A constant frequency power control (CFPC) by phase difference regulation of the gate triggering pulse in the half bridge high frequency inverter (HF-INV) is proposed in this paper. The principle of zero current switching (ZCS) operation utilized an overlapping commutation mode in the HF-INV is numerically analyzed in associated with normalized frequency and load.
The results obtained through the analysis are supplemented with experimental results. Furthermore the design criteria on the basis of numerical analysis are investigated.

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This paper proposes a real-time control method of a series-resonant high-frequency linked DC-AC converter and a feedback control method of its output voltage waveform for applications to UPS, AC motor controller, reactive power compensator, and so on.
An approximate analysis of the basic series-resonant converter is performed, and then practical equations and an equivalent circuit of the converter are obtained by averaging the modified oscillating current of the resonant circuit, from which a real-time control algorithm of the series-resonant converter as well as the conventional PWM inverters is derived. A feedback control is applied using proposed control algorithm to obtain asingle-phase sinusoidal voltage waveform.
Experimental results are presented in the case of linear and nonlinear load to confirm the usefulness of the proposed control algorithm.

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A suitable single-phase inverter for the utility interactive photovoltaic generation system is proposed. The single-phase PWM current source inverter has a novel circuit configuration which is added a auxiliary branch to the normal single-phase bridge circuit. In order to reduce the size and weight of the dc reactor, a double frequency parallel resonance circut (LC tank circuit) is inserted in the dc side of the inverter. In result, the double frequency voltage appeared in the dc side of the inverter due to the pulsation of the single-phase instantaneous power is perfectly suppressed by the tank circuit. The constant dc current without pulsation is supplied from PV array to the inverter. The inverter provide a sinusoidal ac current for domestic loads and the utility line with unity power factor.
The virtual maximum power of the PV array can be obtained without any feedback control. In the system, the PV array can play an important role as a current-limitter by its V-I characteristics. Computed waveformes by simulation are shown. The excellent inverter equipment will be realized with smaller size and lighter weight than a conventional inverter.

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The paper presents a three-phase PWM AC-to-DC converter that employs an inductive energy transfer mechanism (DC reactor). This converter has a wide control range of DC voltage by means of its step-up and step-down characteristics. The source current can be sinusoidally waveshaped in phase with the source voltage by means of the proposed PWM control strategy. The power factor becomes unity in the controlled range of DC voltage. The input filter parameters are decided. Then, waveforms of voltages and currents, input, output and dynamic characteristics are discussed by the computer simulation and their validity is confirmed by experiments.

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A three-phase diode bridge rectifier is one of the simplest and most popular rectifiers in industrial applications. The ac-side currents contain harmonics caused by the nonlinear characteristics of the diodes. So far, the performance, including the effect of the resistance on the ac-side, of such rectifiers has been investigated in computer simulation using the currents and powers expressed by Fourier series.
This paper describes theoretical power flow analysis of a three-phase diode bridge rectifier; the effect of the resistance on the ac-side is considered. The method for calculation effective, reactive and apparent powers in fundamental and harmoinic components without computer simulation is discussed; the powers in the circuit are generalized and classified in the paper. Consequently, it can be stated that the harmionic power dissipated in the ac-side resistance is provided from a part of the input power of the rectifier. It is also clear thet the rectifier acts as both a current source related to harmonic powers and a waveform converter from the viewpoint of power conversion. A new equivalent circuit for the diode bridge rectifier is proposed on the basis of sine-wave approximation from the total effective values of volues of voltages and currents.
The analysis and proposed equivalent circuit are simple and considered to be useful for students and engineers in the field of power electronics.

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Interference from harmonic currents which are generated from home appliances has becoming a problem with popularization of various kinds of domestic electrical goods and OA equipment. This paper describes a new method to improve the power factor of a single phase sinusoidal current input converter. The method provides a sinusoidal input current without using an input current of sinusoidal standard wave form. Experiments confirm the power factor is about 100%. Moreover, the converter can be applied to speed control of DC brushless motors. For this purpose a new control method is proposed. The method uses a PWM control mode for the inverter under light load and a PAM control mode for the converter under heavy load. Overall, this improves efficiency.

