Hisakatsu Kiwaki

A novel technology improving the response of the DCCT for lower sensed power

Current sensors using magnetic cores (i.e. DC current transformers, DCCTs) covering wide ranges of frequency (from DC to HF) and of sensed current magnitude (from several 10−4 A to several 103 A) are reviewed. The wave distortion which is often experienced in the output of DCCTs of small current ratings or low power ratings is analyzed. A novel method of eliminating the wave distortion using a compensating winding and HF filters is introduced. Remarkable (102 – 103) times improvement of the frequency response without increasing the exciting frequency of the DCCT is verified, which promises the expansion of DCCT application fields.

Controllability improvement of zero-power magnetically levitated system by dither

A zero-power magnetically levitated (MAGLEV) system using a permanent-electro hybrid magnet has a defect of current fluctuation due to nonlinearity of the intermittent domain of a PWM-controlled current controller which may cause unfavorable vibration to the levitated object. To improve controllability, application of dither to the current controller is studied. Transfer characteristics of the current controller applied by dither have a tendency to show better linearity but lower gain. Measured and analysis results by the describing function method agree very well. A current controller with 11 kHz PWM carrier and 500 Hz dither frequency shows very little current fluctuation without current feedback. As a result, a MAGLEV model using the current controller realizes very quiet levitation without vibration.

High reliability control circuit of pwm inverter for electric car drive

An inverter controlled induction motor driving system for electric car is developed and made a trial run. The gate control circuit of PWM inverter in this system is composed of PLLs or other analog circuits to make it simple. This paper describes the operation of this gate control circuit and results of tests. Good adhesion characteristics are obtained in running tests.

Thyristor chopper control using magnetic pulse width modulator

The thyristor chopper control technique for electric vehicles using a magnetic pulse width modulator is described and the chopper control system for Japans nation-wide Shinkansen [1] Train car is given as an example. The operating mechanism of a newly-developed magnetic pulse width modulator and its functions are analyzed. Using them to the best advantage has made it possible to integrate the principal functions for the chopper control, whereby a high degree of simplification of the control system has been attained. The excellent stability of the modulator to electrical noise signals, unavoidable to electric vehicles, is noteworthy. Applications of the technique to battery-operated locomotives and battery-operated fork-lift trucks are also mentioned.

Off-gate signals controlled thyristor chopper equipment for battery-operated vehicles using magnetic phase shifter

We have made sustained efforts to develop a method of controlling thyristor chopper equipment by utilizing a magnetic phase shifter. These efforts have crystallized in the production of thyristor choppers used for the Japanese National Railway New Trunk Line cars, battery-operated locomotives used for the construction work of the Seikan Undersea Tunnel, and other projects. We have recently attained further success in developing a new method for controlling thyristor choppers, which is suitable for battery-operated vehicles such as fork lifts and electric cars. In contrast to the conventional method which causes the magnetic phase shifter to control the chopper ON-gate signals, this new method causes the magnetic phase shifter to control its OFF-gate signals. As a result, the choppers region of a low conduction ratio, often used during brake control of battery-operated vehicles, can be controlled by the magnetic phase shifter region nearby its saturated region, thus quickening chopper response. In addition to this feature, the new method offers many additional merits.

Fully digitized traction motor controller for high power AC electric locomotives

A fully digitized traction motor controller, utilizing microprocessors, was developed for high power AC electric locomotives (continuous rated output: 3,000 kW). The control system is composed of a time discrete system (software implementation), a time continuous system (controlled system), a holder (thyristor rectifier bridge) and a sampler. The entire control system was analyzed and synthesized in a frequency domain. As a result, stable and rapid response control characteristics were achieved throughout the running range of the locomotives. This paper describes the controller construction and analyses of the control system.