US2037570A

US2037570A - High speed circuit breaker

Info

Publication number: US2037570A
Application number: US4577A
Authority: US
Inventors: Peter W Forsberg
Original assignee: General Electric Co
Current assignee: General Electric Co
Priority date: 1935-02-01
Filing date: 1935-02-01
Publication date: 1936-04-14
Anticipated expiration: 1953-04-14

Description

April 14, 1936' p w FORSBERG 2,037,570

HIGH SPEED CIRCUIT BREAKER Filed Feb. 1, 1955 '//I/I/'I/III/IIII//III III] I Ihverfi'tor": peter WFonsberg,

LA r-ii zttorneg current.

Patented Apr. 14, 1936 UNITED srArs EFF-ICE General Electric Company,

New York a corporation of Application February 1, 1935, Seriai No. 4,51;

11 Claims.

moving parts and to eliminate so far as possible the necessity for heavy biasing springs. At the same time a suflicient closing bias must be provided to resist the magnetic forces which tend to open the interrupter contacts upon the flow of heavy currents therethrough. Satisfactory protection of an electric circuit subject to various types of overloads requires that the protec tive device shall not only be quickly responsive to the value of current, so as to protect the circuit against a current which increases slowly to an abnormal value, but also must be quickly responsive to the rate of change of current so as to protect the circuit against a suddent rush of Various devices have heretofore been proposed for providing high speed circuit interruption in response to abnormal conditions. Sat-' isfactory operation of such devices, however, in response both to steady currents of abnormal value and to a sudden increase in current has required the use of auxiliary tripping relays or the partial sacrifice of high speed operation due to cumbersome mechanical expedients and the necessity for relatively strong biasing means. Ac cordingly, it is a further object of my invention to provide a high speed circuit breaker in which the closing bias applied to the interrupter contacts depends upon the value of the normal current carried thereby and which is quickly oper able to interrupt the circuit in response either to a sudden rush of current or to an abnormal steady current.

In accordance with one embodiment of my invention, the movable contact of a circuit breaker is carried on a movable supporting conductor a portion of which forms a side of a conductorloop disposed in a magnetic field the strength of which varies as the current through the circuit breaker. When a substantially steady current flows through the circuit breaker, the electrodynamic reaction between the current in the movable conductor and the magnetic field urges the conductor in a predetermined direction and upon the occurrence of a predetermined rate of increase in the current, a circulating current is induced in the conductor-loop by the increase of flux therethrough to cause a reversal of current in the side thereof formed by the movable con ductor, the electrodynamic reaction with the magnetic field then moving the conductor in an opposite direction. More specifically, the movable contact of the circuit breaker is carried by a supporting conductor comprising a pair of hinged arms arranged in endwise relation to form a toggle, one of the arms being pivoted intermediate its ends. The supporting conductor is disposed in the magnetic field-with a portion of the conductor forming a side of a conductor-loop. Spring means are arranged normally to lock the toggle arms in endwise relation and lightly to bias the contact to circuit closing position. Upon the flow of normal relatively steady currents through the circuit breaker, the electrodynamic reactions between the arms and the magnetic field are such as to increase the bias on the circuit breaker contacts. Upon the occurrence of an abnormal substantially steady current, the electrodynamic reactions serve to break the toggle and open the circuit breaker contacts, while upon the occurrence of a sudden increase in current, the electrodynamic reactions move the supporting conductor about its pivot to open the circuit breaker contacts.

For a more complete understanding of my invention, reference should now be had to the drawing in which Fig. 1 is an elevational view partly in section, illustrating diagrammatically a circuit breaker embodying the principles of my invention; Fig. 2 is a sectional view taken along line 2-2 of Fig. 1; Fig. 3 illustrates diagrammatically a preferred form of circuit breaker embodying my invention; Fig. illustrates a suitable control circuit for manually tripping and resetting the circuit breaker shown in Fig. 3, and Figs. 5 to 9 inclusive illustrate diagrammatically various operating positions of the circuit breaker shown in Fig. 3.

