Keisuke Fujisaki

Motor Core Iron Loss Analysis Evaluating Shrink Fitting and Stamping by Finite-Element Method

We describe a method to analyze the effects of shrink fitting and stamping on the mechanical stress distribution and iron loss in motor cores. Shrink fitting and stamping are important processes in manufacture of motor cores from electrical steel. The mechanical stress distribution is evaluated by a structural finite-element method, and the iron loss is evaluated by combined analysis of the electromagnetic field (by a finite-element method) and mechanical stress. The method clearly shows that the iron loss becomes larger as the width of the shrink fit increases, an effect borne out by experiment. In regard to the effect of stamping, calculation results again agree well with experimental data

Magnetohydrodynamic calculation of in-mold electromagnetic stirring

To get the optimal operation of in-mold electromagnetic stirring through the fundamental characteristics, we did the magnetohydrodynamic calculation. The electromagnetic force has the eddy distribution through the electromagnetic analysis in case of the rotating stirring mode which is thought to give the uniform velocity at surface. However, it does not much influence on the fluid dynamics, because the inertial effect and the continuity are large enough.

Fundamental characteristics of molten metal flow control by linear induction motor

Molten metal flow control using linear induction motor is expected much to be a new revolutionary basic technology to realize high quality and low cost processes. We report an experiment with fused metal (melting point: 45/spl deg/C) and 100 kg molten steel. According to the fused metal experiment, the linear induction motor has a good ability for stopping and acceleration as well as braking of metal flow. However, the electromagnetic force to be able to stop the metal flow in vertical arrangement is several times larger than the one in horizontal arrangement because of the liquid metal effect. A resonance condenser is useful to reduce the required power source capacity. Therefore, to control the molten metal flow, voltage (current) regulation is superior to frequency regulation. Though the large air gap also makes the electromagnetic force reduced, a conductive shorting bar (Z/sub r/B/sub 2/), installed inside the non-conductive firebrick, increases the electromagnetic force. >

Magnetohydrodynamic calculation for electromagnetic stirring of molten metal

To get the fundamental characteristics of magnetohydrodynamics is extremely important, because in-mold electromagnetic stirring is required to get high quality steel. We have researched magnetohydrodynamic calculations to estimate the experimental data. At first, we compared the calculation velocity and measurement velocity in a pot mold. There is good agreement, though the calculation data depend upon the procedure after now dynamic calculation. Next, we compared molten metals such as molten steel, mercury and fused metal. Since molten steel provides difficulties for measurements, we often estimate the magnetohydrodynamic characteristics through measurement data from mercury or fused metal. The calculation data show that molten steel has the highest speed, though the fused metal has the lowest speed. Lastly, we compare the fluid dynamic characteristics between a pot mold and an endless mold. Though an endless mold is already used in practice, the experimental mold is a pot one. After we get measurement data from the pot mold, we must estimate the characteristics of the endless mold. The calculated data show that the velocity of the pot mold near the meniscus level is larger than that of the endless mold, because the endless mold has the turned over now from the fixed bottom in the pot mold.

In-mold electromagnetic stirring in continuous casting

To obtain the optimal operation of in-mold electromagnetic stirring (EMS) through the fundamental characteristics, the author developed a 3-D magnetohydrodynamic calculation model, taking into consideration heat transfer and solidification as well as free surface. Comparison between measured velocity and calculated velocity is in agreement. A shadow method that calculates electromagnetic force in consideration of free surface transition is proposed to reduce computing time and keep sufficient accuracy. A calculated free surface of mercury under a 200 Hz magnetic field shows an adequate agreement with experimental data. Calculation results applied to the continuous casting process, taking into consideration heat transfer and solidification, are in good agreement with operational data. This model shows that EMS makes the solidified shell uniform and dynamic deviation of temperature stable.

Comparison of Magnetic Field Analysis Methods Considering Magnetic Anisotropy

The magnetic field analysis results on grain-oriented silicon steel sheet and nongrain-oriented silicon steel sheet by the isotropic method, the two-axis isotropic method, the two-axis anisotropic method, the ¿ anisotropic method, and the ¿HB anisotropic method, which are 2-D magnetic analysis methods, are compared. In analyzing the magnetic field in the isotropic material, the isotropic method is more appropriate than the two-axis isotropic method. For the anisotropic material in which the magnetic flux density is much less than saturation magnetic flux density, the two-axis anisotropic method is more preferable than the ¿ anisotropic method, because the result of the two-axis anisotropic method is similar to that of the ¿HB anisotropic method. However, for the analysis in high magnetic flux density near the saturation magnetic flux density, the ¿ anisotropic method is more suitable than the two-axis anisotropic method.

Three-Dimensional Polycrystal Magnetic Field Analysis of Thin Steel

The 3-D polycrystal magnetic field analysis method by means of coordinate transformation is proposed. The local coordinates are fixed in each crystal grain and the global coordinates are defined in the polycrystal steel. Though it is assumed that each crystal grain has the same magnetized characteristics as those of a single crystal grain, the crystal grain shape and its orientations of alpha, beta, and gamma angles are taken into account. When the proposed model is applied to the real grain oriented (GO) steel with 56 crystal grains in 80-mm × 80-mm, and with 0.35-mm thickness, the calculation results are compared with the grain orientations measured by X-ray diffraction. The GO steel has a higher degree of (110)[001] texture with about 3% silicon. The calculated results of higher magnetic flux density part and lower magnetic flux density part in the real GO steel are explained by the alpha angle distribution. The calculated inclination angle distribution and the measured alpha angle distribution seem to be in good agreement. The calculated normal component of the magnetic flux density reflects the beta angle distribution of the real GO steel. It is concluded that the proposed 3-D polycrystal magnetic field analysis is appropriate.

Magnetohydrodynamic calculation for free surfaces

A magnetohydrodynamic calculation for free surface is used in the design and evaluation of a cold-crucible or initial solidification such as stirring phenomena commonly found in the metal processing industry. A direct calculation of both the electromagnetic field and the fluid dynamics field for the surface of a molten metal that changes with time requires significant computing times, especially for three-dimensional models. An approximate calculation method, the shadow method, is one which uses a fixed mesh. Results obtained by the shadow method show that the shape of molten metal does not collapse under gravity as observed experimentally.

Core Loss Reduction of an Interior Permanent-Magnet Synchronous Motor Using Amorphous Stator Core

The core losses of an interior permanent-magnet synchronous motor (PMSM) have been reduced by about 50% using an amorphous magnetic material (AMM) stator core instead of a nonoriented (NO) steel stator core. Numerical calculation and experimental tests data have been compared to evaluate the reliability of the results. The AMM stator core has been realized using the latest improvements in manufacturing technologies.

Magnetic hysteresis curve influenced by power-semiconductor characteristics in pulse-width-modulation inverter

The influence of power semiconductor characteristic in Pulse-width-modulation (PWM) inverter on the magnetic hysteresis curve in silicon steel is discussed through the measured magnetic hysteresis curves. The magnetic hysteresis curve of PWM inverter-fed silicon steel has a lot of minor loops as closed loops and open loops, which make an influence on the iron loss. Two shapes of minor loops are found to be caused by the voltage shifts and they are derived from the on-voltage of the semiconductors in PWM inverter circuit. Therefore, it is concluded that the power-semiconductor characteristic in PWM inverter makes an influence on the magnetic hysteresis curve in silicon steel.