US2247167A - Electric valve circuits - Google Patents

Description

June 24, 1941. M. A. WA 2,247,167

ELECTRIC VALVE CIRCUITS Filed Oct. 28, 1939 Fig. I.

lzl/a or Kym/6 of I 1": ve n t O T Martin AEdwards, by MWJ His Attorney.

Patented June 24 1941 ELECTRIC VALVE CIRCUITS Martin A. Edwards, Schenectady, N. Y., assignor to General Electric Company, a corporation of New York Application October 28, 1939, Serial No. 301,861

8 Claims.

My invention relates to electric valve circuits and more particularly to control or excitation circuits for electric valve means of the type employing an ionizable medium, such as a gas or a vapor.

Recently rather wide commercial application of electric valve translating apparatus has been obtained by using electric valves of the type employing make-alive or immersion-ignitor control members. An immersion-ignitor control member is that type of control member which comprises a semi-conducting material, such as boron-carbide or silicon-carbide in contact with an associated vaporizable cathode which may either be a solid or a liquid. For example, the cathode may be of a solid, such as cadmium, or may be a liquid such as mercury. In the most common electric valves of this type now employed, the immersion-ignitor control member is arranged to have an extremity thereof extending into the mercury pool cathode, and the initiation of the arc discharge between the cathode and the anode is effected by transmitting a predetermined amount of current through the control member to the cathode. While the exact phenomena which takes place in the initiation .of arc discharges in valves of this kind is not completely understood, it is rather generally accepted that the arc discharge between the anode -.and the cathode is initiated by transmitting through the control member that amount of current which is required to establish a minimum potential gradient at the surface of the mercury pool cathode, thereby initiating the ebullition of the mercury and effecting the ioni- Zation of the ionizable medium. Of course, mercury vapor is the ionizable medium when mercury is employed as the cathode. In accordance with the teachings of my invention described hereinafter, I provide new and improved control or excitation circuits for electric valve translating apparatus employing immersion-ignitor control members, "and which is susceptible of wider application than the control arrangements employed or described heretofore.

It is an object of my invention to provide new and improved electric valve translating apparatus.

It is another object of my invention to provide new and improved control or excitation circuits for electric valve translating apparatus.

It is a further object of my invention to provide new and improved control or excitation circuits for electric valve means employing make-alive or immersion-ignitor control members.

It is a still further object of my invention to provide new and improved control or excitation circuits for electric valve translating apparatus employing immersion-ignitor control members whereby an associated load circuit may be energized over a wide range of power demands even though the current decreases below that value which is required to initiate an arc discharge within the principal or main electric valve.

Briefly stated, in the illustrated embodiments of my invention I provide new and improved control or excitation circuits for electric valve means having immersion-ignitor control members, and in which the excitation circuit is energized in response to the anode voltage of the main or principal electric valve. The excitation circuit may include a control electric valve for transmitting unidirectional impulses of current to the control member and may include means, such as a relay or electric valve, connected between the excitation circuit and the cathode of the main valve to shunt or by-pass the control member of the main valve when the load current decreases below that value which is required to initiate an arc discharge between the anode and the cathode of the main Valve, thereby relieving the duty imposed upon the immersion-ignitor control member under light-load operating conditions.

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 rectifying system and in which a relay is connected between the excitation circuit and the load circuit to bypass the immersion-ignitor control member under light-load operating conditions. Fig. 2 diagrammatically illustrates a further embodiment of my invention in which a control electric valve is employed to by-pass the immersion-ignitor member under light-load conditions.

