US3584261A

US3584261A - Remote control circuit breaker

Info

Publication number: US3584261A
Application number: US753279A
Authority: US
Inventors: Walter M Anderson Jr
Original assignee: Texas Instruments Inc
Current assignee: Texas Instruments Inc
Priority date: 1968-08-16
Filing date: 1968-08-16
Publication date: 1971-06-08
Anticipated expiration: 1988-06-08

Abstract

A circuit breaker comprising a load switching relay and an automatically resettable overload switch remotely operated through a self protected control line, provides trip indication, and is trip free. A silicon controlled rectifier shunts current from the gate of a transistor, the collector-emitter circuit of which is serially connected to the coil of the relay. The power source for the load can be either alternating or direct current. Isolation of the primary power source and load circuit may be provided by the employment of either normally open or normally closed auxiliary contacts. In several of the embodiments the relay is locked out upon the occurrence of an overload.

Description

United States Patent [72] Inventor Walter M. Anderson, Jr.

Bediord, Mass. [2l] Appl. No. 753,279 [22] Filed Aug. I6, 1968 [45] Patented June 8, I971 1 [73] Assignee Texas Instruments Incorporated Dallas, Tex.

[54] REMOTE CONTROL CIRCUIT BREAKER SCR, 33,54, 22, I32, 148.5, I37, 117, 135; 307/94, I30, 131, 140; 323/22 SCR [56] Reierences Cited UNITED STATES PATENTS 2,223,729 12/1940 Kleindienst et al. 317/54 3 l 7/ 148.5

3,414,728 l2/I968 Gilbreathetal.

3,456,l25 7/1969 Cousin etal. 3,365,675 1/1968 Gaddy etal Primary Examiner-J. D. Miller Assistant Examiner-Harry E. Moose, Jr.

Attorneys-Harold Levine, Edward .I. Connors, Jr., John A.

Haug and James P. McAndrews ABSTRACT: A circuit breaker comprising a load switching relay and an automatically resettable overload switch remotely operated through a self protected control line, provides trip indication, and is trip free. A silicon controlled rectifier shunts current from the gate of a transistor, the collector-emitter circult of which is serially connected to the coil of the relay. The power source for the load can be either alternating or direct current.

Isolation of the primary power source and load circuit may be provided by the employment of either normally open or normally closed auxiliary contacts.

In several of the embodiments the relay is locked out upon the occurrence of an overload.

REMOTE CONTROL CIRCUIT BREAKER The invention'relates to circuit breakers. More particularly, it relates to remote control means for setting and resetting the contacts of such circuit breakers to desired positions.

An objective of the present invention is to provide a reliable, low power, remote control means for setting and resetting the contact positions of a device having an overload switch feature.

Another objective of the present invention is to provide a remote control means having a failsafe feature to protect against failure of the remote control means.

Further objects, features and advantages of the present invention may be'best understood by reference to the following detailed description read in conjunction with the accompanying drawings in which like reference numerals and letters indicate like parts and in which:

FIG. 1 illustrates a first embodiment of the present invention;

FIG. 2 illustrates a second embodiment of the present invention employing normally open auxiliary contacts;

FlG. 3 illustrates a third embodiment of the present invention employing normally closed. auxiliary contacts; and

FIG. 4 illustrates a modification of the FIG. 3 embodiment.

Referring now to FIG. 1, a first embodiment of the present invention is illustrated in which DC power sources P1P3 provide power for the system shown. Typical examples would be 30 volts for P1 and 28 volts for P2 and P3. Relay RYI, having contacts RYlA and current responsive automatically resettable overload switch SW2 having contacts K2 comprise a remotely operated circuit breaker assembly. The circuit breaker assembly thus formed controls the flow of power from power source P1 to a load through switch SW2 and contacts RYlA of relay RYl placed in series therewith. Contacts K2 of overload switch SW2 are center tapped at point 21 such that when contacts K2 are closed, voltage from power source P1 is impressed upon point 21. Line L2 connects power source P2 in series with relay coil RYl so that the flow of current therefrom controls the open-close position of contacts K2. The collector of an NPN transistor O1 is connector to relay coil RY 1 with the emitter connected to ground. Thus, the "onoff" state of transistor 01 controls the flow of power through relay coil RYl, transistor Q1 functioning as a current control means controlling the open-close positions of relay contacts RYlA.

