Generally speaking, the characteristics of induction motors (IM) are analyzed using the equivalent circuit with d-q transformation. Though this method is simple, the magnetic flux distribution in stator and rotor is defined as sinusoidal wave. Therefore, the equivalent circuits become complex relatively for the high frequency components and the transient state. For detailed analysis, the finite elements method (FEM) is adopted. FEM can consider the influence of the skewed rotor bars, slots and skin coefficient However, the calculation time for high frequency components and transient analysis isvery long. Therefore, we willpropose anew method of characteristics analysis for IM. The proposed method analyzes magnetic flux simply based onthe construction of IM. It can analyze transient and steady state and high frequency components regardless of any kind of sources. The influence of the skewed rotor bars and slots can also be considered simply. In this paper, the analysis manner, the comparison with the experimental results, the results of proposed method and d-q transformation are described.

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This paper presents the optimum design approach of the low speed, high torque permanent magnet motors. The approach is divided into two steps; the first step is a rough estimation of torque by linear analysis and the second is the optimization of motor configuration based on the non-linear FEM analysis. Under the restricted specifications of dimensions and electrical requirements, the 16-pole, 18-coil permanent magnet motor with 600 Nm, 300 rpm rating has been designed and constructed.

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The DC Decay Testing Method is quite useful at testing large-capacity machines, because it is a simple standstill response testing method and needs only a small capacity of dc power supply equipments. When authors held a field test of the large-capacity alternating current generator (6000KVA-18P), we found that there was an unnecessary small curl in operational impedance locus. And it lead to the error at predicting the machine constants of its generator. So we consider that it is a problm in practice.
In this paper, the investigation of measured data and approximate analytical calculation shows that the curl in operational impedance locus is caused by truncating the dc decay current data. So, authors propose a data processing method by data extrapolation which predicts the decay current after the measured data. And the result of applying the Expanded Dalton-Cameron Method to the total decay current is good agreement with the result of the other measuring methods. The proposed method is also applicable in testing the smalland middle-capacity machines and expands the usefulness of the DC Decay Testing Method.

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This paper proposes as imple PWM scheme which alleviates the common mode voltage problems of the three level inverter applications. The new PWM scheme shows a great potential of reducing leakage current and bearing current problems. Moreover this new scheme uses only seven (7) voltage vectors, and gives the advantage of less complex control circuitry.

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This paper presents an autonomous compensator design using Genetic Algorithms (GA) for vibration suppression control in 2-mass resonant systems. The control system is composed of a robust 2-degrees-of-freedom compensator based on the coprime factorization description. In general, the optimal design for free parameters of the compensator requires the complicated numerical calculation process under given and/or identified plant parameters. In this paper, autonomous algorithms for both the identification of plant parameters and the design of compensator are proposed, where the optimal set of the plant parameters and the free parameters of compensator can be identified in each design phase by the optimization ability of GA. The effectiveness of the proposed optimal design can be verified by experiments paying attention to the vibration suppression characteristics and the robustness against variations of mechanical parameters.

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The three-phase diode-bridge rectifier (TDR) with a DC side capacitor composed of only the diode and the capacitor is widely utilized in various industrial fields for its structural simplicity and low cost. However, its power factor is bad due to distorted waveform of the input current and the circuitry synthesis has been done in empirical trial and error ways until now. Therefore, for intending to give a solution to this, this paper presents a systematic analytical method obtaining rigorously quantitative result.
Overall characteristics of TDR are strictly analyzed by using a parameter of the phase angle. This parameter is decided by the capacitor and load resistance. There exist current continuous and discontinuous modes, and an analytical result of the current of the capacitor gives an important indicator for the selection of the capacity of the capacitor. Analytical results are verified by the experiment.

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It is essential, in beer bottling plants, to reduce the ratio of defective products. One of the best ways to realize it is to detect the abnormally filled bottles as faster as they are filled, and find out which filling valve caused them. There have been a couple of technologies proposed to inspectt products at the last of the manufacturing process; however, there is none that can actualize the above requirement.
We propose, in this paper, a new method, which enables measuring the filling precision of each valve. It employs computer vision to gauge the filled level, and sensors to relate each bottle to the valve that has filled it. The problems of gauging are the frothed bubbles and the rough surface caused by jolts of the conveyer. In order to decrease the turbulent influences, we propose to apply statistical procedures to the measured data.
Through experiments at a test plant and an actual one, we confirmed that the distribution of measured data was approximately normal as we had hypothesized, and the mean value was quite stable. In addition, we verified that the measurement was accurate. As a result, we conclude that our proposed technique is quite effective.

