Low frequency multi-phase sinewave generator circuit

Claim 2

A three phase voltage generating system comprising: a major and a minor bridge circuit network, each bridge circuit network comprising three circuit branches extending between a pair of D.C. voltage input terminals, each bridge circuit branch including a pair of series connected current control devices, three output terminals respectively at the junctures of the three pairs of current control devices of each bridge circuit network which output terminals constitute three pairs of output terminals of three two-branched bridge circuits formed by the three different combinations of circuit branches of each bridge circuit network, first and second groups of control means for respectively alternately rendering conductive and non-conductive the pairs of current control devices in the branch circuits of the major and minor bridge circuit networks, wherein only one of the current control devices of each such pair of current control devices is conductive or non-conductive at any given instant other than the instants where a change of conduction is taking place, said first group of control means associated with the major bridge circuit network rendering the corresponding current control devices in the various branch circuits thereof conductive and non-conductive in identical cyclically varying conduction patterns spaced 120* apart, said second group of control means associated with the minor bridge circuit network rendering the corresponding current control devices in the branch circuits thereof conductive and non-conductive in identical cyclically varying conduction patterns spaced 120* apart and respectively in corresponding phase relationship with, but in different complementary conduction patterns than, the conduction patterns of the current control devices in the branch circuits of the major bridge circuit network, and summation means for providing three resultant substantially identical sinusoidal-like waveforms differing in phase by 120* and each including added together components derived from the outputs at the corresponding pairs of output terminals of the major and minor bridge circuit networks.

Claim 3

The three phase voltage generating system of claim 1 wherein there is provided amplitude differentiating means for providing correspondingly phased voltage components of different amplitudes which are added by said summation means, the added together voltage components derived from the major bridge circuit network having an amplitude several times greater than the amplitude of the voltage components from the minor bridge circuit network.

Claim 4

The three phase voltage generating system of claim 2 wherein said amplitude differentiating means includes at least one three phase transformer having three primary windings respectively connected across said three pairs of output terminals of one of said bridge circuit networks and associated secondary windings, and means respectively coupling at least two of said secondary windings to different pairs of output terminals of the other bridge circuit network.

Claim 5

The three phase voltage generating system of claim 1 wherein said summation means includes a pair of three phase transformers having primary and secondary windings, the primary windings of said pair of transformers being coupled respectively across the different pairs of output terminals of said major and minor bridge circuit networks, and means connecting the corresponding secondary windings of the pair of transformers in series circuit relationship with such series circuits extending to three different respective pairs of output terminals adapted to be Y or delta connected.

Claim 6

The three phase voltage generating system of claim 2 wherein said D.C. voltage input terminals for said major and minor bridge circuit networks are connected to the output of the same D.C. voltage source, and said summation means includes a pair of three phase transformers having primary and secondary windings with different respective turns ratios, the primary windings of said pair of transformers being coupled respectively across the different pairs of output terminals of said major and minor bridge circuit networks, and means connecting the corresponding secondary windings of the pair of transformers in series circuit relationship with such series circuits extending to three different respective pairs of output terminals adapted to be Y or delta connected.

Claim 7

The three phase voltage generating system of claim 1 wherein said pairs of current control devices in each branch circuit are transistors whose emitter and collectors are connected in series current conduction aiding relation and said first and second group of control means are control signal generating means having waveforms corresponding to the desired conduction patterns of the transistors controlled thereby.

Claim 8

The three phase generating system of claim 1 wherein said summation means includes a single three phase transformer associated with one of the bridge circuit networks, said transformer having three pairs of primary windings and at least a pair of secondary windings, the primary windings of said transformer being coupled respectively across the different pairs of output terminals of said bridge circuit networks, and means coupling said pair of said secondary windings respectively between different pairs of output terminals of the other bridge circuit network and different main output terminals, and a third main output terminal coupled to the other output terminal of said other bridge circuit network.

