US2422575A - Vapor electric device - Google Patents

Description

June 17, 1947. F. E. MARSH ET AL 2,422,575

VAPOR ELECTRIC DEVICE Filed Jan 14, 1944 WITNESSES: "if, I F I tlgyENTgRs d r rant/J an; an Z loun g aaaanova. 72w. 4 4 4414 244444 ATTORNEY Patented June 17, 1947 UNITED STATES PATENT OFFICE VAPOR ELECTRIC DEVICE Francis E. Marsh and Louis A. Casanova, Wilkinsburg, Pa., assignors to Westinghouse Electric Corporation, East Pit tion of Pennsylvania tsburgh, Pa., a corpora- 20 Claims.

Our invention relates to a vapor electric device and, particularly, to a control system for vapor electric valves of the make-alive type.

In the operation of make-alive type valves it has heretofore been customary to provide impulsing systems to supply periodic impulses to the make-alive electrodes for initiating the cathode spot at the beginning of each conducting fraction of a cycle in each valve. The systems heretofore provided have had a complete firing circuit including a source of current, a storage capacitor and a firing tube for directly applying potential to each make-alive electrode.

According to our invention, we utilize a single firing circuit to control two alternately conducting make-alive type valves. Our system, therefore, has the advantage of utilizing substantially one-half the equipment heretofore necessary in controlling such valves.

Difiiculty has heretofore been experienced because the peak current required by the make alive electrodes is substantially equal to the peak current carrying characteristic of the control tubes resulting in excessive replacement of the firing tubes.

According to our invention, this difiiculty is eliminated by using a high potential firing circuit and controlling the same by means of high voltage low current firing tubes and utilizing a, high ratio stepdown transformer to provide the relatively low voltage high amperage necessary for initiating the cathode spot.

Difiiculty has heretofore been experienced while utilizing a single transformer to fire two valves because the secondary windings frequently have different electrical characteristics such as total resistance, total length of wire, or inductance. We have avoided this difiiculty by providing a strip-wound transformer core with which is associated two primary winding sections and two sec ondary winding sections. Each of the primary winding sections being of substantially identical characteristics and the secondary windings having also substantially identical electrical characteristics. We prefer to associate one of the primary sections with one of the secondary windings while the other secondary winding is associated with the other secondary section. For low voltage transformers, or for low ratio transformation transformers, the primary sections are of relatively low impedance and are preferably connected in series. However, for high voltage or high ratio transformation, the primary sections are preferably connected in parallel and the current diverted to either of the primary sections by means of suitable polarity selective devices such as unidirectional conductors associated with the secondary windings.

It is, accordingly, an object of our invention to provide an improved control circuit for makealive type valves.

It is a further object of our invention to provide a control circuit utilizing substantially the same equipment to fire two alternately conducting Valves.

It is a further object of our invention to provide a control system utilizing high voltage low current control tubes.

It is a further object of our invention to provide a control circuit in which the control tubes will have a long useful life.

It is a further object of our invention to provide a control circuit which may be adjusted to equalize the current in two valves.

It is a further object of our invention to provide an improved firing transformer for supplying make-alive impulses to the exciting electrodes of vapor electric valves.

Other objects and advantages of our invention will be apparent from the following detailed description taken in conjunction with the accompanying drawing, in which:

Figure 1 is a schematic illustration of a, vapor electric device, according to our invention, and

Fig. 2 is a sectional illustration of an improved transformer according to our invention.

In an illustrative embodiment of our invention, an alternating current circuit In is connected to a load circuit such as a direct current circuit II by means of a converter transformer l2 having a winding l3 connected to the alternating current circuit I0 and a distribution winding having a plurality of star connected winding groups such as M and I5, the terminals l to 6 of which are connected to make-alive type valves IA to 6A. The star connected windings are connected together by suitable interphase transformer means I6. For simplicity of illustration only a single pair of alternately conducting valves IA and 4A are illustrative although it is to be understood that valves 3A, 6A; 2A and 5A will be likewise controlled.

Each of the valves comprises an evacuated envelope 20 containing a main anode 2|, 2, main cathode 22, and a make-alive or exciting electrode 23 for initiating a cathode spot Within the valve at the beginning of each conducting portion of a cycle therein.