A control circuit comprises electrical line 30 with switch SW1 therein which carries current from power source P3 to the base of transistor 01, providing base voltage and current thereto. When switch SW1 is in the off (reset) position, no base current can flow to transistor 01 which is locked in the off state with no power flowing to relay coil RYl, thereby locking relay contacts RYlA in the open position. Resistor R1 is connected in series with switch SW1 and the base of transistor 01, and serves as a biasing resistor and, in combination with the filament of trip indicator lamp LMPl also in line 30, as a voltage dividing resistor.

A semiconductor control rectifier SCR] is connected at its anode to a point on control line 30 intermediate trip indicator lamp LMPl and biasing resistor R1. The cathode of rectifier SCRl is connected to ground so that in the conductive state rectifier SCR 1 shunts current flow away from the base of transistor Q1 turning it off.

Gate circuit 40 provides means for initiating conduction of SCR 1. Gate current to rectifier SCRl and thus its conductive nonconductive state is controlled through gate circuit 40 by position of overload switch SW2 contacts K2. In gate circuit 40, diode D6 is serially connected through the center tap (point 21) to contacts K2. Resistor R5 and Zener diode 21 are serially connected between diode D6 and ground. Resistor R4 is connected at one terminal to a point intermediate resistor R5 and Zener diode Z1 and at its other terminal to the base of second transistor Q2. The emitter of transistor O2 is conthe collector of transistor Q2 through serially connected resistors R2 and R3 while the other terminal of diode D5 is connected to line L1. Diode D5 thus receives voltage and current from power source Pl whether contacts K2 are open or closed.

Zener diode Z2 has its cathode connected to a point intermediate resistors R2 and R3 and its anode connected to ground. Resistor R6 and capacitor C1 are connected in parallel between the collector of transistor 02 and ground, forming a low pass filter. Diodes D3 and D4 are serially connected between the collector of transistor 02 and the gate terminal of SCR]. By means of gate circuit, 40, SCRl is locked in thenonconductive state with no gate current flowing thereto when switch SW2 contacts K2 are closed, but with contacts K2 open gate current flows to SCRl putting it in the conductive state.

When switch SW1 is in the open position, no current flows from remote power source P3 to the base of. transistor 01 and transistor 01 is therefore locked in the off state. Power flow to relay coil RYl is blocked by transistor Q1 and contacts RY 1A are open, blocking power fiow to the load. Normally closed overload switch SW2 contacts K2 are in the closed position. Current flows from power source P1 through the contacts K2 center tap at point 21 to the base of transistor Q2, causing transistor O2 to turn on. Current flows from power source P1 through diode D5, resistors R2 and R3, transistor O2 to ground. Thus the voltage at the collector of transistor O2 is approximately ground voltage so that no gate current or gate voltage is impressed upon the gate terminal of rectifier SCRl locking it in the nonconductive state.

To activate relay coil RYl, switch SW1 is closed. Current flows from remote power source P3 through switch SW1, lamp LMPl, resistor R1 and diodes D1 and D2 to the base of transistor Q1. No current flows through rectifier SCRl since it is still locked in the nonconductive state. Upon receiving base current, transistor 01 turns on and enables power from power source P2 to flow through relay coil RYl causing contacts RYlA to close, permitting power to be transmitted from power source P1 to the load. Although there is a current flowing through the filament of trip indicator lamp LMPl, most of the voltage drop from remote power source P3 occurs across the resistor R1. lnsufficient voltage drop occurs across lamp LMPl filament to cause lamp LMPl to be lighted. It will be seen that after relay contacts RYlA close, gate current to SCR! still does not flow, since the voltages at point 21 and diode D5 have not changed.

