US2460860A

US2460860A - Electronic circuit breaker

Info

Publication number: US2460860A
Application number: US624622A
Authority: US
Inventors: Volpigno Americo
Original assignee: Individual
Current assignee: Individual
Priority date: 1945-10-25
Filing date: 1945-10-25
Publication date: 1949-02-08
Anticipated expiration: 1966-02-08

Description

Feb. 8, 1949. VO PIGNO 2,460,860

ELECTRONIC C IRCUIT BREAKER Filed OCC. 25, 1945 r b J (\J m m m h L,1

Q l/ S! INVENTOR AMERICO VOLPIGNO AT TORNEY Patented Feb. 8, 1 949 UNITED STATES PATENT OFFICE (Granted under the act of March 3, 1883, as amended April 30, 1928; 370 0. G. 757) 3 Claims.

This invention relates to a protective device for electrical apparatus and is illustrated herein as embodied in a sensitive electronic circuit breaker adapted to be inserted in the power supply of electrical apparatus.

A conventional circuit breaker of the type which includes a relay device having its coil connected in series with the power supply to electrical apparatus is not sufllciently sensitive for use with valuable and precise electrical apparatus. Such circuit breakers cannot be made to react to cut off the power quickly enough to prevent serious damage, when a short occurs in internal circuits.

Therefore, it is an object of this invention to provide a protective device for electrical apparatus which is sufliciently sensitive to remove power therefrom before serious damage occurs.

Accordingly, this invention provides an electronic circuit breaker adapted to be inserted in the power supply of electrical apparatus in which a relay in series with an electron tube is used to open the power circuit when a sufficient poten-- tial is set up between the grid and cathode of the tube, this potential being obtained from a point inside the electrical apparatus to be pro tected. As a further feature of this invention, a second relay and a pair of switches are used to maintain the circuit open when once broken and to permit manual operation of the protective device.

With the above and other objects and features in view, the invention will now be described with reference to the accompanying drawing which illustrates a preferred embodiment of the invention and will be pointed out in the claims.

The drawing illustrates schematically an electronic circuit breaker constructed in accordance with this invention.

In the drawing, terminals connected with a source of power supply are indicated at l2 and [3. The terminal I3 is connected directly by connection I4 to the electrical apparatus to which power is to be supplied as shown at l5. In series with the terminal 12 are connected one set of contacts l6 which comprise a portion of 'relay ll.

The relay I! may be a conventional D. C. relay having a coil l8 with a condenser IQ of appropriate capacity across the coil to aid in smooth operation of the relay. One side of the coil I8 is connected at point to the connection 23 and thus through relay contacts 24 to terminal l2. The other side of the coil I8 is connected to the anode of an electron tube 25. The cathode of the electron tube 25 is connected to the lead I l. The tube 25 may be an electron tube of appropriate type having a control grid 26 and other grids as desired.

The control grid 26 is connected to an arm 21 of a potentiometer 28. One side of the potentiometer 28 is connected to lead It and terminal 29 while the other side is connected to terminal 30.

For operation of the circuit breaker, terminals 23 and 30 are connected to some point inside the protected apparatus where the potential changes when a short or improper connection is present. For example, these terminals may be connected across the bleeder resistor of a conventional rectifier power supply. When a short or improper connection is present the voltage across this bleeder resistor decreases and this decreased potential applied to grid 26 through potentiometer 28 and terminals 30 and 23 would affect the circuit breaker as described herein.

The contacts 24 of the second relay 3| are connected in series with the lead 23 and terminal l2. The coil 32 of the relay 3| is connected in series between the terminals l2 and I3 with a rectifier tube 33, a normally closed switch 34, and the contacts 35 of relay H. The contacts 35 of relay I! are closed when contacts I6 are open and vice versa as indicated by the dotted line joining these contacts. A second switch 36, which is normally open, is connected to bridge the contacts 35.

The

filaments

31 and 38 of electron tubes 25 and 33 are connected in series between terminals l2 and I3 with a resistance 39 of appropriate size.

The electron tube 33 is, used to provide rectified A. 0. current so that a D. C. relay 3| may be used.

In operation a source of power input is connected across terminals l2 and I3. The power input to the apparatus being protected is taken from terminals l5 and 40.

When the cathodes of electron tubes 33 and 25 are at the normal operating temperatures and the circuit breaker is operable, the switch 34 is opened, removing power from relay 3|. Deenergizing relay 3! causes contacts 24 to close so that power is supplied to point 20. Electron tube 25 will now conduct and the current flowing through relay coil 18 and tube 25 energizes relay l1 and closes contacts l6, also opening contacts 35. Since contacts 24 and I6 are now closed,

' power is supplied from terminal l2 to terminal 40 and thus to the apparatus connected to terminals 15 and 40. Terminals 29 and 30 are connected to points in the protected apparatus so as to transmit any voltage which arises in the apparatus due to shorts or improper connection therein. When ashort or improper connection is present in the apparatus, the grid 26 of the tube 25 has a smaller signal or potential applied to it.

