US2186815A - Protective system for electric valve translating apparatus - Google Patents

Description

1940- E. F. w. ALEXANDERSON 2,186,815

PROTECTIVE SYSTEM FOR ELECTRIC VALVE TRANSLATING APPARATUS Filed April 7, 193a Fig.1.

" 9 Inventor":

D Ernst FW Alexanderson,

H is Attorny.

current.

I as.

Patented Jan. 9, 1940 A T I Q PROTECTIVE SYSTEM FOR ELECTRIC VALVE TRANSLATING APPARATUS Ernst F. W. Alexanderson, Schenectady, N. Y.,

assignor to General Electric Company, a corpcration of New York Application April 7, 1938, Serial No. 200,813

15 Claims. (01. 175-3 3) g My invention relates to electric valve circuits and more particularly to protective systems for electric valve apparatus of the type employing ionizable mediums such as gases or vapors.

In the use of electric valve apparatus, particularly electric valves employing ionizable mediums, it has been found that it is desirable to delay the application of load to the electric valves for a predetermined time to permit the cathode to attain a temperature sufficiently great to emit the required electron current. If the load current, or in other Words the anode-cathode current, is increased to a value beyond that corresponding to the cathode temperature, there will be a tendency to pull relatively large portions of the elec-- tron emitting surface away from the cathode, thereby reducing the useful life of he valve. In addition, it is important in electric valve circuits to maintain the temperature of the electric valve 'means within a predetermined range of values so that the life of the electric valve means is not unreasonably shortened. Heretofore, the prior art arrangements have increased the excitation of the cathode or the cathode heating element as the anode-cathode current increased in order that the electron emission be commensurate with the load imposed on the electric Valve means. Where electric valve means employing ionizable mediums are involved, considerable heating of the cathode or the cathode heating elem nt is caused due to the anode-cathode This heating, in a general Way, is due primarily to the positive ion bombardment caused the conduction of the anode-cathode current.

In view of these factors, I have found that there is a decided need for newand improved electrical control circuits for electric valve means whereby the temperature oi the electric valve means is maintained within reasonable and safe range of values during operation. 1

It is an object of my invention to provide new improved electric valve circuits.

It is another object of my invention to pro-- vide new and improved protective systems for electric valve translating apparatus. 1

It is a further object of my invention to provide new and improved protective systems for electric valve apparatus of the type employing ionizable mediums and in which the energization of the cathode heating element is varied as the anode-.- cathode current changes.

In. accordance with. oneof the illustrated embodiments of my invention, I provide, a protective system for electric, valve apparatus in which a cathode heating element is initially energized by a relatively largecurrent and in which the cathode heating element is energized by currents which decrease in value from no load value of the anode-cathode current. The cathode heating element circuit includes a source of alternating voltage of substantially fixed phase and magniture and also includes a second source of alternating voltage of fixed phase but displaced relative to the voltage of the firstsource. The second source :is' preferably displaced by electrical degrees relative to the voltage of the first source and varies in magnitude in accordance In accordance with another illustrated embodimerit of my invention, the progressive decrease in energization of the cathode heating element of an electric valve means is obtained by employing a saturable inductive reactance which is connected in series relation between a source of alternati-ng current and the cathode heating element.

The saturable inductive reactance includes a variable impedance winding which controls the resultant voltage impressed across the cathode heating element, a unidirectional magnetizing Winding, and a third Winding which is energized in accordance with the anode-cathode current of the electric valve means and which controls the resultant impedance of the variable impedancev winding.-

In accordance with a still further feature of one embodiment of my invention, I provide a protective system for electric valve apparatus having an anode, a cathode, a'heating element for the cathode, and a control member which controls the current conducted by the electric valve means. lprovide an excitation circuit for controlling the voltage impressed on the control member and" which'ccmprises a phase shifting device of the rotary type having a movable element. There is provided restraining means to prevent operation of the movable element and hence to prevent increase of the anode-cathode current of the electric valves for a predetermined time after the energization of the cathode heating element, thereby aficrding sufiicienttime for the cathode to attain a sufficiently high operating temperature. The restraining means may include a izable medium such as a gas or a vapor.

plurality of electro-responsive relays which control the restraining means so that it may be moved progressively in a direction to increase the anode-cathode current of the electric valves in direct proportion to the period of energization of the cathode heating elements and after the expiration of the initial heating period. The control circuit which electrically energizes the plurality of electroresponsive relays comprises an electric valve of the high vacuum type which comprises a filamentary cathode which is energized simultaneously and concurrently with the cathode heating elements of the main electric valves which are to be protected,

For a better understanding of my invention, reference may be had to the following description taken in connection with the accompanying drawing and its scope will be pointed out in the appended claims.

