Kazurou Harada

Dynamic analysis of a linear oscillatory actuator under feedback control

The dynamic performance of a linear oscillatory actuator (LOA) is computed using the finite element method, when it is operated by feedback control. In this computation, the magnetic field is perfectly coupled with the driving electric circuit and the kinetic motion of the mover. Comparison with the measured results verifies the validity of this analysis. The influence of feedback control function on the mover amplitude is also verified. In addition, the method of feedback control using the signal, obtained by the induced voltage from a sensing coil in place of a optical sensor is investigated. As a result of that, it is found that both control methods produce almost the same performance.

A study on measurement of magnetostriction of silicon steel sheet by laser displacement meter

Abstract A measurement method of magnetostriction with a laser displacement meter on the market has been compared with the other optical method using laser Doppler vibrometer. In the measurement, the frame to excite the specimen is divided into three parts to fix the specimen, and the phase difference must be adjusted. It is shown that the λ p–p characteristics measured by laser displacement meter have good agreement with the other method.

A novel high power factor converter using a magnetic amplifier

A novel high power factor converter is presented in this paper. The proposed converter is a high-frequency forward converter controlled by a magnetic amplifier. This converter has no need of special control to correct the power factor. Power factor is corrected by the automatic variation of the saturation time of the magnetic amplifier according to the input voltage variation. The current stress of the transistor switch is low because this converter operates in the continuous conduction mode of the inductor current. The circuit operation is verified experimentally at a frequency of 500 kHz.

A study of characteristic analysis of the three-phase transformer with step-lap wound-core

In this paper, the analytic algorithm using equivalent magnetization curves is proposed for analysis of the three-phase transformer with wound-core in consideration of a step-lap joint or noncut structure. Influences of differences in step-lap joints and noncut structures on equivalent magnetization curves are examined using the algorithm. Influences on the exciting currents and core losses of the three-phase transformer are also examined.

A proposal for rotating machineries analysis by considering the unknown equal potential condition on FEM

This paper presents a technique for a magnetic field analysis using the Finite Element Method (FEM) which is applied to the rotatory movement of rotating machinery. The proposed technique uses only a couple of meshes because the nodes on an interface are joined under the unknown equal potential condition. This technique is examined by the analysis of the characteristics of brushless DC machines. Calculated results by this technique agree well with the measured ones, so that the utility of this technique is confirmed. >

Analysis and design of ZVS-PWM half-bridge converter with secondary switches

An improved zero voltage switching (ZVS) PWM half-bridge power converter with secondary switches is proposed and analyzed. The proposed power converter is controlled by PWM of the main switches using a novel switching sequence with a constant switching frequency. The main switches operate with zero voltage switching, and the secondary switches turn on and off with zero voltage and zero current. A small saturable inductor is added in series to the secondary switch in order to achieve zero voltage switching easily. From the analysis, steady state characteristics of the power converter and conditions of zero voltage switching are derived.<<ETX>>

Modeling and simulation of a power electronic converter for EMC

With the advancement of high-frequency switching devices, electromagnetic interference (EMI) has become a problem in power electronic converter designs. It is necessary to consider electromagnetic compatibility (EMC) design and possible EMI levels. This paper describes how to compute magnetic fields from converter EMI currents for a converter design. Firstly, modeling techniques for converter circuit components are discussed for a wide band frequency model by the parameter tuning method. Then a derived model is simulated for harmonic distributions of a loop current and its magnetic field. Examples including resonant type converters are discussed.

Performance of the magnetostriction of a silicon steel sheet with a bias field

Abstract The magnetostriction characteristics of a silicon steel sheet with a bias field have been measured using a modified single sheet tester (SST). The magnetostriction characteristics of the sheet change remarkably under the influence of an exciting dc field.

A calculation of torque in motors considering rotor eccentricity

A new analytical approach to the finite element calculation of torque in motors including eccentric rotor, based on the Maxwell stress method, is proposed in this paper, where the effects due to eccentricity on the cogging torque and the torque characteristics with regard to the speed are confirmed. A brushless dc motor is employed as an analytical model for two kinds of eccentricity. Consequently, in the case of eccentric motors, the unbalanced radial force functions as the repulsive force against rotation which causes the reduction of average torque, and two kinds of eccentric motors have the same tendency regarding the effects on the torque. This proposed approach is applicable to any kind of motor including eccentric rotor.

A novel ZVS multi-resonant converter with rectifiers' deadtime control operated in 20 MHz range

A novel zero-voltage-switched multi-resonant power converter is presented. The rectifier deadtime control proposed in this paper enables this power converter to achieve zero-voltage-switching in any load range and to operate from full load to no load within a high and narrow frequency range. Experimental results of two power converters designed for 2 MHz and 20 MHz operation and analysis are presented.<<ETX>>