One of the most convenient ways of energizing immersion-ignitor control members is the use of an excitation circuit which is connected to be responsive to the voltage applied to the anode of the electric valve. The principal advantage of this type of excitation circuit for electric valve means lies in the apparatus economy, since the excitation circuit is energized from the main anode transformer. Within certain ranges of load,

as soon as the arc discharge is established between the anode and the cathode of the main valve, the anode voltage collapses or decays to a value which is approximately equal to the arc drop within the valve, so that the control member is deenergized substantially coincidentally with the initiation of the arc discharge. This feature is a highly desirable one because it lessens the duty imposed upon the control member and, hence, increases the life of the electric valve. I have found that under very light load operating conditions where the value of the load current decreases below that value of ignitor control member current which is required to initiate an arc discharge between the anode and the cathode, the load current is transmitted through the excitation circuit and the control member, thereby causing excessive heating of the control member and, of course, deleteriously affecting its life.

I provide new and improved control systems whereby the duty imposed on the immersionignitor control members under light load operating conditions is substantially reduced. Referring more particularly to Fig. 1, my invention is there illustrated as applied to an electric valve translating circuit for transmitting power between an alternating current supply circuit I and a direct current load circuit 2 through a transformer 3 having a primary Winding 4 and i a secondary winding '5, and through a pair of electric valve means 6 and I. The electric valve means 6 and l are of the type employing an ionizable medium, such as a gas or a vapor, and

each comprises an anode 8, a cathode 9 which 7 electric valve 3 preferably of the type employ- 'ing an ionizable medium, such as a gas or a Vapor, and including an anode M, a cathode l and a control member or grid IS. The excitation circuits H and I2 are connected between the anodes B and the control members ll) of the associated electric valve means and transmit unidirectional impulses of current to the control members Ill. Each of the excitation circuit-s may include suitable means for limiting or controlling the current transmitted to the control members. This cur-rent limiting means may be a suitable impedance, such as a resistance 11, connected in series relation with the control valve [3.

As a means for relieving the duty imposed upon the immersion-ignitor control members In under light load operating conditions inwhich the load current decreases below that critical value of ignition current required to initiate an arc discharge between the anodes 8 and the cathodes 9, I employ suitable means connected between the excitation circuits I l and I2 and the cathodes 9 of electric valves-- and 1 to'bypass the control members [0 so that the load current is transmitted substantially exclusively bythe excitation circuits [1 and I2. passing means may constitute relays I8 and I9 each having an actuating coiland contacts 2lwhich are bridged by a movable contact 22.

=To'effect transmission of the load current exclusively' through the excitation circuits'l l and The by- I2 in response to a predetermined controlling iiifiuence such as the load transmitted by the system, I may employ any suitable means such as a relay 23 having an actuating coil 24 and contacts 25. The relay 23 may be energized in response to the current transmitted by the direct current circuit 2 and may be energized in response to .the voltage appearing across a shunt 26 connected in circuit with the load circuit 2. In the particular arrangement of the relay 23 diagrammatically illustrated, the armature '21 thereof is arranged to be maintained in the position shown so long as the load current remains above a predetermined value. If the load current decreases below that value, the armature 21 is permitted to drop to close contacts 25, thereby effecting energization of the actuating coils 20 of relays I8 and H! from the supply circuit I.

As a means for adjusting the voltages impressed on the grids l6 of control electric valves t3 to control the voltage of the direct current load circuit 2, I provide a suitable control circuit 2-8 which may comprise a transformer 29, a source of negative unidirectional biasing potential such as a battery 30, and current limiting resistances 31, The phase of the voltages impressed on the grids l6 and hence the time at which the energizing impulses are transmitted to the control members 1!] may be controlled or adjusted by means of a suitable phase shifting device, such as a rotary phase shifter 32 which in turn may be energized from supply circuit I.

The operation of the embodiment of .my invention shown in Fig. 1 will be :explained by considering the system when it is operating as an electric valve rectifier to transmit unidirectional current to the loadcircuit .2. As will be well understood by those skilled in the art, the electric valves'ii and 1 will conduct current alternately so that .a substantially constant unidirectional current issupplied to the load circuit for a constant value :of impedance 'inthe load circuit. The magnitudeoi the voltage supplied-to the load circuit-2 will, of course, depend upon the time during the cyclescfappliedanode-cathode voltage at which thexelectric valves '6 and l are renderedconductive. The magnitude of the voltageimpressed Jon the direct current circuit 2 is decreased when the times of initiation of arc discharge are retardedfrom the zero point of the positive half cycles in a lagging direction and, conversely, the voltage impressed on the direct currentcircuit-is increased as the times of initiation of arc discharges are advanced from alagging-positiontoward the zero point of the positive half cycles.