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In this paper, we develop a model of a snake-like robot consisting of n rigid links and propose several control strategies to achieve smooth undulative locomotion and position control. The model is based on nonholonomic velocity conditions that arise from non-slipping assumption about the wheels. Singular postures of the robot are analyzed and they are taken in account while deriving the control law. The control strategies are based on Lyapunov method and on constraining the trace of the snake's head into some kind of serpenoid trace, respectively. The later method is also applied for a simple tracking control method.

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In electric motor coaches, when the adhesion force coefficient between rail and driving wheel decreases suddenly, the electric motor coach has slip phenomena. We have already proposed the anti-slip control system based on ordinary disturbance observer. In order to realize the more stable anti-slip readhesion control in case of large variation of adhesion force coefficient, this paper proposes a new anti-slip readhesion control based on first order disturbance observer and new torque function. In the numerical simulation results in this paper, the proposed anti-slip readhesion control well regulates the driving wheel torque of electric motor coach stably.

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Control strategies for multiple current-source converters ^[1] employing large capacity gate turn-off (GTO) thyristors are applied for a 20MW Superconducting Magnetic Energy Storage (SMES) system. Suitable control method and control block diagrams are proposed by taking much use of the multiple structure. Pulse Width Modulation (PWM) control method of current source converters for the purpose of high efficiency and low harmonic distortion is explained. A unique control method for small power output is shown. The results of digital simulation by Electro Magnetic Transient Program (EMTP) are provided to validate the proposed control methods of SMES power conditioning.

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In power stations and substations of electric power companies, power semiconductor devices such as diodes and thyristors have been used in control power supplies and emergency power supplies since the 1970s. Such equipments designed on the assumption that power semiconductor devices are semipermanent, since their service life is much longer than those of capacitors and resistors. Therefore, it is hard to find studies that systematically examine the long-term reliability of semiconductor devices.
Such studies are very important from the viewpoint of assuring reliability and of improving the renewal period by proper equipment maintenance. This paper presents the long-term reliability of power semiconductor devices used in power station rectifiers and substation rectifiers.

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Recently, in the machinery field, the outoput of actuators becomes greater by the demands for high speed response and high accuracy positioning control. On the other hand, the demands for cost and lighter weight make the machine stand slimer. As a result, the machine stand vibrates at each opertation of actuators and this vibration possibly affects a positioning control. That is, the settling time of the positioning control is prolonged. In order to remove this influence, this paper shows the method of a feedforward controller design for a system including not only a machine but also a machine stand. Moreover, the model for this system is proposed and identified by the genetic algorithm in order to make the feedfoward controller design possible. Effectiveness of the proposed method is confirmed by the experiments.

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We have realized a new inverter circuit which works as a complete current type inverter, using an immittance converter link with a high frequency insulation transformer.
This paper proposes a new utility interactive inverter using an immittance converter on a photovoltaic system that supplies the utility source with the power generated by solar cells. Characteristics of this utility interactive inverter are as follows. In the new inverter, the interconnecting reactor which has heavy weight and low efficiency is unnecessary. The inverter output current is in proportion to only the PWM output voltage of the high frequency inverter, independent of the amplitude or the waveform of the utility source voltage. The inverter output current to the utility source can be controlled easily, and can be maintained at the reference value with very fast response even if the utility voltage changes sharply.

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This paper discusses a soft switching circuit and a control system utilizing resonance operation. The main circuit is composed of a full bridge PWM inverter-converter connecting a capacitor in parallel with each switch and a commutation circuit for DC link voltage resonance. The commutation circuit consists of two switches, a DC capacitor and a reactor. Compared with the ordinary soft switching system, the proposed system has low part count. To control the commutation circuit, commutation switches are controlled, based on the detected values of input-output currents and DC capacitor voltage. This control methodology enables all the switches to softly switch. An experiment on a 10kVA system has verified that the proposed system reduces conduction noise by about 20dB and improves input-output efficiency from 86.9% to 88.7% as contrasted with the hard switching system.

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In this paper, controller performance of three kinds of robust control systems which are Disturbance Observer, Sliding Mode Control (SMC) and H_∞ control are evaluated, when they are applied to positioning control of electrical hydraulic servo system.
We propose several evaluation methods and standard of design considering characteristic of electrical hydraulic system, and decide system parameters for each robust control systems according to the several standard of design. Next, we apply them to actual electrical hydraulic servo system, and evaluate the difference of control performance from the point of view of robustness for parameter variations, characteristic of disturbance cancellation and control input. As a result, all of them has shown good robustness, but H_∞ control shows worse performance in characteristic of disturbance cancellation and control input than other control systems.

