US2431237A

US2431237A - Control circuit

Info

Publication number: US2431237A
Application number: US623309A
Authority: US
Inventors: Keith L Freeman
Original assignee: Westinghouse Electric Corp
Current assignee: CBS Corp
Priority date: 1945-10-19
Filing date: 1945-10-19
Publication date: 1947-11-18
Anticipated expiration: 1964-11-18

Description

1947- K. L. FREEMAN CONTROL CIRCUIT Filed Oct. 19, 1945 load /9 29 FM Q Con/'ro/ INVENTOR K e/fhL/reeman.

ATTORN Va/faye WITNESSES: W

Patented Nov. 18, 1947 CONTROL CIRCUIT Keith L. Freeman, Swlsrvale, Pa., aaaignor to Westinghouse Electric Corporation, East Pittsburgh, Pa.,a corporation of Pennsylvania Application October 19, 1945, Serial No; 623,309

This invention relates to an electronic control system and has particular relation to a system for use in controlling the operation of a load device, such as a relay, energized from an alternating voltage source.

In many control or timing circuits, it is highly desirable to control the energization of a relay from alternating voltage supply lines by the operation of an electric discharge valve of the arelike type, such as a thyratron.

In addition, it is many times desirable to have the relay maintained in its energized position while the controlling thyratron is maintained non-conductive, and changed to its deenergized position when the thyratron becomes conductive. Various circuit arrangements have been devised in the past to accomplish the desired operations.

However, with the greatly increased application.

of electronic control circuits in industry, there has been a corresponding increase in the need for new, improved and simplified systems requiring.

but a minimum number of parts in a' lesslcostly arrangement.

It is, accordingly, an object of my invention ,to provide a new and 'improved'control system for controlling the operation of a load device, such as a relay, from an alternating voltage source.

It is another object of my invention to provide a new and improved control system for controlling the energization of a load device such as a relay from an alternating voltage source by means of an electric discharge valve of the arclike type.

A further object of my invention is to provide a new and improved control system for controlling the energization of a relay from an alternating voltage source by means of an electric discharge valve of the arc-like type in which the number of elements is maintained at a minimum in an inexpensive arrangement.

In accordance with my invention an alternating voltage systemis provided in which a relay may be maintained in its energized position while a control thyratron is non-conductive and in its deenergized position so long asthe control thyratron becomes conductive in each positive haliperiod of the alternating voltage, that is, in each half-period in which the anode of the thyratron is positive with'respect to the cathode. The system employs a minimum number of elements and is simple in construction and operation.

The teatures of my invention. which I consider novel are set forth with more particularity in the appended claims. The invention itself. however, together with additional objects and advantages thereof, may be better understood from the following description of a specific embodlment when read in connection with the acco'mpanying drawings. in which:

4 Claims. (Cl. 175-320) bodying my invention; and

Fix. 2 is a schematic diagram illustrating the structure of a thyratron tube employed in the circuit of Fig. 1.

As shown in Fig. 1. an electric discharge valve 3 of the arc-like type, such as a thyratron, has its anode I and cathode I connected in series with a current limiting resistor 8 and a control switch ll across a pair of alternating voltage supply lines It and It, A control circuit is provided for the thyratron 3 and extends from the control grid l1 thereof through a grid resistor it, a source of biasing voltage illustrated as a battery II, and a source of control voltage 23 to the cathode I.

The operating coil 25 of a direct current relay 21 is connectedin a circuit. extending from the anode 5 of the thyratron 3 to the shield grid 29 thereof. A capacitor is connected in shunt with the operating coil 25. The contact 3| of the relay 21 is arranged to complete a circuit through a load 33 when the relay 2'! is in its energized position.

The source of control voltage '23 may be any suitable source for establishing a desired voltage between the control grid andcathode. The control grid to cathode voltage is to be variable or changeable in some manner, as in accordance with some. electrical or physicalcondition, to cause the thyratron tobe maintained non-conductive at certain times when it is desired to have the relay inits energized position and to cause the thyratron to become conductive in each positive half period of the alternating.v voltage when it is desired to have the relay vinits-deenersizell position. To do this, it is merely-necessary that the control voltage be such as tocausethe control grid to cathode voltage to be-less positive than the critical control grid to cathode voltage for the thyratron when the thyratron is to be maintained non-conductive and more positive than the critical voltage when the thyratron is to be rendered conductive in positive half-periods.

To understand the operation of a circuit as shown in Fig. 1, the structure of a typical thyratron having a shield grid, asshown in'Fig. 2, must be considered. The usual thyratron having a shield grid, such, for example, asthe well known RCA 2050 thyratron or the Westinghouse WI,- 630A thyratron, includes a gas-filled envelope 35 having therein an anode 5 and a cathode I, the latter being heated by 'a filament 31. A control grid I'Ijis also mounted within the envelope 35 becontrol grid arrangement I! with a partition 38 extending between the control grid l1 and the-anode 5. This partition 39 is slotted atll to'perin'it the new ofelectrons from the cathode I past the tion which is so positioned that current may flow 4 from the shield grid to the cathode while a control grid to cathode voltage exists which prevents current flow from the anode 5 to cathode I. It is ternatins voltage supply lines comprising an :;electric valve or the arc-liketype having an enivelope with .an anode' and a1 cathode therein evident, for example, that a portion of the shield grid structure is spaced from the cathode .1 on the opposite side thereof from the control grid H so that current may flow from the'shield grid structure to the cathode 1 while the control grid to cathode voltage is highly negative.

