US2825022A - Triple-diametric rectifier-connections - Google Patents

Description

Feb. 25, 1958 J. L. BOYER ETAL TRIPLE-DIAMETRIC RECTIFIER-CONNECTIONS Filed March 19, 1954 All United States Patent 2,825,022 TRIPLE-DIAMETRIC RECTIFIER-CONNECTIONS John L. Boyer, Pittsburgh, Pa., and Charles R. Marcuru, Newton Highlands, Mass., assignors to Westinghouse Electric Corporation, East Pittsburgh, Pa., 21 corporation of Pennsylvania Application March 19, 1954, Serial No. 417,334

21 Claims. (Cl. 321-26) Our invention relates to improvements in triple-diametric rectifier-connections, or other electric-power trans lation-systems, whereby over-all economies are obtained, and better operation.

A triple-diametric rectifier-connection, with a six-anode mercury-arc rectifier, has been known, at least as early as 1930, as shown by the Marti-Winograd book on Mercury-Arc Rectifiers, first ed., 1930, chapter 6, page 180, Table V.-E. A triple-diametric connection for a sixanode mercury-arc rectifier, with the addition of a special load-balancing reactor or interphase transformer having an air-gapped core having a smaller-sectioned magnetizable core-part bypassing the air gap, was shown in the Maslin Patent 1,979,669, granted November 6, 1934. An application of the triple-diametric connection to igni: trons or single-anode rectifiers, but without the air-gapped core with a bypassing small-sectioned magnetizable part, was shown in a twenty-page trade-publication entitled Oerlikon Mercury-Arc Rectifiers, Circular 1618.E, dated March 1951, Fig. 23c, page 15, published by Ateliers de Construction Oerlikon, Zurich 50, Switzerland.

According to our present invention, we are providing several different connection-assemblies having certain advantages, for certain purposes, in connection with the broad field of triple-diametric connections for rectifiers or asymmetrically conducting devices in general; and also including improvements which are directed to the application of the principle of the air-gapped core with a reduced-section bypassing magnetizable part, to the broad field of triple-diametric connections for a plurality of entirely separate single-phase asymmetrically conducting devices of a type in which the rating of each device is determined more by the peak current carried by the device, than by the average current or by the thermal capacity of the device.

This last-mentioned phase of our invention is predicated upon the following facts. A triple-diametric rectifier-connection requires a larger transformer than a double-Y connection. In large ignitrons, or singleanode vaporizable-cathode rectifiers, with a large diameter of tank, and with large spacings within the tank, the rating of each tank is determined by the peak current, rather than the average current. The are within such a tube or tank is extinguished at the end of each current-conducting period, and the amount of ionization, and hence its rate of decay at the end of each conducting-period, is dependent upon the peak loadcurrent so that the arc-back rate is determined by the peak current and not by the average current. In a multianode rectifier, on the other hand, an arc is playing at all times within the tank, said are terminating on a cathode-pool which is common to all of the anodes, so that the peak anode current does not have the same importance.

Present designs of large ignitron tubes also have an anode which has an anode-surface area which is more than enough for the radiation of the heat-losses on the anode, to the walls of the tube, so that the currentf l ce rating of the tube is not limited by its thermal capacity; in other words, there is an excess of thermal capacity. As compared to the double-Y connection of ignitrons, our triple-diametric connection takes full advantage of this reserve thermal capacity which is inherent in the igintron, as well as the 3-to-2 reduction in the peak current carried by each tube, as compared with a double Y connection.

Added to all this, it may be noted that the lower peak current and the longer conduction-period of the triple-diametric connection of ignitrons results in a lower arc-drop, meaning a higher efiiciency of the rectifier; there is an 18% reduction in the current in each rectifier-phase, thus reducing the current-rating requirements of the anode-breakers and the transformer-bushings; and there is a 42% reduction, or other considerable reduction, in the magnitude of the fault-currents or crest arc-back currents, thus reducing the required amount of transformer-bracing, reducing the current-interruption requirements of the anode-breakers, and reducing the chance of damaging the rectifiers themselves. When all of these facts are taken into consideration in the design of the complete equipment, there is an over-all gain of the order of 15 or 20% in rating, in changing from the double-Y to the triple-diametric connection of ignitrons.

