Operating characteristics of a current source AC/DC converter circuit with energy recovery snubbers and its multi-parallel configuration were studied in this paper. In the circuit, both di/dt and dv/dt stress on switching devices are very low compared with conventional circuits, and energy in the snubber capacitors can be fully recovered. A multi-parallel configuration was studied in order to achieve high current handling capability and reducing harmonics. The multi-parallel configuration is a current source multi-level converter.

抄録全体を表示

A key DC power supply using DC-DC converter for the electron beam acceleration of the millimeter wave high power gyrotron was developed. A Collector Potential Depression (CPD) system which requires an acceleration power supply is employed to enhance the efficiency of gyrotron. The DC-DC converter technique, without series-regulator, incorporating a PWM chopper control circuit, 6 inverters and 12 transformers at frequency of 5kHz is applied to this acceleration power supply whose maximum capacity is 100 kV, 0.3A and own efficiency is 91.3%. The CPD gyrotron using the developed acceleration power supply demonstrated the world highest efficiency of 48% under the condition of 110GHz and 350kW for 5 seconds.

抄録全体を表示

This paper deals with an advanced static var compensator (ASVC) using quad-series voltage-source PAM inverters. The ASVC consists of four three-phase voltage-source inverters with a common dc capacitor and four three-phase transformers, each primary winding of which is connected in series each other. Each inverter outputs a square wave voltage, while the synthesized output voltage of the ASVC has a 24-step wave shape. This results not only in a great reduction of harmonic currents and de voltage ripples but also in less switching and snubbing losses.
In this paper, transient analysis is performed with the focus on the response of reactive power and the resonance between the dc capacitor and ac reactors. Experimental results obtained from a small-rated laboratory model of 10kVA are also shown to verify analytical results based on the p-q transformation. The analytical results help us to design system parameters such as the capacity of the dc capacitor and feedback gains.

抄録全体を表示

In this paper, an analysis of harmonics in the ac and dc sides of voltage-source PWM inverters is presented. The analytical expressions for the total harmonics in the ac side current and in the dc side current and voltage of the inverter as a function of the PWM reference signal are derived. It is shown that, in general, the reference signal which produces a minimum harmonic in the ac side current is different from that which produces a minimum harmonic in the dc side voltage and that they are the same only when the ac side power factor is unity. The total harmonic of the dc side current does not depend on the employed reference signal. From the total harmonic point of view, the addition of harmonics other than the third harmonic into the sinusoidal reference is neither useful nor necessary. Experimental results are included to verify the derived expressions.

抄録全体を表示

Generally, a conventional boost type rectifier with one main switching element has any complicated control such as pulse width modulation (PWM) control or feed back control in order to improve an input power factor and an input current waveform. However, the input current waveform and the power factor of the conventional boost type rectifier can be essentially reduced to some extent without using the complicated control. And also, there is not clearly studied operation of the conventional boost type rectifier without using the complicated control, as well as not clearly studied harmonics of the input current waveform. Hence, this paper studies in detail the conventional boost type sinusoidal rectifier without using the complicated control by theoritical analysis and experimental results.

抄録全体を表示

This paper presents anew approach of direct torque control method for an induction motor. In order to control torque directly, state equations based on energy stored in the rotating field are derived. we clarify the electromechanical energy conversion between magnetic energy converted to torque and that stored in the field. The direct torque control system with torque as the output variable applied on optimal control theory are proposed. Quick torque responses for the desired torque are obtained from simulation results.

抄録全体を表示

To reduce the supply current distortions and low power factor operations with a conventional diode bridge rectifier connected to the utility system, a novel three-phase single-way rectifier is presented in the paper. The circuit configuration is based on the buck-boost DC-DC converter, in which AC flyback inductors play a role of the energy storage/transfer. If the simple pulsewidth modulation with uniform duty factor is introduced and if the rectifier operates in discontinuous current conduction mode, the supply currents can be sinusoidally waveshaped with a near unity power factor. Moreover, the step-up/step-down characteristics of the output voltage can easily be obtained by appropriately adjusting the duty factor of the switches. The experimental setup, employing insulated-gate bipolar transistors as the power switching devices, is implemented and the state-space method is introduced to predict the voltage and current waveforms and steady-state characteristics. The experimental and simulated results confirm the relevance of the presented circuit configuration as an useful rectifier with sinusoidal supply currents and step-up/down output voltage regulation.