The arm 21 of the potentiometer 28 is adjusted along the resistance thereof to such a point that when shorts or improper connection are present in the apparatus, the grid receives a potential such that tube 25 will be cut off and no current will flow through it and coil l8. Thus when a short or improper connection is present, the tube 25 ceases to conduit, relay I1 is deenergized, contacts I6 are opened, and contacts 35 are closed. Opening contacts l6 removes the connection between terminals l2 and 40, so that power to the protected apparatus is removed. In order to maintain this circuit open, contacts 35 of relay II, contacts 24 of relay 3|, and relay 3! are used. At the time contacts I6 ar opened contacts 35 are closed completing a connection from terminal' I! through switch 34, contacts 35, coil 32, and electron tube 33 to terminal l3. Current flowing through coil 32 energizes relay 3| and opens contacts 24. When contacts 24 are open no power reaches point so that electron tube 25 cannot conduct. Thus relay l1 remains deenergized and contacts l6 remain open while contacts are closed. If no short or improper connection is present in the protected apparatus, grid 26 of tube 25 remains at its normal potential and current continues to flow through tube 25, and coil l8 of relay' l1, thus contacts it of relay ll remain closed and power is supplied to the protected apparatus at terminals l5 and 40.

Power to the protected apparatus may be removed manually by closing the switch 36. This switch bridges the contacts 35 of relay H and supplies current to relay 3| to open the contacts 24 and remove power from relay l1 and thus terminals l0 and I5.

While this invention has been described with a particular embodiment thereof it will be understood by those skilled in the art that modifications may be made without departing from the invention. It is therefore the aim of the appended claims to cover all such variations as fall within the true spirit and scope of the foregoing disclosure.

The invention described herein may be manufactured and used by or for the Government of the United States of America for Government purposes without the payment of any royalty' thereon or therefor.

Having described the invention, what is claimed as novel and desired to be protected by Letters Patent of the United States is:

1. An electronic circuit breaker adapted to be inserted in the power supply of electrical apparatus comprising, a pair of leads for conveying current from the power source to said apparatus, a relay having its contacts connected in series with one of said leads and having one end of its coil connected to one of said leads, said relay contacts being closed by current through said coil, an electron tube having its plate connected to the other end of said relay coil and its cathode connected to the other of said leads, a second pair of leads, one of said second pair of leads being connected in the grid circuit of said electron tube and the other of said second pair of leads being connected to one of said first mentioned pair, said second pair of leads being adapted to be connected to points in said apparatus to transmit any voltage change arising in said apparatus due to shorts or improper connections therein and bias said grid beyond cutoff and thereby open said relay contacts, a second relay having its contacts connected in series with said first mentioned lead and having one end of its coil connected to one side or second contacts associated with said first mentioned relay, said second set of contacts being closed when said first mentioned contacts are open, the other side of said second contacts being connected to said first mentioned lead, the contacts of said second relay being opened by current through the coil of said second relay, the other end of the coil of said second relay being connected to theother of said leads, whereb the contacts of said second relay are opened and remain open when said grid is biased beyond cutofl.

2. An electronic circuit breaker adapted to be inserted in the power supply of electrical apparatus comprising, a pair of leads for conveying current from the power source to said apparatus, a relay having its contacts connected in series with one of said leads and having one end of its coil connected to one ,of said leads, said relay contacts bein closed by current through said coil, an electron tube having its plate connected to the other end of said relay coil and its cathode connected to the other of said leads, a potentiometer having one end of its resistance connected to said other lead and having its arm connected to the grid of said electron tube, the other end of said potentiometer resistance being adapted to be connected to a point in said electrical apparatus to transmit any voltage change arising in said apparatus due to shorts or improper connections therein and bias said grid beyond cutoff and thereby open said relay contacts, a second relay having its contacts connected in series with said first mentioned leads and having one end of its coil connected to one side of second contacts associated with said first mentioned relay, said second contacts being closed when said first mentioned contacts are open, the other side of said second contacts being connected to said first mentioned lead, the contacts of said second relay being opened by current through'the coil of said second relay, a second electron tube having its plate connected to the other side of the coil of said second relay and its cathode connected to the other of said leads, whereby the contacts of said second relay are opened when said grid of said first mentioned electron tube is biased beyond cutoff, and a switch in series with the coil of said second relay adapted to remove current from the coil to permit the contacts of said second relay to close to restore power to said apparatus.

3. An electronic circuit breaker adapted to be inserted in the power supply of electrical apparatus comprising, a pair of leads for conveying current from the power source to said apparatus, a relay having its contacts connected in series with one of said leads and having one end of its coil connected to one of said leads, said relay contacts being closed by current through said coil, an electron tube having its plate connected to the other end of said relay coil and its cathode connected to the other of said leads, a potentiometer having one end of its resistance connected to said other lead and having its arm connected to the grid of said electron tube, the other end of said potentiometer resistance being adapted to be connected to a point in said electrical apparatus to transmit any voltage change arising in said apparatus due to shorts or improper connections therein and bias said grid beyond cutoii and thereby open said relay contacts, a second relay having its contacts connected in series with said first mentioned lead and havin one end of its coil connected to one side of second contacts connected in series therewith and adapted to pro-' vide power in the coil of said second relay and thereby open the contacts of said second relay.

ALCERICO VOLPIGNO.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 472,084 Thum Apr. 5, 1892 1,741,691 Fenton -1 Dec. 31, 1929 2,001,494 Jones May 14, 1935 2,147,781 Ward Feb. 21, 1939 2,165,848 Gothe et al July 11, 1939 2,358,215 Darling Sept. 12, 1944 2,424,298 Bailey July 22, 1947