Recent development in power semiconductor devices has made remarkable advances in power electronics. Among them, the gate turn-off thyristor (GTO) is one of the most important devices. The carrier life-time controlled device has been proposed recently to realize low turn-off switching loss. So, the computer simulation for the device is now necessary to predict its characteristics. In this study, we simulated carrier life-time controlled GTO by FEM program. The life-time control, such as heavy metal diffusion and electron beem irradiation, showed trade-off relation between on-state and turn-off condition. The partial life-time control, which generates lattice defects by light ion irradiation locally, showed the possibility to reduce turn-off loss and improve the trade-off relations. Furthermore, the numerical inner analysis showed relations between the location of the radiated point and variations of inner carrier distributions.
This paper proposes a new rectifing system consisting of a series active filter and a double-series three-phase twelve-pulse diode rectifier. The supply current in the proposed system has a sinusoidal wave shape because the series active filter suppresses the current harmonics produced by the diode rectifier. Since almost no 5th- and 7th-harmonics are produced by the double-series twelve-pulse diode rectifier, the required peak rating of the series active filter is only 7% of the diode rectifier. In this paper, the control scheme and operating characteristics of the series active filter are theoretically and experimentally discussed. A novel conception that connection of a parallel capacitor to each diode of the rectifier makes a great contribution to reducing the required rating of the series active filter is also presented and verified by some experimental results.
A DC chopper using an Integrated Voltage Control Method is stable and has no steady state error. A DC chopper using this Integrated Voltage Control Method can be used to extend the DC chopper into a Two- or Four-Quadrant DC chopper easily. A Two- or Four-Quadrant DC chopper utilizing this method has many good characteristics, for example a very simple control circuit, very rapid response and automatic changing of active quadrant without a current feedback loop. Applying this Integrated Voltage Control Method, we constructed a speed control circuit for a DC servo motor drive. This circuit has two feedback loops: the first one is a DC motor speed feedback loop and the second is a DC chopper output voltage feedback loop which is eliminated DC component by a coupling capacitor. This speed control circuit utilizing an Integrated Voltage Control Method is stable and has no steady state error, either. And we can determine a damping factor of this speed control system freely if the DC servo motor is over damping. We investigated the effect of the coupling capacitor in the voltage feedback loop on chopping frequency. If the chopping period becomes large, the speed ripple of DC servo motor becomes large. We found that the coupling capacitor has little effect on the chopping frequency for usual DC servo motor. This speed control circuit utilizing an Integrated Voltage Control Method ensures that the ripple speed of the DC servo motor remains at a low level.
The carrier frequency tends to be raised in the PWM inverter due to the appearance of high-speed switching devices. The PWM inverter which is operated by the high carrier frequency is easily influenced by the switching dead-time in comparison with the square-wave inverter. In case that the load is a motor, it is known that the switching dead-time causes serious problems such as current waveform distortion, increased torque ripples at low speed and light load operation. In this paper, the permanent-magnet AC servo motor driven by the PWM inverter was analyzed in consideration of the output voltage deviation and the zero-current-clamping phenomenon during the switching dead-time. The effect of the output voltage deviation on the current waveform were clarified by the analytic results. The current behavior and the switching states around the zero-current clamps were clarified, too. Furthermore, the compensation for the output voltage deviation was proposed and the effect of the compensation was confirmed by the analytic and experimental results. The analytic waveforms coincided with experimental waveforms and the validity of the analysis was given by the coincidence.
A Vector control of an induction motor is widely used for industrial applications. An on-line parameter identification and the speed sensor-less control are studied actively. The representative method for these problems is an application of the adaptive full order observer. The rotor flux for the vector control is estimated by a full order observer and machine parameters or the rotor speed are determined by an adaptive algorithm. In this paper, a new vector control scheme with parameter identifications is proposed. This method is based on the adaptive full order observer. However, the observed currents which are estimated usually in the voltage model are considered as the commanded currents and the voltage model is used for the current controller instead of the conventional one. As the result, the proposed system is simplified than the conventional adaptive full order observer system. As the proposed system is composed of the induction motor model in a synchronously rotating reference frame, well-known slip frequency control block is contained. An arrangement of the poles which are obtained from the torque transfer function is discussed. A linear model is derived taking into account the effects of the change of the stator and rotor resistances. The trajectories of poles and zeros of the torque transfer function are computed and discussed for various system parameters. An identification of stator and rotor resistances is confirmed by the simulation using a nonlinear system model. The proposed idea is applied to the speed sensor-less system and this system has a similar configuration to the conventional systems under some assumptions.
The Cerebellar Model Arithmetic Controller (CMAC) is a means to achieve neural networks, and this has the advantages that the convergence time is short and learning speed per step is fast, compared with those of standard back-propagation neural networks. In the conventional design method of CMAC, a learning gain and quantizing intervals are determined by trial and error, and these values are constant. Therefore, it is very difficult to improve both the learning speed and the accuracy of CMAC at once through the conventional design method. In this paper, a conventional design method of CMAC has been improved to overcome this problem. Furthermore, a continuous path control system of manipulator using this CMAC is presented. The effectiveness is verified by experimental results.
This paper presents a new unsymmetrical model of synchronous generators for power system transient stability simulations. The symmetrical component method has been used traditionally in the analysis of unbalanced faults in power system. This is mainly because the synchronous generators, which play an important role in the power system, can be easily treated by the method. However, when analyzing a system that has elements with unsymmetrical impedance, it may not be easy to use symmetrical component method. In such cases, the simulations can be easily executed by using the phase coordinate method. However, there are few papers that derive a phase coordinate model of synchronous machines. This paper analyzes synchronous generators under unsymmetrical condition in detail by using the symmetrical component method, and then it derives a model of synchronous generators for the phase coordinate method.
Recently, many types of the linear actuator are studied and used to get the direct linear motion. This paper is concerned with the most simple linear actuator which is constructed with a horizontal rod-type iron core, a single-phase excitation coil and a moving aluminum ring on which the thrust is exerted. This is the same construction as the well-known jumping ring experiment system. To analyze the characteristics of this actuator, the most difficult point for analysis is how to obtain the formula to show the flux distribution because the magnetic circuit is opened. One new method used the infinite element method (FEM) is proposed for the reason that FEM is optimum to know the numerical flux distribution, but the basic method of analysis which was used in earlier papers is based on the equivalent circuit introduced by dual circuit theory. The calculated values of starting characteristics by this proposed method show close agreement with the experimental ones. This new method must be useful for the system having the open magnetic circuit.
Recently, the leakage flux in the railway vehicles have been increasing. Therefore, on every kind of driven controlled vehicle (rheostatic control vehicle, field chopper vehicle, VVVF inverter control vehicle), the leakage flux was measured under the same conditions on the same railway line. And it was found that DC leakage flux above the reactor in the VVVF inverter control vehicle was biggest. Then, the light shield materials and it's suitable configuration were proposed for the sake of keeping down below 1mT of DC magnetic field that is the commendable value of ministry of transport. Besides, the shield structure (materials and configuration) we proposed was taken in the practical vehicle and was tested in the actual line. Through the actual tests and the computer simulations, the effectiveness of this shield structure was confirmed. And it was found that the total weight was about half of the iron shield assured the equal effectiveness. Moreover, we proposed the estimation index that the operation waveform of pace-maker was normal or not for the effectiveness of shield, and tried to show the example of it's operation waveform.