This paper proposes a novel three-phase converter using three-phase series chopper. The proposed circuit is composed by three switching devices, three-phase diode bridge, input reactors, and LC low pass filter. In the conventional circuit which combines three-phase diode bridge and boost voltage chopper, to obtain sinusoidal input current the output voltage must be twice or three times larger than the maximum input line voltage. However, in the proposed circuit, the input current can be controlled to be sinusoidal also when the output voltage is same as the maximum input line voltage. This can be achieved because in the proposed circuit the discharging current of the reactors does not flow through the voltage source. The control method of the proposed circuit is as simple as the one of conventional circuit since all the three switching devices are simultaneously turned on and off.
This paper discusses about the theoretical analysis and the design of the proposed circuit. In addition, simulation and experimental results are reported. The proposed circuit has obtained 93% as the efficiency, and 99.7% at 1.3kW load as the input power factor.

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A single- phase current source type converter generates many harmonic components in the input current. These harmonics may cause various disturbances in the power distribution systems.
In this paper, we propose a reduction method of the harmonic currents based on the principle of constant resistance circuit. The configuration of proposed circuit is simple owing to use of passive elements only. The principle of harmonic currents reduction in this method and the design method of the circuit constants are described. We carry out the analysis of this circuit, and clarify the reduction effects of harmonic currents and the quantity of the power loss.
From these results, it is clarified that this method is very effective and useful.

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By a combination of a loss-less snubber and sensing of the current or voltage, soft-switched high power factor AC/DC converters are realized by a simple circuit construction. In this paper the boost type AC/DC converter applying this soft switching technique is analyzed. In this case, a nonlinear differential equation for the output voltage is obtained and solved under the proper assumptions in order to derive the circuit characteristics such as the power factor and output voltage as the functions of the circuit parameters. Next these analytical results are verified by the experiments. These converters are need two times voltage of the input peak voltage for soft switching. At last, a new technique to spread the range of the soft switching is proposed.

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The active-filter is one of the most efficient methods to improve power factor. However, this method has problems such as increasing switching loss and switching noise.
This paper describes a new power factor correction (PFC) converter called “Partial-switching PFC”, which achieves power factor rate of 99% only by generating a single pulse in the power line cycle with high efficiency and low total harmonic distortion. Its application to our air-conditioners is described at the end.

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This paper presents a novel prototype three-phase current-fed PWM converter with switched-capacitor type resonant DC link commutation circuit operating with a new optimum PWM pattern strategy under a design consideration of low-pass filter, which can operate on the basis of the principle of zero current soft-switching commutation.
In the first place, the steady-state operating principle of this converter with a new resonant DC link snubber circuit is described in connection with the equivalent operating circuit, together with the practical design procedure of the switched-capacitor type resonant DC link circuit. In the second place, the three-phase current-fed PWM converter with the switched-capacitor type resonant DC link circuit is discussed from a theoretical viewpoint on the basis of a design example for high-power applications. The actively delayed time correction method to compensate distorted currents due to a relatively long resonant commutation time is newly implemented in the open loop control scheme so as to acquire the new optimum PWM pattern. Finally, the experiment of set-up in laboratory system of this converter is concretely demonstrated herein to confirm a zero current soft-switching commutation of this converter. The comparative evaluations between current-fed hard-switching PWM and soft-switching PWM converters are carried out from a viewpoint of their PWM converter characteristics.

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For the better performance and/or the high speed running for electric rolling-stocks, high accuracy power factor control with PWM power converter fed by ac power line has become popular. It is practically easy to control actual power factor itself at the input point of the power converter on the rolling-stock, however, the more important is that at substations. Although there are some technical difficulties for detecting the correct voltage phase angle on the train, caused by, for example, interference from thyristor controlled converters, suitable target value for practical power factor can be calculated under reasonable conditions. Among some kinds of control concept, the instantaneous current control referring sinusoidal waveform is the most suitable solution for the Japanese Shinkansen. The test results proved the expected power factor control performance.

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This paper proposes to use a loss-less snubber with switching device to perform soft-switching. It results in not only decreasing switching loss in the device drastically, but also improving input ac current waveform distortion. The computer simulation results show that the input current waveform of proposed converter seems to eliminate 3rd harmonic component. we have performed the analysis of input current waveform and show the requirements necessary for the elimination of the 3rd harmonic component. We also show the procedure to design the parameters of the converter.

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Demand for electronic watthour meters which can carry many functions has been increasing, because power rate systems have become more complicated and automatic meter reading has been introduced in recent years. However electro watthour meters are still expensive compared to the induction type watthour meters, and are therefore not popular. A low cost electronic watthour meter is thus required. The power measurment formula using a Hall element has long been known, and it has been thought that this formula can be used to construct a low cost watthour meter. We have established a method of compensating the temperature characteristics of the Hall element which was required to achieve the practical use in an electric watthour meter, and have reached the required standard.

