This paper describes a new method which predicts the starting performance of a PM motor (double squirrel-cage permanent magnet motor).
As the motor has the field excitation at standstill, it's impossible to determine several constants (synchronous reactance, sub-transient reactance, etc) and the performances using the method of IEC Pub. 34-4 or JEC-114.
This method, named a D. C. decay measurement, is applied to the armature winding of a PM motor at standstill. That is to say, by means of Fourier transformation of the D. C. decay current which is measured when the two terminals of the star-connected armature winding are short-circuited, the direct- and quadratureaxis impedance loci are obtained, and the starting performance is calculated on the basis of two-reaction theory. The starting performance of a PM motor calculated by this method agrees with experimental result. The method can easily calculate the performance of middle and large PM motors in factories, because the capacity of this equipment is very small.

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This paper shows a new emergency demagnetization method of one superconducting coil on one side of a Maglev vehicle when the other superconducting coil on the other side happens to quench. The emergency demagnetization suppresses an abnormal lateral force when the quench happens during vehicle running. We investigated the applicability of the phenomenon that the superconducting coil connecting with a high resistant damp-resistor warms itself and gets quenched by turning-off of the persistent current switch. Then we propose a method of making one superconducting coil quench and demagnetize in an emergency due to opposite superconducting coil accidentally quenching. Similarly we avoid the superconducting coil quenching through a malfunction of the persistent current switch. We designed and constructed the emergency demagnetization apparatus on trial, and examined its performance.

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This paper proposes a novel sinusoidal rectifier which improves input power factor and input current waveform without any complicated switching modulation such as a pulse width modulation (PWM) or a complicated feed back control.
The novel sinusoidal rectifier consists of a pair of capacitors connected in series, a full bridge diode rectifier, a pair of indctors, and a pair of switching devices connected in series. Therefore, the configuration of the sinusoidal rectifier is simple. However, in spite of its simplicity, the sinusoidal rectifier effectively reduces the reactive power and harmonics involved in input line current.
The excellent behavior of the novel sinusoidal rectifier is verified by theoretical analysis and experimental results.

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A matrix converter doesn't have any energy storage components, so it is smaller than a converter-inverter system with same KVA. Though matrix converter requires 18 switching devices instead of 12, each device capacity is 0.383 times and total capacity is 0.575 times that of the converter-inverter system. For the matrix converter, we proposed a firing sequence which eliminated voltage and current spikes in switching operations, and control method I which generated the output voltage of 0.866 times the supply voltage. Moreover, we proposed control method II which improved the waveform distortion of the input current and realized unity input power factor. In this paper, we propose a new VVVF gate circuit based on control method II for matrix converter, which can on-line control input current waveform and output voltage waveform to sinusoidal even if there are fluctuation, asymmetry and/or harmonics in the supply voltage. We also confirm by experiments that the waveform distortion of the input current and the input power factor were greatly improved.

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A simple slip frequency estimation algorithm without a speed or position sensor is proposed, especially aimed at the very low rotor speed estimation. The stator flux is obtained by the simple digital integration from the compensated voltage reference. And the rotor speed is estimated from the slip frequency estimation algorithm, which is useful under any control such as the vector control, the decoupling control, and the slip frequency control. A rotor speed estimation as low as 5 [rpm] is verified through the experiments combined with the voltage command type vector control and the proposed slip frequency estimation algorithm.

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As a linear motor is driven directly, the linear motor system has the problems of how to prevent the bad influence by the inertia perturbation on the performance such as command resonse and disturbance attenuation of the speed control system. Especially, when we apply the linear motor system to the table feed of a machine tool, it is important that we design the control system to consider the inertia perturbation of the system becase the linear motor has no decelerator generally.
In this paper, first, we discuss the problem of the design of speed control systems without an acceleration sensor. Secondly, we propose the new speed control system with the acceleration sensor and its compensators with the proper 2-oder rational function in consideration of the inertia perturbation of the system with acceleration sensor. The characteristic roots of the closed-loop transfer function of the speed control system with the acceleration compensator is mapped in the complex plane freely. The disturbance attenuation and command responce of this propsed speed control system with the acceleration sensor are hardly influenced by the inertia perturbation of the system. Thirdly, we propose the speed control system without acceleration limiter because the speed control system does not need acceleration limit generally.