When a thyratron 3 having a structure as shown in Fig. 2, is employed in the circuit of Fig. l, the operation of the circuit is as follows. With the switch i I closed and a control grid to cathode voltage established which prevents the thyratron from becoming conductive, current flows from one of the supply lines i3 through the switch ii, the resistor 9, theoperating coil 25 of the relay 21, the shield grid 29 and cathode 1 of the thyratron 3 to the other supply line during positive half-periods of the alternating voltage. Current does not flow in this circuit during the negative half-period of the alternating voltage because of the rectifier characteristics of the shield grid to cathode circuit within the thyratron 3. However, the capacitor 28 serves to maintain the relay energized during the negative half-periods of the alternating voltage. In some cases, it may be desirable to use an alternating voltage relay which remains in an energized instead of a direct current relay whereupon the capacitor may be omitted.

When the control grid to cathode voltage is changed by a change in the control voltage so that the thyratron 3 becomes conductive in positive half-periods of the alternating voltage, the operating coil is effectively short circuited during those positive half-periods having only the voltage drop between the anode and the shield grid thereacross. Consequently, the relay 2! is deenergized and the circuit through the load 33 is broken.

While I have shown and described a preferred embodiment of my invention, it is realized that many modifications thereof may be made without departing from the spirit of the invention. It is not my intention, therefore, to limit my invention to the specific embodiment illustrated.

I claim as my invention:

1. A control system for use with a pair of alternating voltage supply lines comprising an electrio valve of the arc-like type having an envelope with an anode and a cathode therein adapted to be connected in a circuit across said lines, said envelope also having therein a control grid mounted between said cathode and anode and an auxiliary electrode spaced from said cathode with a portion positioned so that current may flow from said auxiliary electrode portion to said cathode while a grid to cathode voltage exists preventing initiation of current flow from said anode to cathode, a load device connected in a circuit extending from said anode to said auxiliary electrode, and a control circuit extending from said grid to said cathode for establishing a. voltage between said grid and cathode causing said valve to be maintained nonconductive at certain times and to be rendered conductive in positive half-periods of said alternating voltage at other times. 7

2. A control system for use with a pair of a1- adapted to be connected in a circuit across said lines. said envelope also having therein a control grid mounted between said cathode and anode and an auxiliary electrode spaced from said cathode with a portion positioned so that current may flow from said auxiliary electrode to said cathode while a grid to cathode voltage exists preventing initiation or current flow from said anode to cathode, a relay having an operating coil, connected in a circuit extending irom said anode to said auxiliary electrode, and a control circuit extending from said grid to said cathode for establishing a voltage between said grid and cathode causing said valve to be maintained non-conductive at certain times and to be rendered conductive in positive halt-periods of said alternating voltage at other times, said relay being operable in response to substantial current through said operating coil in each positive haliperiod of each period of said alternating voltage.

3. A control system for use with a pair of alternating voltage supply lines comprising an electric valve of the arc-like type having an envelope with an anode and a cathode therein adapted to be connected in a circuit across said lines. said envelope also having therein a control grid mounted between said cathode and anode and an auxiliary grid mounted between said control grid and anode but with a portion extending on the opposite side oi said cathode from said control grid whereby current may flow from said auxiliary grid to said cathode while a control grid to cathode voltage exists preventing initiation or current flow from said anode to said cathode, a load device connected in a circuit extending from said anode to said auxiliary grid. and a control circuit extending from said control rid to said cathode for establishing a voltage therebetween causing said valve to be maintained non-conductive at certain times and to be rendered conductive in positive half-periods of said alternating voltage at other times.

4. A control system for use with a pair of alternating voltage supply lines comprising an electric valve of the arc-like type having an envelope with an anode and a cathode therein adapted to be connected in a circuit across said lines, said envelope also having therein a control grid mounted between said cathode and anode and an auxiliary grid mounted between said control grid and anode with a portion extending on the opposite side of said cathode from said control grid whereby current may flow from said auxiliary grid to said cathode while a control grid to cathode voltage exists preventing initiation 01' current flow from said anode to said cathode, a relay having an operating coil connected ina circuit extending from said anode to said auxiliary grid, and a control circuit extending from said control grid to said cathode for establishing a voltage therebetween causing said valveto be maintained non-conductive at certain times and to be rendered conductive in positive half-periods of said alternating voltage at other times, whereby a substantialcurrent flows through said operating coil only in positive half-periods or said alternating voltage in which said valve is non-conductive, said relay being operable in response to such substantial current through said operating coil.

KEITH L. FREEMAN.