Kazuhiro Muramatsu

Comparison of coordinate systems for eddy current analysis in moving conductors

The moving and fixed coordinate systems for eddy current analysis with moving conductors are examined and compared. It is shown that the moving coordinate system is superior for transient analysis from the standpoints of accuracy, computer storage, and CPU time. In DC steady state analysis of large Peclet number, spurious oscillations occur when using the fixed coordinate system with the ordinary Galerkin finite element method. The solution using the moving coordinate system, however, can be obtained stably. >

Comparison of various methods for 3-D eddy current analysis

Computer codes developed for the A- phi , A- phi - Omega , A- Omega , T- Omega , and E- Omega methods are considered. Their accuracy, storage requirements, and CPU time are compared for linear eddy-current models. It is shown that the A- phi - Omega and T- Omega methods are preferable from the viewpoint of accuracy. The A- Omega and E- Omega methods are preferable with respect to storage and CPU time. >

Practical analysis of 3-D dynamic nonlinear magnetic field using time-periodic finite element method

A practical 3-D finite element method using edge elements for analyzing stationary nonlinear magnetic fields with eddy currents in electric apparatus, in which the flux interlinking the voltage winding is given, has been proposed. The method is applied to the analysis of magnetic fields in the Epstein frame. >

3-D eddy current analysis in moving conductor of permanent magnet type of retarder using moving coordinate system

A 3-D DC steady state eddy current analysis of a permanent magnet type retarder which rotates at high speed is carried out using a moving coordinate system. The method of DC steady state analysis using a moving coordinate system is described. The calculated results, braking torque etc., are compared with measured ones.

Magnetostriction measurements with a laser Doppler velocimeter

A new method for measuring the magnetostriction of silicon steel sheet using a laser Doppler velocimeter has been developed. This method has the following advantages: (a) non-contact measurement, (b) better resolution (less than 4/spl times/10/sup -8/ m under the condition that the error is within 1%) than conventional methods, (c) measurement of magnetostriction in any direction of anisotropic material and (d) little operator skill required. >

Investigation of effectiveness of 3-D nonconforming mesh

The 3-D finite element domain discretized by a nonconforming mesh using only first-order brick elements in investigated. The accuracy, memory requirements, and CPU time using the nonconforming mesh are compared with those using the ordinary conforming mesh by analyzing a 3-D linear magnetostatic model proposed by the IEE of Japan. It is shown that the memory requirements and CPU time can be decreased to about one-third of those using the ordinary mesh. >

3-D adaptive mesh refinement using nonconforming elements

The conventional method of analysis for nonconforming mesh with 3-D brick elements is improved in order to avoid the error due to the multiapproximation of potential. The method of adaptive mesh refinement using the nonconforming elements is described, and it is applied to a nonlinear magnetostatic model. It is shown that the error in potential at a nonconforming node due to multiapproximation can be avoided by improving the conventional method of analysis for the nonconforming mesh. The accuracy of the flux density using the novel adaptive mesh refinement scheme is improved compared with that using an ordinary conforming mesh with the same number of unknowns. Although the proposed method needs about twice as much CPU time as the conventional method, the mesh can be created automatically. >

Effect of continuity of potential on accuracy in magnetic field analysis using nonconforming mesh

Methods of analyzing magnetic fields in rotating machines using nonconforming meshes, in which only an interpolation technique is applied, are investigated. The effect of the continuity of potentials at nonconforming surfaces on accuracy is examined, it is shown that although the flux distribution is not affected by the discontinuity of the potential, the force and torque are fairly affected by the discontinuity. Therefore, it is shown that a continuous method, or a discontinuous method using a fine mesh should be used especially in force and torque calculation. An analysis of an induction motor is also carried out using a nonconforming mesh.

Investigation of effectiveness of various methods with different unknown variables for 3-D eddy current analysis

Computer codes using the A- phi , A- phi - Omega , A*-0 Omega -E, T- Omega , and E- Omega methods were developed. The effects of the volume ratio of the conductor region to the whole region, the shape of the conductor, and the ratio of the hole region to the conductor region on the computer storage, the CPU time, and the accuracy of the methods are investigated systematically using a few simple models. The effect of the conductivity of the conductor is also examined. The computer storage, the CPU time, and the error are found to increase with increase of the volume ratio of the conductor region to the whole region. The computer storage and the CPU time are affected by the shape of the conductor in some methods of analysis. The error of the A*- Omega (E- Omega ) method is larger than that of the other methods. >

3-D time-periodic finite element analysis of magnetic field in non-oriented materials taking into account hysteresis characteristics

Problems in analyzing 3-D stationary nonlinear magnetic field in non-oriented material taking into account hysteresis characteristics and eddy current, such as finite element formulation and convergence of nonlinear iteration, are discussed.