-limb distribution transformer cores caused by magnetostriction phenomena. The electromagnetic models use 2D finite element representation combined with the time-step approach and consider different structures of core joints: with and without overlapping and with isotropic or orthotropic nonlinear magnetic properties. Magnetostriction forces are calculated on the basis of the Becker-Döring two-constant elongation equation integrated over volumes of interest. The mechanical model is also built within the finite element 3D technology with orthotropic properties of homogenized equivalent materials of the transformer core and windings. Exemplary results of calculations are compared with measurements.

Keywords: Power transformer, vibration, magnetostriction, forces, finite elements

DOI: 10.3233/JAE-150175

Citation: International Journal of Applied Electromagnetics and Mechanics, vol. 51, no. 4, pp. 419-429, 2016

Authors: Hussain, Nazabat | Karsiti, Mohd Noh | Jeoti, Varun | Yahya, Noorhana

Article Type: Research Article

Abstract: Wavelets gained significant attention in science and engineering disciplines due to their remarkable data analyzing capabilities. Wavelets are also used for finding numerical solution of various engineering and geophysical problems. Marine controlled source electromagnetic (CSEM) method is a relatively new geophysical technique used to explore petroleum reserves from shallow and deep water. This work attempts to use periodic and non-periodic wavelets in CSEM for modeling of geophysical problem. This is results in a solution with multi-scale approximations using multiresolution analysis (MRA) algorithm. In this work, Daubechies wavelets are used, as the basis functions for solving the wave equation of marine …CSEM, because of their orthonormality and compact support. Accuracy of the proposed method for marine CSEM is determined by comparing the results with the analytical solution for isotropic problem as well as those obtained using finite element (FE) method. Numerical results show that the governing equations for aforementioned geophysical method yield less obscure results than that of finite element method, for both bounded and unbounded domains. Furthermore, the proposed wavelet based numerical method produces multi-scale approximation that would prove useful for further analysis and data processing. Show more

Keywords: Wavelets, electromagnetics, marine CSEM, geophysical modeling, forward modeling

DOI: 10.3233/JAE-160002

Citation: International Journal of Applied Electromagnetics and Mechanics, vol. 51, no. 4, pp. 431-443, 2016

Authors: Xiong, Zhenyu | Yu, Xudong | Long, Xingwu

Article Type: Research Article

Abstract: This paper presents a finite element simulated model to investigate parametric changes in the peak amplitude of a ring laser gyroscope. The finite element model is validated by comparing the theoretical amplitudes of two ring laser gyroscopes with simulated results, and the errors for the two gyroscopes are 1.3% and 1.6%. Based on this model, the parametric influences on the operation of the mechanical dither are obtained through simulation. The simulation results reflect the relationship between the geometric dimension and the peak amplitude of the mechanical dither. These findings are important for the optimal design and improved accuracy of a …mechanical dithering ring laser gyroscope with bimorph piezoelectric actuators. Show more

Keywords: Finite element model, mechanical dithering, parametric change, peak amplitude

DOI: 10.3233/JAE-160031

Citation: International Journal of Applied Electromagnetics and Mechanics, vol. 51, no. 4, pp. 445-453, 2016

Authors: Bu, Wenshao | He, Fangzhou | Lu, Chunxiao | Li, Ziyuan | Xiao, Juanya

Article Type: Research Article

Abstract: Bearingless induction motor is a multi variable, nonlinear and strong coupling object, in order to achieve its suspension control with high performance, the dynamic model of magnetic suspension system is established; and the radial displacement of bearingless rotor is separated into two parts, include random displacement component and unbalanced vibration displacement component. Then by inverse system method, dynamic decoupling control between the two random displacement components is achieved. On this basis, through the compensation controller of unbalanced vibration, the compensation force of unbalanced vibration is regulated and estimated real time, and the control current of unbalanced vibration compensation force is …calculated. The compensation force is used to counteract the unbalanced exciting force of bearingless rotor. Under the dq coordinate system oriented by the rotor flux-linkage of torque system, the control current compensation of unbalanced vibration is achieved. At the end, simulation verification and analysis are made. From the simulation results, it is clear that when the proposed control strategy is adopted, the unbalanced vibration of bearingless rotor can be inhibited effectively in the start stage; the unbalanced vibration displacement can be eliminated in steady state. The proposed control strategy is effective and feasible. Show more

Keywords: Three-phase bearingless induction motor, modeling of inverse system, radial displacement separation, current compensation, unbalanced vibration control

DOI: 10.3233/JAE-150120

Citation: International Journal of Applied Electromagnetics and Mechanics, vol. 51, no. 4, pp. 455-469, 2016

Authors: Díaz, Guillermo A. | Mombello, Enrique E. | Marulanda, Geovanny A.

Article Type: Research Article

Abstract: This paper proposes a fast and accurate method for determining the electric potential and the radial and axial components of electric field intensity produced by a finite cylindrical surface charge distribution. The surface charge density has been modeled having a linear variation along the axial dimension of the cylinder. This consideration is very important when large bodies are to be modeled by means of an arrangement of elements (such as finite cylinders, disks, cones, etc.) allowing the matching between them and also avoiding discontinuities on charge distribution. The mathematical expressions presented in this paper have shown high computational performance while …ensuring accurate and reliable results. Show more

Keywords: Coulomb's law, electric potential, electric field, semianalytic integral methods

DOI: 10.3233/JAE-150133

Citation: International Journal of Applied Electromagnetics and Mechanics, vol. 51, no. 4, pp. 471-480, 2016

Article Type: Other

Citation: International Journal of Applied Electromagnetics and Mechanics, vol. 51, no. 4, pp. 481-489, 2016