US2707779A

US2707779A - Disconnect of main circuit upon overload in any branch circuit

Info

Publication number: US2707779A
Authority: US
Inventors: Gross Isadore
Original assignee: Burroughs Corp
Current assignee: Unisys Corp
Priority date: 1952-10-31
Filing date: 1952-10-31
Publication date: 1955-05-03
Anticipated expiration: 1972-05-03

Description

May 3, 1955 2,707,779

l. GROSS DISCONNECT OF MAIN CIRCUIT UPON OVERLOAD IN ANY BRANCH CIRCUIT Filed Oct. 3l, 1952 TO LOAD CIRCUIT FIG. 3 7i-(I. A 2. FROM DCQ3 In K *"0 van@ To LQAP C ,2, l mm CWM' D a O l2. D mwen-wh W im EH@ ISAIIGRE @n fia;

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SUPPLY ATTORNEY United DISCONNECT OF MAIN CRCUIT UPON OVER- LAD IN ANY BRANCH CIRCUIT lsadorc Gross, Philadelphia, Pa., assignor to Burroughs Corporation, Detroit, Mich., a corporation of Michigan This invention relates to electronic control systems and particularly to systems in which several fuses are employed for different circuits wherein control relay means is utilized to protect delicate instruments or tubes in event of fuse failure in any one of the fused circuits.

Because the load conditions of several electronic circuits connected to a single power supply, and the time delay requirements for protective devices connected in the several circuits may be different, it is desirable to separately fuse different circuits in accordance with the most desirable protection parameters. When the circuits are separately fused however, the failure of one fuse may remove bias potentials from tubes or otherwise cause too much current to flow in other types of delicate instruments. Accordingly, an associated control relay circuit is desired to afford proper protection where needed by removing the potential from those circuits requiring protection or otherwise actuating protective circuits.

Safety type fuses are available in the art which connect one fuse terminal to an alarm bus when the fuse blows. Therefore these fuses are particularly adapted for connection to energize a relay from the supply voltage source when the fuse fails. Relay contacts may be connected in any desired protective circuit. The control circuit coupled to the alarm 'ous must be of the type which is positive acting where delicate instruments or equipment is utilized, since any failure of actuation of the protective circuit caused by sticking of relay contacts or an open control relay winding would destroy the protective quality of the alarm system and might cause equipment to be severely damaged.

in the interest of circuit economy it is desirable to provide a single control relay for all fused circuits. However, when the described alarm type fuses are connected directly into a plurality of different potential leads with a single alarm bus, in the event that two or more fuses would blow simultaneously, the alarm circuit bus would connect the power supply leads of different circuits toether with possible disastrous results. Also the different power supply leads are not generally of the proper potential for actuating a single control relay. Accordingly, it is desirable to electrically isolate the control circuit coupled to a single alarm bus from the plurality of power supply leads.

lt is, therefore, a general object of the invention to provide improved electronic control systems.

lt is another object of the invention to provide safety alarm fused circuits with a positive acting relay protection device.

It is a further object of the invention to provide an alarm circuit actuated by fuse failure in one of a plurality of power supply leads to actuate a single protective control circuit without interconnecting any of the leads upon the failure of more than one fuse.

In accordance with the teachings of the present invention there is, therefore, provided a fused alarm system utilizing a control relay circuit wherein the control relay winding is normally coupled to a fuse alarm bus and rates Patent fhce 2,797,779 Patented May 3, 1955 a power supply lead to actuate the relay and is adapted to be short circuited upon failure of a fuse. The relay therefore is normally energized so that failure of either a fuse, the relay Winding or relay contacts causes quick and positive actuation of a control or protection circuit.

Other objects and features of advantage of the present invention will be found throughout the following more detailed description of the invention, particularly when considered in connection with the accompanying drawing, in which:

Figs. lA and 1B are perspective views of alarm type fuses in an intact and blown condition respectively;

Fig. 2 is a schematic circuit diagram of a control circuit constructed in accordance with one embodiment of the invention; and

Fig. 3 is a schematic circuit diagram of a further control circuit embodying the invention.

Throughout the drawings like reference characters will be used to designate like circuit elements to facilitate comparison.

Referring in particularity to Fig. l, an alarm type fuse lll is shown having two terminals 1l and l2 supported by a dielectric Abody 13 and electrically coupled by means of a fuse wire l5. A spring assembly i8 is soldered to one end 19 of the fuse wire. A spring plate terminal contact 2i electrically connected to terminal 11 is soldered to the other end of the fuse wire 22. The spring plate 2i; is adapted to engage an external fixed alarm terminal or bus 24 when the fuse wire breaks. Accordingly, when an overload occurs and the fuse fails, the spring plate 2 engages the alarm bus 24 and provides a short circuit electrical connection between bus 24 and terminal 11 of the fuse.

