US2920161A

US2920161A - Magnetic trip device

Info

Publication number: US2920161A
Application number: US787229A
Authority: US
Inventors: Edward P Dessert; Werner F Kussy; Tadeusz J Rys
Original assignee: Square D Co
Current assignee: Schneider Electric USA Inc
Priority date: 1959-01-16
Filing date: 1959-01-16
Publication date: 1960-01-05
Anticipated expiration: 1977-01-05

Description

Jan. 5, 1960 E. P. DESSERT EI'AL 2,920,161

MAGNETIC TRIP DEVICE Filed Jan. 16, 1959 2 Sheets-Sheet 1 INVENTOR Q 59 zywdfzpjdfls'eif erner )1 Kass 35 74 821:: fig:

Jan. 5, 1960 E. P. DESSERT ET AL 2,920,161

MAGNETIC TRIP DEVICE Filed Jan. 16, 1959 2 Sheets-Sheet 2 70 a; if 5 50 MAGNETIC TRIP DEVICE Edward P. Dessert, Detroit, Werner F. Kussy, Birmingham, and Tadeusz J. Rys, Detroit, Mich., assiguors to Square D Company, Detroit, Mich., a corporation of Michigan Application January 16, 1959, Serial No. 787,229

Claims. (Cl. 20095) This invention relates generally to electric circuit breakers and more particularly to an improved adjustable magnetically-responsive trip device for controlling the automatic opening of an electric circuit breaker.

Automatic electric circuit breakers having magnetically-responsive trip devices are often used to protect branch circuits supplying electric motors or other electric translating devices requiring high initial or inrush currents. The magnetically-responsive trip device of such circuit breakers should be adjustable so that tripping of the circuit breaker can be caused to occur at different predetermined current values. To permit use of the same circuit breaker in circuits of widely different loading, selectively, the trip device must be adjustable throughout a wide range of current values.

Accordingly, an object of the present invention is to provide an improved magnetic trip device for a circuit breaker that can be adjusted to respond throughout a relatively Wide range of current values.

Since it is desirable that a magnetic trip device he adjustable so as to not respond to normal inrush current yet be operative to provide positive protection upon the occurrence of currents only slightly greater than the normal inrush current, a trip device should be adjustable in relatively small increments of current value throughout its range of adjustment.

Therefore, another object is to provide an improved magnetic trip device that can be adjusted in relatively small increments of current value throughout its full range of adjustment.

To be acceptable for industrial applications, a trip device should accurately maintain its initial calibration as well as its current response setting even though the circuit breaker is subjected to adverse operating conditions including severe vibration.

Another object is to provide an improved trip device for a circuit breaker which maintains its initial calibration as well as its current response setting for long periods of time and without material deviation due to adverse operating conditions.

A further object is to provide a magnetic trip device including an adjustment means operable to vary simultaneously two factors affecting the amount of magnetic flux required to operate the trip device.

A more detailed object is to provide a magnetic trip device comprising a magnetic core, a winding around said core, a pivoted magnetic armature operatively related with said core, an armature spring biasing said armature to its open position, and an adjustment means operable to increase concurrently the biasing force of the armature spring and the air gap between the core and armature.

Other objects and advantages of the present invention will become apparent from the following description, wherein reference is made to the drawings, in which:

Fig. 1 is a side elevation of a trip device in accordance a United StatesPatent O "ice with the present invention, partially in section, and shown in cooperative relation with a circuit breaker,

Fig. 2 is an enlarged side elevation of the trip device as shown in Fig. 1,

Fig. 3 is a fragmentary top view of the circuit breaker taken as indicated at IIIIII of Fig. 2 and showing the index positions of several of the trip devices in a multipole circuit breaker,

Fig. 4 is a side elevation of the trip device, similar to Fig. 2, but showing the device in the adjusted position requiring maximum current to trip the device,

Fig. 5 is a side elevation of the trip device, similar to Fig. 2 but showing the armature attracted to the core,

Fig. 6 is a view of the trip device taken as indicated at VI-VI of Fig. 2,

Fig. 7 is a cross-sectional view taken as indicated at VIIVII of Fig. 6, and

Fig. 8 is a cross-sectional view taken as indicated at VIIIVIII of Fig. 2.

Referring to Fig. 1, a trip device 10 in accordance with this invention is shown in association with a multi-pole circuit breaker 11 of the general type described and claimed in W. T. Allen et al. Patent No. 2,814,693, issued November 26, 1957. It will be obvious that the trip device can be used as well with other multipole circuit breakers or with single pole circuit breakers. The circuit breaker 11 has a housing 12 of insulating material that serves to enclose and support the operating components of the circuit breaker. The trip device for each pole of the circuit breaker is identical with the others, and therefore only one pole is shown and described. A terminal strip 14 having a fixed contact 15 secured thereto, as by welding, is suitably mounted at one end portion of the housing 12 and passes through the housing wall for connection to an external source of electrical energy (not shown). A movable contact 16 on a movable contact carrier 18 cooperates with the fixed contact 15 to make and break an electrical circuit through the pole, as will be described. The contact carrier 18 is pivotally supported on a transverse pin 19 suitably mounted within the housing 12. An operating member 20 is also pivotally supported on the transverse pin 19 and receives, in a cutout portion 21, an interiorly projecting end portion 22 of a manual operator 24. The manual operator 24 is supported for rotation, with respect to the housing 12, on a pair of axially-aligned trunnions 25 supported in suitable bearing recesses (not shown) in the housing 12. A lever 28, rotatably secured at one end portion to the operating member 20, carries, at its other end portion, a pin 29 which is slidably received in a slot 30 formed in the contact carrier 18. A releasable member 31, pivotally mounted on a transverse pin 32 which is fixedly supported within the housing 12, is provided with an upstanding hook-like portion 34 to which one end of an operating spring 35 is fastened. The other end of the operating spring 35 is fastened to the pin 29. The releasable member 31 is thus biased for clockwise rotation about the pin 32 but is normally restrained from such rotation by engagement of a latching portion 38 thereof with a transverse trip bar 39 common to the several poles.

