This paper proposes a high power facter rectifier composed of only passive devices. It consists of a single phase diode rectifier having a L-C resonant circuit in parallel with the diode output and a series reactor to pumping up the charge stored in the resonant circuit capacitor. It enables wide current conduction width and decreases its peak value. As a result, harmonics in the input current is decreased and the power factor is improved, which will be satisfied the harmonic regulation enforced in near future.
The absence of switching devices as FETs makes high reliability, high efficiency, strength to over load, and no radio noise. In this paper, it is shown input harmonic current components, output voltage, and other characteristics by charts for circuit design. Input power factor of 98.4%, the total harmonic distortion of 17.4%, and the efficiency of 93.3% are confirmed by experiment with rated condition of 1.0kW, 100V system.

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A parallel-connected twelve-pulse thyristor converter consisting of two six-pulse groups with an interphase reactor has been used for low-voltage high-current dc power supplies because of its high efficiency compared with a series one. It seems to be the most suitable converter for superconducting magnetic energy storage systems (SMES), which are expected to be used in actual power systems in the near future as a power system stabilizer. Harmonic reduction on the source side is required for such large-capacity thyristor converters. A number of methods have been proposed. These methods, however, require additional devices. Thus, a simple parallel-connected converter without any additional devices remains to be constructed to reduce harmonic currents on the source side.
This paper attempts to construct a simple 12-pulse thyristor converter by proposing a novel design concept of the interphase reactor. This method proposed here requires no additional devices and only reducing the inductance of the interphase reactor. The source current of the 12-pulse thyristor converter with the reduced inductance interphase reactor approaches sinusoidal waveforms, which are approximately equivalent to those of the 36-pulse thyristor converter. Simulation results show that decreasing the inductance of the interphase reactor contributes to reducing harmonic currents on the source side. In addition to the simulation results, experimental results verify the validity and practicability of the proposed novel design concept of the interphase reactor.

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The neutral point clamped (NPC)-PWM inverter has significant advantages such as its ability to operate the motor with nearly sinusoidal current waveforms. For this reason, in larger capacity inverter systems, NPC-PWM inverters using the GTOs and the like have been also put into practical use, because of great advantages to large capacity ac motor drives, such as lower ripple currents and higher output voltages. With the spread of applications, still larger capacity inverters are also expected. However, since the capacities of such switching devices are insufficient, a certain technique and controlling method are proposed for the parallel connections of NPC inverters. In this paper, the conventional modulation techniques are extended to improve the inverter characteristics, in which the asymmetrical modulation and over-modulation techniques are introduced for the parallel connected NPC inverter.
In the proposed modulation strategies, the waveforms become more complicated, so it is difficult to analyze the output waveforms. For those waveforms, the analytical waveform analysis method using the switching function is proposed. By means of such method, a physical meaning of the harmonic generation can he realized to some extent.

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This paper describes the power loss and efficiency in full-bridged MOS-FET arrays, each consisting of parallel connected MOS-FETs, and those in an output power transformer whose output power is fed to a load at an output power of 1kW at a frequency of 2.5MHz. The power losses within the MOS-FET arrays and output power transformer are estimated based on their thermal resistances which have separately been obtained from the measurement. The drain efficiency is thus obtained from the DC input power, RF output power, and estimated power losses. The output power of the MOS-FET arrays was 1300 to 1400W at a drain efficiency of 74 to 79% at a frequency of 2.5MHz when the DC voltage was 180V.

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Pulsewidth modulation (PWM) control techniques for rectifiers are widely used to improve the source current waveform and the input power factor. Recently, methods to reduce the number of detectors are studied to simplify system configuration of such rectifiers and their control. It is known that a voltage detector on the ac-side can be omitted though a voltage detector on the dc-side is needed for adjustment of the dc-output of a PWM rectifier.
In this paper, a method for controlling a single-phase rectifier without any voltage sensors is proposed. The ac-side voltage can be estimated from the input-reactor voltage when the ac-side of the bridge is short-circuited; the reactor voltage is easily obtained by multiplication of the inductance of the reactor and the derivative of the source current measured. On the other hand, the dc-side voltage can be estimated by calculating the difference between the source voltage at the beginning of every switching period and the reactor voltage sampled and held in the previous bridge conduction mode.
This paper describes the control scheme and its implementation, and performance characteristics of the rectifier. The usefulness of the rectifier is confirmed by experiment. The method is applicable to various types of PWM rectifiers.

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In the resonance ratio control, which is a well-known excellent technique for vibration suppression and disturbance rejection control of torsional systems, the estimation speed of the disturbance observer was assumed to be much faster than the resonance frequency of the controlled object. However, too fast disturbance observer sometimes causes implementation problem. In this paper, we give the optimal speed of the disturbance estimation and propose a novel technique, “slow resonance ratio control”. It enables us to design the speed controller and the vibration suppression controller completely independently.

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In a previous paper, we proposed a new self-excited three-phase synchronous generator in which the 2nd-space harmonic component of the armature reaction field is used for exciting the field system, and clarified its operating principles and basic characteristics by experiment. The new generator has a series excitation characteristic, and responds quickly to a sudden change of load, because an excitation power can be directly obtained from the armature reaction field.
This paper introduces a method for analyzing the steady-state performance of our new generator. In the analysis, an equivalent circuit of the generator is derived from a duality between interlinked electric and magnetic circuits. A simple determination method of parameters in the equivalent circuit is also shown. Calculated results are compared with the experimentally obtained values on a laboratory machine, and good agreement between both values has been observed. The proposed analysis is useful for simulating the steady-state performance of the generator by taking into account the nonlinear effect of the iron core due to magnetic saturation.

