The accidental electric breakdown in arbitrary one of capacitors in a parallel connection of the large slow-capacitor bank may result in serious damages such as mechanical explosion and oil effusion or fire.
Because, breaking of the DC large current of follow in to a breakdown capacitor from normal capacitors is impossible. Therefore, many kinds of protective devices were made designed.
We do report how to get new knowledge about succeeding breaking of DC large current in oil by experiments.
Our view point is effect of surge absorption by parallel normal capacitors conected to the breaking device in accidental electric breakdown capacitor.
The result showed that breaking time is a value less than 2 milliseconds for a parallel connection bank more than 3 capacitors, each one is a SH-type capacitor (1200V in DC, 1200μF).

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A linear pulse motor (LPM) has been widely used because of its simple structure and easy control without the use of feedback. However, there happens the degraded response performance resulting from the occurrence of transient vibration which is inherent to the LPM. The fastest way to suppress the vibration is to close the control loop using the position feedback sensor. But the straight-forward use of such a sensor feedback leads to the high cost and complicated configuration, sacrificing the structural advantage of the LPM. Therefore, the authors propose a Kalman Filter based position sensorless control for suppressing the transient vibration. In this proposed control method, the mover position and speed are optimally estimated using an extended Kalman Filter applied to the nonlinear state equation of excitation winding circuits. Effectiveness of this control method is clarified by the experiments on the prototype LPM system using a DSP.

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In this paper, we discuss the experimental method to evaluate the execution time of Ladder Diagram (LD), which is the most commonly used language in programmable controllers (PCs). First, the fundamental LD is proposed to examine the cyclic scan of PCs. Using real samples of PCs, it is clarified that dispersion of the cyclic scan can not be necessarily neglected. Second, relationship between the execution time of LD and the number of ladder rungs, logical AND and OR operations, which are important components in ladder programming, is examined by adding some rungs and contacts to the fundamental LD. Some experiments are conducted, and then the means and standard deviations are obtained through some measurements. Moreover, the stochastic tests are conducted to verify the relationship between the execution time and the LD components.

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In general, medical-use high-voltage X ray power generator works under a variety of operating conditions of the required output DC voltage and the output current setting values for the X ray tube. A phase-shifted PWM inverter-fed DC-DC power converter with a high-voltage transformer parasitic resonant link which is used for an X ray power generator inherently includes its stiff nonlinear characteristics due to phase-shifted voltage regulation and diode cut off operation in a high-voltage rectifier because of the wide load setting regulation ranges in practical applications. However, superior output voltage response performances of a quick rising time in a transient state and low ripple factor in a steady-state which have to be essentially required for a medical-use X ray power generator could not be sufficiently implemented by various linear modern control approaches because a precise mathematical description with dynamic modeling could not be formulated for wide load variations. For controlling such a nonlinear DC-DC power conversion system, a fuzzy-reasoning-based learning control technique to realize the human capability and much experience to understand the system dynamic and static behavior is more suitable and effective. This paper presents a phase-shifted PWM full bridge inverter type high-voltage DC-DC power converter with a high-voltage transformer parasitic resonant link and its fuzzy-based learning controller, which has excellent dynamic and static behaviors to be utilized in a medical-use X ray power generator operating under conditions of a variety of wide load settings. The effectiveness of feasible fuzzy learning control technique of the DC-DC power converter is discussed and evaluated on the basis of the computer simulation and experimental results in a laboratory set-up. It is proved that the feasible fuzzy-based learning control scheme suitable for this converter is more effective and practical to improve the system output voltage response performances in both the transient and steady states for medical-use X ray power generator. The simulated and experimental results of this converter are actually illustrated in order to substantiate the operating performance validity of the inverter type medical-use X ray power generator operated by the feasible fuzzy-based learning control implementation.

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A controller for high-power electrostatic motor is described in this paper. The controller includes stereo audio amplifiers, small transformers, and a signal generator. The signal generator generates controlled driving signals of dual-frequency driving methods so that a motor can generate commanded thrust force. By using frequencies of several kHz for driving signals and by using resonance between an electrostatic motor and transformers, it became possible to use commercially-available audio amplifiers as voltage sources and to use small transformers. In this paper, design of the signal generator and the transformers are discussed. Also, experimental results using linear type motor is shown.

