[in Japanese]

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The power demand in Japan yearly increases especially in summer, and becomes peak in the daytime. The main cause is the drastically increased load of air conditioners widely used in general homes. The load pattern of air conditioners is very similar to the output pattern of a photovoltaic (PV) array.
Therefore, Sanyo has been developing two types of residential solar-powered air conditioner. One is a uni-directional system by using a DC/DC converter, which controls the voltage of a PV array at its optimal operation point and boosts the voltage up to the DC voltage of an inverter-type air conditioner. The other is a bi-directional system by using a bi-directional current-control converter, which regenerates surplus power into commercial system from a PV array, and suppresses the input current distortion of an air conditioner.
In this paper, the configurations and experimental results are described and discussed.

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Recently, a Brushless DC Motor (BLM) system, which has excellent characteristics, is realized by development of a permanent magnet with large residual magnetic flux density and coercive force, and advancement of power electronics technique. And it has be applied to various industrial fields, For a small size and hand-held type of BLM with low moment of inertia and high generating torque, the purpose of this study is to realize the system with the characteristics of smooth revolution and excellent transient response in a wide operating region. The BLM system applying optimal feedback control is constructed to accomplish high speed transient response and robustness against a disturbance and variation of parameters. To use in a wide operating region for the BLM, it is needed to compensate the nonlinearity by change of motor constants and large variation of a feedback signal. So, it is shown that variable gain control method varying the compensating element is useful. The relation between the weight of quadratics performance index and the characteristics of transient response is shown, then the optimal feedback gain accomplished the good transient response is clarified. It is cleared that the analytical and simulative results of the BLM system applying optimal feedback control with variable gain show the characteristics of excellent response over a wide operating range. The BLM system used DSP in the control circuit is constructed, and the excellent transient characteristics of the system is confined by experiments. Consequently, it is clarified that the variable gain control method is useful for the BLM system with a wide operating region.

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The paper presents a road tunnel ventilation control system for longitudinal tunnels with nonlinear programming and fuzzy control applications. The ventilation control system has two tasks: to keep the pollution level within a proper range, and to save electric power for ventilation equipments. In large-scale tunnels with various ventilators, the system uses ventilators efficiently as the traffic flow varies. The proposed system can operate ventilators based on traffic volume prediction using its daily change pattern with nonlinear programming (multiplier method). Pollution materials in longitudinal tunnels are propagated by the wind, so the process is represented by a distributed parameter system. Moreover, the wind velocity in the tunnel is constantly changing depending on traffic volume and natural conditions, so the process is very complicated. The proposed system, therefore controls not only the pollution level, but also the wind velocity for stable ventilation. Furthermore, fuzzy control is applied for hulnanlike control. The control system has been applied to actual tunnels and is producing satisfactory results.

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The DC brushless motor, Permanent Magnet Type Synchronous Motor (PM motor), has been widely used in the field of the industrial robots, the machine tools for factory and factory automations. Therefore, it is more desirable to improve the performance of PM motor variable speed control system. Though only the torque component current is adjusted as the control method for PM motor, that is named Vector Control, it is expected that the developed characteristics is added to PM motor.
In this paper, new driving methods for PM motor and a new design method for the variable speed control system are presented. The new motor driving methods, which bring to PM motor new driving performance, such as a quick transient response or the high efficiency motor driving, can be implemented by controlling not only the torque component current, but also the magnetizing component current. A developed optimal control theory, Error System Technique, is employed for designing the control system. The control law is endowed with a steady robustness against the variation of the system parameters and the ability of compensating the delay time due to the control processing.
The effectiveness of the proposed method is comfirmed by simulations and experiments.

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The purpose of this paper is to give a basis for developing a current sensor which can contribute to the improvement of reliability in power supplies by detecting faint faults early in the deterioration of insulation in distribution lines, Thus, we develop a method of detecting the zero-sequence current: (i) Each current sensor of the same detection accuracy is installed to each line of the three phase and (ii) Zero-sequence current is identified as a summation of the output signal in each sensor. The detection performance which can be achieved is: For the main current of 100 A, we can detect the zero-sequence current of 0.1 A with the accuracy of 3% regarding the 100% error.

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It has been reported that the acceleration control method realizes a fine and fast motion control. The acceleration control method has an ability to suppress the effects of dynamical nonlinearities rapidly. Moreover, the acceleration control method has an accurate output response for each motion reference. However, when the conventional acceleration control system is designed, it is often difficult to define both its nominal parameters and its frequency characteristics systematically.
This paper proposes the new model following acceleration control system using the auto-tuning fuzzy filter. The structure of the proposed system has no nominal mechanical parameter of actuator. Its frequency characteristics is determined by the auto-tuning fuzzy filter. This fuzzy filter is constructed by the new auto-tuning algorithm based on the simplex design method. Therefore, the proposed acceleration control system is designed automatically, and it realizes a fine motion control easily.

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A method is presented by which the holding torque and the maximum starting torque can be predicted. The pulse rate vs. torque characteristics in ranges of middle- and high-speed operation are calculated taking into account the speed electromotive force and the rise of the current, and the results are compared with test data. It is seen that the measured torque is higher than the predicted value in the high speed range. Effects of the current waveform on the pull-out torque are investigated. The rotor speed oscillation characteristics in the neighborhood of the maximum slewing pulse rate are studied. It is clarified that the frequency of this oscillation decreases as the pulse rate increases, and that the frequency of the current variation coincides with that of the rotor speed oscillation.

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In this paper, the transient stability of the synchronous motor taking account of influence of field circuit is analyzed with Lyapunov method that can directly estimate the system stability without solving the nonlinear differential equations, The influence of machine constants on the transient stability is investigated when the synchronous motor is subjected to load disturbances. The analyzed results show stability limits and rotor swings. The validity of the analytic results is shown by experiment results.

