Keiju Matsui

A voltage source three phase PWM converter with chopper circuit

This paper presents a novel strategy of a PWM power converter to control output voltage using a chopper circuit. Voltage source PWM converters are unsuitable for general purposes with wide adjustable voltage range. However, the surge voltage at switching becomes small and the input current waveforms have low harmonics and less resonant oscillations as compared with the current source power converters. In this circuit, the input current waveform is controlled by the PWM power converter with the fixed optimum voltage modulation factor and the output voltage amplitude is adjusted by the chopper circuit with very fast response and precise control. The results are verified by experiments. Finally, a control scheme for application to an AC motor drive is presented and discussed.

A novel PWM strategy to minimize the surge voltage for current-source converters

This paper presents a novel strategy of PWM wave control method to minimize the surge voltage at the turn off of switching devices. The sawtooth carrier is compared with the reference sinusoidal voltage, in which the polarity of the sawtooth carrier waveform is reversed alternately at every 60/spl deg/ interval relative to the fundamental wave period. It is anticipated that it is difficult to analyze the output waveforms because of its complicated current waveforms. For such waveforms, a frequency analysis approach using the switching function is presented, whose results are verified by experiments.

A simple harmonic meter using phase locked loop

Various harmonics in the power system are measured typically by the heterodyne receiver in analog methods or the FFT (fast Fourier transform) in digital methods. By means of these methods, the harmonics can be analyzed over a wide range of frequency. However, since circuit configurations of such methods become very complicated, the equipment becomes too expensive. This paper presents a harmonic meter using a PLL (phase locked loop) circuit. By means of the feedback loop for phase, the reference sinusoidal wave is locked on to the input signal with the harmonics for measurement and hence the harmonic component in the input signal is easily detected. The usefulness of the proposed harmonic meter is confirmed by experiment.

Improvement of thrust of linear induction motor using modified ladder slits

This paper presents a method to improve the thrust of a linear induction motor (LIM). LIMs are used in many industrial applications such as high-speed material transport systems and the like, because they can obtain thrust directly without auxiliary mechanisms such as gears and links, in addition to having a simple structure. In this paper, the authors propose a secondary conducting plate with novel shape ladder slits in order to improve the motors thrust. The usefulness of the proposed novel ladder slits is discussed through experiments and analytical computation results.

A simple and low cost measuring method for harmonics in the power system

Various harmonics in power systems are measured typically by the heterodyne receiver in analog techniques or the FFT (fast Fourier transform) analyzer in digital methods. Using these methods, the harmonics can be analyzed over a wide range of frequency. However, circuit configurations using such methods become very complicated and the devices become too expensive. This paper presents a harmonic analyzing meter using a PLL (phase locked loop) circuit. By means of the PLL circuit, the reference sinusoidal wave is locked on to the input signal with the harmonics for measurement, and hence the harmonic component in the input signal is easily detected. The usefulness of the proposed analyzing meter is confirmed by experiments.