Fig. 1 diagrammatically illustrates an embodiment of my invention as applied to an electric valve translating system including electric valve means of the type employing an ionizable medium; Fig. 2 represents certain operating characteristics thereof, and Fig. 3 diagrammatically illustrates a still further embodiment of my invention in which restraining means is associated with the excitation circuit of the electric valves to control the rate at which the anodecathode current may be increased immediately after the initial energization period of the cathode heating elements.

Referring now to Fig. 1 of the accompanying drawing, my invention is diagrammatically illustrated as applied to an electric valve translating circuit for transmitting power between an alternating current circuit I and a direct current load circuit 2 which may include an armature circuit 4 of a direct current motor 3. Direct current motor 3, of course, may include a field winding 5 which is energized from a direct current source 6 through a rheostat or adjustable resistance 1. Electric translating apparatus is interposed between the circuits I and 2 and includes a transformer 8 having primary windings 9 and secondary windings I0, and also includes electric valve means II, I2 and I3 which are preferably of the type employing an ion- Each of the electric valves I II3 includes an anode I4 and a hot or thermionic cathode I5, a cathode heating element I6, and may include a control member I1. A suitable circuit interrupting means I8 is interposed between the alternating current circuit I and the transformer 8 and includes an armature member I9, a closing coil 2!} and a trip coil 2I.

To energize the cathode heating elements I6 and to control the current supplied thereto in accordance with the load transmitted by the translating apparatus or to control the current supplied to the heating elements in accordance with the anode-cathode current of the electric valve means, I provide a cathode heating circuit 22 which includes a source of alternating voltage 23 which may be obtained from the alternating current circuit I through a transformer 24 and a switch 25. The cathode heating circuit 22 also includes a second source of alterway of an impedance element such as a resistance 26. To energize the resistance 26 in accordance with the anode-cathode circuit of the electric valves II--I3, I employ a suitable means such as current transformer 21. I interpose between the current transformer 21 and the resistance 26 a suitable phase shifting arrangement such as a rotary phase shifter 28 which is initially positioned to adjust the phase of the second alternating voltage relative to the first. I have found that satisfactory control of the energization of the cathode heating elements I6 is obtained when the second alternating voltage provided across the terminals of resistance 26 is displaced substantially 135 electrical degrees with respect to the source 23 of alternating voltage.

I provide a timing circuit 29 which is energized simultaneously with the closure of the switch 25 to effect closure of the circuit breaker I8 a predetermined time after the switch 25 has been closed so that there is afforded ample time for the cathode I5 to attain a safe operating temperature. The timing circuit 23 comprises a timing element such as an electric valve 30 of a high vacuum type having an anode 3| and a filamentary cathode 32. The electric valve 30 is designed so that its cathode temperature-time characteristic establishes the interval of time required for the proper preheating of the cathodes I5 of electric valves II-I3. The filamentary cathode 32 is connected to be energized from the cathode heating circuit 22 through a transformer 33. The control electric valve 30 effects energization and operation of a relay 34 which includes an actuating coil 35, a pair of stationary contacts 36 and 31 and cooperating movable contacts 38 and 39. A capacitance 40 may be connected across coil 35 so that a substantially constant unidirectional current is transmitted to the coil 35. Contacts 31 and 39 effect energization of the closing coil of the circuit breaker I8 from a suitable source of current such as a battery 4|. Contacts 36 and 38 effect energization of an actuating coil 43 of a time delay relay 42 which is employed to connect the rotary phase shifter 28 to the resistance 26. By employing a time delay relay 42, the resultant voltage impressed across the terminals of cathode heating element I B is not decreased until after the ex piration of a predetermined interval of time to insure sufficient initial heating of the oathodes I5.