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Magnetic flux in a synchronous generator is saturated by an iron core in magnetic path. Conventionally, saturation characteristics of generator are examined in the case of no-load saturation test and zero power factor test. In these cases, the path of magnetic flux is limitted in d-axis direction. Therefore the saturation characteristics are grasped by measurements of terminal voltages and currents with regarding a generator as a black box. On the other hand, an on-load saturation characteristics have never been discussed in experiment. However, the conventional treatment of saturation characteristics are considered to be reasonable in physical meaning, because the analysis based on conventional assumptions does not contradict their experimental results. In this paper, the on-load saturation characteristics are discussed experimentally based on the experimental results at a generator operating onto an infinite bus system. As results, the harmonic components of air-gap flux density depend only upon the shape of salient rotor at no-load state. As for the tested generator, the saturation characteristics of d-axis component are independent of q-axis component in despite of the existence of q-axis current. Moreover, the on-load saturation characteristics for d-axis current corresponds to the shifted curve of the no-load saturation characteristics by a constant flux components with taking the ratio of field and d-axis current in consideration.

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A magnetically anisotropic conductor was applied to the damper-wedge which acts as a slot wedge and damper bar in electrical rotating machinery. This conductor is composed of copper clad steel wires of 1.6mm diameter, which are aligned in the same radial direction. This means permeability in the direction of the wires, i.e. the thickness direction of the damper-wedge, is larger than the permeability perpendicular to this direction, and electrical conductivity is good. In order to evaluate the electromagnetic characteristics, a trial damper-wedge, 1.2m in length and with a steel space factor of 40% to total volume, was manufactured and mountained in a stand-still model iron core. Test results were as follows when the magnetically anisotropic damper-wedge was employed.
(1) As the magnetic flux flowed well in the radial direction, the flux distribution at the core slot portion was flattened. Consequently, the ripple amplitude became small and the average flux density increased compared with cases when the non-magnetic or magnetic isotropic conductor are used.
(2) The damper-wedge had a smaller skin effect for AC current than a conventional copper damper bar. The losses concentration for the damper system was relieved, so that better machine performance under heavy load condition would be obtained.

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A rectifier fluxpump (superconducting rectifier) is one of power source units for a superconducting magnet. This apparatus converts an AC current having a small amplitude into a large DC current suitable for the superconducting magnet using a superconducting transformer and two superconducting switches. A typical conventional rectifier fluxpump with the superconducting transformer by using an air-core has such defects that the pumping flux is small and decreases as charging current for the superconducting magnet increases. We noted the fact that a magnetization curve of magnetic core of the superconducting transformer is related with pumping flux of the rectifier fluxpump and studied a new-type rectifier fluxpump with the superconducting transformer by using a saturable iron-core, namely, saturable transformer fluxpump.
In this paper, we consider principle and theoretical performance of the saturable transformer fluxpump with a resistive commutation method. The analysis shows the high pumping flux, constant rates for increasing the charging current and high efficiency.

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We proposed, in the previous papers, a “half-wave rectified brushless synchronous motor” as a novel servo motor. The rotor winding emf of the motor is induced by the stator current mmf which rotates at synchronous speed and pulsates at bias frequency. The field excitation is produced by the field current obtained from rectifying the emf with a diode inserted into the field winding. In order to improve the power factor and the efficiency, we also proposed a new type half-wave rectified brushless synchronous motor with permanent magnets.
In this paper, we analyze the flux distribution and the torque characteristics of the new type half-wave rectified brushless synchronous motor using the finite element method. We confirm the computed torque characteristics with the experimental results.
Furthermore, We derive the steady state characteristic equations and investigate the effect of the modulation function wave forms on the motor performance. The theory is also confirmed by the experiments.

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The constants of each phase of linear induction motor(LIM) are different, because of it's structure. It is important that the method of calculating asymmetrical constants is established, because the asymmetrical constants cause the thrust pulsation. In this paper, a new method of calculating asymmetrical constants of LIM is proposed. Moreover, the results of simulation performed by the calculated constants are compared with the experimental results.
The test machine of LIM is single-sided, short-primary-type, three-phase and 4-poles. The primary winding wires are double layer winding, concentrated winding and full pitch winding. In this paper, first, the asymmetrical equivalent circuits and voltage equations of LIM are showed on suitable d-q axis. Next, the asymmetrical constants are obtained by the calculations based on d axis equivalent no-load test, q axis equivalent no-load test, three-phase equivalent no-load test, d axis lock test and q axis lock test. Here, the equivalent no-load test is the lock test removed the non-magnetic conductor plate from LIM. Finally, it is showed that the simulations results of thrust containing pulsation and primary currents performed by the calculated constants are satisfactorily agreed with experimental results.

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Static characteristics of 6 kVA scaled-down synchronous generotor under the extreme unbalanced-load conditions are discussed. The waveforms of field and armature currents, and the flux linkage of a search coil are measured and simulated for different single-phase loads and unbalanced three-phase loads. Simulations are carried out by using the permeance-based air-gap flux analysis method which have been developed in our previous paper.
The simulated results are well agreed with experimental ones not only for fundamental components but also for higher harmonic components. It shows that our permeance-based method can be used to estimate easily a air-gap flux as well as electrical characteristics of a synchronous generator under various static load conditions. The following features are made clear quantitatively. The higher harmonic components are superposed in field currents as well as armature currents under unbalanced-load conditions. Resonance behaviors occur for not only fundamental component but also higher harmonic components under the capacitive-load conditions. The demagnetization and magnetization in a synchronous generator are estimated easily by using our permeance-based method.

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