When current conditions to the load are such that overload switch SW2 contacts K2 are caused to trip open, current flow to the base of transistor Q2 through resistors R4 and R5 and diode D6 is interrupted, forcing transistor 02 into the off state. The voltage at its collector increases such that a gate voltage and gate current are thus impressed upon SCRl, gating it into the conductive state. Current flow to the base of transistor Q1 immediately is shunted through the conductive SCRl to ground and transistor 01 turns off. Trip indicator lamp LMPl lights up as the voltage drop from power source P3 to ground occurs across the lamp LMPl filament. As transistor 01 turns off, power flow to relay coil RYl is blocked and relay contacts RYlA are caused to open.

SCRl remains conductive and relay contacts RYl remain openeven though overload switch SW2 contacts K2 recycle and close. The reclosing of contacts K2 causes gate current to SCRl to cease, but SCRl remains conductive so long as voltage is impressed across it' and anode current flows through it from remote power source P3.

To reclose relay contacts RYIA switch SW2 contacts K2 are allowed to recycle (close upon cooling). Switch SW1 is first set to the open or off-reset position and then reset. to the closed or on position. The open switch SW1 blocks voltage and current to SCRl which, lacking both gate voltage and current and anode voltage and current is forced into the nonconductive state. Immediately after switch SW1 has been set to Q1 and results in 'the closing of relay contacts RYlA as described above.

To open relay contacts RY1 under normal conditions, switch SW1 is opened which blocks current flow to transistor Q1 and causes contacts RYlA to open.

Thus, by means of switch SW1 and the remote control line 30, relay contacts RYIA can be opened and closed during normal operation and can be reset to close after switch SW2 trips. Also, due to the interactions of the switch SW2 and SCRI, relay contacts RYlA are caused to trip at the same time as contacts K2 trip. Contacts RYlA, however, remain open until reset by switch SW1. It is to be noted that relay contacts RYlA cannot be reset until switch SW2 has recycled and contacts K2 are closed.

The function of diodes D5, D6 and Zener diodes Z1 and Z2 is to allow the embodiment of FIG. 1 to be used with both AC and DC power sources P1 of various outputs. A power source of 110 volts AC for instance, could be employed for P1. Diodes D5 and D6 block the negative half cycle of such an AC power source from transistor 02 and the gate terminal of SCRl. Zener diodes Z1 and Z2 regulate the maximum voltage appearingat the collector and emitter of transistor 02. The filter comprised of resistor R6 and capacitor C1 filters out power source harmonics which might result in gate voltage to SCRl sufficient to cause it to become conductive at an improper time.

For a strictly DC power source Pl diodes D5 and D6, resistor R6 and capacitor C1 can be deleted from the embodiment. For power sources of proper voltage output, Zener diodes Z1 and, Z2 may also be deleted, or replaced with properly scaled voltage dividing resistors.

Diodes D1, D2, D3 and D4 are safety devices to protect the system should the control line 30 become shorted. The control line 30 itself is self-protected in case of shorting. Diodes D1 and D2 are serially connected to the base of transistor Q1 between the base and resistor R1. Diodes D1, D4 protect transistor 01 and SCRl from back biasing.

If control line 30 shorts, transistor 01 turns off and relay contacts RYIA are caused to open. Note that trip .indicator lamp LMPl lights up if control line 30 becomes shorted.

Referring now to FIG. 2, a second embodiment of the present invention is illustrated. The illustrated embodiment employs switch SW2 as in the FIG. 1 embodiment but provided with an auxiliary pair of normally open contacts K3 to obtain isolation of the remote control line 30 and associated components from the power source P1load circuit. The position of the auxiliary contacts K3 is determined by the position of switch SW2 contacts K2 and controls the flow of power from power source P2 to SCRI. Relay contacts RYlA, switch SW2 contacts K2, AC or DC power source P1 and the load are connected in series as they were in the embodiment of FIG. 1. Also as in the embodiment of FIG. 1, switch SW1, trip indicator lamp LMPl, resistor R1, diodes D1 and D2 are connected in series between remote power source P3 and the base of transistor 01. Power source P2, relay coil RYl and the collector of transistor Q1 are connected in series, with the emitter of transistor 01 connected to ground. SCRI is connected to ground in parallel to resistor R1 and in series with power source P3. These features also are the same as in the embodiment ofFIG. l. v

In the embodiment illustrated in FIG. 2, however, the auxiliary pair of normally open contacts K3 are connected in parallel to relay coil KY! and in series with power source P2. Voltage dividing resistors R7 and R8 are connected in series between contacts K3 and ground. The gate terminal of SCRl is connected intermediate resistors R7 and R8.