The operation of the embodiment of my invention shown in Fig. 1 will be explained by considering the system during the starting operation when it is desired to subsequently effect energization of the direct current circuit 2 from the alternating current circuit I. Circuit breaker Ill and switch are initially in the open circuit positions. Upon the closure of switch 25, the cathode heating circuit 22 will be energized and the voltage of that circuit will be that provided by the source 23 which in turn is supplied by transformer 24. As soon as the switch 25 is closed a relatively large current is transmitted to the cathode heating elements I6. Current is also supplied to the timing circuit 29. As soon as the cathode 32 of the control electric valve reaches a temperature sufiiciently high to pass an appreciable anode-cathode current, actuating coil of relay 34 will be energized, effecting closure of contacts 36, 38, and 31, 39. This time interval, of course, is preestablished so that the cathodes [5 of electric valves II--I3 attain a control the magnitude the current transmitted if fi is energized to connect the transformer ii to v the alternating current circuit i. Goncurrently with this operation, the operating coil 43 of the time "delay relay s2 is energized and after a predcterm'inc-rd time the relay this moved to the closed circuit position, connecting the phase shifter it to the resistance 245. Brier to the time of the closure of the relay A'Lthe current transniitted to the cathode heating elements It 'is maximum.- However, after the. closure of the relay &2, the cathode heating current varies with the load and progressively/decreases :in magnitude from a maximum value at'no loadtoa minimum value at full load, therebyreducing the amount of current "required Ito operate the electric valves l l-i3 under full loadconditions. This may be" accomplished without sacrificing the operating characteristics and without shortening the life of the tubes since an appreciable heating of the cathodes l5 occurs due'to the anode-cathode currents conducted by the electric valves. I

A better understanding or the manner in which the cathode heating current varies inresponseg actuating handle 69 so that the handle fit may to changes in the anodeazathcde current may be obtained by reference to the operating character; s shown in Fig. 2 Where the vector OA represents the voltage of source and the vectors AB, AC, and AD represent the voltages appearing across the terminals of resistance 25 under various load conditions. Accor ingly, vectors A, OB, OC and 0D represent the resultant voltages ini'oressed across the terminals of the cathode heat ng element under corresponding conditions and hence representthe magnitudes of the currents transmitted to thc anode-cathode elements under these conditions. It will be noted that initially the energization of the cathode heating elements is maximum, corresponding to vector 0A, and that the energizaticn thereof is decreased as the load increases from no load to normal or full load. Furthermore, it will be noted that the energization of the cathode heat ing elements it progressively increases in the overload region, i. e in the region above normal or full load.

In Fig. 3, there is shown a further embodiment of my invention in which a direct current electric valve means 6Q, 56) and iii, which electrio valve meanest-i is of the type employing an ionizable inedium and which coir-n anode 52, a cathode lit, a cathode heating element a control. member or grid I A switch 55 is interposed between the alternaf' gcurrent circuit and the transformer d effects energization oi the cathode heat elements it through a transformer lll. I To the'anode-cathode current of the elect. ic'valves it- 5L I employ a saturable inductive reactance Ell comprising avariable impedance winding 'unidirectionalmagnetizing winding may he iced with direct current from any suitable source" such as from a direct current source 62 ductive. 1 r

through. a switch 63 which is arranged to be operated simultaneously with the switch "I provide an excitation circuit tit for energizing the grids '55 of electric valves til-5i to control the current conducted by these electric valves. excitation circuit 8d includes a suite e meansfor controlling the voltages impressed on grids 55, such as a rotary phaseshifter 65, ineluding a stationary winding and a relatively movable winding 32 which controls the phase of the alternating voltages impressed on grids 55 relative to the anode-cathode voltages of the electric valves ill-5i;