Preferably the transformer I2 is connected to the alternating current circuit by means of a 3 circuit breaker 52 so that the transformer i2 may be isolated from the alternating current circuit iii. For similar reasons, the circuit ii is usually provided with a breaker E2.

The control system for the Valves comprises a source of alternating current of suitable fre-- quency for supplying the impulses to the makealive electrodes 23 and herein illustrated as a connection to the alternating current circuit l5. This connection is provided with a suitable disconnect or breaker 3| for removing power from the control system. A similar control system is provided for each pair of alternately conducting valves such as valves 1A and 4A. The system comprises a charging or supply transformer 25 connected to the source of control potential, a suitable electrical storing device such as a capacitor 25 connected across the charging transformer and connected between the source it and the capacitor 26 is a current control impedance, preferably in the form of a linear reactor 2?. For purpose of illustration the reactor 27 is shown as a separate element but normally it will be designed into some part of the circuit, as, for eX- ample, the transformer 25. Connected across the terminals of the energy storing capacitor 28 is a suitable impulsing transformer 39 to be hereinafter described.

Included in the connections between the ire-- pulsing transformer .39 and the energy storage device 26 is a bi-directional valve arrangement,

herein shown as back-to-back grid controlled tubes 32 and 33, for passing controlled current impulses during both the positive and negative half cycles of the control potential source to the primary winding of the impulsing transformer 33. Each of the back-to-back or inversely connected grid controlled valves 32 and 33 is provided with a grid control circuit comprising a source of alternating current 35 of suitable frequency and a source of variable pulsating unidirectional current The unidirectional current is preferably provided by means of a bridge connected rectifier 3'! or 38 fed from a suitable transformer 39, the potential of which is controlled by any means such as the variac 49. Because the pulsating unidirectional potential produced by such a device may produce undesirable effects in the grid circuit of the control tubes, we have provided means for reducing this pulsating current to a substantially direct current which includes providing acapacitor ii across the terminals of the bridge connected rectifiers 3':'-38 and an im-- pedance, usually in the form of a resistor 12, across the terminals of the rectifier and the capacitor ii, and connecting at least a major portion of the impedance 42 in series circuit relation with the alternating grid potential and the grid 45 or A6. A second capacitor 43 is then provided across that portion of the impedance 42 which is connected in series between the alternating grid potential and the grid.

We have found that such a combination impresses upon the control grid the sum of a substantially constant direct current and the alternating current. By varying the portion of the impedance connected in series with the various valves, the control valves 3233 can be adjusted to operate to produce impulses which are spaced exactly 180 apart or to so space the impulses that the main valves iA-QA will carry current exactly 180 apart so that the resultant current in each of the valves is substantially equal to each other.

To control the current in the main Valves 4 lA-dA over a normal operating angle, the direct current component of the grid potentials ap-- plied to the control tubes 3233 may be varied by controlling the variac 4-;- in series with the potentials supplied to the bridge connected rectifiers 37-38.

However, if it is desired to control over a large angle, varying the grid potential may shift the firing point too early or too late on the potential stored by the capacitor 26, so that the impulse may not positively operate the make-alive electrodes 23. Therefore, we have provided a phaseshifting device such as an induction phase-shifter 55 to shift the phase of the entire impulsing system so that the phase may be shifted a full without disturbing the relation between the maximum charge on the capacitor 25 and the dis-- charge interval.

If desired, an impedance such as an air core reactor 5; nay be placed in series with the bidirectional discharge device and the coupling transformer 33 to control the rate of rise of the current discharge from the capacitor 25 to the coupling transformer 39.

It has been heretofore customary to use a low ratio transformation in the coupling transformers, usually a ratio of one to one. However, this has required such current peaks in the control tubes that the life of these tubes has been unsatisfactory. We have eliminated this difficulty by using a higher ratio in the coupling transformers, preferably a. ratio of from ten to one or larger, so that the inversely connected tubes 32-33 operate at high potential of the order of three to five thousand volts, and a relatively low current of the order of five to three amperes respectively. A high ratio transformer then produces the necessary voltage usually of the order of three to five hundred volts and the necessary high peak current for operating the make-alive electrodes 23. These high voltage tubes are, therefore, operated considerably below their maximum operating characteristics and, therefore, have to be replaced very infrequently.

