The University of Texas System

John S Hsu

Herbert H Woodson

Amr M Amin

Improved techniques and circuit arrangements are provided for generating gating signals for firing the switching devices of an inverter circuit or like power electronics generator to generate harmonics of a fundamental frequency source and for providing an adjustable phase offset between the harmonic and the fundamental signals. According to a line-frequency signal modification method, a set of line-frequency sine wave signals disposed at equidistant phase angles are generated from a multi-phase fundamental input voltage. Firing pulses are produced from the line-frequency signals by accurately detecting the points of zero-crossings for the signals and subsequently detecting the overlapping segments of similar polarity between successive line-frequency signals. Two different schemes for conveniently generating the required line-frequency sine wave signals are present. According to a digital technique, a series of logic counters are used to generate the required M-phase, Nth-order harmonic gate timing signals. A first counter is used to generate a train of a predefined number of equidistant pulses corresponding to N and M, per fundamental line frequency cycle. A second counter is provided for generating a phase-delayed signal for adjusting the phase angle of the gate timing signals with respect to the line-frequency signal. A third counter is provided for distributing the train of pulses among the plurality of switches of the harmonic generator. The arrangement is such that the train of pulses generated by the first counter is locked to the phase-delayed signal generated by the second counter.

Generation of multi-phase multiple-order harmonics of a fundamental

A method and apparatus for improving the performance of polyphase AC machines. The polyphase AC machines are excited both with a fundamental frequency and with an odd harmonic of the fundamental frequency. The fundamental flux wave and the harmonic flux wave will travel at synchronous speed in the air gap. This facilitates redistributing the flux densities in the machine and thereby increasing the total flux per pole in the machine.

Method and apparatus for improving performance of AC machines

A method and apparatus for improving the performance of polyphase AC machines. The polyphase AC machines are excited both with a fundamental frequency and with an odd harmonic of the fundamental frequency. The odd harmonic flux wave is phase controlled so as to interact with otherwise waste harmonic flux waves generated by the rotor. The interaction of the harmonic flux waves enhances the pull-out torque, power factor, and efficiency of the polyphase AC machine.

A method and apparatus for improving the performance of polyphase AC machine is provided. The machines are excited with both a fundamental frequency and with an odd harmonic of the fundamental frequency so that a fundamental flux wave and an odd harmonic flux wave travel at a synchronized speed within the air-gap of the machine. The phase angle between the fundamental and odd harmonic excitation is controlled to increase the magnetic loading of one portion of the machine, while reducing the magnetic loading of the another portion of the machine. In this manner, redistribution of the flux densities is effected to more efficiently use the various components of the machine to increase torque.

Growing community of inventors

Austin, TX, United States of America

John S Hsu