US2372106A - Circuit control system - Google Patents

Description

March 20, 1945. G. w. N AGEL CIRCUIT CONTROL SYSTEMS Filed Feb. 5, 1943 INVENTOR George 14 Nayefi BY ATTORNE WITNESSES: 2M l ll' tive; under this condition no current will flow through the load 3 from the lines I, 2 or in any part of the circuit whatsoever, To initiate current flow through the load, the switch blade 9 is moved into contact with the terminal 8, thereby connecting the control electrode 1 of the tube to the cathode 6. The tube 5 is of such a type that when its control electrode I and its cathode 6 are at the same potential, the voltage of the lines, I, 2 will be suflicient to initiate current flow from the anode 4 to the cathode 6 through the load 3. The switch blade 9 may then be released, if desired, so that its mechanical bias will return it to open circuit position, but current will still continue to flow through the load 3 and the tube 5 by reason of the well-known properties of gaseous electrical discharge devices. Such current flow continues until it is desired to interrupt it.

It will be observed that the capacitor 22 is shunted across the terminals of the gaseous discharge tube 5 and hence is charged to the relatively low voltage characteristic of the arc drop in a gaseous discharge tube. Thus the potential of the cathode 2| of the tube I6 is more positive than the potential of the positive terminal of the bias source I2, by the amount of the arc drop in tube 5, and so the control electrode I5 of the tube I 6 is negative relative to its cathode 2| by the sum of the arc drop in tube 5 and the bias source I2, thereby insuring that the tube I6 remains nonconductive as long as the system is in the condition just described.

When it is desired to-interrupt current flow through the load 3, the switch blade 9 is moved into contact with the terminal I4, thereby connecting the control electrode I5 to the left-hand terminal of the capacitor 22, and reducing the potential difference between the control electrode I5 and the cathode 2| to the comparatively small value existing, between the plates of the capacitor 22, that is the arc drop in tube 5. As a result of this effective removal of the bias potential of source I2 from control electrode I5, the tube I6 is rendered conductive to current fiow. It will be noted that while current flow continued through the load 3 and the discharge tube 5, the capacitor I9 had its right-hand plate connected to the positive line wire I and its left-hand plate connected -to the anode of tube 5, which latter difiered in potential from the negative line wire 2 only by the small arc drop through the tube 5, It will be evident, therefore, that the capacitor I9 stood charged to a voltage equal to that of the directcurrent lines I, 2 minus the small arc drop through the tube 5. Now when the tube I6 has been rendered conductive, as above described, by

moving the switch blade 9 into contact with pole I4, the capacitor I9, charged nearly to the full voltage of the lines I, 2, initially impresses its voltage between the anode I1 and the cathode 2I of the tube I6 and starts to discharge through the anode 4 of the tube 5 as the other path. Since the plates of the condenser 22 differ from each other only by the small arc drop of the tube 5, and the resistor 23 is given a comparatively to exceed the current flowing from the anode to I the cathode thereof through the load 3, thereby reducing the net current flow from the anode to the cathode of the tube 5 to zero which causes deionization of the space between the anode 4 and the cathode 6. The tube 5 having thus been rendered non-conductive, the current previously flowing through the load 3 now is forced into the path through the condensers I9 and 22 and the tube I6. The charging of these condensers quickly reduces the current flow through the load to zero and likewise stops current flow through the tube I6 permitting it to deionize. The system'has thus returned to the initial condition from which this description of its operation began; namely, both the'tubes 5 and I6 arenon-conductive and no current fiows from the line wires I, 2 to the load 3. The switch blade 9 may then be released to be held in the open-circuit position shown in the drawing by its bias arrangement previously described. One complete cycle comprising the initiation of current flow through the load 3, its maintenance for any desired period and its interruption by proper manipulation of the switch 9 has thus been described.

It will be noted that current flows through the tube I6 only during the transient period when current flow through the load is being reduced to the zero value. In most practical circuits the length of this transient period will be much less than one second, which is so small compared with those times during which a steady current flows through the load, or during which the load current flow is zero; that the life of the tube I6 under practical conditions should be enormous.

The resistors II, I3 and 23 can be given relatively high values so that the currents which flow through them during the operations of the system described above are minute relative to the current through the load 3. -The resistor I8 may likewise have such a value that the current flowing through it to the condenser I9 is small compared with the normal current through load 3, since the only function of resistor I8 is to permit the charging of capacitor I9 to nearly full voltage of the line I, 2 during the periods that the load 3 carries steady currents. To give a typical example of the use of my invention, the voltage difierence between the supply lines I, 2 may be 300'volts, the load 3 may be designed to carry .075 ampere, the tube 5 (RCA884) may have a (plate) rating of 18 volts and .075-ampere; the tube I6 (RCA884) may have a rating of 18 volts at .075 ampere, the capacitor I9 may be of .25 microfarad; the capacitor 22 may be of .25 microfarad; the source I2 may be of 45 volts; the resistor II may have a value of 1 megohm, the recharge device.

trol electrode and its associated cathode, a manually operable switch connected between said control electrode and said cathode, a capacitor and a resistor in shunt with said load, a second grid controlled gaseous discharge device having its anode connected to the common terminal of the last-mentioned resistor and said capacitor and having a capacitor connected between its cathode and the cathode of the first-mentioned electrical discharge device, a connection through a resistor from the control electrode of the second-mentioned electrical discharge device to said bias battery, a switch connected between the control electrode of the second mentioned discharge device and the cathode of the first-mentioned discharge device and a resistor connected between the cathode of the second-mentioned discharge device and the anode of the flrst-mentioned dis- 2. In combination, a direct-current source, a load having one terminal connected to the positive terminal of said source and its other terxninal connected to the anode of a gaseous electrical discharge device provided with a control electrode, a connection between the negative terminal of said source and the cathode of said electrical discharge device, a bias source and a resistor connected between the control electrode of said discharge device and its cathode, a single pole double-throw switch having one side connected in shunt to said source and the last-mentioned resistor, a resistor having one terminal connected to the positive side of said line and its other terminal connected to one terminal of a capacitor, the other terminal of said capacitor being connected to the anode of the above-mentioned electrical discharge device, a second electrical discharge device having its anode connected to the common terminal of the last-mentioned resistor and the last-mentioned capacitor and having its cathode connected through a capacitor to the negative terminal of said source, a resistor connected between the control electrode of said second discharge device and the common terminal of said bias source and the resistor previously specified as connected thereto, a connection between the grid of said second discharge device and the other side of said double-throw switch and a resistor connected between the anode of the first-mentioned electrical discharge device and the cathode of the second-mentioned electrical discharge device.

GEORGE W. NAGEL.

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