In, order to secure substantially identical impulses to the make-alive electrodes, we have provided a coupling transformer 10 having a core 60 composed of a Wound ribbon of high quality steel such as now sold under the trade name Hypersil. The primary winding is divided into two substantially identical sections 6i62, each of which is of relatively high impedance and closely coupled with each of these primary sections is a secondary winding, the two secondary windings 6364 being substantially identical as to number of turns, length of Wire, total resistance, total impedance, etc.

The two primary winding sections (ii-62 are connected in parallel across the impulsing source and each of the secondary windings 63-454 is connected to its individual make-alive electrode 23. For instance, as shown, one of the secondary windings 63 is connected to the make-alive electrode 23 in valve IA while the other secondary winding 64 is connected to the make-alive electrode 23 in valve 4A.

The two secondary windings as shown are at the same potential because of the common cathode connection of the valves IA4A. It is frequently desired to use the valves in other arrangement such as for example a bridge connection in which the cathodes would be at high potential difference with respect to each other. Therefore, it is desirable to provide the secondary windings 63-454 with sufiicient insulation to Withstand the maximum potential appearing eltherin the main circuit or in its control circuit.

Polarity responsive devices such as unidirectional conductors 8566 are provided in series with each of the make-alive electrodes 23, so the current flows in its associated secondary winding63 or 64 only when the polarity is of the right direction to initiate the cathode spot in the main valve. Because of this blockin of the secondary current on the inverse direction, it is found that one or the-other of the primary winding sections carries substantially all of the currentduring the individual hall-Waves so that little, if any, current flows in a parallel section. Therefore, one of theprimaries carries the positive' impulse of the primary current and the other carries thenegative impulse.

In the operation of our system the breaker 3| will be closed to energize the impulsing circuits, the charging transformers will then charge the capacitors through the control impedance to substantially equal charges for both positive and negative half cycles of the control potential. The control circuits of back-to-back tubes will be adjusted so that one tube will discharge the capacitor at or near the maximum charge of one polarity while the other tube will similarly discharge the charge of opposite polarity. The impedance not only controls the flow of charging current for the capacitor but at the instant of capacitor discharge may, if desired, be suflicient to substantially prevent flow of follow current through the bi-directional discharge device.

The impulses of both polarities are impressed on the primary windings of the impulsing transformer. When high impedance parallel primary windings are used it is found that the load current flows almost exclusively in that primary winding associated with the secondary winding which at that polarity feeds current to it connected exciting electrode.

In the normal application of our system, the grid voltage for the bi-directional tubes 3233 is so adjusted that the impulses to the makealive electrodes 23 is such as to initiate the oathode spots substantially 180 electrical degrees apart, so that the main valves lA-4A carry substantially identical currents during the alternate periods. For normal variations in the current carried by the main valves, the grid control of both tubes 32-33 is varied simultaneously by operating the contacts on the variac 40 controlling the direct current component of the grid potential. However, when a wide range of current variation with advance or delay is required, the entire system is advanced or retarded by means of the rotatin phase-shifter 50, so that the impulse system operates at maximum efficiency over the entire phase range.

For purposes of illustration, we have shown and described a specific embodiment of our invention but it will be apparent that changes and modifications can be made therein Without departing from the true spirit of our invention.

We claim as our invention:

1. In combination, an alternating current circuit, a load circuit, electric translating apparatus connected between said circuits and comprising apair of electric valve means each having an anode, a, cathode, and a make-alive electrode for forming a cathode spot, a source of alternating current, a capacitor, means for connecting said capacitor-with said sourceto establish a charging circuit therefor, a pair of circuits each'including the make-alive circuit of one of said electric valve means, each of said circuits also including means for rendering said circuits selectively responsive to impulses of voltage of opposite polarity, a pair of inversely connected electric valves, control means for said inversely connected valves, means connecting said inversely connected valves across said capacitance to establish a discharge circuit therefor, said inversely connected valves being operable during a predetermined portion of each 'half cycle of voltage of said sourc to transmit impulses of current from said capacitor to the pair of circuits including the make-alive electrodes of said electric valve means selectively during half cycles of voltage of opposite polarity of said source.

