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The main issue of a billet heater using induction heating is to avoid billets that were not heated at a desired temperature. In order to improve the induction heating system, it is necessary to clarify the heating property of an object due to eddy current loss and to investigate the temperature distribution in an object by the magneto-thermal coupled analysis. In this paper, the eddy current and temperature distribution of a billet heater is analyzed considering the heat emission, heat conduction, and temperature dependence of magnetic characteristics of the billet. It is shown that the calculated values of temperature in the center and surface of a billet are in good agreement with measured values. The precise analysis is possible by considering the temperature dependence of magnetic characteristics, heat conductivity, etc. The detailed behavior of the heat generation in the billet is clarified. The skin depth is increased because the resistivity of the billet is increased and the permeability is decreased at high temperature. As a result, the flux in the billet is reduced, and then the power (eddy current loss) in the billet is decreased. Index Terms--Finite element method, induction heating, magneto-thermal coupled analysis, temperature dependence of magnetic characteristics.

We performed the stress analysis of a SPM motor core with the shrink fitting, and calculated the iron loss by FEM using the B-H curve and iron loss measured under a compressive stress. We examined the effect of shrink fitting on iron loss of an actual motor and the validity of the estimation of the iron loss by FEM analysis using the measured properties affected by the stress. It is shown that the magnetic properties under the compressive stress should be considered for the precise estimation of the iron loss in a motor with the shrink fitting. Index Terms--Estimation of iron loss, finite element methods, permanent magnet motors, shrink fitting.

The topology optimization, which determines the optimal topology of nonmagnetic material in which the eddy current flows, such as an electromagnetic shield, by distributing the nonmagnetic conducting materials in the design domain, is attractive for designers of magnetic devices, because an initial conceptual design can be obtained. In this paper, the ON/OFF method which was developed for the static field problem is extended to the dynamic field problem. The method makes them particularly useful in topology optimization, where the parameterization enables all feasible shapes of electromagnetic devices to be explored. We applied the ON/OFF sensitivity method to the steady state linear eddy current problem in order to determine the optimal topology of the electromagnetic shield. As a result, the optimal shape of electromagnetic shield, which we could not imagine beforehand can be obtained using the ON/OFF method. Index Terms--Eddy-current problem, forward difference method, ON/OFF method.

In large permanent magnet motors, the permanent magnet in the motor is segmented into parts in order to reduce the eddy current loss. It is reported that the insulation between Nd-Fe-B sintered magnets is possible only by contacting the segmented permanent magnets without the insulation. But the mechanism for such a phenomenon has not been clear yet. In this paper, the effect of force on the apparent contact resistance between permanent magnets is examined. The idea of contact resistance coefficient is also discussed. It is shown that the eddy current loss of segmented sintered Nd-Fe--B magnets is almost the same as the loss of the ease when an insulating material is inserted between magnets. Index Terms--AC magnetic loss, contact resistance, eddy current, segmented magnet.

A magnetic recording head for 600 Gb/[in.sup.2] with a gh recording head field, which is called a 'standard model' is proposed after deep consideration by utilizing the numerical analysis. In order to improve the topology of the having a higher writing field and higher field gradient, the introduction of a 3-D topology optimization method, which is called the 'ON/OFF method', is indispensable. In this paper, an advanced topology of the standard head model is obtained using the ON/OFF method. The recording field of 1.7 T and the field gradient of 0.0314 T/nm with low stray field of 0.1 T at the center of an adjacent track are obtained. The leakage flux in the adjacent track, which is the cause of the crosstalk, is reduced to 50%, which is the most significant improvement. Index Terms--Finite-element analysis, magnetic recording head, topology optimization.

The magnetization loss characteristics of the high temperature superconducting (HTS) layer of the coated conductor with magnetic substrate are studied. The magnetization losses in the superconducting layer of the HTS conductors having the magnetic substrate are much larger than the losses of that having the non-magnetic substrate under the external AC magnetic field parallel to the wide face of a conductor.

The AC transport current loss characteristics of high temperature superconducting (HTS) coated conductor with magnetic substrate is studied. The results have shown that the AC transport current loss is increased until the magnetic saturation in the substrate, as the current distribution in superconducting layer has changed due to the concentration of magnetic flux in the substrate.