抄録全体を表示

In the most of the study of the stability problem in inverter-induction motor drive systems, the stability at the equilibrium point has been assumed to be globally stable in the whole system. Induction motor drive systems, however, inherently have a nonlinear nature. In this paper, two nonlinear phenomena in the system are studied by numerically integrating the equation describing the system. One of them is a chaos, that occur in the system having ordinary values of the motor parameters. Another nonlinear effect is existence of two or more attracters at the same system parameters, whitch is the very important fact to the system design and operation. Namely, it means that the trajectry may converge to oscillatory solutions at parameters of the system having a stable equilibrium point. Regions in the parameter space for such nonlinear effects are shown.

抄録全体を表示

Hough transform is widely used for detection of some parameters of a figure or figures in a digital image. One of the bottle neck of Hough transform is its processing speed. It takes so much time for accumulation in the θ-ρ plane that caused by the “time consuming” ρ value calculation.
This paper proposes a new fast Hough transform which employs the table look-up method for ρ value calculation. The ordinary table look-up method in Hough transform, in which the sinusoidal function is calculated beforehand and saved in memories, has had the defect that the size of the look-up table has become so much big although the processing speed has been improved remarkably. The new method solves this problem by introducing the “bit block dividing” principle for the image position variables x and y. The actual system can easily be realized by using simple hardware devices on the basis of this principle. The total throughput is improved more by employing pipe line processing.
The proposed principle is described and the comparisons with other ordinary methods are mode in the beginning part of the paper. The examination and the trial structuring are explained on the hardware system in the next. The result of the evaluation test on the trial made hardware is shown and the discussion on it is done in the last part.

抄録全体を表示

Although brushless resolvers have been widely used as angular position transdusers, they are expensive due to the intricate construction having rotary transformer which supplies the exciting coils wound on the rotor poles with the current.
The authors have shown theoretically in the present paper that the resolver without rotary transformer or brushes can be realized by the simple construction which consists of the stater core with both 4-poles exciting windings and 2-poles output ones and the rotor core carrying no windings. In this resolver the rotor core has the minimum gap at one side and the maximum gap at another side of a diameter and is characterized by the outer surface form which makes the fluctuation part of gap permeance vary in proportion to cos θ, where θ represents angular position of a point in the air gap with respect to the origin on the rotor, the point of minimum air gap. The method determining the rotor form to embody the above mentioned gap permeance variation is also shown.
It has been comfirmed by not only simulation but also experiment that the 2 phase output voltages of a model designed based on the theory have sinusoidal waveforms with very small harmonic contents. Moreover, the rotor position detected by processing the output voltages through the conventional resolver/digital converter was within acceptable engineering accuracy.

抄録全体を表示

In pneumatic servo systems, since the change in load mass and air compressibility cause parameter variation of the plant, it is difficult to achieve high control performance. It is well-known that an adaptive control method is effective for such a plant with parameter variation. As the construction of the adaptive control system is usually complex, it is often realized as a discrete-time form by using a digital computer. In that case, the discrete-time model of the plant often become non-minimum phase. It is impossible to construct model reference adaptive control system (MRACS) for such a non-minimum phase plant.
In this paper, we propose a new design scheme of MRACS for a pneumatic servo system whose discrete-time model is non-minimum phase. In this design scheme, a δ-operator is introduced to construct MRACS for a non-minimum phase plant. We also show an improved design scheme which can achieve high positioning accuracy. The effectiveness of the proposed design scheme is verified by experiments using the existent servo system.

