This paper deals with the current state and future prospect of the electromagnetic field analysis as a basic technology supporting the power and energy fields. Moreover, applications in the field of electrical machines, problems in view of the industrial area and the corresponding analysis technologies are also introduced.
A modification method of finite element meshes based on the adaptive meshing for optimization of electric machines is proposed. In the optimization process of the machine, the proposed method generates the mesh for the new shape from the previous mesh with minor modification. The locations of the nodes for the new shape are decided by solving the Laplace's equation, whose unknowns are displacements of the nodes. The advantages are clarified by the application to the shape optimization of an IPM motor.
Electrical loss of an interior permanent magnet motor (IPM motor) driven by the pulse width modulation inverter (PWM inverter) is analyzed using the three-dimensional finite element method (3-D FEM). The distributions of the eddy currents in the permanent magnet, the iron loss characteristics, and the torque characteristics were quantitatively clarified.
This paper describes a benchmark model proposed for the clarification of the characteristic of various methods for modeling the laminated iron core. In order to obtain a reference solution of the benchmark model, a large-scale nonlinear magnetostatic field analysis with a fine mesh enough to represent the microscopic structure of the laminated iron core is carried out by using the hybrid finite element-boundary element (FE-BE) method combined with the fast multipole method (FMM) based on diagonal forms for translation operators. The computational costs and accuracy of two kinds of the homogenization methods are discussed comparing the reference solution. As a consequence, it is verified that the homogenization methods can analyze magnetic fields in laminated iron core within acceptable computational costs.
In order to evaluate the heated process of the target, S parameter, and initial design of cavity size in the furnaces for dielectric heating such as microwave oven, the coupled analysis of electromagnetic wave and heat conduction (EM-HC coupled analysis) is a useful tool for practical design. In this paper, valuable EM-HC coupled analysis method with rotational motion of heated target such as turntable and temperature-dependent complex permittivity by using edge-based finite element method is proposed. As a result of useful investigation of the proposed method, the effectiveness in tracing the detailed temperature rise of dielectric target is demonstrated.
Finite element analyses of electromagnetic field are commonly used for designing of various electronic devices. The scale of the analyses becomes larger and larger, therefore, a fast linear solver is needed to solve linear equations arising from the finite element method. Since a multigrid solver is the fastest linear solver for these problems, parallelization of a multigrid solver is a quite useful approach. From the viewpoint of industrial applications, an effective usage of a small-scale PC cluster is important due to initial cost for introducing parallel computers. In this paper, a distributed parallel multigrid solver for a small-scale PC cluster is developed. In high frequency electromagnetic field analyses, a special block Gauss-Seidel smoother is used for the multigrid solver instead of general smoothers such as Gauss-Seidel smoother or Jacobi smoother in order to improve a convergence rate. The block multicolor ordering technique is applied to parallelize the smoother. A numerical exsample shows that a 3.7-fold speed-up in computational time and a 3.0-fold increase in the scale of the analysis were attained when the number of CPU was increased from one to five.
In this paper, we propose new method based on multi-order vector finite elements in three dimensional eddy current analysis. Edges, faces, and volume of the multi-order element have orders of shape functions, respectively. In order to realize high efficiency of numerical calculation, high-order elements are assigned in the important area of the eddy current model, and low-order elements in the surrounding area, and multi-order elements in the middle area to bond two areas, respectively. The results obtained by multi-order elements are compared with those by full high-order elements and by full low-order elements.
A new multigrid method based on high-order vector finite elements is proposed in this paper. Low level discretizations in this method are obtained by using low-order vector finite elements for the same mesh. Gauss-Seidel method is used as a smoother, and a linear equation of lowest level is solved by ICCG method. But it is often found that multigrid solutions do not converge into ICCG solutions. An elimination algolithm of constant term using a null space of the coefficient matrix is also described. In three dimensional magnetostatic field analysis, convergence time and number of iteration of this multigrid method are discussed with the convectional ICCG method.
In recent years, induction-heating cookers have been disseminated explosively. It is wished to commercialize flexible and disposable food containers that are available for induction heating. In order to develop a good quality food container that is heated moderately, it is necessary to analyze accurately eddy currents induced in a thin metal plate. The integral equation method is widely used for solving induction-heating problems. If the plate thickness approaches zero, the surface integral equations on the upper and lower plate surfaces tend to become the same and the equations become ill conditioned. In this paper, firstly, we derive line integral equations from the boundary integral equations on the assumption that the electromagnetic fields in metal are attenuated rapidly compared with those along the metal surface. Next, so as to test validity of the line integral equations, we solve the eddy current induced in a thin metal container in induction heating and obtain power density given to the container and impedance characteristics of the heating coil. We compare computed results with those by FEM.
The carbon dioxide gas was injected into Ar induction thermal plasmas to investigate the plasma-quenching efficiency of CO2 and N2. In the experiments, C2 molecular band spectra and N2+ molecular spectra were found. Theoretical calculation of the radiation intensity for C2 Swan system and N2+ first negative system was carried out as functions of excitation temperature, rotational temperature and vibrational temperature. The fitting technique between the experimental and theoretical radiation intensities of the C2 Swan spectra and N2+ spectra was used for determination of rotational and vibrational temperatures. It was found that vibrational temperature was decreased with increasing CO2 admixture ratio into Ar thermal plasmas, which may be related with a decreased electron temperature.
This paper has proposed an analytical method of solving electromagnetically induced voltages and currents on a pipeline and/or on a communication line from a power line. The method is based on a solution of a differential equation expressing the electromagnetic induction on a distributed line system, and is formulated in the same manner as a four-terminal parameter circuit equation by introducing an ideal induced current which is given as the ratio of the induced voltage and the induced circuit impedance. The application of the method is exactly the same as that of an well-known two-port circuit analysis. The method is applied to induced voltages on a pipeline. Analytical results evaluated by the method are compared with EMTP simulation results, and the accuracy of the method is confirmed to be high. Also, a qualitative characteristic of the induced voltages is made clear based on the analytical results of various grounding resistances, including currents and circuit composition.
We propose two schemes for improving the performance of electromagnetic voltage transformers. The first uses a high gain amplifier in conjunction with a capacitive divider that serves as a reference. The second uses a unity gain amplifier. Simulation studies and experimental results are shown in order to validate the methods.