Duncan A Grant

The Use of Harmonic Distortion to Increase the Output Voltage of a Three-Phase PWM Inverter

By adding a measure of third harmonic to the output of each phase of a three-phase inverter, it is possible to obtain a line-to-line output voltage that is 15 percent greater than that obtainable when pure sinusoidal modulation is employed. The line-to-line voltage is undistorted. The method permits the inverter to deliver an output voltage approximately equal to the voltage of the ac supply to the inverter. Thus an induction motor of standard rating with respect to the ac supply to the inverter can deliver very nearly full power at rated speed when supplied from the inverter. This is achieved without pulse dropping or any other form of mode-changing.

Synthesis of Tapped-Inductor Switched-Mode Converters

A classification scheme is used to categorize tapped-inductor switched-mode power supplies. This new scheme allows the many possible circuit variants to be displayed in a logical manner and analyzed for practicality and performance. The scheme offers a way of ensuring that no tapped inductor converter circuit is neglected when a tapped-inductor circuit is to be chosen for any particular application.

A New High-Quality PWM AC Drive

The development and realization of an economic low- powered ac drive system which sets new standards in reducing environmental pollution is reported with applications in industrial and office equipment. Pulsewidth modulation (PWM) digital techniques are used for accurate three-phase waveform synthesis using an asynchronous ultrasonic carrier and metal-oxide semiconductor field effect transistors (MOSFETs) for the power switching elements.

Efficiency of low power audio amplifiers and loudspeakers

This paper looks at the load presented to audio amplifiers by real transducers. We consider the power losses in class-AB and class-D amplifier topologies, and determine that in order to predict the efficiency it is necessary to consider the amplifier/transducer combination. The ability of the class-D amplifier to recycle quadrature load current offers new ways to improve the efficiency.

Power semiconductor devices — continuous development

Abstract Power electronics embraces many disciplines but the role of the power semiconductor device remains pivotal. New developments in device technology are eagerly anticipated since an improvement in the characteristics of the power semicondutor devices can have a major influence on the cost, weight and volume of the equipment in which they are used. This paper reviews presently available power semiconductor devices and highlights recent developments.

20th International Conference on Consumer Electronics, ICCE 2001, Los Angeles, USA, 19-21 June

This paper looks at the load presented to audio amplifiers by real transducers. We consider the power losses in class-AB and class-D amplifier topologies, and determine that in order to predict the efficiency it is necessary to consider the amplifier/transducer combination. The ability of the class-D amplifier to recycle quadrature load current offers new ways to improve the efficiency.