Electrical engineering in the vehicular technology is very promising. In this paper, improvements in the conventional engines, hybrid vehicles, motor drives, power electronics, sensing technologies, control and information technologies are discussed.
Variable speed and constant frequency power generating systems using rotor excitation of the wound-rotor induction machines have been used for such applications as variable speed pump generators and flywheel energy storage systems. However, the stand-alone generating system of this type, has only been reported and has not yet been practically used. On the other hand, the stand-alone generating systems using diesel engines have been widely used for emergency supply of plants or isolated islands and so on. However, in these cases, the synchronous generators are usually used. If the output frequency is to be kept constant, there is the need to control the speed of the engine using a high performance governor. Even then, the output frequency changes in case of a sudden load change. This paper proposes a new stand-alone power generating system. In this system, the constant frequency output voltage can be obtained even though rotor speed changes by several percent.
This paper concerns software development methods for railway signalling applications built based on the draft safety-related international standards and the evaluation of the methods. In safety-related computer systems in railway signalling applications, as the greater sophistication of the required functions leads to a larger volume of software, in order to ensure the safety and improve the productivity of the software, it is necessary to build up software development methods to ensure that the work in each phase of the software lifecycle can be strictly implemented, with no loss of time. The author first discusses the experience of establishing and implementing software development methods based on a draft of the international standard IEC 61508, which prescribes the development process for safety-related software. In addition, the author makes a comparison verification between the case in which conventional mainstream methods are used and case in which methods are used that conform to the international standards, using field data based on examples of the same system; the author finds that the latter are more effective for productivity and software quality improvement, and make clear the usability of the safety-related international standards.
The rotor flux has been constant and the core loss has been ignored in the conventional vector controller of induction motor. So far, in the stability analysis of vector control without a speed sensor, the core loss has also, been ignored. We propose a novel stability analysis method by introducing a new differential equation and analyze the stability of the vector control without speed sensor considering core loss by the analysis method. The vector control of the induction motor without a speed sensor requires the estimations of the rotor flux and the rotor speed. Since the estimations use the machine parameters and the stator voltage and current components as input quantities, the stability of the system is sensitive to the variations of the machine parameters. The errors of measured stator voltage and current are compared with those of the vector control system with a speed sensor. The stability of the vector control system of the induction motor without a speed sensor, in which the rotor flux speed is controlled with the torque producing current and the rotor flux is calculated from the stator voltage and current, is studied. At first, a novel differential equation for the rotor flux _??_ and torque-producing current _??_ estimator taking core loss into account is introduced and stability analysis method is proposed. Next, theoretical stability is analized by the method and the theoretical stability of rotor speed is compared with the experimental stability to verify the validity of the proposed stability analysis method.
The output voltage waveform of PWM inverter to use for the adjustable speed drive of the motor is the voltage which the pulse widths differ. When surge voltage of PWM inverter is applied to the motor, the surge voltage propagates in the motor winding. The propagation of surge voltage in the motor winding differs with the propagation in the cable, because interturn capacitance is much larger than ground capacitance. In case of the steep-fronted inverter voltage, the larger voltage is developed in the interturn and it might cause the interturn insulation breakdown of stator winding, which often leads to earth insulation failure. This paper states about the result of calculation and measurement for 600kW measurement motor to examine for the surge voltage propagation in the motor winding.
In most variable-speed drives of PMSM, some type of shaft sensor such as an optical encoder or resolver is connected to the rotor shaft. However, such sensor presents several disadvantages such as drive cost, machine size, reliability and noise immunity. Therefore, the sensorless control of PMSM is desired and various sensorless control strategies have been investigated. This paper presents a novel sensorless control strategy for an interior permanent magnet synchronous motor (IPMSM). A new model of IPMSM using an extended electromotive force (EMF) in the rotating reference frame is utilized in order to estimate both of position and speed. The extended EMF is estimated by the least-order observer, and the estimation position error is directly obtained. The proposed scheme corrects the estimated position and speed so that the estimation position error becomes to be zero. The proposed system is very simple and the design of the controller is easy. Several drive tests are carried out and the experimental results show the effectiveness of the proposed sensorless control system.
