US3798580A

US3798580A - Circuit interrupter with induction type trip unit

Info

Publication number: US3798580A
Application number: US00339671A
Authority: US
Inventors: A Cellerini
Original assignee: Westinghouse Electric Corp
Current assignee: CBS Corp
Priority date: 1973-03-09
Filing date: 1973-03-09
Publication date: 1974-03-19
Anticipated expiration: 1991-03-19
Also published as: JPS54132767U; JPS5030062A; CA988972A; AU6606674A

Abstract

An improved circuit breaker of the type characterized by an enclosed protective device for responding to abnormal currents in the conductors of an electrical distribution system and for actuating the circuit interrupter to open upon the occurrence of predetermined operating conditions, the protective device including a magnetically permeable structure around each conductor, a multiturn winding around a portion of the magnetically permeable structure, a U-shaped bimetal member having leg portions mounted on an insulating housing of the circuit breaker, the lead wires of the multiturn coil being connected separately to the leg portions of the bimetal member and forming an electric loop therewith, and the bimetal member being movable to a tripping position to actuate a trip bar for opening the circuit through the circuit interrupter in response to a predetermined abnormal current through any one of the conductors.

Description

United States Patent [191 Cellerini [4 1 Mar. 19, 1974 CIRCUIT INTERRUPTER WITH INDUCTION TYPE TRIP UNIT Albert R. Cellerini, Beaver, Pa.

[73] Assignee: Westinghouse Electric Corporation,

Pittsburgh, Pa.

[22] Filed: Mar. 9, 1973 [21] Appl. N0.: 339,671

[75] Inventor:

[52] US. Cl. 335/37, 337/145 [51] Int. Cl. H01h 77/04 [58] Field of Search 335/35, 145, 43, 37; 317/142 TD [56] References Cited UNITED STATES PATENTS 2.831.935 4/1958 Page 335/37 Primary Examiner-Harold Broome Attorney, Agent, or Firm-L. P. Johns 5 7] ABSTRACT An improved circuit breaker of the type characterized by an enclosed protective device for responding to abnormal currents in the conductors of an electrical distribution system and for actuating the circuit interrupter to open upon the occurrence of predetermined operating conditions, the protective device including a magnetically permeable structure around each conductor, a multiturn winding around a portion of the magnetically permeable structure, a U-shaped bimetal member having leg portions mounted on an insulating housing of the circuit breaker, the lead wires of the multiturn coil being connected separately to the leg portions of the bimetal member and forming an electric loop therewith, and the bimetal member being movable to a tripping position to actuate a trip bar for opening the circuit through the circuit interrupter in response to a predetermined abnormal current through any one of the conductors.

9 Claims, 4 Drawing Figures CIRCUIT. INTERRUPTER WITH INDUCTION TYPE TRIP UNIT BACKGROUND OF THE INVENTION thermalaction of the trip unit.

SUMMARY OF THE INVENTION Generally, in accordance with this invention it has been found that an improved induction type trip unit may be provided, comprising a circuit breaker having an insulating housing, a circuit breaker mechanism within the housing and comprising separable contacts forming part of an electrical distribution system, a trip device within the housing comprising a current monitoring magnetic structure for each conductor of an electrical distribution system, a current sensing winding on the structure for sensing current in the structure, a trip bar pivotally mounted on the insulating housing and being movable between tripping and non-tripping positions of the circuit breaker mechanism, a current conducting bimetal mounted on the insulating housing and being part of an electrical loop including the winding, and the current-conducting bimetal being movable to a tripping position of the trip bar in response to a predetermined abnormal current through any one of the conductors.

The advantage of the device of this invention is that only one core and coil assembly is necessary and thereby conserves space which enables the use of a larger core and coil. Moreover, a bimetal member is heated directly which enables the use of ratings down to about 100 amperes. Finally, a more economical device is provided.

BRIEF DESCRIPTION OF THE DRAWINGS DESCRIPTION OF THE PREFERRED EMBODIMENT In FIG. 1 a circuit breaker, generally indicated at 3, comprises an insulating housing 5 and circuit breaker mechanism 7 supported within the housing. The housing 5 comprises a base 9, and a cooperating cover 11 both of molded insulating material. The circuit breaker is of the type known in the art as a molded-case or insulating-housing type that is more specifically described in US. Pat. No. 3,296,564, issued Jan. 3, 1967, to Albert R. Cellerini, for which reason an abbreviated description of the circuit breaker is set forth herein.