The circuit of Fig. 2 is adapted to utilize fuses lil or other protective devices ot' the type described, where a failure causes a member to contact a unitary alarm bus 2.4 with a power supply terminal strip l1 upon overload in any one of the separate circuits. Control relay winding 29 is connected between terminal strip 1l and alarm bus 24. One end of winding 29 is connected to ground through the current limiting device 3l so that it is normally energized from the voltage source 32 at lead 33.

ccordingly, the relay contacts upon deenergization of winding 29 actuate any desirable control or protection circuit so that any circuit failure will cause a control circuit to assume a position which affords protection. As any fuse liti is blown, the control relay winding is short circuited and accordingly, the relay quickly and positively actuates its contacts to return the control circuit into a protective position so that there is little chance for damaging delicate equipment connected in the separately fused load circuits when one of the potential sources is removed.

At times it is desirable to fuse a plurality of diverse leads derived from a direct current power supply. Thus, a bias source, for example, having 25 volts available Vwould be fused differently than a B supply voltage having +400 volts available. However, a fuse blowing in the bias potential supply would not remove the B+ potential f and accordingly electronic circuits or tubes might be damaged. An alarm type circuit as shown in Fig. 2 with a single alarm bus, is not in this case desirable, however, since two fuses might simultaneously fail and connect the 25 volt supply directly to the +400 volt supplv.

Accordingly, the circuit of Fig. 3 may be utilized to obtain satisfactory operation where the separate volt age leads are to be separately fused with devices of the type hereinbefore described. In the illustrated embodiment, the control relay is actuated by an alternating current supply adapted to provide a single operating potential to the relay winding 29 which is short circuited upon failure of the safety fuses through a series of relatively low impedance capacitors 35 oi suiicient voltage rating to electrically isolate the alarm bus from the supply leads to prevent any damage when two or more fuses would otherwise interconnect the voltage sources at any two or more of the leads A through F. `he current limiting device di), together with the particular capacitor 35, which is connected across the control relay winding 29 when the fuses blow, may serve as a load circuit to prevent the secondary winding of transformer 42; from being short circuited when the fuse connects one of the voltage terminals 11 to the alarm bus 24. Therefore it is seen that in accordance with the present invention a control relay winding is connected in a normally energized manner so that the failure of any one of several fuses may cause the relay winding to be short circuited thereby positively actuating a control circuit.

ln the embodiment shown in Fig. 3 the control circuit coupled to the alarm bus 24 is electrically isolated from the power supply leads by means of capacitors 3 Accordingly, an improved alarm circuit is provided which assures positive operation and the protection of expensive or delicate electronic circuits even when a plurality of power supply leads are separately fused.

Having therefore described detailed embodiments of the invention, setting forth its organization and its mode of operation, those features believed descriptive of the nature of the invention are defined with particularity in the appended claims.

What is claimed is:

l. An electronic control circuit comprising in combination, a plurality or direct current leads from a corresponding plurality of power supply terminals, a plurality of output leads to separate electronic circuits, a plurality of alarm type fuses coupled between said direct current leads and said output leads, an alarm bus adapted for connection to one of said direct current leads upon failure of a corresponding fuse, an alternating current supply source, a control relay, a circuit including an impedance device coupling said alternating current supply source to said relay by way of said alarm bus and a further lead, and a plurality of capacitors coupling each of said direct current leads to said further lead, whereby failure of more than one fuse will short circuit said control relay without interconnecting any of the power supply terminals.

2. A control system comprising, in combination, a circuit connectible to a source of electrical energy, a plurality of direct current voltage terminals connected into said circuit, a plurality of load circuit leads connected to said terminals, an alarm bus connected to the circuit, a plurality ot' alarm type fuses, one for each of said leads, each of said fuses normally being out of engagement with the alarm bus but operable upon fuse failure to connect its lead to the alarm bus, and an alternating current control relay including an energizable winding and an armature controlled switch, the winding of the relay being electrically connected to the alarm bus and capacitively coupled to each of said leads, a further lead electrically connected to said circuit and directly to the capacitively coupled side of said winding, the switch of the relay being operable to open and close the connection of said circuit to its source of electrica] energy.

3. A control system comprising, in combination, a circuit connectible to a source of electrical energy, a plurality of Voltage terminals connected in to said circuit, a plurality of load circuit leads connected to said terminals, an alarm bus, a plurality of alarm type fuses, one for each of said leads, each of said fuses normally being out of engagement with the alarm bus but operable upon fuse failure to connect its lead to the alarm bus, and a control relay including an energizable Winding and an armature controlled switch, the winding of the relay be ing electrically connected between said alarm bus and said circuit, the switch of the relay being operable to open and close the connection of said circuit to its source of electrical energy.

4. A control system comprising a power supply circuit connectible to a source of electrical energy, a plurality of load circuit leads each connected to said power supply circuit, an alarfn bus connected to the power supply circuit, an alarm type fuse in each of said load circuit leads, each fuse normally being out of engagement with the alarm bus but operable upon overload and corresponding use failure to connect the lead with which it is associated to the alarm bus, a control relay including an energizable winding and an armature actuated switch, said relay winding eing electrically connected between the alarm bus and the power supply and normally energized as a result thereof, said relay switch normally act- `ing to close said power supply circuit when the relay winding is thus eneroized but actuable to open the circuit when the winding is Cie-energized by the shorting of any one of the circuit leads with the alarm bus caused by the engagement of any one of said alarm type fuses with the alarm bus.

References Cited in the le of this patent