2. An electric current translating system utilizing electric valves to transfer energy between two electric circuits comprising at least a pair of alternately conducting electric valves, each of said valves including a pair of main electrodes and an exciting electrode, a source of alternating exciting potential, a transformer, a winding on said transformer for each of said exciting electrodes, said winding having substantially identical characteristics, means including unilaterally conducting devices for connecting said windings to the respective exciting electrodes, bi-directional valve means for impressing an impulse from both positive and negative half cycles of said source on said transformer, control means for said bi-directional valve means and means for adjusting the positive and negative impulses for equalizing the currents carried by said alternately conducting valves.

3. An electric current conversion system interconnecting two dissimilar electric circuits at least one of which is an alternating current circuit comprising at least a pair of main electric valves connected electrical degrees apart, a makealive electrode in each of said valves, a transformer connected to said make-alive electrodes, at source of alternating control potential, means including a pair of back-to-back controlled valves for impressing a current impulse on said transformer from both positive and negative half cycles of said control potential, and polarity selective means associated with each of said makealive electrodes.

4. An electric current conversion system interconnecting two dissimilar electric circuits at least one of which is an alternating current circuit comprising at least a pair of main electric valves connected 180 electrical degrees apart, a make alive electrode in each of said valves, a transformer connected to said make-alive electrodes, a source of alternating control potential, means including a pair of back-to-back controlled valves for impressing a current impulse on said transformer from both positive and negative half cycles of said control potential, means connected to said controlled valves for maintaining said impulses 180 electrical degrees apart including for each of said baCk-to-back valves a source of alternating control potential, a source of pulsating unidirectional control potential, a capacitor connected across said pulsating potential, an impedance other than a, capacitor connected across said pulsating potential, at least the major portion of said impedance being connected in series with said alternating control potential and a capacitor connected across that portion of the impedance connected in series with said alternating potential.

5. An electric current conversion system comprising at least a pair of alternately conducting valves, a make-alive electrode in each of said valves, a. source of alternating current, a transformer, means including a pair of back-to-back electric valves for impressing substantially symmetrical impulses from both positive and negative half cycles of said source on said transformer, a pair of output windings on said transformer and connections including polarity responsive means for selectively impressing the output potential of said output windings on the respective makealive electrodes.

6. In combination, a source of alternating current, an output circuit energized from said source for producing an alternating voltage of peaked wave form comprising a capacitor connected to be charged from said source during both the positive and negative half cycles of the voltage of said source, an impedance connected in circuit with said source nd said capacitor, a discharge circuit for said capacitor including a pair of inversely connected electric discharge devices for passing impulses of current of both positive and negative polarity and a transformer connected across said capacitor and in series relation to said discharge devices, a pair of load circuits associated with said transformer and polarity selective means for alternately energizing said load circuits.

'7. In combination, a source of alternating current, an output circuit energized from said source for producing an alternating voltage of peaked wave form comprising a capacitor connected to be charged from said source during both the positive and negative half cycles of the voltage of said source, an impedance connected in circuit with said source and said capacitor, a discharge circuit for said capacitor including a pair of inversely connected electric discharge devices for passing impulses of current of both positive and negative polarity, a transformer connected across said capacitor and in series circuit relation to said discharge devices, said transformer having a pair of secondary windings and unilateral conducting means associated with said secondary windings whereby one of said secondary windings carries current when said transformer is energized by current of one polarity and the other of said secondary windings carries current when the transformer is energized by current of the opposite polarity.

8. An impulsing system comprising a source of alternatin current, a capacitor connected to said source to be charged therefrom, impedance means for controlling current flow between said source and said capacitor, a load circuit connected to be energized from said capacitor, a pair of inversely connected discharge devices for periodically energizing said load circuit and control means for said pair of inversely connected discharge devices.