Since the triple-diametric connection involves a serious voltage-rise at low loads, which seriously limits the utility of this connection, it is usually necessary to provide the bypassed air gap of the Maslin patent, before the fullest advantage can be taken of our invention, the effect of this bypassed air gap being to reduce the minimum useful load, which does not involve a voltagerise, to a value which is small enough to be economically taken care of by a small permanently connected dummyload, which does not detract too seriously from the efficiencies and economies which are obtained by our invention.

In the application of our triple-diametric connections to semiconductor-rectifiers, it is to be noted that, in this kind of rectifier, the voltage-drop is determined by the peak-current, so that the reduction in this peakcurrent not only increases the ratings of the semiconductor-rectifiers but reduces the losses, thus increasing the efliciency. Semiconductor-rectifiers are also particularly susceptible to damage depending upon the magnitude of the fault-currents to which they are subjected, and hence the 42% reduction in the magnitude of the fault-current is of particular significance in the application of our invention to semiconductor-rectifiers.

As a result of the foregoing and other considerations, it will be seen that we obtain significant rating-increases, cost-reductions, better efiiciencies, and less damage from fault-currents, in our complete assembly of rectifiers, transformers and breakers, by using the principles of our present invention.

With the foregoing and other objects in view, our invention consists in the circuits, systems, apparatus, combinations, parts and methods of design and operation, hereinafter described, and illustrated in the accompanying drawing, in which:

Fig. l is a schematic circuit diagram illustrating one embodiment of the invention; and

Figs. 2, 3 and 4 are similar diagrams illustrating modified embodiments of the invention.

Fig. 1 shows a basic form of the invention, using six ignitrons or entirely separate single-phase rectifiers R1 to R6, or other asymmetrically conducting devices of a type in which the rating of each device is determined more by the peak current carried by the device than by the thermal capacity of the device. Each rectifier may comprise a single main anode 7, a grid 8, an ignitor or makealive electrode 9, and a cathode-pool 10, usually of mercury or other vaporizable metal. Thus, each of the six rectifiers R1 to R6, in Fig. l, constitutes a vapor-electric device having a single-phase space-current path between an anode-means and a cathode-means, and each vaporelectric device has its "own individual cathode-means.

Our invention relates to electric-power translationsystems of "the type in which triple-diametric connections of a plurality of entirely separate single-phase asymmetrically conducting devices are used to interchange power, in one direction or the other, between a first polyphase system and a second system which may be cit er a direct- ,current system or an alternating-current system having a frequency which is different from said first polyphase sys- 'tem.

The rawing shows electric-power translation-systems of the type in which power is taken from a three-phase power-supply system, including the power-leads A, B and C, and is transmitted, through an asymmetric-conductor assembly, to a unidirectional-current load-circuit, having the power-leads (l) and In order to greatly simplify the language which is necessary to'explain the invention, it will be described as if the power is transferred from the three-phase power-leads A, B and C to the unidirectional-current power-leads and but it is to be distinctly understood that, by the use of simple and well-known inverter control-connections, the direction of power-flow could be reversed. For the same purpose of greatly simplifying the language necessary to explain the invention, the unidirectional-current power-leads and will be described as if they were a direct-current power-line which receives power from the three-phase power-line A, B, C, but it is to be distinctly understood that the unidirectionalcurrent line could be either the anode-terminal circuit or the cathode-terminal circuit of one phase (or the phase) of a second, diiierent-frequency, alternatingcurrent system which receives power from, or which transmits power to, the three-phase system A, B, C, provided that suitable rectifier-controlling means are provided, as shown, for example, in the Boyer and Hagensick application Serial No. 307,294, filed August 30, 1952, now Patent No. 2,707,258 of April 26, 1955, or any modification or variation thereof.