The arcldischarges within electric valves 6 and I are'initiated by the transmission of unidirectional impulsesof current tothe control memberslil'by the excitation circuits II and I2, respectively. 'Ofcou-rse, inlthi-stype of excitation circuit it is preferable to .retard the .time of transmission of the-energizing impulses to .the control members [2 until the anode-voltage of theassociate'd main valve has reachedlan appreciable value solthat when the control valves I3 arerendered conductive impulses or peaks of current will 'be' transmitted to'the control members H] effecting positive initiation of the discharges.

So long as the load current transmittedto circuit 2 'remains'abovethat minimumor critical value of control member current which'is required to initiate a "dischargawithin the .electric'v-alve m-eanst and 1, the'relays l8, l9 and 23 remain in the position shown in Fig. 1, the load current is transmitted through the secondary winding of transformer 3 and electric valves 6 and 1. Of course, the energizing current for the control members It is transmitted through the excitation circuits I l and i2. As soon as the arc discharge is initiated, the control members H! are deenergized since the voltage transmitted to the excitation circuits is very substantially reduced.

If the impedance of the load circuit increases to that value effecting a reduction in the load current below the critical ignition current, relay 23 operates to effect energization of the actuating coils 2B of relays l8 and I9, thereby by-passing the control members ill so that the load current is not transmitted through these control members. Under the light load operating conditions the load current is transmitted by the secondary winding 5 of transformer 3, resistances I'l, control valves l3 and contacts 2| of relays l8 and I9. In this manner the duty imposed upon the immersion-ignitor control members Ill under lightload operating conditions is substantially reduced, thereby aiiording a longer life to the electric valve means 6 and I.

Fig. 2 diagrammatically illustrates a further embodiment of my invention and shows a fragmentary portion of certain elements of the arrangement of Fig. 1. Corresponding elements have been assigned like reference numerals. Instead of employing relays having movable contacts, in the arrangement of Fig. 2 I have chosen to employ an electric valve 33 of the controlled type, and preferably comprising an ionizable medium, connected between the excitation circuits and the cathodes 9 of electric valves 6 and 1 to bypass the control members I 0 under light-load operating conditions. The electric valve 33 comprises a control grid 34 which is energized in response to the load current. As a means for controlling the valve 33 in response to load current. I have chosen to employ the voltage appearing across the shunt 26 as the controlling influence to control the conductivity of valve 33. So long as the load current remains above a predetermined value, the negative voltage appearing across the terminals of the shunt is sufiicient to overcome the efiect of the positive biasing voltage furnished by the battery 35, and thereby maintain the valve 33 nonconductive. However, if the load current decreases sufiiciently, the negative voltage produced by the shunt 26 also decreases, permitting the positive biasing voltage furnished by battery 35 to render valve 33 conductive. When the valve 33 is conductive, the load current is transmitted through resistance I1, electrice valve l3 and electric valve 33. Otherwise the operation of the embodiment of my invention shown in Fig. 2 is substantially the same as that explained above in connection with Fig. 1.

While I have shown and described my invention as applied to particular systems 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, aim 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, a supply circuit, a load circuit, electric translating apparatus connected between said circuits and comprising a winding and an electric valve means of the type comprising an anode, a cathode and a control member of the immersion-ignitor type in contact with said cathode, an excitation circuit for energizing said control member including a control electric valve responsive to the voltage of said anode for transmitting impulses of unidirectional current to said control member to initiate arc discharges within said first mentioned electric valve means, and means responsive to the current transmitted by said electrical valve means for causing said control electric valve exclusively to transmit the load current.