When switch SW1 is in the open or off-reset position, switch SW2 contacts K2 are closed and the normally open auxiliary contacts K3 are open. With no current flowing to the base of transistor Q1, transistor O1 is off and no current flows through relay coil RY] from power source P2 and relay contacts RYlA are thus open. SCR] is nonconductive with no gate current flowing thereto. To close relay contacts RYlA, switch SW1 is put in the closed position. Current flows from remote power source P3 to the base of transistor 01 turning it on and power from power source P2 then flows through relay coil RYl, causing relay contacts RYIA to close. SCRl is nonconductive and remains nonconductive as long as auxiliary contacts K3 are open. The voltage drop across the filament of trip indicator lamp 3! is insufficient to cause the lamp to be lighted.

If switch SW2 contacts K2 are caused to open, auxiliary contacts K3 respond by closing. Thus if switch SW2 contacts K2 open while switch SW1 is in the closed position, contacts K3 close and gate current is conducted from power source P2 to SCRI initiating conduction and shorting current away from the base of transistor 01. Transistor Q1 turns off, blocking power flow to relay coil RYl and relay contacts RYlA are forced to open. Trip indicator lamp LMPl lights up due to the voltage drop which now occurs across it.

As switch SW2 contacts K2 recycle and close, auxiliary contacts K3 return to their normally open position, blocking gate current to SCRI. SCRl remains conductive, however, due to the anode current and voltage provided to it by power source P3. Thus relay contacts RYIA are locked open while contacts K2 and K3 cycle to their normal positions.

To reclose relay contacts RYlA, switch SW1 is opened and then reset to the closed position. In the open position, switch SW1 causes SCRl to become nonconductive evenwhen switch SW1 is reset to the closed position. Once nonconductive SCRI will remain nonconductive, when contacts K3 are cycled and open, and gate current flows to transistor Q1, turning it on. Relay coil RYI received power from power source P2 and relay contacts RYlA close. To open contacts RYlA during normal operation, switch SW1 is set to the open position blocking current flow to the base of transistor 01.

It is to be noted that, as in the embodiment of FIG. 1, operation of switch SW1 to recycle contacts K1 is not effective until switch SW2 contacts K2 have recycled.

By employing normally closed auxiliary contacts K4, the FIG. 2 circuit may be modified. This is shown in FIG. 3, wherein auxiliary contacts K4 are connected through resistor R9 to control line 30 in parallel with SCRl. The gate terminal of SCRI is connected to a point intermediate resistor R9 and contacts K4.

Normally closed contacts K4 therefore, directly control the gate voltage, and hence the gate current of SCRl. When switch SW2 contacts K2 are closed, auxiliary contacts K4 are closed and the gate terminal of SCRI is shorted to ground. When switch SW2 contacts K2 are open, auxiliary contacts K4 are open and the gate terminal of SCRl receives gate voltage and current from power source P3 through resistor R9. SCRl is thus gated on when switch SW2 contacts K2 trip open as in the embodiments previously described. SCRl in the conductive state causes transistor 01 to turn off and relay contacts RYlA to open. SCRl remains conductive and contacts RYlA remain open until switch SW1 is opened and then reset to the closed position.

FIG. 3 may be modified as illustrated in FIG. 4 in which the gating impulse to SCR is amplified. One terminal of normally closed auxiliary contacts K4 is connected through resistor R9 to control line 30. The other terminal of contacts K4 is connected to ground. The base tenninal transistor 03 is connected intermediate contacts K4 and resistor R9. The emitter of transistor 03 is connected to the gate terminal of SCRl while the collector is connected to line 30 through resistor R10. Normally closed auxiliary contacts K4 thus control the base voltage and base current to transistor Q3. When switch SW2 contacts K2 are closed, auxiliary contacts K4 are closed and the base of transistor Q3 is shorted to ground. Transistor O3 is locked off and no gate current flows from the emitter of transistor 03 to SCR], keeping SCRl nonconductive. When switch SW2 contacts K2 trip open, auxiliary contacts K4 open and transistor Q3 receives base current and base voltage from power source P3 through resistor R9. Transistor Q3 is caused to turn on, conducting gate current to SCRl and forcing it conductive. As previously described when SCRl conducts, transistor 01 turns off and relay contacts RYlA open. SCRl remains conductive, transistor 01 remains off, and relay contacts RYlA remain open until switch SW1 is opened and then reset to the closed position.