In Fig. 1, there are three 2-phase power-leads A, B, C, supplying power to a power-transformer, which may be either a 3-phase transformer or an assembly of suitably connected single-phase transformers, as will be readily understood. The power-transformer is provided with a 6-phase secondary winding, having terminals numbered from 1 to 6, according to the phase sequence. In Fig. 1,

the three single-phase secondary windings which are pro- 7 vided with the pairs of diametrically opposite terminals, such as 14, 36, and 5-2, are provided with separate or unconnected midtaps A, B and C, respectively.

In Fig. 1, the direct-current power-leads are indicated at and respectively. R6 are connected, in individual rectifier-phases or circuits, between the positive direct-current lead and the six secondary terminals 1 to 6 which constitute 6-phase power-leads for these rectifiers. Usually, each rectifierphase also includes an anode-breaker 15. The three separate secondary midtaps A, B and C are connected, in three separate circuits, to the negative direct-current lead The connections thus described are the triple-diametric connections, which practically amount to three doublewave single-phase rectifiers which are energized in ac cordance with the three phases A, B and C. It is usually desirable, in such triple-diametric connections, to provide a load-balancing reactor-means, for substantially balancing the direct currents of the respective rectifiers. This need arises from the fact that the triple'diametric rectifier-connections are such that different rectifier-phases 1 to 6, which are energized by the instantaneous voltages of different phases of the polyphase circuit, are at times operated so as to be conducting in parallel with each other,

The six rectifiers R1 to so as to simultaneously supply power to, or receive power from, the same unidirectional-current power-circuit or bus. Heretofore, a suitable load-balancing reactor-means, or interphase reactance-rneans, as it might be called, has been serially included, in some way, in these rectifiereonnections, so that this interphase reactance-means will develop the instantaneous voltage-difierences which are necessary to permit the parallel operation of a plurality of rectifier-phases having terminal-voltages which do not reach their peaks at the same instant. Such an interphase reactance-means is capable of absorbing or developing the necessary alternating-current voltage-diiferences or ripples, to permit such parallel operation of rectifier-phases, and in this ripple-balancing sense it may be regarded as a means for balancing the unidirectional currents of the parallel-operating rectifier-phases.

in Fig. 1, we have provided a novel form of such load-balancing means, in the form of three separate reactor-means A, B" and C, each having its own individual air-gapped magnetizable core 29, for balancing the total'direct currents of said three double-wave singlephase connections, in pairs. Thus, the core 2% of the reactor A is provided with two windings 21 and 22, the core 20 of the reactor B is provided with two windings 23 and 24, and the core 29 of the reactor C is provided with two windings 25 and 26. The windings 21 and 24 are serially connected between the midtap A and the negative lead while the windings 23 and 26 are similarly connected between the midtap B and said negative lead and the windings 25 and 22 are connected between the midtap C and the negative lead The direct-current components which are carried by the three midtaps A, B and C are thus balanced, in pairs, since the reactor-windings 21 to 26 all have the same number of turns, and the reactors are otherwise similar to each other.

In accordance with the principles described in the Maslin patent, each of the reactor-cores 2% has a cross-section which is large enough for the expected unbalanced currents, each has an air gap 27 therein for the purpose of preventing core-saturation during the flow of heavy unbalanced currents, and each has a smalLsectioned magnetizable core-part 2% which bypasses the air gap 2? to reduce the magnetizing current of the reactor at very low direct-current loads on the rectifier-assembly. Our three 2-coil load-balancing reactors A, B and C thus act more individually than a 3-phase reactor, and the three individual reactor-cores 2i are susceptible to more individual design-treatment than would be the case with a 3-phase core. If there is an unbalance in current in the two windings which are placed on any one of the cores 20, a flux will be produced, in that core, which induces a voltage in the windings, which tends to balance the two currents, one against the other. I

' In Fig. 1, we have shown a small-current permanently connected resistance-load 29, which is connected across the direct-current power-leads and for the purpose of adapting the device for use with direct-current systems in which the load-current may fall to zero or to a value below the critical value at which the lay-passing core-sections 223 permit a voltage-rise. It will be understood that this small dummy-load 29 could be used in any of the other forms of embodiment of our invention. In the case of inverter-operation, the dummy resistanceload 29 would be placed across the alternating-current leads, which would then constitute the load-leads or output-leads of the assembly.