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This paper describes the damping effect by cage bars of self-starting permanent magnet synchronous motors when load changes suddenly. A time-stepping finite element method including the rotor movement is used, where both terminal voltage and load torque are given as the known values. Transient current, torque and angular speed are computed respectively. In simulating the rotor movement, the suitable time step to take account of the effects of space harmonics, is determined. The agreement between calculated and measured results of the transient performance in an experimental motor is good.

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In this paper, a variable structure controller with prescribed transient response is proposed for uncertain systems. By using a function augmented sliding hyperplane, it is guaranteed that the output tracking error converges to zero in finite time. In addition, the proposed scheme eliminates the reaching phase problem so that the closed-loop system always shows the invariance property to parameter uncertainties and external disturbances.

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This paper consists of two main parts. The first part newly proposes a basically and commonly important mathematical model in new closed form for synchronous motors of salient pole characteristics, which indicates with clear physical meaning motor dynamics, torque generation relation and energy transfer relation in general frame. The second part extends the former model-based analytical results to the analysis of energy-efficient but desired-torque-producing current controls such as minimum current control, unity power factor current control and maximum power factor current control. New analytical methods for generating current command in real time based on torque command are given, which are essential for realizing these attractive energy-efficient control schemes. Interesting phenomena of interior states of motors occurring during the controls are also newly clarified. Analysis with clear physical meaning is carried out in general frame and most of the results are new.

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Soft-switching power supplies and their related application systems have attracted because soft-switching scheme has remarkable advantages such as lowered switching loss, reduced dynamic electrical stresses, reduced EMI noise and so on. However most of soft-switching power conversion systems include some inherent difficulties. For example, power conversion efficiency is lowered by conduction losses caused by significant circulating current and resonant current due to soft-switching operation. To solved their difficulties, authors have proposed a new phase-shift PWM control scheme and have already reported before about quasi-resonant high-frequency AC link DC-DC converter and single phase DC-AC converter applied for proposed control scheme. They have some features such as circulating current reduction, lowered conduction losses and easily achieved soft-switching and so on.
In this paper, authors apply a proposed control scheme to a quasi-resonant high-frequency AC link three-phase DC-AC converter. Its new operation principle based on time shared space vector theory is proposed and unique features are described. Operating performance and evaluation of THD (Total Harmonic distortion) of this three-phase DC-AC converter in steady-state are illustrated by means of simulating results.

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A method is given for calculating the single-step response with one-two-phase-on drive, and the response characteristics are compared with that of the one-phase-on and two-phase-on drives. Oscillation characteristics of the hybrid stepping motor with one-two-phase-on drive are measured, and compared with that of the other drive methods. It is shown that the oscillation curves with one-two-phase-on drive have two peaks due to exciting conditions, and relations between the single-step response and oscillation characteristics are investigated. The maximum slewing pulse rate f_M with one-two-phase-on drive are compared with that of the other drive methods. The oscillation characteristics in the neighborfood of f_M are studied.

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The simulation program is an extremely powerful tool to examine the substation capacity, pantograph voltage and effects of improving electric facilities of the DC feeding system, which should further be improved to be easier to use at higher precision and also to cut computing time.
We improved the program, therefore, to make it possible to keep the train operation time constant by computing run curve data for this purpose in advance. To do this, we also control traction currents to suppress changes in train speed due to fluctuation of pantograph voltage. To Simulate train operation more closely to actual situations, we improved the program to enable simulation in optional time zones.
In addition, we clarified the theory of repeated convergence computation, improved the methods of averaging and judging computation results, and expedited the computation to attain earlier convergence.

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This paper proposes a series-resonant high-frequency AC linked DC-AC new-type converter and an improved realtime control approach for sinusoidal output voltage waveform, which is less influenced by the input voltage and load variations. By using application software of MATLAB, the simulation of this converter is offered to compare the performances of converter by applying the conventional control method and the proposed control method. The operation of the proposed converter with the proposed control method is verified by experiment and simulation results.

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計算機による人間の表情理解は,よりよいユーザインタフェースの構築のために重要な技術である.本論文では,顔の表情動画像から連続的な表情変化を認識する手法を提案する.本手法では,まずリンクの重みを考慮したラベル付けグラフ・マッチングを用いて,顔特徴点の局所特徴及び空間的位置関係両方とも考慮し,顔表情動画像から顔特徴点を追跡する.次に,顔特徴点の推移をB-spline曲線で近似した表情変化モデルと,追跡軌跡との距離により表情を識別する.表情のカテゴリーだけでなく,フレームごとの表情変化の程度も認識することができる.この表情変化の程度情報により入力動画像とモデルとの時間差を吸収できる.また,現フレームで得られた表情情報を次フレームの追跡処理にフィードバックし,処理時間を短縮する.