Thus a circuit breaker made in accordance with this invention is extremely flexible in use since the control switch SW1 can be located in a central control location remote from the actual load line interrupting switch SW2 and relay. A light control line connects the two locations and carries a signal from SW1 to the relay to switch the load on or off or to reset the device and further carries trip information back to the lamp which preferably is located near switch SW1. As explained supra, the control line is itself protected. Another advantageous feature is that the circuit breaker is so-called "tripfree, that is, the circuit breaker cannot be held on when a fault exists thereby protecting the load from deleterious overload effects. lf a fault does occur, either in the load line or in the control line, lamp LMPl is energized and the load disconnected from the power source. Should there be a power failure or in the event of shut down, the circuit breaker returns to the on" condition (or off" if so set manually). Thus, the present invention provides a circuit breaker having reliable, low power, control means. The remote switch SW1 provides complete remote control of the position of the circuit breaker contacts K2 while carrying minimal current. The circuit breaker contacts K2 are automatically caused to open when an overload occurs and are locked open by the SCRl latching operation. Should the remote power supply fail, or some other failure in the control system occur, the circuit breaker contacts are automatically caused to open and remain open until the failure is corrected.

It is to be understood that the embodiments described herein have been for illustrative purposes only and that persons skilled in the art may devise other embodiments without departing from the scope of the invention as defined by the appended claims.

lclaim:

1. Circuit interrupting apparatus comprising:

a. current-control means including a gated semiconductor, a relay coil connected to the current control means, and means connected to the gate of the semiconductor for initiating conduction of the semiconductor to control current flow in the relay coil;

b. a contr'oicircuit including means to normally bias the current control means to allow current to flow through the relay and to supply voltage to the anode-cathode of the semiconductor and an on-off switch; and

c. a load circuit including amoverload switch and a first set of contacts responsive to current flow in the relay coil, and means causing the first set of contacts to open when the on-ofi switch is off and when the overload switch is open.

2. Apparatus according to claim 1 in which an indicating lamp is included in the control circuit and is visibly incandescent when the overload switch trips open and when a short circuit occurs between the lamp in the control circuit and ground.

3. Apparatus according to claim 1 in which the current control means includes a transistor, the collector-emitter circuit of which is serially connected to the relay coil, and the base of the transistor is connected through a resistor to the anodecathode circuit of the gated semiconductor device and the control circuit, whereby conduction of the gated semiconductive device shunts the base current of the transistor, turning it off.

4. Apparatus according to claim 3 in which the gate of the gated semiconductive device is connected to a second transistor and the load circuit, the base of the second transistor being connected to the load circuit intermediate a load and the overload switch.

5. Apparatus according to claim 3 further including as a part of the means for initiating conduction, a second set of contacts connected to the gate of the semiconductor and adapted to open and close dependent upon the position of the overload switch.

6. Apparatus according to claim 5 in which the second set of contacts is open when the overload switch is closed.

7. Apparatus according to claim Sin which the second set of contacts is closed when the overload switch is closed.

8. Apparatus according to claim 6 further including a power source for the current control means and the relay coil and a pair of serially connected resistors, one side of the second set of contacts is connected intermediate the power source and the coil, and the other side is connected to the pair of resistors, the gate of the gated semiconductor is connected intermediate the pair of resistors, whereby upon closing of the second set of contacts, the gated semiconductor conducts shunting current from the base of the transistor turningit off and locking the first set of contacts open until the on-off switch is turned off and then on.