biasing potential. I provide a suitable actuating member such as a handle 852, for moving the winding El relative to the Winding 66 tocontrol the phase oithe alternating voltages impressed grids 55 ,As a means for restraining the movement of the handle '89 for a predetermined time after the energization of the cathode heat-' ing elements 5??{1 provide a device lii'comprising a plurality of 'detent members "ii and i2 and associated electroresponsive actuating devices l3 and M. The detent members H and it may he s.. In; biased to engage an extension "la": of the movement of the actuating member 69 in direct relation to the period of energization of cathode heating elements lid after the expiration of an initial preehating period, the electrorespcnsivc devices .l3and l4 rnay be. t vely energized. That is, deVices'TS and i may be'arranged'so that the detent members H and i2 thereof larc. retarded for different values of current conducted through the actuating'coils thereof. The restraining device "iil includes [a spring biased armature which tends to return the actuating member tothe initial vertical position when reset coil Til is .de'energized. 'Ihis reset action may be effected by any suitable means and is diagrammatically illustrated as comprising a pavvland ratchet mechanism 78 and a sliding connection id. The armature '16 returns the winding t? to a position which maintainselectric valves td-di non-con- I provide a controland timing circuit which effects selective energization of the electrorespcnsive devices l3 and it and which controls these devices in response to the period of energization of the cathode heating elements Control circuit 89 comprises an electron discharge device ill of the high .vacuurn type including filamentary cathode 32 which is connected be energized concurrently and simultaneowlv with the energizationofthe cathode heating l ments 5% from the alternatingv current circuit thr fu 'h transformer .83. The, electron dis-- charge device 3i is designed so that it ailfords an appreciable' interval of time for the energizai an of the cathodeheating'elernents ii iolf electric valves l95l before :it permits the movement of theactuating member til.

The operation of the embodiment of any in vention shown-[in Fig. will be vexplained by encrgization of considering the system under starting conditions when it is desired to direct current circuit it from the alternating current circuit 45;, Unciithe closure of switches '56 and 63, current is supplied tothc cathode heating elements'54 of electric valves litiii and e A battery [is may be em ployed to impress on the grids 5'5 a unidirectional arrangedto be selcc-- tary cathode 82 of the discharge device Bl. The control circuit 80, which is also a timing circuit, will delay the transmission of current from the direct current source 62 to electroresponsive devices l3 and M until the cathodes 53 of electric valves G95| have attained a safe operating value. After the expiration of a predetermined time interval, current will be transmitted by the electron discharge device 8! to efiect the movement of the detent member l! associated with the electroresponsive devices 13 out of engagement with the extension 15 so that the actuating handle 69 may be moved to the dotted position. By such movement, the phase of the voltages impressed on the control members 55 is advanced relative to the anode-cathode voltages so that the current conducted by the electric valves 49-5l is increased by increments from a zero value to a predetermined value corresponding to the movement of the actuating handle 69. Subsequently, the current transmitted by the electron discharge device 6| increases to a still greater value, effecting movement of the detent member 72 out of engagement with the extension '15 so that the current conducted by electric valves 5l may be still further increased. Of course, to permit this movement of actuating member 59, the coil Tl is energized moving the armature Hi to the position shown. If the source of alternating voltage fails, the armature ill will be moved to the right-hand position, returning the actuating member 69 to'the vertical initial position in which electric valves 495l are controlled to conduct substantially no current.

The saturable inductive device 58 controls the resultant voltage impressed across the primary winding of the transformer 51 in accordance with the anode-cathode current of electric valves l9-5l The windings Gil and BI of the saturable inductive reactance are oppositely disposed and by virtue of this fact the heating element current is maximum when the anode-cathode current of the inductive reactance of winding 58 is minimum. As the anode-cathode current increases, inductive reactance of the winding 59 increases to decrease the resultant voltage impressed on transformer 57. In this manner, at low values of anode-cathode current, a relatively large current is transmitted to the cathode heating elements and as the anode-cathode current increases. the cathode heating current is progressively decreased in value.

While I have shown and described my invention as applied to a particu ar system of connections and as embodying various devices diagrammatically shown, it will be obvious to those skilled in the art that changes and modifications may be made without departing from my invention, and I, therefore, in the appended claims to cover all such changes and modifications as fall within the true spirit and scope of my invention.

