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Recently, the request for the compactness of rotating machines such as traction motors has been increasing and thus the rotating machines should be of high power density. The compactness of motors makes the problem of the magnetic saturation more serious. With this background, this paper describes the design optimization of air-ducts in induction motors. By investigating the relationship between the rotor-yoke configuration with air-ducts and the magnetic flux density in the air-gap, we determine the desirable air-ducts arrangement. Some numerical results, which demonstrate the validity of the proposed approach, are also presented. Index terms - air-duct, design optimization, hybrid FE-BE method, magnetic saturation, rotating machines, space harmonics.

This paper describes the method that makes it easy to simulate the magnetic levitation system by using the Boundary Element Method (BEM) or the hybrid Finite Element(FE)-Boundary Element(BE) Method. The proposed approach enables us to simulate a nonlinear control system in consideration of both the motion equation and the voltage equation. And the voltage equation contains the term of the leakage inductance that we have to consider in the actual model.

This paper describes a hybrid approach of the finite element method and the boundary type solutions, i.e. the Trefftz method and the boundary element method, for analyzing the magnetic field in rotating machines. This approach has the advantage of obtaining continuous physical quantifies precisely without the singularities in calculating boundary integrals. Its application to a concrete model is also presented.

There are several difficulties in calculating eddy currents in plates with thin slits by the finite element method (FEM). Under the influence of flat finite elements at slits, the accuracy of analysis decreases and the computation time increases. In this paper, using the A - [Theta] method, we propose a novel technique, which overcomes those defects. The feature of the method is to adopt double nodes for the electric scalar potential [Theta] at slits, but not to the magnetic vector potential A. Adopting this technique, slits are equivalent to current barriers that have infinitesimal width. Some numerical results, which show the validity of the proposed method, are also presented.

An analytical approach for calculating magnetic fields and potentials of massive current coils is presented. The proposed approach enables accurate, fast, and systematic evaluation of magnetic field intensity, vector potential, and scalar potential due to massive currents by means of simple and similar algorithms.

This paper describes the hybrid finite element (FE) and boundary element (BE) method for the eddy current problem including moving conductors. Electromagnetic phenomena due to the three-dimensional movement of conductors can be computed easily and naturally by the presented formulation. Its application to a simple model which has only one conductor is also given.

The finite element method (FEM) and the boundary element method (BEM) have entirely different characteristics. The FEM suits the analysis of a complicated region which includes nonlinear materials, and the BEM is useful for analyzing very large linear fields. This paper describes the hybrid finite and boundary element method which has the advantages of both methods. Here, we adopt the hybrid method to a 2D nonlinear magnetic problem with the moving boundary and make its advantages clear.

This paper proposes a smoothing method using the boundary element method(BEM) for the finite element(FE) analysis of the electromagnetic fields. This method has the advantage of obtaining the physical quantities continuously with good precision. This approach is also easily applied to a complicated region which could include non-linear materials or eddy currents. To verify this approach, the numerical results obtained by the proposed method are compared with the theoretical values.

A magnetic levitation system with both permanent magnets and electromagnets has less powerloss than a conventional attractive-type system. In this paper, we propose an analysis procedure of the hybrid magnet in the experimental levitation system. First, we make a two-dimensional analysis of the hybrid magnet. Though the vector potential A method is often adopted to solve magnetic problems, we propose the magnetic field intensity H method. Second, utilizing the sequential quadratic programming method, we attempt to optimize the arrangement of permanent magnets, which have the maximum guidance force. Finally we investigate the responses of our experimental magnet levitation system by simulations.

This paper deals with a boundary element method using edge elements for 3-D eddy current problems. In this method the eddy current region is formulated only by means of the electric field intensity E, while the free space only by the magnetic field intensity H. In each region, both unknown variables are independently expressed from each other. By both physical consideration and the appropriate boundary element discretization, these physical quantities can be connected on the interface with ease. To verify this approach some numerical results obtained by the proposed method are compared with measured ones.

This paper presents the hybrid finite element and boundary element method using edge elements for a 3-D electromagnetic problem with open boundary. In this method we adopt the modified magnetic vector potential A(super *) and the magnetic field intensity H as the physical quantities. The appropriate boundary element discretization described in this paper makes it easy to couple the BE region with the FE region through the transformation of unknown variables. To verify this approach some numerical results obtained by the proposed method are compared with measured ones.

Magnetic stimulation therapy without pain is being studied as an alternative to electrical stimulation therapy with pain. This paper presents a novel coil arrangement including the two sub-coils besides the main coil. This scheme results in the desired flux distribution penetrating more deeply into the tissue. Each optimal coil current and the optimal sub-coil location are derived with the aid of numerical magnetic field analysis. The derivation is carried out by means of the genetic algorithm combined with the finite element method. Moreover, we incorporate the circuit equations with the above methods. The results suggest that the magnetic stimulation with plural coils is effective for the pudendal nerve in the deep site. Index Terms - Finite Element Method, Genetic Algorithm, Magnetic Stimulation, Nerve Stimulation Site.

