This paper introduces an axial gap type self-bearing motor. It is intended for a disc type flat motor to have both functions of rotation and axial position control. This motor is simple in construction and requires a simple control system. A permanent magnet type motor is analyzed theoretically and tested experimentally. The torque characteristics of the tested motor is measured with the various axial force and air gap. Independent control of the axial force and torque is introduced for the servo motor control and synchronous motor control. The results are showing high possibility of the proposed motor and control system.

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A type of mag-lev system with permanent magnet motion control is proposed, analyzed, and examined experimentally. This mag-lev system has the structure that the levitating object hangs on the upper iron rail and such parts as magnets, sensors, and actuators are installed on the object. This levitation method is very useful for noncontact conveyance systems, because the conveyance path is very easy to make. This paper describes the success of the construction of the hanging type magnetic levitation system using magnet motion control mechanism.

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In this paper, a linear induction motor (LIM) for transportation with a new type of secondary member is studied analytically to get high performance by measures reduced the end effect. That is the multi-phase ladder shaped secondary conductors with conducting bar pitch of pole pitch. First, a new analytical method is shown, that is the two-dimensional analysis which can determine the current in each conducting bar considering with time harmonics of secondary current. As a new viewpoint making the most of feature, the waveforms of thrust acting on each conducting bar of ladder, the current in each bar and linkage flux density are studied respectively, and the physical phenomenon of end effect is shown clearly. The result shows that the current component of end effect can not be canceled by adjusting the pitch of conducting bar. Furthermore, it shows that the basic solution for the end effect is to have the period of thrust waveform equaled to the half-period of slip frequency as short as possible to the passing time of primary core at a secondary point. Still this analysis will be useful for other type of LIM with secondary current circuits.

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The magnetically levitated vehicle (Maglev) system is the most promising system for high speed mass transportation in the near future. We have carried out running tests at Yamanashi Maglev Test Line since April 1997, and attained the speed of 550km/h in December, the world speed record of the railway systems.
In Yamanashi Maglev Test Line, the vehicles are automatically driven by three pairs of inverter in the power conversion station. The automatic drive control system requires the instantaneous location of the vehicle to generate the current references for LSM. The location signal is detected by the inductive radio wires along the guide-way. And it is superposed with some disturbances, which may cause the fluctuation of the propulsion force.
On the other hand, load variation occurs according to the change of vehicle's weight and running resistance.
We need to design the drive control system considering ride quality as well as speed following performance in spite of the distorted location signal and load variation.
In this paper, we describe the design procedure, the drive control characteristics and the test results in the Yamanashi Maglev Test Line.

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Miniaturization, increased speed, and higher accuracy for industrial positioning devices have recently been the main requests for industry upgrades. Using linear motors is an effective way to meet these requests. This paper discusses a linear DC motor (LDM) for high-speed positioning. From transfer function of LDM, it is shown that the electrical time constant and the mechanical time constant are reduced for high-speed positioning. The electrical time constant and the mechanical time constant of LDMs are considered to decrease their constants. The LDM for high-speed positioning was designed and manufactured within the overall dimensions: 72×75×62mm³. The positioning device with the manufactured LDM positions the 0.2 kilogram load within the 10 millimeter stroke in 22 milliseconds.

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While the commercial motor produces only one-dimensional (linear or rotary) motion, we propose a new type of tubular linear induction motor (TLIM) with two-dimensional motion in this paper. The proposed motor consists of plural short primary LIMs arranged on the same circumference and a common secondary. By applying independently energized ring-windings of double-layer to the primary, we can achieve both the reduction of coil-end region and the freedom of alternating current supply. The secondary conductor is capable of producing any one of rotary, linear, and helical motions by controlling the phase of supply currents in each primary winding. We first investigate the driving characteristics of the proposed motor by three-dimensional finite element analysis, in order to obtain the optimal feeding conditions to increase the subsidiary rotary-force. Then, we make the experimental machine based on the analysis results. In addition, we deduce an optimal arrangement of the primary slot currents enhancing the secondary thrust in the short primary LIM. Finally, we confirm the adequacy of analytical results by experimental ones.

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High-speed and high-precision hydraulic valves have been widely required in the industry. The authors have been developed the hydraulic servo valve (LSV) using a linear DC motor (LDM). This paper describes a design method of the magnetic circuit and the optimization of the electrical time constant on a moving-magnet-type LDM. The electrical and mechanical time constants of the LDM are required to have small values so as to realize a high-speed-response LDM. The expressions of the electrical and mechanical time constants of the LDM is derived using the permeance method. These constants are also computed using the finite element method (FEM) combined the electric circuit equations. The measured electrical time constant is 10.5ms. The calculated values of the electrical time constant obtained by the permeance method and the FEM are 13.4ms and 10.2ms, respectively. It is clarified that two methods are useful for calculating the electrical time constant of the LDM.