What I claim as new and desire to secure by Letters Patent of the United States, is:

1. In combination, an alternating current circuit, a load circuit, electric translating apparatus connected between said circuits and comprising electric valve means having an anode, a cathode and a heating element for said cathode, a circuit for energizing the cathode heating element comprising a source of alternating current for transmitting a relatively large current to the cathode heating element to increase the temperature of the cathode to a suitable value for operation, means for energizing the anode-cathode. circuit of said electric valve means, and time delay means responsive to the energization of the cathode heating element circuit for reducing the value of the current supplied to said cathode heating element as the current transmitted by said translating apparatus increases.

2. In combination, a supply circuit, a load circuit, electric translating apparatus connected therebetween and comprising an electric valve means having an anode, a cathode and a heating element for said cathode, means for supplying a relatively large current to the cathode heating element for a predetermined interval of time to increase the temperature of said cathode to place said electric valve means in condition for operation, means for energizing the anode-cathode circuit of. said electric valve means at the expiration of said interval, and means responsive to the current transmitted by said translating apparatus for progresively decreasing the value of the current supplied to the cathode heating element as the current transmitted by said translating apparatus increases from no load to full load value.

3. In combination, a supply circuit, a load circuit, electric translating apparatus connected therebetween and comprising an electric valve means having an anode, a cathode and a heating element for said cathode, means for supplying a relatively large current to the cathode heating element for a predetermined interval of time to increase the temperature of said cathode to place said electric valve means in condition for operation, means for energizing the anode-cathode circuit of said electric valve means at the expiration of said interval, means for energizing the cathode heating element comprising a source of alternating voltage, and means responsive to the current transmitted by said translating apparatus for impressing on said cathode heating element a resultant voltage the magnitude of which varies in accordance with the load transmitted by said translating apparatus.

4. In combination, an alternating current circuit, a load circuit, electric translating apparatus connected between said circuits and comprising electric valve means having an anode. a cathode and a heating element for said cathode, circuit interrupting means for connecting said translating apparatus to said alternating current circuit and including a closing coil, a circuit for energizing the cathode heating element and compris ing a source of alternating current, time delay means responsive to the energization of the oathode heating circuit for initiating energization of said closing coil, and means responsive to said time delay means for introducing into the cathode heating circuit an alternating voltage which varies in accordance with the current transmitted by said electric translating apparatus to control the current supplied to said cathode heating element.

5. In combination, an electric valve means having an anode, a cathode and a heating element for said cathode, means for energizing the cathode heating element comprising a source of alternating voltage, and means for impressing on said heating element a resultant voltage which varies in magnitude in accordance with the anode-cathode current of said electric valve means comprising a source of alternating voltage displaced in phase relative to the voltage of said first mentioned source and being variable in magnitude in accordance with the anodecathode current of said electric valve means.

6. In combination, an electric valve means havode heating element comprising a source oralternating voltage, and means for controlling the resultant voltage impressed on said cathode heating element in accordance with thecurrent oi the anode-cathode circuit of said electric valve means and comprising a secondsource of alternating voltage displaced substantially 135 electrical degrees with respect to the voltage of said first mentioned sourceand which varies in magnitude- .in accordance with the anode-cathode 'currentso thatthe voltage impressed across said heating element is maximum at no load and minimum at full load. j

Z;. In combination, an electric valve means having ananoole, a cathode and a heating elementfor said cathode meanafor energizing the cathode heating element comprising a. source of alternating voltage, and means for controlling the resultant voltage impressed across said cathode heating element comprising a second source of alternating voltage connected in series relation with the first mentioned. source and which varies in accordance with the anode-cathode current of said electric valve means and which is displaced substantially 135 electrical degrees relative to the voltage of said first mentioned source so that the resultant voltage impressed across said cathode heating element is maximum at no load, minimum at the normal full load current of said electric valve means and is progressively increased for anode-cathode currents above the full load value.