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A squirrel-cage induction motor (abbr. IM) produces the electromagnetic vibration and the electromagnetic noise by the interaction between many harmonic fluxes in the air gap. Recently, reduction of such vibration and noise has become important subject from the standpoint of environmental improvement. The electromagnetic vibration caused by IM has been studied for many years and its basic phenomena have been analyzed. However, the electromagnetic vibration under load conditions has not been analyzed sufficiently.
In this paper, the effects of slot-combination and skewed slot on the dominant electromagnetic vibration under load conditions are theoretically and experimentally studied. First, general equations of electromagnetic force waves are derived in order to discuss easily, and the characteristics of the force waves for slot-combination and skewed slot are theoretically clarified. Next, the electromagnetic vibration for the several kinds of poles, rotor slots and skewed angles are measured, taking the effect of natural frequency of the motor into consideration. The effects of slot-combination and skewed slot on these measured vibration are characterized by the proposed theory.

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This paper discusses a distributed constant circuit model of power cables for representing high-frequency oscillatory currents, and evaluates electromagnetic interference (EMI) generated by a PWM inverter-fed induction motor drive system. While the lumped constant circuit model which has already been proposed by the authors has only one resonant frequency, the distributed model proposed here can simulate plural resonant phenomena existing in a high frequency range over the first resonant frequency. Frequency characteristics of both common-mode and normal-mode currents are analyzed by using a circuit simulator with the distributed model. As a result, it is shown experimentally and theoretically that the resonant phenomena in the high frequency range are originated from behavior of the power cables as the distributed constant circuit, and that the common-mode transformer (CMT) and the normal-mode filters (NMF's) can damp the resonances.

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This study aims to realize high precision repetitive positioning control of a linear pulse servo motor. By using this method the systematic error which may makes the precision worse can be suppressed easily. And also it shows that Power OP-Amp drive system enables the random error to be suppressed in comparison with PWM control drive system using IGBT inverter. As a result of the suppression of systematic and random error, improved performance of a linear pulse servo motor with repetitive positioning control is shown by experimental results. Moreover, the study examines the repeatability positioning precision of variable distance repetitive positioning control, other than the conventional equal distance positioning.

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Generally speaking, new products, new inventions, innovations and whole new industries often originate from ideas inspired by natural laws (physical laws, effects, and so on). So, we think natural laws are important information for supporting invention and development of artifacts, and that, we think it is attractive work to present their information to engineers. In this paper, theoretical knowledge on inventions, developments and natural laws is described as 'constraints of views and behaviors of artifacts'. And they are divided into some constraints. We propose a new method for analyzing the invention process of a real developed artifact with natural laws. Specifically we describe theoretical knowledge of artifact can be represented by adding some constraints on natural law and combining some natural laws with basic knowledge. Finally we inspect on the effectiveness. As a result of our study, we are sure of offering one of the artifact invention supporting system.

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A compact Scherbius drive employing a boost chopper and a PWM inverter has been developed for general-purpose industrial uses. The latter provides a unity displacement factor and reduction of harmonics compared to the thyristor inverter, while the former ensures a small capacity for the inverter and dispenses with starting equipments. Thus, this Scherbius drive is much smaller in size and more efficient. Besides introducing this Scherbius drive, this paper gives an analysis of the transient rotor voltages followed by line voltage recovery just after an instantaneous power failure whether residual voltages of the wound-rotor induction motor exist or not. From the analysis it is confirmed that a dc reactor and a discharging resistor are effective to sup-press rotor transient voltages and they are applied to the commercial compact Scherbius drive which allows uninterrupted pumping operation of public utilities.

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The torsional vibration is often initiated by the momentary impact which occurs when a load is connected to a motor by several mechanical coupling parts. An industrial servo system is basically represented as a multi-mass system. To suppress the vibration generated in the two-mass load, many control methods have been developed for practical use. In this paper, however, the authors propose a simple vibration suppression strategy for the multi-mass system which employs two variable parameters consisting of resonance ratio and damping factor along with a state feedback approach. The excellent vibration suppression control, as an example, for a three-mass system, resulting in excellent vibration suppression even for a small resonant ratio, is verified by simulations and experiments.

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This paper presents a new model description method for AC motors such as salient-pole synchronous motor, synchronous reluctance motor and induction motor. The method uses specific 3×3 balanced circular matrices together with 3×l balanced vector signals. It does not require concept of rotational orthogonal coordinates but has the same vector description form as the orthogonal coordinates. The method is useful for easy comprehension of motor dynamics especially by students and engineering-beginners.

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