9. A control circuit for controlling a pair of alternately conducting make-alive type valves comprising a make-alive electrode in each of said valves, a source of alternating current control potential, a capacitor, means for connecting said source in charging relation to said capacitor, transformer means including a pair of secondary windings and at least a primary winding, circuit means including polarity responsive means for connecting said secondary windings to the respective make-alive electrodes, means including a pair of inversely connected discharge devices for connecting said primary winding across said capacitor and means for controlling said inversely connected valves.

10. A control system for a pair of alternately conducting vapor-electric valves comprising an exciting electrode in each of said valves for initiating a cathode spot therein at the beginning of each conducting fractioned cycle, a source of alternating current control potential, a capacitor, means for charging said capacitor from both positive and negative half cycles of the potential of said source, a discharge circuit for said capacitor including a transformer having two substantially similar windings connected in parallel across said capacitor, electric valve means connected between said windings and said capacitor, control means connected to said valve means for passing substantially equal positive and negative current impulses from said capacitor to said windings, a second winding for each of said first mentioned windings, said second windings being closely pled to the respective first mentioned windings, connection from one of said second windings to one of said exciting electrodes, connections from another of said second windings to the other exciting electrode.

11. A control system for a pair of alternately conducting vapor-electric valves comprising an exciting electrode in each of said valves for initiating a cathode spot therein at the beginning of each conducting portion of a cycle, a source of alternating current control potential, a capacitor, means for charging said capacitor from both positive and negative half cycles of the potential of said source, a discharge circuit for said capacitor includin a transformer having two substantially similar windings connected in parallel across said capacitor, current controlling valve means connected between said windings and said capacitor for passing substantially equal positive and negative current impulses from said capacitor to said windings, a second winding for each of said first mentioned windings, said second windings being closely coupled to the respective first mentioned windings, connections from one of said second windings to one of said exciting electrodes, connections from another of said second windings to the other exciting electrode, and unidirectional conductors in said connections.

12. A current conversion system interconnecting two dissimilar electric circuits at least one of which is an alternating current circuit comprising at least a pair of alternately conducting valves, each of said valves containing a main anode and cathode, and an exciting electrode for creating a cathode spot in said valve, a source of alternating exciting potential, a capacitor, means for charging said capacitor from both positive and negative half cycles of said source, a transformer, means including a bi-directional valve means for connecting said transformer across said capacitor, means for controlling said valve means to transmit impulses of both positive and negative polarity from said capacitor to said transformer and connections including polarity selective means for transmitting said impulse to one or the other of said excitin electrodes.

13. A control system for a pair of alternately conducting valves each of which includes a makealive electrode, comprising a source of alternating potential, means including a pair of inversely connected electric valves for producing from said source alternate positive and negative impulses of substantially equal magnitude, a transformer including a low leakage core, a pair of primary windings of substantially identical characteristics on said core, a pair of substantially identical secondary windings each of said primary windings being closely coupled with respective ones of said secondary windings, connections for impressing said impulses in parallel on said primary wind" ings, means for connectin the secondary winding to the respective make-alive electrodes, and unidirectional conducting means in series with each of said secondary windings.

14. A control system for a pair of alternately conducting valves each of which includes a make alive electrode, comprising a source of alternating potential, means for producing from said source alternate positive and negative impulses of substantially equal magnitude, a transformer including a low leakage core, a pair of primary windings of substantially identical characteristics on said core, said primary windings being substantially loose coupled to each other, a pair of substantially identical secondary windings each of said primary windings being closely coupled with respective ones of said secondary windings, said secondary windings being connected to the respective malse-alive electrodes, valve means for impressing said positive and negative impulses in parallel On said primary windings and unidirectional conducting means connected between the secondary windings and the make-alive electrodes.

15. A control system for a pair of alternately conducting main valves comprising an exciting electrode in each of said main valves, a source of alternating current potential, a transformer having a primary winding and a pair of secondary windings, connections from said secondary windlugs to said exciting electrodes, said connections including a unidirectional conductor in series with each of said exciting electrodes and means including a pair of inversely connected grid controlled valves, means for impressing control potential on the grids of said valves for passing impulses from both positive and negative half cycles of said source to the primary winding of said transformer.

