US1992055A

US1992055A - Photo-electric relay apparatus

Info

Publication number: US1992055A
Application number: US619920A
Authority: US
Inventors: William D Cockrell
Original assignee: General Electric Co
Current assignee: General Electric Co
Priority date: 1932-06-29
Filing date: 1932-06-29
Publication date: 1935-02-19
Anticipated expiration: 1952-02-19

Description

Feb. 19, 1935.

w. D. COCKRELL 1 ,992,055

PHOTOELECTRIC RELAY APPARATUS Filed June 29, 1932 Inventor:

VSfil-liam D. Cockrel l,

His A tt orneg.

Patented Feb. 19, 1935 UNITED STATES PATENT OFFICE PHOTO-ELECTRIC RELAY APPARATUS William D. Cockrell, Schenectady, N. Y., assignor to General Electric Company, a corporation of New York Application June 29, 1932, Serial No. 619,920

Claims. (01. 250-415) In the single figure of the drawin which is a circuit diagram illustrating my invention, leads land 2 represent a source of supply of alternating current which for example may be at 110 volts, 60 cycles. Connected across these leads is the are or vapor electric discharge device 3 having the anode 4, the cathode 5, and the control grid 6. In the anode circuit of'this device is the load device '1 to be controlled thereby which in the present case is illustrated as a relay arranged to control the circuit 8 through its moving contact 9. The cathode 5 is'supplied with heating current from the. secondary winding 10 of the transformer whose primary 11 connects across the supply circuit 1, 2, the midpoint ofthe secondary 10 being connected with the lead. 2. The charge on the grid 6 of the vapor electric device 3 is controlled by the photo-electric device 14, such for example as a photo-electric tube which is connected in shunt with a portion of the voltage divider 15. Inasmuch as the device 3 is an are or vapor electric discharge device it is desirable that it should be caused to pass current by the photo-electric device at the beginning of that half cycle upon which it operates rather than at some later time in the half cycle. For this reason I have provided the out-of-phase voltage divider 15 which includes the-capacitor 16, which for example may have a .value of .5 mid, the

resistors

17, 18 and 19, whose values may be respectively 1000 ohms, 2000 ohms and 1000 ohms, the potentiometer 20 which may have a total resistance of 1000 ohms and the secondary winding 21 which may be wound to produce 30 volts. It will be seen that by reason of the presence of the capacitor 16 in the voltage divider the current flowing in the divider will lead the voltage of the supply circuit, the amount of lead being suflicient when the photo cell is exposed to light to supply the grid 6 with a charge such as to 50 cause the device 3 to pass current at the instant the supply voltage passes beyond the zero value.

With the photo-electric device connected directly across a portion of the voltage divider, for example, between the potentiometer 20 and the point 23, I have found that with no light on the photo tube or at least with insuflicient light thereon to cause the passage of current through the device 3 operation of that device will sometimes occur due to transient or harmonic impulses at the instantthat the supply voltage began to rise 5 from the zero value. Since the supply voltage at this time is but slightly above the zero value, I havetermed this voltage as substantially zero. To overcome such undesired operation oi device 3, I have provided the secondary winding 21 which 10 is arranged to produce current flow in. the voltage ,divider 15 in the same direction as that produced therein by the potential difference between the supply leads 1 and 2, and in the connection between the photo-electric device 14 and the point 5 23 of the voltage divider I have provided the small capacitor 24. which for example may have a value of .0001 mfd. Preferably though not necessarily this capacitor is shunted by the resistor 25 which may have a value of 10 megohms. 20

In the operation of the above described apparatus if a beam of light falls upon the photo tube 14 its resulting decrease in resistance supplies a positive charge to the grid 6 to cause the operation of the device 3 at the beginning of each 2 positive half cycle, or in other words at the beginning of each half cycle at which the anode 4 is made positive with respect to the cathode. Current therefore flows through the load device 7 through each positive half cycle as long as the photo device is exposed to light. When the photo device is dark there will be a suflicient grid current because of the secondary 21 during each negative half cycle of the supply voltage to produce a charge on the capacitor 24, that side 5 of the capacitor which connects with the grid being left with a negative charge. This charge although small is enough nevertheless to maintain the grid 6 sumciently negative after the supply voltage passes zero and begins the positive half cycle to prevent accidental operation of the device due to transient or harmonic impulses. It will be understood that after the supply of voltage has arisen to an appreciable amount in the positive half cycle, that the grid will be maintained negative by reason of the voltage of the secondary winding 21 to prevent any undesired operation.

I have chosen the particular embodiment described above as illustrative of my invention and it will be apparent that various other modifications may be made without departing from the spirit and scope of my invention which modifications I aim to cover by the appended claims.

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

1. In combination, a source of alternating current, a load device connected to be supplied from said source, a grid controlled vapor electric discharge device connected to control the current taken by said load device, aphoto-electrlc device, means for producing from said source a voltage which leads the voltage of the source, means for supplying said voltage to the grid through said photo-electric device and means for supplying a negative voltage to said grid from said source when the voltage of the source is substantially zero.

2. In combination, a source of alternating current supply, a vapor electric discharge device having a control grid and a load circuit connected across said supply, a voltage divider across said supply constructed to advance the phase of the current therein, photo-electric device connect- :iiig divider with grid and charge to said eubstan rent supply, a vapor electric discharge having control grid end load circuit connect 1 divider across ing said divider with said grid and means comprising a transformer and a capacitor for supplying a negative charge to said grid when the voltage of said alternating current supply is substantially zero.

4. In combination, a source of alternating current supply, a vapor electric discharge device having a control grid and a load circuit connected across said supply, a transformer excited from said source of supply, a voltage divider connected across said supply and including a capacitor and the secondary of said transformer, photoelectric device connected between said divider and said grid, and a capacitor connected between said grid and said divider.

In combination, a source ol' alternating cur-- ply, vapor," electric c ergo device ilith a contro or and cepaci 1or EOlllllEU' di ist