抄録全体を表示

Solar energy is very attractive as a future power source because of an clean and inexhaustible supply. However electric power of solar batteries is variable according to weather conditions. Therefore it is stabilized by storage batteries or supplied to the utility line through an inverter for utility interconnection. These systems, however, have some problems of cost and maintenance.
This paper proposes a new utility interactive system which is composed of an induction machine A related to a solar battery through a general purpose inverter and another induction machine B interconnected with the utility line. The frequency of the inverter to drive the machine A is given so that the solar power can be utilized maximumly. This system can stably supply a mechanical load with the desired power by parallel operation of two induction machines even in rainy weather, and moreover regenerate extra power of the solar battery to the utility line in fine weather. This proposed system is economic and useful as a small decentralized power supply because a power filter for rejecting high frequency noises and a detector for a power failure are not necessary.

抄録全体を表示

An intra-aortic balloon pump (IABP) is an effective device for supporting the circulation in the event of acute heart failure. Small IABP devices are strongly needed in medical related fields. The authors have been investigated an IABP device using a linear pulse motor (LPM) in order to actualize a small IABP device to reduce the load of the nurses. This paper discusses the characteristics of the LPM developed by the authors for the IABP drive, and performance evaluation of an LPM-driven IABP.
Our investigation revealed as follows; (1) The trial LPM had the volume of 1.3 liters and the mass of 6.3kg. It is capable of reduction the weight of the IABP device. (2) The LPM had a high thrust/volume ratio of 0.88 newtons/mL. (3) The driving characteristics of the LPM-driven IABP was evaluated by means of a mock testing device. The volume of operating balloon was measured with the electrical resistance between two electrodes. The maximum pumping rate of the IABP device was approximately 160 beats/min. The LPM-driven IABP will be possible to apply clinical study as small-sized device from the result of experiment.

抄録全体を表示

Superconducting Magnetic Energy Storage system, SMES, is considered to be useful in electrical power systems because of high efficiency and quick response. So, there have been two types of SMES researches, one aims at large scale SMES for nighttime energy storage and daytime power supply, and the other aims at medium or small scale SMES for multi-purpose usage in power systems such as compensation for impulsive loads and system stabilization for disturbances. For both of these applications, the efficiency of SMES considering thyristor loss at energy conversion will be important in order to use it in utility power systems.
In this paper, the results of experiments using a 1 MJ SMES system connected to a miniature power system model for measuring its efficiency between charging and discharging are presented and a consideration for the design and the operation of SMES is proposed after calculating mathematical model of several kinds of SMES derived from this experimental results.

抄録全体を表示

Superconducting magnets offer stable high magnetic fields without power consumption, and have wide application in magnetic resonance imaging equipment (MRI), superconducting magnetic energy strage (SMES), superconducting generators and so on. However, the magnets frequently suffer from quench fenomena and do not necessarily achieve the conductors'short sample critical currents. Mechanical disturbances, such as abrupt conductor motion, are the major reason for degraded magnet performance.
This paper discribes a magnet design approach for controlling the frictional spring force in dry-wound solenoids. This method was applied to analyze the behaviors of two high-field NbTi test coils. Experimental results show that stabilization can be achieved by allowing all potential conductor motions to take place during the low field portion of the magnet's charge up sequence, where its quench energy margin is greatest.

抄録全体を表示

There have been growing demands for automatic placement of parts on printed circuit boards (PCBs). Since the parts have wide variety in size and these parts should be placed under various constraints, the automatization of parts placement is a very difficult task. The authors proposed a method using the genetic algorithm (GA) for the automatic placement on highly dense PCBs. The study was, however, done on an imaginary board. Many factors, such as gaps between parts, lining up of parts of same type, etc. were not considered.
This paper presents three new coding methods for the automatic placement on the PCBs. The three proposed methods incorporate rotating angle of parts, gaps between parts, forming of parts of same type in lines as well as dense placement of parts. Actual PCBs are used for showing and comparing the effects of the new coding methods. The results show that the proposed methods are feasible for the automatic placement of parts on highly dense PCBs.

抄録全体を表示