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AssigneeWestinghouse Electric Corp.
InventorAlberto Abbondanti
Estimating the term…
Pulse width modulation is produced by digital means. Pulse width modulated waves are stored digitally in a memory and retrieved under control of a voltage signal in order to generate a pulse width modulated wave of predetermined pattern for any discrete value of successive desired output voltage levels. Optimal waveforms are selected and stored which extend only for one quadrant but an alteration of the addressing code based on symmetry yields the mirror image of the stored quadrant while sign modification provides symmetry about the abscissa axis. Also, only a single phase is stored and phase shifting by code alteration of the coded information provides the other phases after retrieval. The notches characterizing a particular pattern are stored in the form of a digital representation one level along several possible levels defining subdivisions of a given time interval which is itself a submultiple of the total duration of the stored quandrant. A comparator responsive to a series of ramp signals detects in real time the stored levels thereby to effect switching from one state to the other and define one edge of a notch. The notches may extend over several of the ramp signals. The invention provides, with substantially the same hardware, for a fixed pattern mode of operation in the normal frequency range, and for a free running triangulation mode for the lower frequency range. The invention applies to the field of induction motor drives with adjustable speed.
A pulsewidth modulator comprising:
A digital system for generating a pulse-width modulated signal comprising:
In an AC motor drive including at least one AC motor, a DC supply, an inverter connected in circuit between said DC supply and said AC motor, and a pulse-width modulator responsive to a frequency reference signal representing a desired motor frequency and to a voltage reference signal representing desired motor voltage levels for controlling said inverter in accordance with an outputted pulse-width modulated signal to operate said AC motor at a speed determined by said frequency reference signal and under flux conditions determined by said voltage reference signal, the combination of:
In a static AC power supply providing AC power to an AC load at a given fundamental frequency and given voltage with reduced harmonic contents and including a DC supply, an inverter connected in circuit between said DC supply and said AC load and a pulse-width modulator responsive to a frequency reference signal representing the desired fundamental frequency, and to a voltage reference signal representing the desired power supply fundamental voltage for controlling said inverter in accordance with an outputted pulse-width modulated signal to energize said AC load at the fundamental frequency under voltage conditions defined by said voltage reference signal, the combination of:
Dependencies are inferred from the claim text.