8. In combination, an alternating current circuit, a load circuit, electric translating apparatus connected between said circuits and including an electric valve means having an anode, a cathode and a heating element therefore, switching means iorconnecting said translating apparatus to said alternating current circuit and including a closing coil, a circuit for energizing said heating element, a source of alternating voltage for energizing the heating element circuit, time delay means for energizing said closing coil a predetermined time after the energization of the cathode heating circuit, means responsive to the current consumed by saidtranslating apparatus for introducing into the cathode heating circuit a component of voltage of hired phase displacement and variable magnitude relative to the voltage of said source and comprising an impedance element connected in series relation With said source and a phase shifting circuit for controlling the phase of the voltage appearing across the terminals of 'said impedance element, and means responsive to the operation of said time delay means for connecting said phase shifting circuit to said impedance element a predetermined time after the operation of said time delay means.

9. In combination, a supply circuit, a load circuit, electric translating apparatus connected between said circuits and comprising an electric valve means having an anode, a cathode,

a heating elementior said cathode and atomtrol member, an excitation circuit for energizing said control member comprising control means for impressing thereon a voltage to control the current conducted by said electric valve means,

and means responsive to the period of energization of said heating element for controlling said control means to limit the rate of increase of the current conducted by said electric valve means. 1

.10. Inrcombination, an alternating current circuit, a load circuit, electric. translating. apparatus connected-between said circuits andincluding anelectric valve means having an anode, a cathode, aheating'element'for said cathode anda control; member for controlling the conductivitythere'oi, an excitationcircuit for energizing said control member to eftectcontrol of the'magnitude of the-current conducted by said electric valvemeans and including means for controlling the voltage impressed on said control member, and meansassociated with said last mentioned means to prevent operation thereof for a predetermined time after the energization of said translating apparatus.

11. In combination, an alternating currentcir cuit, a load circuit, electric-translating apparatus connected between said circuits and comprising an electric valve me'ans'including an anode, a cathode, a heating element for said cathode. and a control member, switching means for connecting said translating apparatus to said alternating current circuit, an excitation circuit for energizing said control member to control the current conducted by said electric valve means and including a device for controlling the voltage impressed on said control member, means for operating said device, and means for preventing the operation of said last mentioned means for a predetermined time after the energization of said translating apparatus by the closure of said switching means.

12. In combination, an alternating current supply circuit, a load circuit, electric translating apparatus connected between said circuits and comprising an electric valve means having an anode,

a cathode, a heating element for said cathode and a control member, an excitation circuit for en ergizing said control member to control the magnitude of the current conducted by said electric valve means and including a phase shifting device for controlling. the phase of the voltage impressed on said control member relative to the anode-cathode voltage, and means for preventing operation of said phase shifting device for a predetermined interval of time after the energization of said translating apparatus.

13. In combination, an alternating current supply circuit, a load circuit, electric translating apparatus connected between said circuits and comprising an electric valve means having an cathode and a control member, an excitation circuit for energizing said control member to con trol the magnitude of the current conducted by said electric valve means and including a phase shifting device for controlling the phase of the electric valve means having an anode, a cathode anode, a cathode, a heating element for said 1 I and a control member for .controlling the conr ductivity thereof, an excitation circuit for energizing said control member and comprising a phase shifting device of the rotary type for impressing on said control member an alternating voltage variable in phase with respect to the anode-cathode voltage of said electric valve means, means for operating said phase shifting device and being biased to a position to maintain said electric valve means substantially nonconductive, means for preventing operation of said phase shifting device comprising an electroresponsive relay, and a control circuit comprising an electronic discharge device having an anode and a cathode which is energized from said alternating current circuit concurrently with said translating apparatus to control the energization of said electroresponsive relay.

15. In combination, an alternating current circuit, a load circuit, electric translating apparatus connected between said circuits and including an electric valve means having an anode, a cathode and a control member, an excitation circuit for energizing said control member and comprising a phase'shifting device for impressing on said control member an alternating voltage variable in phase with respect to the anode-cathode voltage of said electric valve means and having a movable member, means for biasing said member to a position to maintain said electric valve means nonconductive, means for rotating said member, a plurality of detent members arranged to permit progressive movement of said member and comprising actuating coils, and a control circuit connected to be energized concurrently with said translating apparatus and including an electronic discharge device for selectively energizing said actuating coils in accordance with the period of energization of said translating apparatus.

ERNST F. W. ALEXANDERSON.

Images