Referring to Figs. 1 and 2, the circuit breaker comprises a pair of relatively movable contacts in and i i disposed in a suitable arc chute l2, the movable contact it! being carried by a movable conductor member l3 pivotally supported on a pin l4 and biased to circuit closing position by a spring 95. The fixed contact II is connected in series circuit relation with a magnetic blow out coil 86 arranged to furnish a. suitable blow= out flux in a well-understood manner. In addition, the blow-out coil l5 serves to establish a magnetic flux through a magnetic circuit comprising the core member H, the opposed pole pieces 99 and i9 and the air-gap 2d. Connected to the pivot pin i4 is a fixed conductor 2i which cooperates with the movable conductor member 33 and a flexible conductor 22 to form a conductor-loop disposed in the air-gap 2c and enclosing a portion of the flux therethrough.

With normal steady current flowing in the circuit to be controlled, represented by the line conductors 23 and 2d, the line current will divide through the fixed conductor 29 and the movable conductor 6 3 as indicated by the solid arrows (Fig. 1), and the coil 58 will be energized to establish a magnetic field which extends across the airgap 253 in the direction indicated by the conventional symbols N and S (Fig. 2) on pole pieces l9 and i8 respectively. Under these conditions the electrodynamic reaction between the current in v the arm is and the magnetic field will tend to as indicated by the broken arrows (Fig. 1).

move the lower part of the arm in a clockwise direction about the pivot M whereby a contact pressure which increases approximately as the square of the current is obtained without the use of a heavy biasing spring.

"Upon the occurrence of a sudden rush of current through the contacts 10 and H and the blow-out coil iii, there will be a corresponding increase in the flux enclosed by the conductor-loop consisting of a portion of th arm l3, the fixed conductor 2! and the flexible conductor 22. This sudden increase of flux through the loop will causean induced current to flow therein in a direction tending to oppose the increase of flux If the rate of increase of current is sufilciently high, this induced current will cause the current in the lower part of the movable member l3 to reverse and flow downwardly instead of upwardly, the electrodynamic reaction of this reverse current with the magnetic field immediately causing the pivoted conductor member I3 to move in a counterclockwise direction to open the contacts. It will be apparent that the arrangement provided assures a very light high speed circuit breaker which will trip on a. predetermined rate of change of current and in which suitably high contact pressures are obtained without resort to heavy biasing springs.

The circuit breaker illustrated in Figs. 1 and 2 will not, however, trip on relatively steady abnorma] currents and while any suitable means may be employed for accomplishing overload trip, the circuit breaker illustrated in Fig. 3 represents a preferred embodiment of my invention which will trip on either substantially steady abnormal currents or in response to a predetermined rate of change of current. 1

Referring now to Figs. 3to 9, in this embodiment of my invention a second conductor member I3 is interposed between the contact In and the arm I3, the arms I3 and I3 being arranged in endwise relation and hinged together at 25 to form a toggle. An overcenter spring .26 having one end fastened to the arm 13' at 21- and the other end fastened to a pin 28 on a. movable carrier 29 serves to lock the toggle arms-13 and i3 in straight line relationsand to bias the contact ill to circuit closing position. It will be observed that the line of action of the spring 26 is such as to exert a relatively weak biasing force on the contact I0 and a. relatively strong locking force on the toggle arms. The movable carrier 29 is plvotally supported on the pin H by means of an arm 30 and carries a pin 3| which, to-- gether with the spring supporting pin 28, coopcrates with a finger 32, insulatedly mounted on the lower end of the arm 13, to manually trip and reset the circuit breaker in a manner to be more fully described later. A pair of stop members 33 and 3311 are provided for engaging the arms i3 and i3 respectively to limit the movement thereof when the circuit breaker is operated.

When normal current flows in the circuit to be controlled the current divides through the movable arm is and the fixed conductor 2! in the same manner as set forth in connection with the circuit breaker shown in Fig. l and flows through the conductor arm i3',,the contacts l0 and H and the blow-out coil i6, thereby setting up a magnetic field between the pole pieces l8 and I9. Under these conditions the electrodynamic reaction tends to move the arms l3 and I 3' to the left as viewed in Fig. 3. The portion of arm l3, however, which is arranged in the magnetic field to react therewith is considerably greater than the portion of the am It so arranged, so that the reaction on the arm 13 is stronger than the reaction on the arm l3, and accordingly the arms l 3 and l 3 tend to move together in a clockwise direction about the pin 14 whereby an additional closing bias is exerted on the contacts, the spring 25 serving to maintain the toggle arms I3 and 13 in straight line relation.