Fig. 2 shows a modified form of our circuit, in which the reactor-windings 21 to 26 are placed in the anodeeads or in the respective rectifier-phases. In this case, the two'windings of each pair of diametrically opposite phases are put on an individual magnetizable core-leg 20', and each of these individual legs is preferably provided with its own air gap 27 and reducedsection bypassing core-part 28, as previously described. in 2, as further indicating a possible change in design, the

three core-legs 20 are legs or phases of a 3-phase reactorcore 30, each core-phase or leg 20 carrying two diametrically opposite windings. in Fig. 2, since the load-balancing reactors are in the anode-leads or rectifier-phases, the secondary winding of the power-transformer may be connected as a star-connected 6-phase secondary, having a common star-point connection N, which is connected to the negative direct-current lead The operation of the apparatus shown in Fig. 2 is similar to that which is shown in Fig. 1, with the changes noted, except that the anode-lead connections, in Fig. 2, may serve to limit the arc-back current, or fault current, in any rectifier, somewhat better than is the case with the reactor-connections of Fig. 1, for example.

Pig. 3 shows a still further form of application of our triple-diametric connections, in which the currents in the three phases can be different from each other. In this case, instead of using the load-balancing mutual reactances A, B" and C of Figure 1, we use self-inductance devices or reactors A", B' and C, each having an air-gapped magnetizable core 31, and each having an individual winding 32 which is connected between the negative lead and the appropriate midtap A, B or C, as the case may be. The circuit of Fig. 3 can be used in applications where it is desirable to be able to remove some of the tubes R1 to R6 from operation, without substantially changing the average direct-current voltage.

In the three forms of embodiment which we have thus far shown, for our invention, We have shown a 3-phase system of double-wave single-phase rectifiers in which a midtap of the transformer-winding is used for the returncircuit of the rectifiers. We wish it to be understood, however, that in general, a bridge-type rectifier-connection can be used, in which twice as many individual rectifiers will have to be used, and in which each of the six rectifierphases or circuits contains, in effect, two rectifiers in series with each other, so that the voltages of the powerleads can be doubled, throughout.

We have shown such a rectifier-bridge circuit in Fig. 4, in which the three secondary phases 1-4, 3-6 and 52 are the same as in Fig. l or in Fig. 3, without the midtaps A, B or C. In additionto the six previously described rectifier-units R1 to R6, our Fig. 4 connection uses six more units, with primed numbers, R1 to R6, each connected in a direct-current circuit or branch in series with its correspondingly numbered rectifier-unit without the prime, so as to provide three rectifier-bridges, (-)-R11-R1BAR44R4'; ()-R33- R3-BBR6-6R6; and (-)R55R5BC-- R2-2--R2'.

The three bridge-points BA, BB and BC in Fig. 4 are connected to the positive direct-current lead through any suitable load-balancing reactor-means, such as a threephase reactor-core 50 whichis provided with reactorwindings XA, X8 and XC which are disposed on the several legs or phases of the three-phase core 50; or any other suitable load-balancing means could be used, such as the means shown in Fig. 1. Preferably, the individual reactor-legs of the three-phase reactor-core 59 in Fig. 4 are each provided with an air gap 27, which is bypassed by a reduced-section core-part 28, as previously described. The rectifier-bridge connection of Fig. 4 has the advantage that 180 conduction is maintained in the rectifying devices, thus producing a minimum loss, and making the possible maximum fault-current considerably lower in value. The inductance of each leg of the reactor 50 prevents heavy fault-currents from being sent back from the direct-current leads and to any faulted rectifier-unit.