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New control methods are described which can suppress instability generated at high frequencies when an induction motor is driven by a PWM inverter. The methods are discussed according to two categories of motor driving system: using closed loop control with current regulators; and using open-loop control with only PWM controllers. The former prevents instability of the primary currents from occurring at high frequencies by controlling the amplitude and the frequency of the carrier wave. The latter prevents oscillations of primary currents from occurring at high frequencies by generating PWM signals while controlling the sampling time of the space vector control so that the ratio of 2π to the instantaneous phase of the primary magnetic flux reference can be kept integer. Experiments confirm that both methods enable induction motors to be smoothly driven up to high frequencies such as 500Hz.

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It is desirable that ac/dc converter for system interconnection (such as High Voltage Direct Current transmission system) should have following performance. (1) The converter does not fail to carry out commutation even when a voltage dip or distortion has broken out in the ac system. (2) The converter is able to send power from a healthy ac system even when another ac side has completely failed. (3) The converter is able to reduce generation of harmonics power in the network. It is necessary to improve characteristics of power semiconductor devices besides adoption of self-commutated ac/dc converter and development of control scheme. IGBT (Insulated Gate Bipolar Transistor), IEGT (Injection Enhanced Gate Transistor), GCT (Gate Commutated Turn off Thyristor) and Static Induction Thyristor (SITh) will be able to refine the characteristics. Especially SITh has high di/dt and dv/dt critical ratio and high switching characteristics. It is expected to apply SITh to power system in the future.
From these background, 4.5kV-1kA SITh which consists of 70mm in diameter pellet with the planer gate structure has been developed. This SITh shows a normally-off characteristic because of a low concentration p-base layer under n-emitter, and has a pin-base structure. For lifetime control, electron irradiation and proton implantation were used. A 5kHz-frequency test in a chopper drive was achieved in condition of 2250V as a supply voltage and 270A as a rectangular on-state current. Adopting a hard drive operation, a snubberless turn-off drive of I000A as an anode current was also achieved.

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Recently, qualitative decline in electric power due to harmonic effect is causing trouble in the electric power system. Further, faults due to condensive capacitor series reactor bum are causing problems. Thus, a positive harmonic countermeasure is expected by both consumers and suppliers of electric power.
This thesis proposes a new harmonic countermeasure in the electric power system of the large consumer with harmonic occurrence source load leading to extra-high tension receipt of initial power. That is, it is the proposal of a harmonic restraint system that combines a voltage detection system series active filter with the current detection system shunt active filter. The authors carried out theory analysis and simulation by numerical value example. Consequently, this is being reported because of positive effectiveness. With a shunt active filter and series active filter used together, the series active filter compensates harmonic voltage on the load side. It then becomes possible to use a current detection system shunt active filter for the harmonic occurrence source load containing the above system's capacitive load. Furthermore, using this system, inflow of the current harmonics to the capacitive load can be restrained by harmonic expansion phenomenon and anti-resonance phenomena. This proposal is related to the system employing a series active filter together with a shunt active filter. The authors are reporting this thesis because the above system was considered in detail and hasn't been published as far as they know.

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For the rectifier circuits with small capacity such as for consumer electronics and appliances, the capacitor input type rectifier circuits are generally used. Consequently, various harmonics much generate in the power system, so hereafter harmonic problem will become more serious. We discuss harmonic reduction method by the parallel connection of the conventional converters in the power system. For such parallel connection, the current harmonics in the power system, especially the lower order harmonics such as the fifth or seventh, can be largely reduced due to the phase difference of the harmonics between conventional converters. Especially when numerous rectifier circuits with different constants are connected in the power system, the harmonic characteristic can be significantly improved, where the lower order harmonics such as fifth and seventh orders are much reduced. Above results are confirmed by theoretical and experimental implementations.

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In recent years, the authors have proposed that Δ∑ modulation signal processing circuit is effectively applied for an inverter system with a PWM pulse pattern generating scheme. But if Δ∑ modulation processing circuit is applied to switching mode DC-DC converter, the major advantageous feature of spread spectrum characteristic disappears. In this paper, the authors propose a novel Δ∑ modulation circuit suitable for switched mode DC-DC converter application. In addition to this, there is the feature of automatic amplitude control scheme for this converter treated here. From the simulation results, unnecessary signals out of signal frequency band are much reduced and the voltage fluctuations of input side DC supply are minimized at the output side of the converter. Furthermore, the system design simplification can be achieved for the Δ∑ modulated converter system.

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