Upon the occurrence of a substantially steady but abnormal current how, the electrodynamic force exerted on the arms 13 and I3 becomes suflicient to overcome the locking force of the spring 26 and break the toggle joint. As soon as the spring pressure is overcome the arms 13 and 13' move quickly to the, position shown in Fig. 6. interrupting the circuit. It will be observed that when the arms l3 and I3 move about the hinge 25, the spring 26 is carried overcenter and in the position shown in Fig. 6 is effective to latch the circuit breaker in open circuit position.

The circuit breaker is also adapted for high speed operation in response to a sudden rush of current. Upon the occurrence of a sudden increase in the current, a circulating current will be induced in the conductor-loop in the manner described in connection with Fig. 1 and the electrodynamic forces will then tend to move the arm I 3 to the right, as viewed in Fig. 3, and to move the arm l3 to the left, whereupon the arms will move about the pivot point 14 in a counterclockwise direction to the position shown in Fig. 5, thereby interrupting the circuit. In this position of the circuit ,breaker the spring 28 is carried overcenter relative to the pivot II, but not relative to the hinge 25, and therefore the spring 26 in this position serves to maintain the toggle arms in straight line relation and also to latch the circuit breaker in open circuit position.

Manual tripping and resetting of the circuit breaker may be accomplished by moving the carrier 29 about the pivot point I. Although any suitable means may be employed for obtaining the desired movement of the carrier 29, I have shown in Fig. 4, a preferred arrangement for manually tripping and resetting the circuit breaker. As shown in Fig. 4, the carrier supporting arm 30 provided with a latch 34 arranged to cooperate with a pivoted finger 35 to hold the carrier 29' in its reset position against the force exerted by an operating spring fastened to a finger 31 on the carrier. The pivoted finger 35 is normally held in latching position by a tripping coil 35 against the force exerted by a tripping spring 49. Connected to the finger 31 on the carrier 29 by means of a pin and slot connection 4!, is an operating rod 42, the other end of the rod 42 being connected to the core 43 of a solenoid having an operating winding 44. In order selectively to energize the operating winding 44 and the tripping coil 39, I provide manually operable trip button 45, a reset button 49 provided with a sealing-in contactor 41 and a limit switch comprising a switch arm 48 movable between the com tacts 49 and 59 arranged to be actuated into engagement with the contact 49 by a finger 5i carried by the solenoid core 43, and into engagement with the contact 59 by a finger 52 carried by the trip button 45. An overcenter spring 53 is provided for ensuring that the switch arm 48 will occupy one or the other of its extreme positions.

Assume now that the circuit breaker is in the reset position shown in Fig. 4 and that it is desired to manually trip the circuit breaker. In this position the sealing-in contactor 41 is in circuit closing position, the operating coil for the contactor being energized through a circuit which may be traced from the positive control bus 54 through the contacts of the sealing-in contactor 41, the contacts of the trip button 45, the conductor 55, the conductor 56 and the operating winding of the sealing-in contactor to the negative control bus 51. The finger 35 is held in its latching position by the trip coil 39, the energizing circuit therefor extending from the positive control bus 54 through the contacts of the sealing-in contactor 41, the contacts of the trip button 45, the conductors 55 and 56', the switch arm 48, the contact 49, the conductor 51', the trip coil 39 and the

conductors

58 and 59 to the negative control bus 51. Actuation of the trip button 45 opens the energizing circuits for the sealing-in contactor 41 and the trip coil 39, allowing the sealing-in contactor to open and the pivoted finger 35 to move to its releasing position. At the same time, the finger 52 on the trip button moves the switch arm 48 out of engagement with the contact 49 and into engagement with the contact 58. The control circuit is now completely deenergizedand when the finger 35 moves out of engagement with the latch 34, the carrier 29 is moved by the spring 36 to trip the clrcuit'breaker. The respective positions of the circuit breaker operating mechanism and the carrier 29 during the manual tripping operation is illustrated in Figs. "I and 8. In Fig. 7, the circuit breaker is shown at an instant when, with the carrier moving toward the left, the spring 29 has just moved over center relative to the pivot point l4 and the pin 29 on the carrier has engaged the finger 32 on the supporting arm l3. As the carrier 29 continues to move to the left, the arm I3 is rotated about the pivot 54 and the toggle hinge 25 begins to open against the force exerted by the spring 29. As soon as the spring 29 moves overcenter relative to the hinge 25, however, the force exerted thereby assists in breaking the toggle and the contact In moves to its open position with a snap action! position of the circuit breaker at the end of the manual tripping operation is shown in Fig. 8.