The circuit breaker mechanism 7 comprises an operating mechanism 13 and a trip device or trip unit 15. The circuit breaker 3 is a three-pole unit comprising three compartments disposed in a side-by-side relationship within the insulating housing 5. The center compartment or pole unit is separated from each of the outer pole units by a separate

insulating barrier

17, 19 molded integral with the cover 11 and base 9, respectively. The operating mechanism 13 is a single operating mechanism disposed in the center pole unit for simultaneously operating the contacts of all three of the pole-units.

Each pole unit comprises a stationary contact 21 which is fixedly secured to a rigid main conductor 22, that is in turn secured to the base 9 by means of bolts 25. In each pole unit a movable contact 27 is welded or brazed to a contact arm 29 that is pivotally mounted on a switch unit 31 by means of a pivot pin 33. Each of the switch arms 31 is pivotally supported at one end thereof on a separate support bracket 34 by means of a separate pivot pin 35. The switch arm 31 for all three of the pole units are connected to move in unison by means of a common tie bar 37 that is rigidly connected to all three of the swtich arms. Each of the contact arms 29 is biased about the associated pivot 33 by means of a spring 39 to provide contact pressures in the closed position.

The switch arms 31 are operated to the open and closed positions by means of the operating mechanism 13 which comprises toggle links 41 and 43 which are pivotally connected together by a knee pivot pin 45. Two overcenter springs (only one of which is shown in FIG. 1) are connected under tension between the pivot pin 45 and the upper end of an operating lever 49 which is part of an insulating handle 51 which is movable between ON and OFF positions. The upper end of the toggle link 43 is pivotally connected to a cradle or releasable member 51 by means of a pivot pin 53. The member 51 is pivotally supported at one end thereof on a supporting bracket 34 by means of a pivot pin 55. The other end 57 of the releasable member 51 is held in a latched position by a latch member 61.

For each pole unit, the circuit breaker 3 is provided with two rear-

type terminal connectors

63 and 65 suitably secured at opposite ends at the back or bottom of the circuit breaker. As shown in FIG. 1 the circuit through each pole unit of the circuit breaker 3 extends from the right-hand terminal 63 through the conductor 23, contacts 21, 27, the contact arm 29, flexible conductors 67 that are secured to the contact arm 29, and to a terminal member 69 which in turn is secured to a unitary rigid main conductor 71 that is connected to the terminal connector 65.

As set forth in other US. Pat. Nos. 3,287,534, 3,343,042 and 3,538,475, the circuit breaker 3 is manually operated to the open position by movement of the handle 51 in a counterclockwise (FIG. 1) direction of the OFF position. During this movement all of the switch arms 31, by means of the common tie bar 37, move the three switch arms 31 to the open position, that is, separation of the contacts 21, 27. Conversely, the circuit breaker is manually closed by the reverse movement of the handle 51 to the ON position, whereby the movable contacts 27 are brought into contact with the stationary contacts 21 simultaneously to the closed position.

As shown in FIGS. 1, 3, and 4 the trip device 15 comprises a molded insulating base 73 and a molded insulating cover 75 cooperable with the base to enclose three thermal-and-magnetic trip means which are disposed within three compartments in the trip unit housing. The compartments are separated by cooperating insulating barriers 77 and 79 (FIGS. 3 and 4) that are molded integrally with the base 73 and cover 75, respectively. The train device 15 comprises a trip structure 81 including a molded insulating trip bar 83, three similar bimetal members 85 (one for each pole unit compartment), and three thermal-and-magnetic trip means 87 (one for each pole unit) which are disposed generally below the trip bar 83.