9. Apparatus according to claim 7 further including a power source for the current control means and the relay coil and a first resistor, one side of the second set of contacts is connected to ground, the other side is connected to the first resistor which is connected to the control circuit, the gate of the gated semiconductor is connected intermediate the second set of contacts and the first resistor; wherein upon opening of the second set of contacts the gated semiconductor conducts shunting current from the base of the transistor turning it off and locking the first set of contacts open until the on-off switch is turned off and then on.

10. Apparatus according to claim 9 further including a transistor, the emitter thereof connected to the gate of the gated semiconductor, the collector connected to the control circuit through a second resistor and the base connected intermediate the second set of contacts and the first resistor to amplify the gate current of the gated semiconductor.

11. Circuit interrupting apparatus comprising:

a. a control circuit including an on-off switch;

b. current control means including a gated semiconductor, a relay coil connected to the current control means, and means connected to the gate of the semiconductor for initiating conduction of the semiconductor to control current flow in the relay coil; and

c. a load circuit including an overload'switch and a first set of contacts responsive to the current flow in the relay coil; and means causing the first set of contacts to open when the on-off switch is off or when the overload switch is open.

12. In a circuit breaker system comprising a relay coil and a first set of contacts controlled by the relay coil and an overload switch, a remote control system comprising;

a remote power source, a control line connected serially to the remote power source, a switch in the control line, the position of the switch controlling current flow through the control line; a transistor, the control line connected to the transistor so current from the remote power source flows to the base of the transistor and controls the off-on state thereof, the transistor being connected to the relay coil and controlling current flow through the relay coil, a gated semiconductor connected at its anode terminal to the control line between the switch and the transistor and shorting base current away from the transistor when in the conductive state, and gating means for controlling the gate current to the semiconductor in accordance with the position of the overload switch whereby:

the position of the first set of contacts is determined by the position of the switch and the position of the overload switch through the effect of the positions upon the conductive nonconductive state of the gated semiconductor device.

13. in a circuit breaker system comprising a relay coil, a first set of contacts controlled by the relay coil and an overload switch, a remote control system comprising:

3 5 8 4 2 6 1 7 8 a remote power source, a control line connected serially to switch, a remote control system comprising: the remote power source, a switch in the control line, the

a remote power source, a control line connected serially to position of the switch controlling current flow through the control line; a transistor, the control line connected to the remote power source, a switch in the control line, the position of the switch controlling current flow through the transistor so current from the remote power source 5 the control line; a transistor, the control line connected to flows to the base of the transistor and controls the off-on the transistor so current'from the remote power source state thereof, the transistor being connected to the relay flows to th ba f he tr n is r and con rols he off-0n coil and controlling current flow through the relay coil, 3 state thereof, the transistor being connected to the relay gated semiconductor connected at its anode terminal to and controlling current flow through the relay 3 vthe control line between the switch and the transistor and 10 gated Semiconductor connected at Its anode terminal to shorting base current away f th transistor h i the control line between the switch and the transistor and the conductive state, and gating means including a second shorting e current y f the transistor when set of contacts, the position of which is dependent upon the cohductwe State ahfigatlhg meahslhcludlhg a Second the overload switch for controlling the gate current to the set of contacts, Posmoh ofwhleh dependent p semiconductor i accordance with the position f the the overload switch for controlling the gate current to the overload switch and hence the second set of contacts, Semiconductor in accordance with the Posltloh of the whereby upon tripping of the overload switch, the second overload swttchhhfi hence the second e of contacts set of contacts close, gating the semiconductor which will whereby F'P 'PP of h overload r the secohd remain conductive shunting base current from the e of eohtacts P h gat|h8 the Semiconductor Whleh transistor and keeping the first set of contacts open until {emam condueflve Shuntmg base current from h the remote power source is interrupted by the Switch in transistor and keeping the first set of contacts open until the comml the remote power source is interrupted by the swltch m 14. In a circuit breaker system comprising a relay coil, a first the comm! set of contacts controlled by the relay coil and an overload

Claims

1. Circuit interrupting apparatus comprising: a. current control means including a gated semiconductor, a relay coil connected to the current control means, and means connected to the gate of the semiconductor for initiating conduction of the semiconductor to control current flow in the relay coil; b. a control circuit including means to normally bias the current control means to allow current to flow through the relay and to supply voltage to the anode-cathode of the semiconductor and an on-off switch; and c. a load circuit including an overload switch and a first set of contacts responsive to current flow in the relay coil, and means causing the first set of contacts to open when the on-off switch is off and when the overload switch is open.