2. In combination, a supply circuit, a load circuit, electric translating apparatus connected between said circuits and including a winding and an electric valve of the type comprising an anode, a cathode and a control member of the immersion-ignitor type in contact with said cathode requiring the transmission of a predetermined minimum value of current therethrough to initiate an arc discharge within said electric valve, an excitation circuit responsive to the voltage of said anode and comprising a control electric valve having an anode and a cathode connected in circuit with said immersion-ignitor control member, and means connected between said cathode of said control electric valve and said cathode of said first mentioned electric valve to effect transfor of the load current through said control electric valve when the current transmitted by said first mentioned electric valve decreases below said predetermined minimum value.

3. In combination, a supply circuit, a load circuit, electric translating apparatus connected between said circuits and including a winding and electric valve means having an anode, a cathode and a control member, an excitation circuit connected between said anode and said control member and comprising a control electric valve having an anode and a cathode, and means for shunting said control member and the cathode of said first mentioned electric valve means to effect transfer of the load current through said excitation circuit when the load current decreases below a predetermined value.

i. In combination, an alternating current supply circuit, a load circuit, electric translating apparatus connected between said circuits and comprising a winding and a main electric valve having an anode, a cathode and an immersionignitor control member in contact with said cathode, an excitation circuit connected between said anode and said control member and comprising a control electric valve having an anode, a cathode and a grid for transmitting unidirectional impulses of current to said control member to render said main electric valve conductive, means for energizing said grid to control the time during cycles of voltage applied to said main electric valve at which said main electric valve is rendered conductive, and means connected between said control electric valve and the cathode of said main electric valve for effecting the transfor of load current through said excitation circuit exclusively when the load current decreases below a predetermined value.

5. In combination, a supply circuit, a load circuit, electric translating apparatus connected between said circuits and including a winding and an electric valve having an anode, a cathode and an immersion-ignitor control member, an excitation circuit connected between said anode and said control member and comprising a control electric valve .for transmitting unidirectional impulses of current .to said control member, means for connecting-saidexcitation circuit to the cathode ofsaid electric valve means comprising a relay having contacts connected betweensaid cathode of said control electric valve and the cathode of said electric valve means, said relay having an actuating coil, and means responsive to thecurrent of said load circuit for effecting energization of said actuating coil to close said contacts when said load current decreases below a predetermined value.

6. In combination, a supply circuit, a load circuit, electric translating apparatus connected between said circuits and including a winding and. electric valve means having an anode, a cathode and a control member, an excitation circuit connected between said anode andsaid controlmemher. and comprising a control electric valve having an anode and a cathode, and means for shunting said control member and the cathode of said first mentioned electric valve means and comprising a second control electric valve connected betweenthe cathode of said control electric valve and .said cathode of said first mentioned electric valve'for effecting transfer of the'load current substantially exclusively through said excitation circuit when the load current decreases below a predetermined value.

7. In combination, a supply circuit, a load circuit, electric translating apparatus connected between said circuits and including a winding, an

electric valve-having an anode,:a cathode and an immersiomignitor control member, an excitation circuit connected between said anode and said control member for transmitting impulses of currentto said control member to render said electric valve conductive, and means responsive to the current conducted by said electric valve means for causing said control electric valve exclusively to transmit the load current.

8. In combination, a supply circuit,- aload circuit, electric translating apparatus connected between said circuits and including a winding, an electric valve means having an anode, a cathode and an immersion-ignitor control member and employing an ionizable medium capable of supporting an arc discharge, an excitation circuit connected between said anode and said control member for transmitting impulses of current to said control member to render said electric valve means conductive, means comprising an electric valve connected between said excitation circuit and said cathode and having a control grid, and means for controlling the potential of said control grid in response to the current of said load circuit to render said second mentioned electric valve conductive thereby preventing the transmission of a load current through said immersio-n-ignitor control member when the value of'the load current transmitted through said control member is insufiicient to. initiate an arc discharge within said electric valve means.

MARTIN A. EDWARDS.

Images