This paper presents a novel design approach composed of two sequential processes for 3D magnetic shielding problems, which results in the global optimum solution in a shorter time. The feature of the proposed approach is the adoption of the specific boundary element with permeability of infinity. Assuming the permeability of infinity enables us to regard the thickness of ferromagnetic shields as infinitesimal, and thus to simplify the investigated model adequately in numerical analysis. This reduces the number of unknown variables and saves us a large amount of CPU-time for grasping the broad characteristics of the model. Some numerical results that demonstrate the validity of the proposed approach are also presented. Index Terms - Genetic Algorithm, Hybrid FE-BE Method, Magnetic Shield, Specific Boundary Element Technique, Two Sequential Optimizing Processes.

This paper treats a two-dimensional motion by means of commercial electric motors. The proposed motor consists of four stators of induction motor (IM) and a common solid-conductor. By controlling the phase of supply voltage for each stator winding, the rotor is capable of producing any one of rotary, linear, and helical motions. From 3-D finite element analysis and the experiment, an optimized structure of the motor is derived.

There are several ways to define the gauge condition in the A - Phi method for the 3-D eddy current analysis: e.g. the Coulomb gauge, the Lorentz gauge, etc. Unlike the Coulomb gauge, the physical meaning of the potentials in the Lorentz gauge is not obvious. Therefore this paper introduces a novel physical meaning of the Lorentz gauge, and describes the relationship between these gauge conditions in the A - Phi method systematically from a physical viewpoint.

This paper describes the hybrid finite element and boundary element method for the electromagnetic problems. To attain good accuracy, we adopt the magnetic field intensity H as much as possible as the physical quantity in the hybrid method. We also propose a new boundary element discretization in the H formulation, which makes it easy to couple the BE region with the FE region by introducing the edge boundary element. Some numerical results obtained by the proposed method are compared with measured ones.

For hard disk drives (HDD's) having multiple disk rotational speeds, a new data channel and head positioning servo system was developed. Head positioning performance at the low spin-speed was preserved by using a synchronous servo scheme with more servo areas than the conventional scheme. Using a common physical disk format, sufficient servo performance and the same data recording density of 1.3 Gbit/[inch.sup.2] were obtained on two 2.5 inch prototype HDD's with a low spin-speed 37.5 Hz and a high spin-speed of 75 Hz. Disk interchangeability was also confirmed. Index Terms--Magnetic disk drive, disk rotational speed, sampiing frequency, synchronous servo.

In this study, we attempt to analyze characteristics of Single-sided Linear Induction Motor with a short primary member and a complicated secondary structure, which consists of solid-plate conductor section and a winding one. For this purpose, electromagnetic field analysis by 3-D FEM is combined with electric circuit analysis and motion equation. Here, electric circuit analysis involves the primary and secondary windings. Focusing on the distributions of secondary induced current and thrust force, we discuss various transient phenomena that develop at the boundary between different secondary structures. Finally, to suppress the aggravation of characteristic caused by the secondary structural transition, we improve the boundary. Index Terms--Linear Induction Motor, wound secondary member, Finite Element Method, nodal force method.

This paper treats a novel linear hybrid motor (LHM) by both induction and synchronous operations. The proposed motor consists of one pair of linear synchronous motors (LSMs) and a linear induction motor (LIM). The primary-cores of both LSM and LIM have a common ring winding, and the secondary solid-conductor is arranged in both LIM and the interpole space of LSM. The feature of the motor is that the undesirable vertical force in LSM is offset by the symmetrical double-sided construction and the secondary is capable of self-starting by induction operation. From the investigation by the three-dimensional finite element analysis and experiment, we derive an optimal exciting condition for starting, and then verify that the proposed LHM is effective for practical use. Index Terms -- Linear hybrid motor, induction operation, synchronous operation, finite element analysis.

This paper treats the optimization of rotor construction in the permanent magnet synchronous motor (PMSM). While the field system of PMSM has generally one magnet per pole, we replace the magnet into plural sub-magnets. The dimensions of each sub-magnet are determined by the concept of pulse width modulation (PWM). By adopting the proposed rotor construction, we can not only reduce the space harmonics of the air-gap field but also provide space for damper winding around the direct-axis. From the investigation by hybrid FE-BE (coupled finite element and boundary element) method combined with both electric circuit and motion equation, we verify that the proposed construction is effective for practical use in view of both the harmonics reduction and the damping effects. Index Terms--Permanent magnet synchronous motor, space harmonics, damper winding, hybrid FE-BE method.