In Fig. 1, We have shown the rectifiers as being ignitrons. In Figs. 2, 3 and 4, we have shown the rectifiers by means of a conventional rectifier-symbol, which is intended to be applicable to any kind of rectifier. In carrying out our invention, in any of its forms of embodiment, we contemplate that, in each case, each in- 6 dividual rectifier shall be of a type in which the rating is determined by the peak-current rather than by the thermal capacity of the rectifier. Two outstanding forms of such rectifiers were discussed in the opening portions of our description, namely the ignitron and any one of the large number of forms of static or semiconductor rectifiers, and we desire that our invention shall be understood as including the use of either one of these two general types of rectifiers.

While we have illustrated our invention in only four suggested illustrative forms, we wish it to be understood that our invention is not limited to these particular forms, and that it is susceptible of various modifications and substitutions of equivalents, without departing from the essential spirit of the invention.

We claim as our invention:

1. An electric-power translation-system, including direct-current power-leads, three-phase power-leads, sixphase power-leads, a power-transformer connected be tween said three-phase power-leads and said six-phase power-leads, a plurality of entirely separate single-phase asymmetrically conducting devices of a type in which the rating of each device is determined more by the peak current carried by the device than by the average current of the device, and a triple-diametric connectionmeans for providing three double-wave single-phase connections for operatively connecting said asymmetrically conducting devices between said direct-current powerleads and the three pairs of diametrically opposite terminals of said six-phase power-leads, said triple-diametric connection-means including a load-balancing reactormeans for substantially balancing the direct currents of the respective asymmetrically conducting devices, and said load-balancing reactor-means having one or more airgapped magnetizable cores having a core-section large enough for the expected unbalanced currents, and having a smaller-sectioned magnetizable core-part bypassing the air gap to reduce the magnetizing currents of the loadbalancing reactor-means at very low loads.

2. The invention as defined in claim 1, characterized by each of the asymmetrically conducting devices being a vapor-electric device having a single-phase space-current path between an anode-means and a cathode-means, each vapor-electric device having its own individual cathode-means.

3. The invention as defined in claim 1, characterized by each of the asymmetrically conducting devices being a semiconductor-rectifier.

4. The invention as defined in claim 1, in combination with a means for permanently connecting a small-current load-means across the output power-leads of said triplediametric connection-means, the current-consumption of said small-current load-means corresponding approximately to the aforesaid very low loads.

5. The invention as defined in claim 1, characterized by each of the three double-wave single-phase connections including four asymmetrically conducting devices in a bridge-connection.

6. An electric-power translation-system, including direct-current power-leads, three-phase power-leads, sixphase power-leads, a powertransformer connected between said three-phase power-leads and said six-phase power-leads, a plurality of entirely separate single-phase asymmetrically conducting devices of a type in which the rating of each device is determined more by the peak current carried by the device than by the average current of the device, and a triple-diametric connection-means for providing three double-wave single-phase connections for operatively connecting said asymmetrically conducting devices between said direct-current power-leads and the three pairs of diametrically opposite terminals of said six-phase power-leads, said triple-diametric connectionmeans including three separate load-balancing reactormeans, each having its own individual air-gapped magnetizable core, for substantially balancing the total direct currents of said three double-wave single-phase connections, in pairs.

7. The invention as defined in claim 6, characterized by each air-gapped reactor-core having a core-section large enough for the expected unbalanced currents, and having a smaller-sectioned magnetizable core-part bypassing the air gap to reduce the magnetizing currents of the load-balancing reactor-means at very low loads.

8. An electric-power translation-system, including direct-current power-leads, three-phase power-leads, sixphase power-leads, a power-transformer connected between said three-phase power-leads and said six-phase power-leads, a plurality of entirely separate single-phase asymmetrically conducting devices of a type in which the rating of each device is determined more by the peak current carried by the device than by the average current of the device, and a triple-diametric connection-means for providing three double-Wave single-phase connections for operatively connecting said asymmetrically conducting devices between said direct-current power-leads and the three pairs of diametrically opposite terminals of said sixphase power-leads, said triple-diametric connectionmeans including a three-phase load-balancing reactor having a three-phase magnetizable core, each phase of said reactor-core having winding-means thereon for exciting said phase in accordance with the total direct current in a different one of said three double-wave single-phase connections, for substantially balancing said total direct currents, each phase of said reactor-core further having an air gap therein, and having a core-section large enough for the expected unbalanced currents, and having a smallersectioned magnetizable core-part by-passing the air gap to reduce the magnetizing currents of the load-balancing reactor at very low loads.

