Kazuo Bessho

Harmonic balance finite element method applied to nonlinear AC magnetic analysis

The harmonic-balance finite-element method (HBFEM) is used to analyze the time-periodic magnetic field. The calculation is similar to that for the static nonlinear magnetic problem. The procedure is applied to a simple reactor with a saturated core and to calculate the field of an electromagnet. Comparison with results obtained from static FEM solutions confirms the validity of the approach. >

Harmonic field calculation by the combination of finite element analysis and harmonic balance method

A finite-element-method (FEM) time-periodic magnetic-field calculation is described. An AC calculation involving saturation characteristics requires many iterations and much storage space. The combination of FEM and the harmonic balance method enables the harmonic magnetic flux distribution under AC magnetization to be calculated economically. The method is applied to the magnetic-field analysis of a reactor and an electromagnet. >

Calculation of nonlinear eddy-current problems by the harmonic balance finite element method

The harmonic balance finite element method proposed solves the nonlinear time-periodic solution expressed as the sum of fundamental and harmonic components. A procedure for calculation which emphasizes the field computation in the harmonic domain is described. As a result, a reduction of the memory and calculation time is achieved. >

Harmonic balance finite element method taking account of external circuits and motion

AC electric machines are usually excited by voltage sources and the external elements are connected in the magnetizing circuit. Therefore, the magnetic fields, including nonlinear characteristics, voltage sources, and external circuits, should be considered together in an analysis model. The motion effects in the field problem of electric machines must be taken into account. An approach for analyzing the time-periodic nonlinear magnetic field problems, considering external circuits and motion in the harmonic domain by using the harmonic balance finite element method is described. The system equation for governing magnetic fields with motion and circuits is investigated. Applications are discussed. >

BIOLOGICAL RESPONSES IN CAENORHABDITIS ELEGANS TO HIGH MAGNETIC FIELDS

Here we describe a device for testing possible influences of high magnetic fields on biological processes, by which alternating-current magnetic stimuli as high as 1.7 T can be administered. Experiments with a simple multicellular organism, the nematodeCaenorhabditis elegans, revealed that intermittent exposure to the magnetic fields modestly inhibited the animals reproduction as well as its post-embryonic development, and caused a marked but transient derangement in its locomotory behavior. Available evidence indicates that alternating high magnetic fields can elicit both chronic and acute biological effects, but that the effects may be well tolerated or compensated for by the living organism.

The transient magnetization process and operations in the plunger type electromagnet

D.C. electromagnets are generally used in electric devices such as an electromagnetic switch, an electro-magnetic relay, an electromagnetic value, etc.. The transient magnetization affects the determination of the electromagnetic force and the performance characteristic. However, there are few reports on the details of the transient phenomena in an electromagnet. The purpose of this paper is to describe two phenomena which are obtained from the numerical analyses and some experiments. One is the time lag of magnetic flux due to the skin effect. The other is the transient magnetization process near the gap in the plunger type electromagnet made of solid core.

Time-periodic magnetic field analysis with saturation and hysteresis characteristics by harmonic balance finite element method

The authors discuss the harmonic-balance finite-element method (HBFEM) for a time-periodic magnetic field with saturation and hysteresis characteristics and its applications. The HBFEM makes it possible to calculate the distribution of harmonic magnetic flux at an AC magnetization, and it does not require the intricate calculation associated with the time variation. Comparisons between numerical analysis and experimental results are presented. It is shown that the HBFEM can be efficiently used to design a triplex and a special hybrid high-speed motor connected to a power source and external circuit in which the third harmonic components play an important role. >

Some experiments and considerations on behavior of the power converter with bridge-connected reactor circuit

Recently, a new type of a parametrically excited power converter which is made by two C-cores rotated at 90° was proposed and called as Paraformer [1]. The novel characteristic of this device has been remarked as one of the important phenomena which permit to expand the new region of nonlinear magnetics [2], although the operation principles are not yet clearly understood. It is concluded from the present work that the performance characteristics of the bridge-core circuit which we designed are completely agreed with that of the Paraformer, and a novel characteristic of the Paraformer is generated by the bridge circuit. By using the symmetrical or the asymmetrical bridge-core circuit, it is possible to make not only a practical high efficient and high sensitive voltage regulator but also a power converter which can change the output frequency. Furthermore, a large capacity power converter can be achieved by constructing a bridge circuit with 3-5 separate reactors.

Four component three dimensional FEM analysis of flux concentration apparatus with four plates

The authors deal with the four-component three-dimensional finite-element analysis of a flux concentration model with four thick conducting plates placed between a pair of AC-excited coils. An improved formulation thats based on the Galerkin method is used. The distributions of flux densities, eddy currents and scalar potentials are calculated, and the results are discussed. The role of the scalar potential in the 3-D analysis is clarified. It is shown to be necessary when treating a model including conductors with any discontinuity or gaps in the streamlines similar to the flow of the impressed currents. >

3-D finite element analysis of flux reflection and flux concentration effects of eddy currents

This paper deals with the flux reflection effect and the flux concentration effect of eddy currents induced in a pair of conductors with small slit between them under an a.c.-excited coil. To perform this analysis an iterative method of FEM calculation using four components is applied to the 3-D model. By this method, the computer memory for the main system matrix can be reduced to one sixteenth, compared with the 3-D methods conventionally used. The model analyzed is a flux concentration apparatus for producing a state of high flux density through utilization of eddy currents.