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Although general-purpose inverters have been used for variable speeds driving of AC motors, these are only for induction motor (IM) driving. Synchronous motor (SM) with permanent magnets has many advantages compared with IM; Small size, high efficiency, driving only synchronous frequency, and so on. In this paper, “general-purpose inverter for SM driving” is discussed. Following characteristics are required for the achievement of this inverter; (1) Stable driving without position sensor. (2) Performance characteristics equal to DC motor driving. (3) Robust control system with the estimating functions of motor parameters.
This paper describes practical methods that attain the above characteristics by controlling primary flux of SM. In addition, it is shown that the estimating functions of motor parameters and the inverter circuits generating voltages equal to reference are indispensable to achieve high performance over all working regions.

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In recent yeas several harmonic problems have been occured in distribution system by load current harmonics of many smart machines with power electronics technology. Although, in this situation, the guidelines have been instituted in 1994 for harmonics reduction, they are not sufficient for securing against all the harmonic problems. So, we developed active filter with neural network control to suppress harmonic voltage. This paper describes the suppression performance analysis of this active filter experimentally adapted in distribution network.

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A suitable structure for small-capacity generator must be simple, robust, highly reliable and maintenance-free.
The authors present an original brushless cylindrical-rotor type 4-pole three-phase synchronous generator without excitor. The stator is provided with a 4-pole three-phase main winding and a 2-pole single-phase exciting winding, and rotor field coils are connected with diodes, respectively, so as to make the same pole magnetic field as the stator main winding. The each field coil is consisted of a half-wave rectification circuit. The rotor field excitation is controlled proportionally by the stator dc exciting current.
By the scheme that the stator main winding is connected to leading capacitors at the terminals for shunt excitation, and connected to the full-wave rectifier at the neutral point and the rectified current supplied to the stator exciting winding for series excitation, a brushless self-excited three-phase synchronous generator has been achieved.
In this paper the circuit configuration of the generator and the experimental results using a 2kVA prototype machine are shown.

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So far, Two-Degree-of-Freedom control system has been used to realize desirable transient response in the tracking system of a Hard Disk Drive (HDD). It is easy to realize a high speed seek, if the actuator of the HDD has a resonance mode at a much higher frequency domain than the desired control domain. However, it is generally difficult to design an actuator that has a resonance mode in a high frequency domain. So, in order to realize a high speed seek, it is important to design a digital control system in consideration of the resonance mode of the actuator. In this case, if the Nyquist frequency of the control system is higher than the resonance mode of the actuator, the control system can be designed by using a method such as a H∞ control theory in consideration of the resonance mode. However, if the Nyquist frequency isn't higher than the resonance mode of the actuator, it is very difficult to realize a high speed seek without mechanical vibration using a conventional method. Then, in this paper the method of applying the N-Delay control theory to the design of the feedforward controller in a Two-Degree-of-Freedom system, and searching for the optimum time allocation of the N-Delay controller based on an evaluation function are proposed. Using these methods, the frequency component of the feedforward control signal can be diminished at the desired frequency point higher than the Nyquist frequency. The validity of the proposed method is confirmed by the numerical and experimental results with a miniature 2.5-inch hard disk drive.

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In large capacity drives such as blower, pump, linear railway and steel rolling mill drives, AC motors rated more than several thousands kW are used. In such cases, even though semiconductor switching devices of maximum capacity are used, the realizable capacity of the drive inverters are insufficient. Hence usually, for such drives, two or more inverters which operate with suitable phase differences have been combined using transformers or two inverters have been combined using inter-phase reactors. However, transformers and reactors have problems of acoustic noise and high losses, and in addition they are bulky and expensive.
To overcome these problems, in this paper, a new configuration for high-power drives using a wound rotor induction motor and two inverters, is proposed. In this configuration, the outputs of the two inverters are combined electro-mechanically in the machine, and hence the motor speed correspond to the sum or difference of the inverter frequency, and novel features can be obtained.

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A novel magnetic damper, named the MS-damper, was developed based on a newly discovered energy conversion method, by which mechanical vibratory energy is converted to electromagnetic energy. The structure of the MS-damper is based on a magnetic seesawing effect or the oscillation-induced portioning out of flux from a permanent magnet. This paper discusses damper principles, followed by an outline of analyses on damping forces using Bessel-Kelvin functions. Frequency characteristics of damping coefficients are introduced as well. Test results which show good agreement with analytical results are discussed as well. All in all, the damping coefficients obtained from the test results were ten-times larger than the most favorable coefficients obtained from conventional dampers.

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