This paper describes the development of a driver assistance system for improving passenger ride comfort of automobiles. Based on results of psychophysical experiments of subjective ride comfort evaluation, a linear multiple regression model that evaluates the ride discomfort index (RDI) is proposed using longitudinal acceleration and jerk of the automobile as explanatory variables. In order to reduce the ride discomfort caused by the velocity fluctuation of an automobile, a microcomputer-based driver assistance system that evaluates the RDI and informs the driver of the RDI in real time by both visual and auditory means is developed. Experiments show that, with the help of the system, a driver can improve his/her driving skills and modify his/her driving behavior to provide passenger-friendly maneuvers and improve passenger ride comfort, thus verify the usefulness of the proposed driver assistance system.
The market of the electrical power steering is expanding rapidly because of its fuel efficiency. The DC motor is generally used in this system, whose noise reduction is demanded. The DC motor has some dispersion in contact number of segments or contact resistance between the brush and the commutator. When these conditions are different with plural brushes, currents in armature coils are in asymmetrical distribution and the unbalanced magnetic pull occurs in radial direction. We measured the radial force and currents in armature coils with the developed experimental apparatus that can also set up the eccentricity of rotor to stator. In this paper, we investigated the factor and the process of the radial force generated in the DC motor. Then we propose short circuit wires for symmetrical position that makes winding current symmetrical and realizes the noise reduction.
This paper deals with a series active filter for harmonic-current compensation of a large-capacity diode rectifier with a capacitive load. Flux satulation may occur in a series matching transformer for connecting the series active filter to the ac side of the diode rectifier. This paper develops an analog controller of a dc magnetizing current flowing in the matching transformer, along with a model for the controller, to avoid the flux satulation. Operating characteristics of the controller are theoretically and exprimentally discussed, taking into account both an offset voltage in the controller and an error in a current sensor. Finally, this paper discusses a relation between magnetizing characteristics of the matching transformer and the amplitude of the magnetizing current.
This paper presents the nonlinear modeling of a permanent-magnet induction machine (PMIM). The PMIM has a permanent-magnet (PM) rotor that is free to rotate inside a squirrel-cage rotor. The internal self-excitation from this PM rotor allows the PMIM to operate at a higher power factor. Utilizing a duality between magnetic and electric circuits, an electrical equivalent circuit that can accurately include the nonlinearity of the excitation circuit is derived. Based on this equivalent circuit, a measuring method of circuit parameters and a calculation method of the steady-state performance are explained. In addition, the generating characteristics of the PMIM in the grid-connected mode are theoretically calculated to verify the validity of the derived equivalent circuit, and the results are confirmed through experiments.
This paper describes about new method of low torque ripple operation, and wide range velocity control from 10 to 40000rpm of a brushless motor. The proposed method uses only three position signals of Hall elements arranged in the motor and does not need a position-sensor with high resolution or a velocity-sensor which used conventional control system. A sinusoidal wave drive or a square wave drive is selected according to the motor speed and the switch-over is implemented at an appropriate timing to keep out the transitional oscillation. In low speed range, the motor is operated as a plain synchronous motor using sinusoidal wave. The other hand, in high speed range, the motor is driven by square wave generated by position signals of Hall elements, and rotational speed is controlled using PI scheme. If the brushless motor is driven as a synchronous motor, the motor can be made to turn smoothly at low speed range. However, this drive method of the motor is inefficient and also the motor itself heats up at low load. In order to get a high efficiency drive method of the motor, the apply voltage to the winding is adjusted by the torque angle detected by the phase difference between the Hall element signal and the excitation voltage. A technique of switch-over without transitional oscillation which causes when the synchronous speed and the real motor speed are not the same at switch-over point, is also described here. This proposal method will be useful for the application of brushless motor which can be not attached a position-sensor with high resolution or a velocity sensor for small size or environment of operation such as dental hand-piece.
In this paper, the time ratio pulse modulation type series resonant soft switching high frequency inverter using a single auxiliary active power switch is presented, which includes zero current soft switching-assisted lossless inductors, along with its output power regulation characteristics under the condition of a constant operation frequency and complete soft commutation.