Claim 9

A three phase voltage generating system comprising: a major and a minor bridge circuit network, each bridge circuit network comprising three circuit branches extending between a pair of D.C. voltage input terminals, each bridge circuit branch including a pair of series connected current control devices, three output terminals respectively at the junctures of the three pairs of current control devices of each bridge circuit network which output terminals constitute three pairs of output terminals of thrEe two-branched bridge circuits formed by the three different combinations of circuit branches of each bridge circuit network, first and second groups of control means for respectively alternately rendering conductive and non-conductive the pairs of current control devices in the branch circuits of the major and minor bridge circuit networks, wherein only one of the current control devices of each such pair of current control devices is conductive or non-conductive at any given instant other than the instants where a change of conduction is taking place, said first group of control means associated with the major bridge circuit network rendering the corresponding current control devices in the various branch circuits thereof conductive and non-conductive in identical cyclically varying conduction patterns spaced 120* apart, one cycle of the conduction pattern of each such current control device being 180* of conduction followed by 180* of non-conduction; said second group of control means associated with the minor bridge circuit network rendering the corresponding current control devices in the branch circuits thereof conductive and non-conductive in identical cyclically varying conduction patterns spaced 120* apart and respectively in corresponding phase relationship with, but in different complementary conduction patterns than, the conduction patterns of the current control devices in the branch circuits of the major bridge circuit network, one cycle of the conduction pattern of each current control device of the minor bridge circuit network comprising relatively short conducting intervals at the beginning and end of a conducting half cycle of the correspondingly phase current control device of the major bridge circuit network and a relatively long half cycle centered conducting interval preceded and followed by relatively short non-conducting intervals for the other half cycle during which the correspondingly phased current control device in the major bridge circuit network is non-conductive, and summation means for providing three resultant substantially identical sinusoidal-like waveforms differing in phase by 120* and each including added together components derived from the outputs at the corresponding pairs of output terminals of the major and minor bridge circuit networks.

Claim 10

A three phase voltage generating system comprising: a major and a minor bridge circuit network, each bridge circuit network comprising three circuit branches extending between a pair of D.C. voltage input terminals, each bridge circuit branch including a pair of series connected current control devices, three output terminals respectively at the junctures of the three pairs of current control devices of each bridge circuit network which output terminals constitute three pairs of output terminals of thrEe two-branched bridge circuits formed by the three different combinations of circuit branches of each bridge circuit network, first and second groups of control means for respectively alternately rendering conductive and non-conductive the pairs of current control devices in the branch circuits of the major and minor bridge circuit networks, wherein only one of the current control devices of each such pair of current control devices is conductive or non-conductive at any given instant other than the instants where a change of conduction is taking place, said first group of control means associated with the major bridge circuit network rendering the corresponding current control devices in the various branch circuits thereof conductive and non-conductive in identical cyclically varying conduction patterns spaced 120* apart, one cycle of the conduction pattern of each such current control device being 180* of conduction followed by 180* of non-conduction; said second group of control means associated with the minor bridge circuit network rendering the corresponding current control devices in the branch circuits thereof conductive and non-conductive in identical cyclically varying conduction patterns spaced 120* apart and respectively in corresponding phase relationship with, but in different complementary conduction patterns than, the conduction patterns of the current control devices in the branch circuits of the major bridge circuit network, one cycle of the conduction pattern of each current control device of the minor bridge circuit network comprising relatively short conducting intervals at the beginning and end of a conducting half cycle of the correspondingly phase current control device of the major bridge circuit network and a relatively long half cycle centered conducting interval preceded and followed by relatively short non-conducting intervals for the other half cycle during which the correspondingly phased current control device in the major bridge circuit network is non-conductive, and summation means for providing three resultant substantially identical sinusoidal-like waveforms differing in phase by 120* and each including added together components derived from the outputs at the corresponding pairs of output terminals of the major and minor bridge circuit networks.

Claim 11

The three phase voltage generating system of claim 8 wherein said summation means includes a pair of three phase transformers having primary and secondary windings, the primary windings of said pair of transformers being coupled respectively across the different pairs of output terminals of said major and minor bridge circuit networks, and means connecting the corresponding secondary windings of the pair of transformers in series circuit relationship with such series circuits extending to three different respective pairs of output terminals adapted to be Y or delta connected.

Claim 12

The three phase voltage generating system of claim 8 wherein there is provided amplitude differentiating means for providing correspondingly phased voltage components of different amplitudes which are added by said summation means, the added together voltage components derived from the major bridge circuit network having an amplitude several times greater than the amplitude of the voltage components from the minor bridge circuit network.

Claim 13

The three phase voltage generating system of claim 9 wherein said D.C. voltage input terminals for said major and minor bridge circuit networks are connected to the output of the same D.C. voltage source, and said summation and amplitude differentiating means include a pair of three phase transformers having primary and secondary windings with different respective turns ratios, the primary windings of said pair of transformers being coupled respectively across the different pairs of output terminals of said major and minor bridge circuit networks, and means connecting the corresponding secondary windings of the pAir of transformers in series circuit relationship with such series circuits extending to three different respective pairs of output terminals adapted to be Y or delta connected.

Claim 14

The three phase generating system of claim 8 wherein said summation means includes a single three phase transformer associated with one of the bridge circuit networks said transformer having primary and secondary windings, the primary windings of said pair of transformers being coupled respectively across the different pairs of output terminals of said major and minor bridge circuit networks, and means coupling only a pair of said secondary windings respectively between different output terminals of the other bridge circuit network and different main output terminals, and a third main output terminal coupled to the other output terminal of said other bridge circuit network.