9. An electric-power translation-system, including direct-current power-leads, three-phase power-leads, sixphase power-leads, a power-transformer connected between said three-phase power-leads and said six-phase power-leads, said power-transformer providing a separate midtap lead for each of the three pairs of diametrically opposite terminals of the six-phase power-leads, a plurality of entirely separate single-phase asymmetrically conducting devices of a type in which the rating of each device is determined more by the peak current carried by the device than by the average current of the device, three separate reactor-means, each having its own individual airgapped magnetizable core, a means for connecting said asymmetrically conducting devices between one of said direct-current power-leads and said six-phase power-leads, respectively, and a means for connecting said three separate reactor-means between another of said direct-current power-leads and said three separate midtap leads, respectively.

10. The invention as defined in claim 9, characterized by each of said three separate reactor-means being a twowinding load-balancing reactor-means, having its two windings in series-circuit connection to two diflerent midtap means, respectively, for substantially balancing the direct currents of the respective midtap means, in pairs.

11. The invention as defined in claim 10, characterized by each air-gapped reactor-core having a core-section large enough for the expected unbalanced currents, and having a smaller-sectioned magnetizable core-part bypassing the air gap to reduce the magnetizing currents of the loadbalancing reactor-means at very low loads.

12. The invention as defined in claim 9, characterized by each of said three separate reactor-means being a singlephase reactor.

13. An electric-power translation-system, including direct-current power-leads, three-phase power-leads, sixphase power-leads, a power-transformer connected between said three-phase power-leads and said six-phase power-leads, a plurality of entirely separate single-phase asymmetrically conducting devices of a type in which the rating of each device is determined more by the peak current carried by the device than by the average current of the device, a means for connecting said asymmetrically conducting devices in six separate phase-connections between one of said direct-current power-leads and said sixphase power-leads, respectively, said six separate phaseconnections including a load-balancing reactor-means for substantially balancing the tota'lized direct-currents in the three pairs of diametrically opposite phase-connections, and a means for providing an opposite-potential connection between another of said direct-current power-leads and the power-circuits for said six separate phase-connections.

14. The invention as defined in claim 13, characterized by said load-balancing reactor-means having one or more air-gapped magnetizable cores having a core-section large enough for the expected unbalanced currents, and having a smaller-sectioned magnetizable core-part bypassing the air gap to reduce the magnetizing currents of the loadbalancing reactor-means at very low loads.

15. An electric-power translation-system, including direct-current power-leads, three-phase power-leads, sixphase power-leads, a power-transformer having a threephase winding-connection which is connected to said threephase power-leads, and a star-connected six-phase windingconnection which is connected to said six-phase powerleads, a plurality of entirely separate single-phase asymmetrically conducting devices of a type in which the rating of each device is determined more by the peak current carried by the device than by the average current of the device, a means for connecting said asymmetrically conducting devices in six separate phase-connections between one of said direct-current power-leads and said six-phase power-leads, respectively, said six separate phase-connections including a load-balancing reactor-means for substantially balancing the totalized direct-currents in the three pairs of diametrically opposite phase-connections, and a means for providing an opposite-potential connection between another of said direct-current power-leads and the star point of said star-connected six-phase windingconnection.

16. The invention as defined in claim 15, characterized by said load-balancing reactor-means having one or more air-gapped magnetizable cores having a core-section large enough for the expected unbalanced currents, and having a smaller-sectioned magnetizable core-part bypassing the air gap to reduce the magnetizing currents of the load-balancing reactor-means at very low loads.