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It is well-known that the angle dependent disturbance in a servo motor caused by nonuniformity of field windings, armature cogging, rotor imbalance, nonuniform load etc., may influence the speed control performance greatly. This often leads to large speed fluctuations which are undesired in practical situations. Therefore speed fluctuation reduction techniques in the presence of angle dependent disturbance are strongly required and have been being challenged by a lot of researchers. In this paper, the authors propose a new approach to this problem via adative control with the aid of a radial basis function (RBF) network composed of gaussian basis functions. The angle dependent disturbance which are viewed as a periodical nonlinear function with a period of 2π[rad] in the angle domain, is approximated by a RBF network in [0, 2π) [rad]. Then an adaptive linearization control system employing the RBF network which compensates the disturbance is proposed. The RBF network has the advantage that it is linear-in-parameter and hence the parameter adaption is very fast and easy to implement. It is proved through theoritical analysis that the stability of the adaptive control is guaranteed by the Lyapunov stability theory. Finally, simulation and experimental results are included in the paper to show the excellent performance of the proposed method.

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In the industrial motor drive systems such as industrial plants and industrial robots, a torsional vibration is often generated because of the elastic elements in torque transmission. This vibration makes it difficult to achieve quick responses of speed and may result in damage to the plant. Such system is simply modelled as a two-mass system. Many control methods have been examined to suppress the torsional vibration. One of the typical approach is the state feedback control using the observer. Another approach is based on the modern robust control theory. In this paper, the closed-loop characteristics of two types of speed control systems such as the resonance ratio control using the disturbance observer, which is based on the state feedback approach, and H^∞ control, which is based on the modern robust control theory, are compared. The control performance such as the vibration suppression and the disturbance rejection are examined by the simulations and the experiment. The robust stability against the parameter variation, the model uncertainties and noise is also examined. From several examinations, the feature of these control system are clarified.

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Water purification plants are appointed a mission to produce always enough drinking water economically for time variable water demand and time variable conditions of intake water quality. To perform it, intelligent plant operation based on knowledge accumulated at the plant is required. Especially, even now, some of the plant operations depend on human operators' help.
In this paper, an intelligent filter basins control system is shown. Using an on-line expert system, stable water filtration operations come to be automatically controlled without human operator's help. The expert system determines refresh timing and washing time for each filter basin considering for reduction of washing water volume for the filter basin refresh. Also, the expert system determines the refresh timing to avoid over concentrated refresh request from the filter basins. This expert system is installed into a distributed process controller at a filter facility control part of a large scale supervisory control and data acquisition system. The newly developed system has been applied to an actual plant.

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The proposed reluctance motor has a rotor which consists of flux barrier type iron cores with slits to isolate magnetic flux. The iron cores are processed with press machines, and are easy for mass-production and assembly. The stator has the same structure as that of an induction motor. The motor has excellent controllability and very small torque ripple.
We have made up an experimental motor and have evaluated the performances. As the results, the motor has been shown to have 1.7 times continuous torque as large as that of the conventional synchronous motor with ferrite magnet, peak to peak torque ripple of 3% of a nominal torque at rated torque, and speed response of 200Hz.
In this paper, firstly, the structure of the motor is discussed. Secondly, analytical results of flux distribution and resulting torque are shown. Finally, the characteristics of the experimental motor are discussed.

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A large superconducting coil needs a large resistor which dissipates the gigantic stored energy for emergency situations such as quench events. Simple dump resistor, which is made of stainless steel wire ropes with normal air-cooling, has been selected through the consideration of its feature. The results of the experiments using the wire ropes in diameter 26mm and 4mm, show their soundness as electrical resistance up to 800°C. It has been found that the inductance of this dump resistor is low enough. As an example, the dump resistors for the toroidal field coils of the International Thermonuclear Experimental Reactor (ITER), which is under design, has been designed.

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In a previous paper, we proposed a new single-phase capacitor self-excited induction generator with a selfregulating feature, and clarified its operating principles and basic characteristics by experiment. The new generator consists of only a three-phase squirrel-cage induction machine and three capacitors. Therefore, the system configuration of this generator is very simple. Moreover, it has a feature that, when the three capacitors are properly selected, an output voltage of almost constant value can be automatically obtained due to the effect of these capacitors.
This paper presents an algorithm to select the proper capacitors for obtaining a constant voltage characteristic. By using this algorithm, selection of the three capacitors can be easily performed on the basis of the magnetization characteristic and simplified equivalent circuit of the generator. In this paper, the theory of the proposed algorithm is described and its validity is confirmed by experimental investigation with a laboratory machine.

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