US 4,063,144 A · Inverter for providing a sinusodial output having a low harmonic content

Abstract

A DC to AC inverter in which a composite waveform synthesizing a sinusoidal waveform and having three incremental steps for each quarter cycle is formed by summing an alternating stepped waveform having three steps for half cycle, with a square wave in phase therewith and having a frequency three times greater than the alternating stepped waveform. In a three-phase embodiment of the inverter, each of three stages has a coil that is appropriately switched to opposite polarity terminals of a DC voltage source to form beginning and end segments of the alternating waveform, and a single square wave for all three phases is developed by three series-connected windings respectively inductively coupled with the three coils. The single square wave is added to all three alternating stepped waveforms to form the three composite output waveforms of the inverter.

Claims18

Dependent claims

An inverter comprising:

means for generating an alternating stepped waveform having a magnitude which varies incrementally during each half cycle, said magnitude having a first value at the beginning and end segments of each half cycle thereof and a second value greater than said first value during a segment intermediate said beginning and end segments;
means for generating a rectangular wave, having a constant magnitude during each half cycle, in fixed phase relationship with and having a harmonic frequency greater than that of said alternating stepped waveform, the duration of the rectangular wave being shorter than the duration of the second value of the alternating stepped waveform during each half cycle of the alternating stepped waveform;
and
means for summing said alternating stepped waveform and said rectangular wave to form a composite waveform approximating a sinusoidal waveform, said composite waveform having three steps in each quarter cycle thereof.

1 more element

Dependencies are inferred from the claim text.

Inverter for providing a sinusodial output having a low harmonic content

Life of this patent

Inverter for providing a sinusodial output having a low harmonic content

Life of this patent

Abstract

Claims18