Assume now that a is desired to reset the circuit breaker after the circuit breaker has opened either in response to an abnormal steady overload or in response to a sudden rush of current. As the first step in the resetting operation The' it is necessary to actuate the trip button to move the operating mechanism of the circuit breaker from the open positions shown in either Fig. 5 or Fig 6 to the manually tripped position shown in Fig. 9. As pointed out above, this actuation of the trip button also serves to move the switch 49 into engagement with the contact 59 to prepare an energizing circuit for the solenoid operating winding 44. Actuation of the reset button 46 will now complete an energizing circuit for the operating winding 44 which may be traced from the positive control bus 54 through the contacts of the reset button 45, the contacts of the trip button 45, the conductors 55 and 5d, the switch arm 48, the contact 59, the operating winding 44 and the conductor 59 to the negative control bus 51. A circuit is also completed through the reset button for energizing the sealing-in contactor 4'! which, when closed, lay-passes the reset button and maintains an energizing circuit for itself and for the operating winding 44. Energization of the operating winding 44 causes the solenoid plunger 43 to move quickly to the right whereby the carrier 29 is moved to the extreme right-hand position shown in Fig. 9. As the carrier 29 moves to the right, the pin 3| carried thereby engages the finger 32 and rotates the arm I3 about the pivot M. Fig. 6 illustrates the position of the circuit breaker at the instant that the pin 3| has just engaged the finger 32. Continued movement of the carrier to the right moves the spring 26 overcenter relative to the hinge point 25 and the arms l3 and I3 move into straight line relation with a sna action. When the carrier reaches the extreme right-hand position, shown in Fig. 9, the spring .26 has moved overcenter relative to the pivot 54 and is effective to move the arms l3 and I3 about the pivot to circuit closing position. When the plunger 43 reaches its extreme right-hand position, the finger 5| carried thereby moves the switch arm 48 to 'deenergize the operating winding 44 and close the energizing circuit for the trip coil 39. Upon deenergization of the operating winding 44, the carrier 29 starts to move to the left under the force exerted by the spr ng 36 but is prevented from moving beyond its reset position, shown in Fig. 4, by the latch fingers 34 and 35, the pivoted finger 35 now being held in latching position by the trip coil 39. In this position of the carrier 29 the spring 28 is eflective lightly to bias the circuit breaker contacts to the closed position.

It will be evident now that I have provided a circuit breaker of very light and simple construction which will permit high speed, tripfree operation in response to either abnormal substantially steady currents or to a sudden rush of current and which may be manually tripped and reset as desired.

While I have shown a particular embodiment of my invention, it will be understood. of course. that I do not wish to be limited thereto since many modifications may be made. and I. therefore, contemplate by the appended claims to cover any such modifications as fall within the true spiritand scope of my invention.

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

l. A circuit breaker comprising a pair of reatively movable contacts, a movable conductor for actuating one of said contacts, said conductor being electrically connected in series with sa d contact, means for biasing said conductor to close said contacts, electromagnetic means in serice with said contacts for establishing a magnetic field, a portion of said conductor being disposed in said magnetic field for applying to said closed contacts an additional closing bias proportional to the electrodynamic reaction between said magnetic field and the current in said conductor and means including said conductor portion and said magnetic field for opening said contacts upon the occurrence of a predetermined rate of change in the current.

2. A circuit breaker comprising a pair of relatively movable contacts, a movable conductor for supporting one of said contacts, said conductor being electrically connected in series with said contact, means for biasing said conductor to contact closing position, electromagnetic means in series with said contacts for establishing a magnetic field, a portion of said conductor being disposed in said magnetic field for applying to said contacts a closing bias proportional to the electrodynamic reaction between said magnetic field and the current in said conductor portion, and conductor means connected with said conductor portion to form a conductor-400p in said magnetic field for opening said contacts upon the occurrence of a predetermined rate of increase in the current.

3, A circuit breaker comprising a pair of relatively movable contacts normally biased to circuit closing position, a movable conductor for supporting one of said contacts, said conductor being electrically connected in series with said contact, means for establishing a magnetic field proportional to the current fiow through said contacts, a portion of said conductor being disposed in said magnetic field for applying to said closed contacts an additional bias, and shunt means connected to said portion of said conductor cooperating with said magnetic field to reverse the direction of current flow through said portion upon the occurrence of a predetermined rate oi increase in the current through said contacts whereby said conductor is moved to open said contacts.