Each of the thermal-and-magnetic trip means 87 comprises an electromagnetic trip means 89 and a thermal trip means 91. The electromagnetic trip means 89 (FIGS. 4 and comprise a generally U-shaped member 93 of magnetically permeable material, such as soft iron, and a clapper type armature 95 which is also of a magnetically permeable material. As shown in FIG. 4 the U-shaped member 93 and the armature 95 are both laminated to reduce eddy currents. A generally V-shaped notch 97 (FIG. 4) is formed at the upper end of one of the legs of the U-shaped member 93. The armature 95 comprises a knife-edged pivot portion 99 which is seated in the notch 97. A coil spring 101 is attached at one end of the armature 95 to bias the armature in a retracted position with respect to a pole end face 103 of the leg of the U-shaped member 93. In the closed position the armature 95 is lowered against the pressure of the spring when predetermined abnormal currents pass through the conductor 71 around which the U-shaped member 93 is disposed.

The air gap between the end of the armature 95 and the pole end face 103 is adjusted by an adjustment screw 107 (FIG. 3) which is of the type specifically described in the patent to G. F. Thomas et al., U.S. Pat. No. 3,073,925, issued Jan. 15, 1963. The adjusting screw 107 is part of an adjusting mechanism which also comprises a lever 109 which is pivotally supported intermediate the ends thereof on a supporting bracket 111 by a pivot pin 113. A rod 115 having an adjustment knob 117 extends from a cam 119 whereby rotation of the cam enables rotation of the lever 109 and therefore adjustment of the space between the pole end face 103 and the end of the armature 95, thereby varying the magnetic air gap to vary the minimum overload current which will be required to effect an instantaneous magnetic tripping operation. The circuit breaker 3 is tripped open instantaneously upon the occurrence ofa sever overload of for example ten times the normal rated current, through any of the three pole units of the circuit breaker.

Upon the occurrence of a sever overload or short circuit through one of the conductors 71, the magnetic flux generated in the associated U-shaped member 93 is strong enough to attract the armature 95 toward the pole end face 103 against the tension of the spring 101, the armature moving pivotally in the notch 97. As the armature 95 moves into engagement with the pole end face 103 a rod 121 which is pivotally supported to the armature by a pivot pin 123 (FIG. 3), is pulled down whereupon a head portion 125 (FIGS. 3 and 4) on the rod engages a part 127 causing the trip bar to rotate in a counterclockwise (FIG. 4) closed direction about the pivot pin 129. This movement effects a releasing movement of the latch 61 to disengage the latch from the cradle 51 (FIG. 1). Release of the cradle 51 enables the overcenter springs 47 to rotate the cradle in a clockwise direction about the pivot 55 and to collapse the toggle 41, 43 to thereby pivotally move the three switch arms 31 in a counterclockwise direction to the open position.

The above-described structure and operation sets forth the magnetic trip means for the circuit breaker which means function on heavy overloads. Where normal overloads occur, the thermal trip means 91 is operative. It comprises a core 131 and coil 133. The core 131, like the U-shaped member 93, is a laminated member composed of pieces of magnetically permeable material, such as soft iron, which pieces are secured together and mounted on a mounting bar 135 by suitable means such as rivets 137. Opposite end portions of the mounting bar 135 are secured by suitable means such as screws 139 secured to the legs of the U-shaped member 93, whereby the core 131 is disposed between the leg members at a position between the conductors and the upper ends of the legs. As a result a flux path A is formed. The coil or current sensing winding 133 includes

coil end portions

141 and 143, one of which portions is attached to one end of the U-shaped bimetal member and the other end portion of which is attached to the other end of the bimetal member, whereby a closed pass or loop is formed with the coil winding 133. As a result an induced current is caused by the load current passing through the conductor 71 so that the bimetal may be deflected against the lower side of the trip bar 83 to deflect it counterclockwise and thereby trip the circuit breaker 3.

On normal overloads only the flux path A is effected because the reluctance is low as compared to a flux path B which extends around the U-shaped member 93 and the armature 95. On heavy overloads, however, path A becomes saturated and path B assumes the excess induced flux whereby the armature is actuated to provide instantaneous magnetic tripping.

The assembly of the core 131 and coil 133 enables flexibility to obtain an entire range of thermal ratings involved in a particular line of circuit breakers. Each rating is obtained by using a coil 133 which applies to that particular rating. Inasmuch as the entire assembly of the core 131 and coil 134 is removable the coil may be changed readily and thereby enable any desired thermal rating.