3. Apparatus according to claim 1 in which the current control means includes a transistor, the collector-emitter circuit of which is serially connected to the relay coil, and the base of the transistor is connected through a resistor to the anode-cathode circuit of the gated semiconductor device and the control circuit, whereby conduction of the gated semiconductive device shunts the base current of the transistor, turning it off.

7. Apparatus according to claim 5 in which the second set of contacts is closed when the overload switch is closed.

8. Apparatus according to claim 6 further including a power source for the current control means and the relay coil and a pair of serially connected resistors, one side of the second set of contacts is connected intermediate the power source and the coil, and the other side is connected to the pair of resistors, the gate of the gated semiconductor is connected intermediate the pair of resistors, whereby upon closing of the second set of contacts, the gated semiconductor conducts shunting current from the base of the transistor turning it off and locking the first set of contacts open until the on-off switch is turned off and then on.

11. Circuit interrupting apparatus comprising: a. a control circuit including an on-off switch; b. current control means including a gated semiconductor, a relay coil connected to the current control means, and means connected to the gate of the semiconductor for initiating conduction of the semiconductor to control current flow in the relay coil; and c. a load circuit including an overload switch and a first set of contacts responsive to the current flow in the relay coil; and means causing the first set of contacts to open when the on-off switch is off or when the overload switch is open.

12. In a circuit breaker system comprising a relay coil and a first set of contacts controlled by the relay coil and an overload switch, a remote control system comprising; a remote power source, a control line connected serially to the remote power source, a switch in the control line, the position of the switch controlling current flow through the control line; a transistor, the control line connected to the transistor so current from the remote power source flows to the base of the transistor and controls the off-on state thereof, the transistor being connected to the relay coil and controlling current flow through the relay coil, a gated semiconductor connected at its anode terminal to the control line between the switch and the transistor and shorting base current away from the transistor when in the conductive state, and gating means for controlling the gate current to the semiconductor in accordance with the position of the overload switch whereby: the position of the first set of contacts is determined by the position of the switch and the position of the overload switch through the effect of the positions upon the conductive nonconductive state of the gated semiconductor device.

13. In a circuit breaker system comprising a relay coil, a first set of contacts controlled by the relay coil and an overload switch, a remote control system comprising: a remote power source, a control line connected serially to the remote power source, a switch in the control line, the position of the switch controlling current flow through the control line; a transistor, the control line connected to the transistor so current from the remote power source flows to the base of the transistor and controls the off-on state thereof, the transistor being connected to the relay coil and controlling current flow through the relay coil, a gated semiconductor connected at its anode terminal to the control line between the switch and the transistor and shorting base current away from the transistor when in the conductive state, and gating means including a second set of contacts, the position of which is dependent upon the overload switch for controlling the gate current to the semiconductor in accordance with the position of the overload switch and hence the second set of contacts, whereby upon tripping of the overload switch, the second set of contacts close, gating the semiconductor which will remain conductive shunting base current from the transistor and keeping the first set of conTacts open until the remote power source is interrupted by the switch in the control line.

14. In a circuit breaker system comprising a relay coil, a first set of contacts controlled by the relay coil and an overload switch, a remote control system comprising: a remote power source, a control line connected serially to the remote power source, a switch in the control line, the position of the switch controlling current flow through the control line; a transistor, the control line connected to the transistor so current from the remote power source flows to the base of the transistor and controls the off-on state thereof, the transistor being connected to the relay coil and controlling current flow through the relay coil, a gated semiconductor connected at its anode terminal to the control line between the switch and the transistor and shorting base current away from the transistor when in the conductive state, and gating means including a second set of contacts, the position of which is dependent upon the overload switch for controlling the gate current to the semiconductor in accordance with the position of the overload switch and hence the second set of contacts, whereby upon tripping of the overload switch, the second set of contacts opens, gating the semiconductor which will remain conductive shunting base current from the transistor and keeping the first set of contacts open until the remote power source is interrupted by the switch in the control line.