This paper presents several converters which, having only a single active switch, are able to operate with PWM characteristics in a soft switching way. In addition such converters can work in high switching frequencies for wide load range without great limitations. In order to illustrate the operating principles of these converters a detailed analysis, including simulations and experimental tests are carried out. The validity of these converters is assured by the obtained results.

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As the Application Specific Electric Motors (ASEM), design and analysis of the brushless motor for ball screw drives are presented. Since the motor should be designed as the built-in structure for the machining equipment, the motor dimensions are restricted. The new design concept for such applications is presented. Under various number of combinations of motor dimensions and electric parameters, the motor performances are simulated by the personal computer, among which the optimized parameter combination can be selected. Based on the optimized parameters, the prototype motor is constructed to prove the validity of the proposed design procedure.

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The no-load saturation curve, a fundamental machine characteristic, is normally measured as the relation between field current and terminal voltage of a synchronous machine rotating at its rated speed.
In this paper, we propose a static method to measure the no-load saturation curve of a synchronous machine at stationary condition by changing the field current.
When testing a synchronous machine at stationary condition, large expenditures are required for such items as depreciation of the test equipment, test engineers, electric power, etc. Therefore, omitting the rotating test will reduce testing costs and delivery time.
In this paper, an experimental generator (2kW, 1500rpm) and a practical generator (1200kVA, 900rpm) are used to evaluate the no-load saturation curve for different types of synchronous machines, stationary rotor positions, field current excitation methods, etc. The results were confirmed to be satisfactory for practical use.
Further, the influence of higher harmonics of gap flux and a damper winding was examined and verified that they do not affect the measured values.

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In recent years, attention has been paid to the concept of FACTS (Flexible AC Transmission Systems), along with significant progress in power electronic technology. A high speed phase shifter, which is one of the most promising devices in the FACTS concept, has the potential of power flow control and/or voltage stability in power transmission systems.
In this paper, theory and experiment reveal that conventional high speed phase shifters may cause power swing in a transient state as a result of coupling between instantaneous active and reactive power control loops. Then, a couple of new control schemes for a high speed phase shifter are proposed to achieve both power flow control and power swing damping. The second proposed control scheme is based on the control scheme of an already proposed series active filter. Simulated and experimental results agree well with analytical results, not only in steady states but also in transient states.

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In this paper, we propose a new design method of continuous deadbeat control system without using delay-element, and apply it to a speed control of the current type inverter-induction motor system.
The dynamic characteristic of the system is expressed by the step or impulse response, then the deadbeat control signal which designed to minimize the quadratic form of the input and output errors can be easily obtained by the matrix computation using sampled data of these responses.
The method of designing the continuous deadbeat controller which composed of both the pre-compensator and state feedback compensation is derived by use of the sequence of the deadbeat control signal.
An actual continuous deadbeat controller is constructed by the microprocessor and it is found from experimental results that the speed control system proposed here gives stable operations and good transient performances for the step change of the desired value and disturbance.

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We developed a new crane control system that has accurate anti-sway position control function of a hanged object. The control system consists of two blocks. One is for anti-sway control, and another is for the position control. Each output of the control blocks is calculated individually, and becomes the velocity reference for the trolley of the crane. The anti-sway control was realized by the acceleration feedback, and the position control is carried out by following the pattern that is calculated so that the trolley stops smoothly at the predetermined standstill position. We confirmed the effectiveness of this controller through experiments.

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An Interlocking System consists of an interlocking logical unit and power controlling unit. After this logical unit calculates the relationship among the train position, the rail shifting position and the signal, it decides the aspect of signal. Power controlling unit supplies electrical power to the switch motor and the bulb of signal according to the decision of the logical unit. This paper proposes a small-sized interlocking system which uses triplex redundant off-the-shelf controller with fail-safe checker as a interlocking logical unit. 2-outof-3 voter circuit ensure the safety of parallel output from the interlocking logical unit. This circuit satisfy the condition of “Totally Self-Checking” (by D. A. Anderson) and also the condition of “High Availability”. In other words, any kind of a single fault never leads hazardous state and this circuit has ability of safety after single fault occurring.

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Highspeed Permanent Magnet Synchronous Machines (P. M.) become more and more popular for their small weight and low noise. As the residual magnetism of rare-earth magnets is temperature dependent, eddy-current losses in the supporting-ring of radial-airgap constructions play an important role in the design of such machines. This paper presents a solution for the harmonics, due to slotting, in the flux-density waveform on the surface of the supporting-ring, using a Fourier-Series-Method. A fast approximate solution for loss-calculations at no-load is shown and the results are compared with measured values of an experimental machine, rated at 1000kW, 1250V, 15000rpm.