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Permanent magnet synchronous (PM) motors are widely used for industrial applications. The PM motors generally have two classifications such as the surface permanent magnet (SPM) motors where the magnets are mounted on the cylindrical rotor surface and the interior permanent magnet (IPM) motors where the magnets are buried into the rotor core. The geometric difference affects the machine parameters as well as the operating characteristics of the PM motors. In this paper, the operating characteristics of SPM and IPM motors are examined and compared each other based on the several drive tests with respect to the three types of prototype PM motors, where the prototype PM motors have the same stator, but the rotor configurations are different. The suitable control method is also examined in order to expand the operating limits considering the current and voltage constraints. From the examinations, the features of PM motors such as SPM motor and IPM motor are discussed and the preferable applied fields are clarified.

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Permanent magnet synchronous (PM) motors are widely used for industrial applications. In the PM motor drives, it is difficult to achieve the wide speed and constant power operations, which are desired in traction and spindle drives, because the field-flux of PM motor is uncontrollable and as a result the field-weakening control is not available. The air-gap flux, however, can be weakened by the demagnetizing effects due to the d-axis armature reaction (flux-weakening control). In this paper, the wide speed control method of the interior PM (IPM) motor, which includes the maximum torque-per-ampere control and the flux-weakening control, is proposed. In the high-speed flux-weakening region, there are some cases where the control performances become worse and the control system becomes unstable because of the saturation of current regulator and the effects of magnetic saturation. The high performance current regulator compensating these effects is also proposed. The control performances of the proposed control system are confirmed by the several drive tests with respect to the prototype IPM motor.

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This paper presents a method of off-line signature recognition using feature strokes and a fuzzy net. For getting feature strokes a pre-processing of signature data is studied. The pre-processing consists of a thinning method and a method of extracting feature strokes from an original signature and corresponding strokes from new signatures. The structure of fuzzy net is a simple perceptron and each unit in the input layer has a fuzzy membership function. From the connection weights of the trained network, it is easy to know which features of input data are important for signature recognition, i.e. the personal characteristics of the signatures are known from the fuzzy net. An experiment is done to show the feasibility of the new method.

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An H_∞ control system design for a magnetic levitation system by 4 points attraction is presented. In the levitation system, a vehicle which runs as the secondary in a reluctance-type linear motor is levitated by four pairs of attraction forces and guided by two pairs of attraction forces. Because it has contactlessness, in the field of semiconductor products, its application is favorable for ultra-clean environments in microscopic processing. In the control system design, we consider the influence of both disturbances and uncertainties in the model. The main disturbances stem from the position sensors. The uncertainties are divided into electromagnetic and mechanical ones: the former are due to the gain change in the current amplifier, the influence of leakage flux and linearization error in the magnetic circuit and the latter are due to the changes of the mass and the monment of inertia of the vehicle. Therefore, the designed controller is indispensable to guarantee robustness of this system for both stability and performance. The controller design is based on the standard H∞-optimal control problem. As the novel features in this paper: We have obtained the low sensitivity and the robust stability for this system design. Further, (1) there are two-poles on j ω-axis in the controlled model; (2) an integrator is included in the controller so that equivalently there are three poles on j ω-axis in the model. Finally, several experiments, comparisons and simulations are carried out to verify the low sensitivity and robustness of the designed control system.

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Recently, the necessity of analytical method for inverse problems has become much higher because of their usefulness in various application fields, such as non-destructive inspection and so on. Most inverse problems are, however, suffering from ill-posed problems. As a result, they are difficult to solve analytically and uniquely. We have been investigating an estimation of static two-dimensional current distribution in materials, using the observed external magnetic fields as a practical example. By discretizing the above problem, it can be regarded as a combinatorial optimization problem. And we proposed the estimation method by incorporating Genetic Algorithms. Genetic Algorithms are heuristic search algorithms that find solutions to problems based on the mechanism of natural selection. In this paper, we discuss the estimation method for uneven current distribution by devising a coding method. Finally, the feasibility of the proposed method is quantitatively confirmed by simulations.

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A conventional method to measure the position of a buried line has been used. This method is based on the measurements of magnetic field around a line which conducts a current. However, the pitfall is that the magnetic field generated by an induced current in a secondary line affords considerable measurement errors. This paper describes a novel method to exclude such errors caused by the induced current. While the magnetic field generated by the current in the primary line is in phase with the current, that generated by the induced current delays more than 90° compared to that of the current in the primary line because of a reluctance component of the secondary line. Hence, the 90° component of the magnetic field results from the induced current. This component is measured by a solenoid coil and a lock-in amplifier; the 0° component is measured also and corrected by using the 90° component. Thus, the net magnetic field generated by the current in the primary line is calculated; it is used to determine the correct position of the primary line. The new method is tested by using two buried lines and is proved to be useful.

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