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The vector control of the induction motor without a speed sensor required the estimations of the rotor flux and the rotor speed. Since the estimations use the machine parameters and the stator voltage and current components as input quantities, the stability of the systems is sensitive to the variations of the machine parameters and the measured stator voltage errors and the current control errors compared with the vector control systems with a speed sensor.
In this paper, the small signal stability analysis is carried out on the direct field oriented control system of the induction motor without a speed sensor using the adaptive rotor flux observer (MRAS method) and allows for the stability effects of the stator resistance and rotor resistance and the gain of the speed controller to be studied. The stability effects of the MRAS method are compared with that of the vector control system of the induction motor without a speed sensor based on _??__1q-feedback control (_??__1q-feedback method). Furthermore, theoreitical step responses of the rotor speed are compared with the experimental results.

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A resonant pulse soft-switched drivecircuit for a switchedreluctancemotor is proposed. There are nines witching devicesin the circuit with three phase motor windings, three devices for main circuit, three devices for auxiliary circuit, and three devices for charging circuit. Auxiliary thyristor is used so resonance currentpulse tail-length is fast cut off. Transformeris used so that the excessive energy is restored to the source and voltage of capacit or is limited. By the simulation and experimental, it is clarified that the output torque is increased. The system yields less EMI, because of soft switching.

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This paper proposes an analysis method of AC-AC direct converters which are Matrix converter et, al.. The proposed analysis method, is described by a switch matrix and instantaneous space vectors of the input voltage and the output voltage, is uniformly able to analyze the characteristics of the AC-AC direct converters, because the output voltage range and the controllability of input current are clearly defined. In addition, a novel circuit was invented by using the proposed analysis method. The novel circuit, called Delta converter, realizes VVCF operation and high input power factor regardless of load power factor.
In this paper, the proposed analysis method is applied to five types of the AC-AC direct converters and the features of each circuits are compared and discussed.

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The vector control method is widely used for induction machine drives. Recently, sensorless vector control for induction machine has been investigated and proposed. The speed range for the drives is limited to about 1:100 in industry. The main reason for this limitation is the inaccuracy of stator voltage measurement. The lower rotor speed becomes, the lower stator voltage is. Therefore, it is difficult to detect the stator voltage accurately in the lower speed region, and difficult to control motor speed and motor torque precisely. This paper presents a method of improving the lower speed performance of sensorless vector controlled induction machine drives using offset compensation of stator voltage. The offset is compensated by using the fluctuation of the estimated rotor flux. The validity of the proposed method is verified by experimentation.

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In order to compensate for the reactive power and to eliminate harmonic components of the current in single phase power lines, an active power filter with an FIR (finite impulse response) digital filter technique is worked out. The validity of the proposed method is studied by computer simulations and model experiments. In the experiments, the active power filter which consists of a single-phase full-bridge power MOS-FET inverter is used. The inverter is controlled by a DSP (digital signal processor). The active power filter is connected in parallel between the voltage source and the full-bridge diode rectifier as a load. Digital filtering operation done by the DSP provides the load current of the fundamental frequency. The voltage-in-phase load current of the fundamental frequency is computed with the phase signal of the line voltage. Subtracting the voltage-in-phase load current from the total load current, the reference of the compensation current is obtained. Comparing the reference and measured compensation currents, the voltage pulse width pattern of the inverter is generated.
The digital filter used in this study was designed as a band-pass filter of 50Hz. Its filter length and the sampling frequency are 200 and 10kHz, respectively. Therefore, the time length of the sampling data of the measured load current required for the digital filtering operation is 20ms, i.e. one period for 50Hz. In other words, the transient response time for the reactive power compensation including harmonic current elimination is 20ms.
With the active power filter, both of the third and fifth harmonics of the source current were reduced by 1/7.

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For ideal induction motor driving, we must control primary flux to make rotating field according to order. “Primary Flux Control Method for Induction Motor” is one of the useful methods to achieve this control in practical use. Therefore, this method is applied to “General Purpose Inverter for Induction Motor” and this type inverter comes onto market already.
However, this method has unstable region under regenerative operation in low speed. Although this problem is discussed in many papers, these are not all enough solution. As general-purpose-inverter are used in wide spread industrial field, induction motor is drive under various conditions.
In this paper, we studied about the reason of unstable operating and proposed the method for improving the performance characteristics of induction motor with regenerative load in low speed region. Otherwise, to achieve this control, we have to use the inverter whose output voltage is equal to command voltage. Therefore, we also proposed “Voltage Control Type Inverter” in practical use.

