In the speed sensorless control of the induction motor, the machine parameters (especially the rotor resistance R₂) have a strong influence to the speed estimation. In addition, the output voltage error due to the dead time and the voltage drop of the inverter influence on the rotor flux estimation, but the simultaneous compensation of the output voltage and the stator resistance R₁ is very difficult. In this paper the new algorithm of R₂ estimation with utilizing only stator current is proposed. In the high frequency range, the R₂ is estimated in the transient state, and in the very low frequency range, R₂ is estimated in proportion to the estimated R₁ when the ideal voltage source by the power op-amp is used instead of the voltage source inverter to avoid the output voltage error. In use of these algorithms, the low speed estimation was possible and the zero speed control was achieved under the 5_??_40% load condition in two motors. This paper clarified that the zero speed estimation is possible with the stator and rotor resistance estimations when the output voltage is ideal.

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The popular totally enclosed fan cooled motors less than 100kW in capacity rating have a structure where a radial fan is mounted as an external fan and air flow blew by the fan cools the outer surfaces of bearing brackets, and a stator frame. Increase in the amount of wind generated by the fan is essential to better cooling performance of this type motors. This paper proposes a new design index to increase the cooling wind without growth of fan-related noise on the basis of theoretical prediction and experimental verification. The resultant optimum external fan provides appreciable increase in the wind amount while suppressing its total pressure. An experiment on a four-pole motor running at 60Hz has demonstrated about 20% increase in the wind amount, also about 20% decrease in fan-driving power, and about 2dB decrease in fan-related noise.

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It is considered that encorders which are used for positioning control of motors representing Linear motors are improving on the resolution year by year in order to obtain higher positioning accuracy.
However, increasing the resolution and increasing the traveling speed are contradicted each other due to the characteristic of encorders. In general, when the resolution is pursued, traveling speed has to be sacrificed.
To overcome this problem we represent the high resolution technology for encorders which is compatible with high speed response and not affected by various speeds. And we also represent new method of rectifying positioning errors which enable us to obtain high accuracy relating with high resolution of the encorder.
It is considered that these newly introduced methods can be utilized for high speed positioning control which is represented by a Linear motor drive.

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High precision of 0.1μm, high speed of 30-60m/min, and durability are all required in position sensing for machine tools and robots, today. In addition, compact size and low price are necessary for practical use. Inductosyn scale is one of the most widely used position sensors; however, it does not attain both the precision and speed at the same time. In this paper, we propose new techniques, which achieve them.
Firstly, we propose a new coherent detection circuit, which detects the amplitude of the induced carrier signals by digitizing and integrating them. It enables fast and high precision detection. Secondly, to optimize the precision of the above detection, we proposed an automatic phase adjustment circuit, which adjusts the phase of the carrier signal so that the integration can obtain maximum dynamic range. Those circuits can be implemented in a single chip ASIC, which ensures compact size and low price.
We prototyped a test system, and confirmed, through several experiments that our new technique worked as was anticipated and accomplished our goals, sub-micron precision, sensing speed of 41m/min, on a solidly structured system.

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A new current control method based on the internal model principle in control theory is proposed. It uses a sinusoidal internal model, but it does not use any coordinate transformations. The method can be used for tracking an arbitrary number of harmonics, a DC component or a fundamental frequency component signal. It is applied to a single-phase PWM inverter and an active filter. Simulation and experimental results confirm the validity of the proposed method.

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In this paper, the authors describe a method to identify equivalent circuit constants of the main and auxiliary windings.
According to this method, the DC decay testing method is applied to the main or auxiliary winding of capacitor-start single-phase induction motor, and the operational impedance are calculated for each winding. From the operational impedance thus calculated, we use the relation between the main winding and auxiliary winding converted to main winding based on electric energy conservation law to calculate the equivalent. circuit constants.
The usefulness of this method is proven by comparing the measurements and the values calculated from identified equivalent constants.

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At every switching time, a PWM inverter produces high-frequency leakage currents flowing through stray capacitors. As the inverter for a trash conveyance crane is installed far away from a motor, shield power cables between them become long, leakage currents pass each stray capacitors of the shielded cables and flow to the ground. This paper proposes a model circuit for analyzing leakage currents which flow into the shield of the cables. The effectiveness of the proposed model circuit is verified through the compares of simulated leakage currents using the proposed method and measured leakage currents.