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We proposed in a previous paper a new self-excited single-phase induction generator with a self-regulating feature, and clarified its operating principles and basic characteristics by experiment. This generator consists of a three-phase squirrel-cage induction machine Yconnected with three capacitors, and one of these capacitors is connected with a single-phase load. Thus, the system configuration of the generation set is very simple, and by selecting the values of the three capacitors properly, this system exhibits a better voltage regulation.
This paper introduces a method for predicting the steady-state performance of the generator. In the analysis, the method of symmetrical coordinates is used to derive an equivalent circuit of the generator. A computational procedure and a mathematical model for predicting the steady-state performance are also shown. Calculated results are compared with the experimentally obtained values on a laboratory machine, and a reasonable correlation is observed. The proposed analysis is useful for simulating the steady-state performance of the generator by taking into account the nonlinear effect of the iron core due to magnetic saturation.

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The three-phase squirrel cage induction motor (IM) has been used in all types of industry, because of robustness and simplicity of its structure, lower cost and easiness of maintenance. Due to the resultant air gap flux wave, IM produces electromagnetic vibration and noise more or less regardless of slot-combination. Recently, reduction of electromagnetic vibration and noise becomes important subject from standpoint of environmental improvement.
Vibration caused by IM at no-load has been studied for many years and its basic factors have been analyzed. However, electromagnetic vibration under loaded condition is not analyzed enough. Since vibration under loaded condition are affected by load and installation, analysis of this vibration is rather difficult task. But study of electromagnetic vibration of motor itself under loaded condition is basically most important item.
This paper clarifies theoretically and experimentally causes and characteristics of the electromagnetic vibration of IM under loaded condition. Firstly, general equations are derived for dominant electromagnetic force waves that produce electromagnetic vibration. Cause and vibration mode are clearly classified and theoretical analysis is provided basic concept of electromagnetic vibrations.
Secondly, the electromagnetic vibrations for various loads are measured, taking the effect of natural frequency of the motor into consideration. These measured data are classified and analyzed in detail, based on the proposed theory.

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In the superconducting maglev system it is important to develop a non-contact on-board power source without environmental pollution such as a noise and an exhaust gas, therefore, an inductive power collection (IPC) which utilizes a harmonic magnetic field generated by ground coils in EDS is being studied. However, alteration to a null-flux EDS which has a high drag ratio reduces the power collecting capacity in the IPC system. In addition, power collecting coils locate on a cryostat of superconducting coil (SC), so eddy current at the cryostat also reduces the power collecting capacity. Therefore, an exclusive SC type which locates the exclusive SCs for IPC and power collecting coils such as to face the upper and lower coils of ground coils, respectively, is examined, but we aim to improve the conventional type. After analyzing the influence of eddy current at cryostat in detail and improving the composition of power collecting coil and cryostat, we found that the conventional type has the same capacity as the exclusive SC type. In order to prove the above-mentioned result, we measured induced voltage of new type coils in a test run at Miyazaki test track and confirmed the output of this IPC system in a synthetic bench test of full scale with PWM converter and magnetic field simulator.

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Various new Techniques are developed for controlled motors in industrial use. For example, small size, high output power, heavy duty, low cost, high precision and the other characteristics are demanded. It is very important to make a size of position sensor small, in order to realize miniature equipments for position control.
In the present work, a new position sensor which enables to make small sized controlled motor is suggested and we actually made controlled motors which eqqipped with this new type sensor in order to investigate the performance and characteristics. For this position sensor, it is noted that the sensor coils are set at the stator of motor. According to that, it is possible to make small sized and heavy duty controlled motors. The basic principles of this sensor is such that the inductance varies with rotor magnets. We can get rotational angle easy from the induced voltages of sensor coils. Since the authors know no conventional position sensor based on the same technology as the present. we have just named this new type sensor the magnetic modulation type differential resolver.

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This paper presents a position sensorless drive of a salient-pole brushless dc motor with a sinusoidal flux distribution. The algorithm is based on the estimation of back emf which is identified by the errors between the actual and estimated currents. Since the direction and amplitude of the estimated emf correspond to the rotor position and speed respectively, the position and speed can be estimated. The stability of the estimation and the design of the estimation gains are examined.
The proposed algorithm were verified by using a 6-pole, 200W, 3000rpm test motor. In the results, the sensorless speed control range from 50rpm to 4000rpm under 0_??_100% load was obtained. The estimation algorithm is stable for any position error and any emf error.

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A new design method based on the linear-quadratic control theory is developed for the control of PWM rectifiers with sinusoidal input current. The PWM rectifiers are promising because they can supply DC power while keeping a sinusoidal AC current with unity in the fundamental power factor. There are two types, a voltage-source rectifier and a current-source rectifier. The former is required to simultaneously control both the fundamental power factor and DC voltage, while the latter does so for both the fundamental power factor and DC current. State feedback control is essentially suited for multi-input and multi-output systems such as those. Here a discrete-time optimal regulator is applied to their control because it provides a microprocessor-based robust feedback system without steady-state errors in response to step reference and/or disturbance change. The regulator is implemented using a digital-signal-processor. Experimental results demonstrate the validity.

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