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This paper describes reliability estimation of electric parts using image processing and a neural network. Efficiency of carbon film resistors in reliability test is estimated from colour image features by feed-forward network. In general, image processing techniques play important roles in many engineering applications and developments. Thus, intelligent image processing techniques are required in the reliability fields in order to establish more efficient quality control schemes. This paper describes some experimental results on reliability estimation using a neural network and image processing for reliability test. Performance degradations of carbon film resistors are estimated from their colour images. We attempt to find appropriate estimated value of resistance at every testing hours, in order to establish a convinient method for reliability estimation. We first discuss some essential issues to be considered in reliability problems. It is shown that the image processing and neural network approarch give good results compared with multiple linear regression and real measured results. Furthermore, the efficiency of the method is indicated by applying it to image data for calculation of MTTF.

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This paper presents decentralized control application for stabilization of strip tension in Hot Strip Finishing Mill. Hot Strip Mill, in particular, thickness deviation at head-end and tail-end becomes more serious problem. In order to stabilize strip tension, feedforward decentralized control system has been proposed with the high performance of automatic gage control system. This control method has been confirmed effectiveness by simulations and applying in hot strip mill has shown thickness improvement.

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Recently, the power semiconductor devices for higher voltage and higher current capability are developed. The thermal behavior analysis for improvement of these devices is very important.
There is an apparent hot spot in semiconductor devices, particularly when current is concentrated in a small area of semiconductor device.
This paper describes important information for the thermal behavior analysis of thyristors under operation.

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In this paper, an evaluation factor of permanent magnet motors is enhanced by accounting effects of copper and iron losses as well. A new evaluation factor k_M is obtained by the product of an old motor constant k_MC and a modification factor k_a which is calculated from iron loss ratio.
Next, the evaluation method is applied to permanent magnet motors with non-lap concentric windings. The results show that an improvement by increase of magnetic flux is reduced under consideration of iron losses and the evaluation factor k_M is rapidly saturated over 0.7 tesla in air-gap magnetic induction.

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Electric railway vehicles have come to use regenerative braking in normal operations, but not in the total operation range from the top speed to the complete stops (zero speed).
Not only in case of lacking regenerative load or electrical braking power, but also in case of lower speed, for example under 10km/h, mechanical braking takes the place of electrical braking.
If we realize all electrical braking to zero speed, easier can we use higher deceleration Automatic Train Operation, lighter can be the weight of baking systems, and lesser can be the braking shoe changing maintenance. New control algorithm is necessary for the stable control of electrical braking to zero speed, when the speed sensor becomes to be unable to measure the accurate speed.
In this time, we developed halting algorithms with all electrical braking, especially new “Gradient estimating feed forward torque pattern control” algorithm and tested them on our rolling stock test bed. The result shows that a vehicle wheel stopped completely and maintained the halting state more than 5 seconds only by electrical braking, even on the ±20‰ simulated gradient.

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Many studies of the ac power supply have been reported. There are ac chopper circuits in these reports. The ac chopper circuits are effective method for ac power control. But, the ac chopper does not apply to practical use because it has some problems that needs bi-directional switch and ac snubber.
In this paper, I propose the novel PWM controlled ac power supply based on ac chopper technology. Proposed PWM controlled ac power supply can solve problems of devices and snubber circuits because this circuit uses bilateral switch circuit instead of bi-directional switch. This paper describes circuit configuration and operation of PWM controlled ac power supply, and explains ac voltage regulator and series voltage compensator for application example through experimental results.

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For the purpose of implementating a highly reliable self-commutated power converter system with gate turn-off (GTO) thyristors, we developed for the first time a triple redundant controller for the system. The triple redundant controller consists of triplicated sub-modules that generate gate pulses for each thyristor and voters that select one of the gate pulses from the triplicated sub-modules in 2 out of 3 fashion. The controller continue to provide correct gate pulse even in the presence of a single module fault. On the other hand, selecting gate pulse can cause gate pulse inaccuracy problem. Time lag between gate pulses of the triplicated sub-modules causes gate pulse inaccuracy, and consequently, causes over-voltage to the thyristors which leads to the destruction of the thyristor. We developed a new method of synchronizing the gate pulses of the three sub-modules for gate pulse accuracy, and applied it to the triple redundant controller. As a result, the maximum time lag between the gate pulses of the three sub-modules become under 0.1μs; so it is possible to produce accurate gate pulses even when single module fault occurs. Mean time between failures (MTBF) of the developed controller is shown to be ten times longer than the MTBF of an non redundant controller.

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