17. An electric-power translation-system, including direct-current power-leads, three-phase power-leads, sixphase power leads, a power-transformer having a threephase winding-connection which is connected to said three-phase power-leads, and a star-connected six-phase winding-connection which is connected to said six-phase power-leads, a plurality of entirely separate single-phase asymmetrically conducting devices of a type in which the rating of each device is determined more by the peak current carried by the device than by the average current of the device, and a means for connecting said asymmetrically conducting devices in six separate phaseconnections between one of said direct-current powerleads and said six-phase power-leads, respectively, said six separate phase-connections including a three-phase load-balancing reactor having a three-phase magnetizable core, each phase of said reactor-core having two windings thereon, for exciting said phase with the sum of the direct currents flowing in the two phase-connections of a different pair of diametrically opposite phase-connections.

18. The invention as defined in claim 17, characterized by each phase of the reactor-core further having an air gap therein, and having a core-section large enough for the expected unbalanced currents, and having a smaller-sectioned magnetizable core-part bypassing the air gap to reduce the magnetizing currents of the loadbalancing reactor at very light loads.

19. An electric-power translation-system, including direct-current power-leads, three-phase powerleads, sixphase power-leads, a power-transformer connected between said three-phase power-leads and said six-phase power-leads, a plurality of entirely separate single-phase asymmetrically conducting devices of a type in which the rating of each device is determined more by the peak current carried by the device than by the average current of the device, and a triple-diametric connection-means for providing three double-wave single-phase connections for operatively connecting said asymmetrically conducting devices between said direct-current power-leads and the three pairs of diametrically opposite terminals of said six-phase power-leads, each of the three double-wave single-phase connections including four asymmetrically conducting devices in a bridge-connection, said triplediametric connection-means including a load-balancing reactor-means for substantially balancing the currents in the three double-wave single-phase connections.

20. An electric-power translation-system, including: unidirectional-current power-leads; three-phase powerleads; six-phase power-leads; a power-transformer-means, connected between said three-phase power-leads and said six-phase power-leads; an asymmetric-conductor assembly having six phase-circuits, said asymmetric-conductor assembly comprising a plurality of entirely separate singlephase asymmetrically conducting devices of a type in which the rating of each device is determined more by its peak current than by its average current; a triplediametric connection-means for providing three doublewave single-phase connections for operatively connecting said asymmetrically conducting devices between said unidirectional-current power-leads and the three pairs of diametrically opposite terminals of said six-phase powerleads; and an interphase reactance-means which is serially included in said connection-means, said interphase reactance-means comprising a plurality of air-gapped magnetic core-members having a core-section large enough for the expected unbalanced currents, and having a smaller-sectioned magnetizable core-part bypassing the air gap to reduce the magnetizing currents of the load- 1O balancing reactor-means at very low loads, each coremember having thereon windings for developing the instantaneous voltage-differences which are necessary to permit a plurality of asymmetric-conductor phases to operate in parallel wtih each other at times.

21. An electric-power translation-system.including: unidirectional-current power-leads; three-phase powerleads; six-phase power-leads; a power-transformer-means, connected between said three-phase power-leads and said six-phase power-leads; a vapor-electric assembly having six phase-circuits, said vapor-electric assembly comprising a plurality of vapor-electric devices, each having a single-phase space-current path between an anode-means and a cathode-means, each vapor-electric device having its own individual cathode-means; a triple-diametric connection-means for providing three double-wave singlephase connections for operatively connecting said vaporelectric devices between said unidirectional-current powerleads and the three pairs of diametrically opposite terminals of said six-phase power-leads; and an interphase reactance-means which is serially included in said connection-means, said interphase reactance-means comprising a plurality of air-gapped magnetic core-members having a core-section large enough for the expected unbalanced currents, and having a smaller-sectioned magnetizable core-part bypassing the air gap to reduce the magnetizing currents of the load-balancing reactor-means at very low loads, each core-member having thereon windings for developing the instantaneous voltage-differences which are necessary to permit a plurality of vaporelectric phases to operate in parallel with each other at times.

References Cited in the file of this patent UNITED STATES PATENTS 1,211,380 Thomas Ian. 2, 1917 1,976,580 Rose Oct. 9, 1934 1,979,699 Maslin Nov. 6, 1934 2,069,283 Slepian et al. Feb. 2, 1937

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