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Sinusoidal PWM control method is widely applied to power electronic converters. Its carrier frequency of recent converter product gradually becomes higher in order to decrease current harmonics as much as possible. However, in DC filter circuit of large capacity converters, the capacitance of an unit capacitor is relatively large, and busbars are relatively long. Therefore, its resonant frequency is lower than that of small capacity ones. Consequently, there is concern that the carrier frequency will become close to the resonant frequency which will cause some troubles. On the other hand, it is often necessary to decrease the inductance of the loop circuit which is composed of a switching device and its by-pass circuit, in order to suppress switching surge voltage.
In both cases described above, it is important to be sure of the exact value of busbar inductance for reliable designing. In this paper, a simplified calculating method of busbar inductance is proposed. This method is based on the partial inductance theory. Especially, the characteristics of a pair of busbars are described, and its utilization is proposed. Finally, the application for stray resonance analysis in DC filter circuit of three level inverter is described in comparison with experimental data. From these results, it is confirmed that the proposed method is suitable to estimate busbar inductance quickly and also exactly.

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Stepping motors are used mainly in OA and FA systems due to the merit of their digital driving behavior using switching devices. They are driven by closed-loop control in the systems where special performance such as prevention of out of synchronism or highspeed drive is required.
It is well known that rotor oscillation is one of the principal problems in switched drive of a stepping motor, and nowadays several methods for damping of oscillation in which switching sequence is changed in respective manners have been suggested. In such method, the exciting time of stator windings must be tuned appropriately, or effect of damping becomes insufficient and oscillation may be even amplified in some circumstances. To resolve this problem, some adaptive methods for tuning of the exciting time have been developed. However, they have the disadvantage that there must be a period to tune the exciting time to the optimal value at the beginning of control or when the machine parameter is varied by changing of driving condition.
The authors developed a new method for rotor oscillation damping of a stepping motor in a closed-loop system. It is based on the technique of sliding mode control and designed to be robust to variation of rotor inertia which affects significantly to the oscillatory characteristic. In this method, a lower-order dynamical model, obtained by reaching to a sliding mode where the angle-torque characteristic of the motor is bound to a certain linear function, is made to be non-oscillatory by pole assignment over a certain region of varying rotor inertia. Applying this method to the experimental system, rotor oscillation is damped excellently in the cases of single-step and low-speed-multi-step drive. On the other hand, it is shown that deceleration must be needed near the last step in the case of high-speed drive.

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In the linear induction motor (LIM), the secondary can move in two directions (X and Y) by placing the primary coils twodimensionally. When these coils are excited in the direction of 45 electrical degree, the secondary moves to the direction, which is determined by the pole pitches of both directions and the load condition. In this paper, we propose a new type of winding scheme composed of four groups of primary exciting coils, which are shifted π/2 spatially in both directions. These coils are energized by twophase supply with independent phase shifters. By using this winding scheme, all sides of the primary coils contribute to the secondary movement. Next, we compare the proposed winding scheme with another one using two kinds of independent exciting coils in both directions. The feature of the former is driven by a traveling magnetic field with constant amplitude when the primary coils are excited in the direction of 45 electrical degree, while the latter is simple in construction of the primary coils.
We first made both of flat type X-Y LIMs with the proposed winding scheme and with a normal one. And then, we analyzed the magnetic fields in the air-gap of these motors by the three-dimensional finite element analysis based on A-φ method, and compared the results with experimental ones. Finally, we apply the motor with the proposed winding scheme to a branch apparatus.

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Stepping motors are used in many systems due to their simple driving method using open-loop control with switching devices. In the case such that a stepping motor is driven at low speed, the profile of angular displacement of the rotor becomes stepped one and rotor oscillation occurs in each step because of its switched operation. It is well known that microstep drive is one of the solutions of this problem, however currents in stator windings must be controlled precisely for execution of microstepping and consequently the drive circuit becomes complicated and expensive.
The authors suggest a method to adjust the waveform of angular displacement in a step response of a stepping motor. In this method, the waveform is adjusted only by tuning the exciting sequence used for switching of the applied voltage on each winding, therefore no modification for the drive circuit is required. By adjusting the waveform appropriately, the profile of angular displacement becomes smooth even in the low-speed region.
For tuning of the exciting sequence, genetic algorithm is used in the present work. In this algorithm, the step response of the motor is modeled as an individual of artificial life which has a genotype constructed by coding the exciting sequence. Each individual is evaluated by its fitness of the waveform to desirable one. Applying this method to the tuning process of the exciting sequence, it is shown that the waveform of angular displacement can be adjusted to a ramp function. Moreover, the driving characteristic in lowspeed region is improved by using the tuned exciting sequence.

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This paper describes a high voltage switch with MOSFETs connected in series employing a novel driving method in which the turn-on of the master stage by the input signal simultaneously puts other stages in conduction. Stages comected in series except for the master one are driven using the displacement current which flows just when the master stage is turned on. The displacement current can simultaneously drives those stage because the current flows in series through those stages. Hence, the fast switching speed can be obtained even with many stages connected in series. A prototype high voltage switch has been built and its characteristics has been investigated. We found that the parasitic capacitances between the stages and the ground position make the switching characteristics worse and that optimizing the circuit condition makes fast switching possible even with the parasitic capacitances. We have showed that the rise time is almost constant even with the increase in the series number, and that the rise time of 22ns in obtained with 10 MOSFETs' stage in series under an output power condition of 8kV and 120A.

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