16. A control system for a pair of alternately conducting main valves comprising an exciting electrode in each of said main valves, 2. source of alternating control potential, a transformer having a primary winding and a pair of secondary windings, connections from said secondary windings to said exciting electrodes, said connections including a unidirectional conductor in series with each of said exciting electrodes and means including a pair of inversely connected grid controlled valves for passing impulses from both positive and negative half cycles of said source to the primary winding of said transformer, a source of alternating grid potential, at source of direct current grid potential, means for impressing the sum of said alternating and direct current grid potentials on the grid of said inversely connected valves and means for adjusting the direct current grid potentials to equalize the currents conducted by said main valves.

17. A current translating system including at least a pair of alternately conducting electric valves comprising at least a pair of vapor electric valves, each of said valves having a pair of main electrodes and an exciting electrode for initiating a cathode spot at the beginning of each conducting half cycle of said valve, a source of alternating control potential, a capacitor, connections for charging said capacitor from both positive and negative half cycles of said source, a discharge circuit for said capacitor including a transformer having two primary windings connected in parallel across said capacitor, bi-directional valve means connected between said primary windings andcapacitor for passing symmetrical positive and negative current impulses from said capacitor tosaid primary windings, two secondary windings on said transformer, circuit means for connecting one of said secondary windings to one of said exciting electrodes, circuit means for connecting the other secondary winding to the other exciting electrode, and polarity responsive means in said circuit means.

18. An electric current conversion device including at least a pair of valves connected electrical degrees apart, each of said valves including a pair of main electrodes and an exciting electrode forinitiating a cathode spot in said valve, an impulsing system for energizin said exciting electrode comprising a source of alternating current, a capacitor, means for charging said capacitor from both positive and negative half waves of said source, a transformer having a pair of primary windings and a pair of secondary windings, said primary windings being substantially identical and said secondary windings bein substantially identical, one of said secondary windings being closely coupled with one of said primary windings and the other secondary winding being closely coupled with the other primary winding, means including a controlled bidirectional valve means for connecting said primary windings in parallel across said capacitor and polarity selective means for connecting the secondary windings to the respective exciting electrodes.

19. An electric current conversion system comprising at least a pair of make-alive type valves, each of said valves including a main anode and cathode and a make-alive electrode for establishing a cathode spot therein at the beginning of each conducting interval, a source of alternating current control potential, a transformer including a pair of high potential high impedance windings, a pair of low potential windings, one of said low potential windings being closely coupled to one of said high potential windings, the other low potential winding being closely coupled to the other high potential winding, means including polarity selective means for connecting the low potential windings to the respective make-alive electrodes, means including a, pair of back-toback grid controlled valves for connecting said high potential windings in parallel across said source, a source of alternating control potential for each of said grid controlled valves, a source of pulsating unidirectional control potential for each of said grid controlled valves, means for converting said pulsating control potential to substantially constant direct current and connections for impressing said alternating control potential and said direct current potential on the grids of said grid controlled valves.

20. An electric current conversion system comprising at least a pair of make-alive type valves, each of said valves including a main anode and cathode and a make-live electrode for establishin a cathode spot therein at the beginning of each conducting interval, a source of alternating current control potential, a transformer including a pair of high potential high impedance windings, a pair of low potential windings, one of said low potential windings being closely coupled to one of said high potential windings, the other low potential windin being closely coupled to the other high potential windings, means including polarity selective means for connecting the low potential windings to the respective make-alive electrodes, means including a pair of back-to- 11 back grid controlled valves for connecting said high potential windings in parallel across said source, a source of alternating control potential for each of said grid controlled Valves, a source of pulsating unidirectional control potential for each of said grid controlled valves, mean for connecting said pulsating control potential to substantially constant direct current and connections for impressing the source of said alternating control potential and said direct current potential on the grid of said grid controlled valves, means for shifting the phase of said alternating control potential and means for varying the direct current potential.

FRANCIS E. MARSH.

LOUIS A. CASANOVA.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,078,110 Troger Apr. 20, 1937 2,094,792 Herskind Oct. 5, 1937 2,242,897 Staggs 1 May 20, 1941 2,356,589 Hessenberg Aug. 22, 1944 2,359,143 Myers Sept 26, 1944 2,238,625 Cox Apr. 15, 1941 2,372,104 lvLvers Mar. 20, 1945

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