4. A circuit breaker comprising a pair oi. relatively movable contacts normally biased to circuit closing position, a movable conductor for supporting one of said contacts, a magnetic blow-out coll adjacent said contacts in series therewith, means associated with said coil for establishing a magnetic field when said contacts are closed, a portion of said movable conductor being disposed in said magnetic field for applying to said closed contacts an additional closing bias and means including said conductor and said magnetic field for opening said contacts upon the occurrence of a predetermined rate of increase in the current.

5. A circuit breaker comprising a pair of relatively movable contacts normally biased to closed circuit position, a. pivoted conductor bar for supporting one of said contacts, electromagnetic means in series with said conductor and said contacts for establishing a magnetic field, a portion of said conductor being disposed in said magnetic field for operation in one direction about said pivot when a substantially steady current flows through said circuit breaker and means including said conductor portion and said magnetic field for moving said conductor about said pivot in another direction in response to'a predetermined rate of increase in the current through said circuit breaker.

6. An electroresponsive device comprising a conductor-loop having a movable leg forming a side thereof, circuit connections Ior supplying current to said leg, and means for establishing a magnetic field through said loop to move said leg in a predetermined direction upon the flow of a substantially steady current through said loop, said loop and said field field being so related as to induce a reverse current in said leg upon a predetermined rate of change of current in said leg to move said leg in an opposite dlrection.

'7. A circuit breaker comprising a pair of relatively movable contacts, overcenter spring means for actuating one of said contacts between open and closed circuit positions, means for moving said spring means overcenter to open said contacts, a trip-free means electrodynamically responsive to a steady overload current for moving said one contact to open circuit position, and means including said last mentioned means electrodynamically' responsive to a predetermined rate of increase in current for moving said contact to open circuit position.

8. A circuit breaker comprising a pair 01' relatively movable contacts normally biased to closed circuit position, a pair of conductor arms hinged together in endwise relation to form a toggle support electrically and mechanically connected to one or said contacts, said support being pivotally mounted intermediate the ends of one of said arms, means for establishing a magnetic field adjacent said arms proportional to the current in said circuit breaker, said arms being disposed in said field for moving said one contact about said hinge to open circuit position in response to a predetermined value of current through said circuit breaker, and means including said arms and said field for moving said one contact about said pivot to open circuit position in response to a predetermined rate of change of current.

9. A circuit breaker comprising a pair of relatively movable contacts normally biased to closed circuit position, a pair of conductor arms hinged together in endwise relation to form a toggle support electrically and mechanically connected to one of said contacts, said support being pivotally mounted intermediate the ends of one of said arms, means for establishing a magnetic field adjacent said arms proportional to the current in said circuit breaker, said arms being disposed in said field for moving said one contact about said hinge to open circuit position in response to a predetermined value of current .to one of said contacts, said support being pivotally mounted intermediate the ends or one of said arms, means for establishing a magnetic field adjacent said arms proportional to the current in said circuit breaker, said arms being disposed in said field for moving said one contact about said hinge to open circuit position in response to a. predetermined value of current through said circm't breaker, and shunt means connected in parallel circuit relation with one of said arms. said shunt means being disposed in said magnetic field to form a loop circuit including said one arm, said loop circuit and said magnetic field reacting upon a predetermined rate of increase of current to induce a circulating current in said loop of sufiicient magnitude to reverse the normal flow of current through said one'arm, whereby said one contact is moved about said pivot to open circuit position.

11. A circuit breaker comprising a pair of relatively movable contacts, a support for one of said contacts comprising a pair of conductor arms hinged together in endwise relation to form a toggle electrically and mechanically connected to one of said contacts, said support being pivotally mounted intermediate the ends of one of said arms, overcenter spring means having an end connected to one of said arms for normally biasing said contacts to circuit closing position and for locking said toggle, means for moving the other end of said spring relative to said contact support to move said spring overcenter and open said contacts, electromagnetic means in series with said contacts disposed to react electrodynamically with a predetermined value of current in said arms to move said contact about said hinge to open circuit position, and means including said arms disposed to react electrodynamically with said magnetic field upon a predetermined rate of increase in current to move said one contact about said pivot to open circuit position.

PETER W. FORSBERG.