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In the drive of an open-loop-controlled stepping motor, it is well known that the natural oscillation of the motor causes harmful phenomena like the low-frequency resonance, the increase of the settling time and the acoustic noise. Microstepping is known as a method for suppression of rotor oscillation; it is effective especially in the constant-speed drive. However, the rotor oscillation occurs in the transient region even in the case of microstepping, provided that the dynamic property of the system is not taken into account.
In the present work, the authors suggest to use a pre-compensator to suppress the natural oscillation of the microstepped stepping motor. In the design of the compensator, guarantee of robustness to the variation of the inertial load which causes the variation of oscillatory characteristic is regarded as the main point. In addition, prevention of phase lag to the reference signal which has a harmful influence on the case of path following control is also taken into consideration. The adoption of a preview type FIR low-pass filter is shown to be suitable for the above purpose through the analysis of the system in the frequency domain. The effectiveness of this method is evaluated by the experiment, and it is confirmed that the rotor oscillation is suppressed excellently.

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We usually use the Finite Element method (FEM) to calculate the load loss at the outer vessel of super conducting coil. There is also a method called the Monte Carlo method (MCM) to analyze thermal transfer models. Methods to use random numbers for calculation are generically called the MCM. For instance, we use the MCM for thermal transfer analysis quickly out put the temperature at one point.
In this paper, we use the MCM to calculate the temperature of outer vessel of super conducting coil and linear generator coils for the maglev system. We also measure the temperature of these equipment items at bench tests by a simple wind tunnel. The results of MCM are found to be consistent with those bench tests and analysis.

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Along with wide and deep dissemination of electronics application to our modern society voltage dips and momentary interruptions mainly due to lightning on overhead transmission lines has become to disturb normal operation of loads. UPS, which is mostly employed to protect sensitive loads from them, has such limitations that it dissipates not less energy in running operation because currents flow through two converters in series, that it is poor to feed electric motors which occupy main loads in industrial plants and that it costs high to be applied in common. UPS can be regarded not as omnipotent against voltage dips.
We have developed a novel power apparatus termed QBS (Quick Backup System) to supplement above drawbacks in UPS, employing one reversible ac/dc converter and one high-speed switch. Normally QBS supplies power directly from a commercial network to critical loads while the reversible converter interconnects with it to charge the battery. When the critical bus voltage deviates from the tolerance range QBS disconnects the high-speed switch and continues to feed the critical loads in UPS mode. The whole power transition is completed within 2ms. This paper presents constitutional technologies developed to realize QBS and obtained experimental data in the field demonstration test of a 100kVA QBS.

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A position-fixing control system for rolling stock using a location-speed pattern was studied. It was clarified that following the pattern causes a positive feedback effect on the speed control system. The effect becomes more effective in the low speed region and causes detrimental influence to the stabilization of the control system.
A nonlinear speed control system was proposed. Adopting the control system makes comfort characteristics compatible with the stabilization in low-speed region. According to this control system, when the speed deviation and the acceleration deviation are small, rolling stock does not receive acceleration rate limiting. On the one hand, the deviations are big, the acceleration rate is limited to permissible value, and comfort characteristics are obtained.
The effects of this control system were tested in the simulation.

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This paper presents new block diagrams for induction and synchronous motors with stator core losses such as eddy-current and hysteresis losses. The proposed block diagrams succeed in realizing simple and clear configurations with physically meaningful vector signals, which are helpful for understanding motor electromagnetic mechanism and useful for designing controllers for them. Vector signals which are defined in the general reference frame are utilized as transfer signals between blocks. The proposed vector-signal block diagram in the frame can be directly and easily reduced to the one in such a specific frame as stationary and synchronous frames simply by adding certain constraints to it. Shown are three configurations for induction motor, two for synchronous motor including permanent magnet cylindrical motor, permanent magnet salient-pole motor and reluctance motor.

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This paper presents a new configuration for high performance three-phase voltage boost regulator. For this new configuration, a control methodology is proposed to provide regulated ac output voltage. The new boost regulator has nearly unity input power factor for a change in the load voltage from 100% to more than 200% of the supply voltage. At these conditions, a nearly ripple free output voltage is achieved. The four-quadrant nature of the proposed regulator enables it to accept reactive loads. Theoretical analysis and practical controller implementation are presented and the efficacy of the proposed regulator has been confirmed.

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