Three-dimensional (3-D) hexahedral finite element method (FEM) was used for examining the current distribution and AC loss in each shield layer of the co-axial multi-layered High Temperature Superconducting (HTS) power cable. Findings revealed that the current distribution in the shield layers can be controlled by adjusting the pitches of shield layers.

The effects of the magnetism of substrate on the AC transport current loss of a high temperature superconducting (HTS) conductor with ferromagnetic substrate are explained. The AC transport current loss is found to increase with the concentration of the magnetic flux in the substrate.

The detailed analysis of residual magnetization in permanent magnet type of magnetic resonance imaging (MRI) is important for the improvement of MRI image. The behavior of residual magnetization produced by the z-gradient cot is already reported. As 3-D analysis is strictly required for investigating the residual magnetization produced by the x- or y-gradient coil, the report about such a behavior is few. In this paper, the minor loop and residual magnetization produced by the x-gradient coil in a 3-D model are examined. The useful knowledge for understanding the behavior of the disturbance field due to the residual magnetization in the pole piece, etc., is obtained. Index Terms--Finite-element method (FEM), hysteresis, magnetic resonance imaging (MRI), minor loop.

The eddy current is induced in silicon steel sheets of core block of power reactor due to the fringing flux, and this causes a local overheating. An exact and quick calculation using three-dimensional finite element method is important in order to design a reactor without such a local overheating. If each lamination of core is subdivided into a fine mesh, the number of unknown variables becomes huge and the calculation is difficult within an acceptable CPU time. Therefore, a practical modeling method of lamination of core should be investigated. In this paper, an exact and quick practical nonlinear analysis is performed by subdividing only the region near the surface of lamination into a fine mesh, and by modeling the inner part of lamination as a bulk core having anisotropic conductivity. A criterion how to determine the surface region of lamination which should be subdivided into a fine mesh is denoted. It is shown that the number of elements can be considerably reduced by classifying the analyzed region into two kinds of parts with fine mesh and coarse mesh. Index Terms--Eddy current loss, finite element method, reactor.

Air-gapped iron-cores are widely used for power reactors. Eddy currents are induced in silicon steel sheets due to fringing flux, and this causes local overheating. In order to avoid local heating and to design reactors with high efficiency, the analysis and experiments for evaluating local losses in the core block of the reactor are necessary. In this paper, the modeling of laminated core for practical and accurate analysis is investigated. The number of elements can be reduced by classifying the analyzed region in terms of the amount of fringing flux penetration. The eddy-current losses due to fringing flux are examined using three-dimensional finite-element method and experiments. New concepts for optimal designing of slits are shown. Index Terms--Eddy-current loss, finite-element method, reactor, slit.

NdFeB sintered magnets are widely used in rotating electrical machines. In order to develop an efficient rotating machine, it is important to estimate ac loss of the permanent magnet of rotor precisely. In this paper, the ac losses of the permanent magnet of IEEJ model (surface permanent-magnet motor model) are examined by using the three-dimensional finite-element method taking into account the newly measured hysteresis losses of permanent magnet. The result shows that we should consider not only the eddy-current loss but also the hysteresis loss, when the frequency of ac field due to a slot ripple is of the order of several hundred hertz. Index Terms--Eddy-current loss, hysteresis loss, NdFeB magnet, SPM motor.

An experiment is conducted for analysing the current distribution in high T(sub c) superconducting (HTS) power cable based on E-J power law. The results show that the AC losses in shield layer with intervals are increased when the interval between wires becomes large.

A method for analyzing the current distribution in high-To superconducting (HTS) power cable is examined by the aid of the novel use of anisotropic conductivity and three-dimensional finite element method in consideration of the E-J power law characteristic. The detailed current distribution in the cable is illustrated and the shielding effect of HTS shield is also examined. Index Terms--E-J power law characteristics, HTS power cable, HTS shield, three-dimensional finite element analysis.

AC transport current losses of two kinds of thin film YBCO-coated conductors are examined. Transport current loss characteristics did not accord with the Norris strip model, as had been expected.

A high current density YBCO tape conductor was investigated to determine Ac transport current loss measurements, which showed frequency dependency.