What is claimed is:

1. A circuit interrupter protective device for responding to abnormal currents in the conductors of an electrical distribution system and for actuating a circuit interrupter to open upon the occurrence of predetermined operating conditions, comprising a circuit breaker having an insulating housing, a circuit breaker mechanism within the housing and comprising separable contacts forming part of the distribution system, a trip device within the housing comprising a current monitoring magnetic structure for each conductor of an electrical distribution system, a current sensing winding on the structure for sensing current in the structure, a trip bar pivotally mounted on the insulating housing and being movable between tripping and nontripping, positions of the circuit breaker mechanism, a current conducting bimetal member mounted on the insulating housing and being part of an electrical loop including the winding, and the current-conducting bimetal member being movable to a tripping position of the trip bar in response to a predetermined abnormal current through any one of the conductors.

2. The device of claim 1 in which the current monitoring magnetic structure is a magnetically permeable member around each conductor 3. The device of claim 2 in which the current sensing winding is a multiturn coil around each current monitoring magnetic structure.

4. The device of claim 3 in which the current conducting bimetal has a U-shaped configuration comprising two leg portions,'one lead wire from the multiturn coil being electrically connected to one leg portion and the other lead wire from the multiturn coil being electrically connected to the other leg portion.

5. The device of claim 4 in which the leg portions of the bimetal are secured to the insulating housing.

6. A circuit interrupter protective device for responding to abnormal currents in the conductors of an electrical distribution system and for actuating a circuit interrupter to open upon the occurrence of predetermined operating conditions, comprising a circuit breaker having an insulating housing, a circuit breaker mechanism within the housing and comprising separable contacts forming part of the distribution system, a trip device within the housing comprising a current monitoring magnetic structure for each conductor of an electrical distribution system, the current monitoring magnetic structure comprising a magnetically permeable U-shaped member adapted for encompassing each conductor and comprising U-legs extending beyond one side of the conductor, an armature for each U-shaped member which armature in the closed position extends across the ends of the U-legs at a position spaced from the corresponding conductor, the trip device also comprising a trip bar operable to open the contacts, the armature being connected to the trip bar to effect opening of the contacts when the armature is in the closed position, current sensing means comprising a magnetically permeable element and a winding on the member and between the armature and the conductor, the magnetically permeable element extending between the U-legs, a current conducting bimetal member mounted on the insulating housing and being part of an electric loop including the winding, and the current-conducting bimetal member being movable to a tripping position of the trip bar in response to predetermined abnormal current through any one of the conductors.

7. The device of claim 6 in which the winding is a multiturn coil around the magnetically permeable element.

8. The device of claim 7 in which the current conducting bimetal member has a U-shaped configuration comprising leg portions, one lead wire of the multiturn coil being electrically connected to one leg portion and the other lead wire from the coil being electrically connected to the other leg portion.

9. The device of claim 8 in which the leg portions of the bimetal member are mounted between the trip bar and the insulating housing.

Claims

1. A circuit interrupter protective device for responding to abnormal currents in the conductors of an electrical distribution system and for actuating a circuit interrupter to open upon the occurrence of predetermined operating conditions, comprising a circuit breaker having an insulating housing, a circuit breaker mechanism within the housing and comprising separable contacts forming part of the distribution system, a trip device within the housing comprising a current monitoring magnetic structure for each conductor of an electrical distribution system, a current sensing winding on the structure for sensing current in the structure, a trip bar pivotally mounted on the insulating housing and being movable between tripping and non-tripping, positions of the circuit breaker mechanism, a current conducting bimetal member mounted on the insulating housing and being part of an electrical loop including the winding, and the current-conducting bimetal member being movable to a tripping position of the trip bar in response to a predetermined abnormal current through any one of the conductors.

2. The device of claim 1 in which the current monitoring magnetic structure is a magnetically permeable member around each conductor.

3. The device of claim 2 in which the current sensing winding is a multiturn coil around each current monitoring magnetic structure.

4. The device of claim 3 in which the current conducting bimetal has a U-shaped configuration comprising two leg portions, one lead wire from the multiturn coil being electrically connected to one leg portion and the other lead wire from the multiturn coil being electrically connected to the other leg portion.