As will become apparent, upon automatic operation of the circuit breaker, the trip bar 39 rotates clockwise, as shown in Fig. 1, about trunnions 40 thereon and retracts from its engagement with the latching portion 38 of the releasable member 31 to allow the releasable member 31 to rotate about the base pin 32 under the bias of the operating spring 35. This rotation of the releasable member 31 carries the line of action of the spring 35 upwardly across a line between the pin 29 and pivotal connection of the lever 28 to the operating member 20 Patented Jan. 5, 1960- thereby biasing the contact carrier 18 to turn counterclockwise to separate the contacts 15 and 16.

Referring principally to Fig. 2, the trip device 11) comprises a U-shaped magnetic core 41 having a bight portion 42 and spaced leg portions 44-. The core 41 may be supported within the enclosure 12 as by a pair of shoulders 45 that extend outwardly from opposite sides near the bight portion 42 and are received in respective grooves (not shown) formed in the side walls of the enclosure 12. Each of the leg portions 44 is provided with a planar pole face 46. An electrical conductor 48 is Wound about the bight portion 42 of the magnetic core 41 and is connected at one end to a terminal member 49 as shown in Fig. l. The terminal member 49 is secured to an external ledge on the enclosure 12 as by a screw 59. A conventional solderless connector 51 is engaged with the terminal member 4% to facilitate connection of the circuit breaker 11 to an external load. The other end of the conductor 48 is electrically connected through a flexible conductor 52 to the movable contact carrier 18.

in accordance with this invention, an armature 53 is supported for rotation with respect to the core 41 by a pin 54 that passes through spaced ears 55' formed on the armature 53 and is received in spaced bearing recesses 56 formed on the upper edges of the leg portions 44 of the core 41. The armature 53 is provided with an integral fian e '7 formed to provide a spring retainer cup 58 for the acceptance of the lower end of an armature spring 59. The armature 53 has an upper extension 66 that limits rotation of the armature under the bias of the spring 59, as will be described, and a lower extension 61 that is operatively aligned with the pole faces 46 of the core 43. Preferably, the ears 55, flange 57, retainer cup 58 and upper extension 60 are made of non-magnetic material and the lower extension 61 is made of magnetic material.

The lower extension 61 of the armature 53 is biased to the unattracted position, with respect to the pole faces 46 of the core 4-1, by the spring 59. The spring 59 is preferably a helical compression spring and extends between the spring retainer cup 58 and the lower end face of an initial adjustment screw 62 having an externally threaded lower portion 64- that engages an internally threaded central bore 65 of a slidable member 66. The member 66 is mounted in a U-shaped frame 69 having a bight portion 76 and horizontally disposed upper and lower leg portions '71 and '72. The frame 69 is supported within the housing 12 by spaced ears 74 extending rearwardly from the bight portion '76 and received in respective recesses in the housing.

The member 66 is non-circular in cross-section and is received for slidable translation with respect to the frame 69 within a complementary non-circular cutout 75 in the lower leg portion 72 of the trip frame 69. The non-circular configuration of the member 66 and the cutout 75 restrains the member 66 from rotation with respect to the frame 69. Turning of the initial adjustment screw 62 moves it axially with respect to the slidable member 66 thereby changing the length of the spring 59 to vary its bias on the armature 53.

The slidable member 66 has a planar upper edge face 76 disposed at an angle other than a right angle with respect to the axis of the initial adjustment screw 62. An upper portion '78 of the initial adjustment screw 62 extends above the top edge face 76 and is provided with a slot '7) for the acceptance of a screwdriver to faciiitate turning thereof.

A field adjustment cam 86 of circular cross-section is supported for rotation in a circular cutout 81 in the upper leg portion '71 of the frame 69 in axial alignment with the initial adjustment screw 62 and is provided with a planar lower edge face 32 that is disposed at the same angle with the rotative axis thereof as that between the upper edge face 76 and the axis of the slidable member 66.

The field adjustment cam 36 is provided with a central bore 84 that accepts the upper extension 78 of the initial adjustment screw 62. The field adjustment cam 80 has an intermediate eccentric cam portion of generally circular configuration having a central axis parallel to, but displaced from, the rotative axis of the field adjustment cam 86 (Fig. 8) in the direction of the lowermost portion of the lower edge face 82 thereof. The cam portion 85 of the field adjustment cam 80- engages the upper extension 611) of the armature 53 and upon turning of the cam 89, positions the lower armature extension 61 different distances from the pole faces 46 of the core 41.

An insulating knob 86 extends through the housing 12 and releasably engages the field adjustment cam 80. Rotation of the insulating knob 86 is transmitted to the field adjustment cam Sit by a hexagonal extension 87 which is seated in an upwardly directed hexagonal recess 88 (Fig. 7) in the field adjustment cam 86.

The upper leg portion 71 of the frame 69 has an outer edge face 89 generally concentric with the circular cutout portion 81 thereof and provided with a plurality of equally and circumferentially spaced radially outwardly extending ridges 96 (Fig. 7) which cooperate with an index spring )1 to index rotation of the field adjustment cam 89. Preferably the index spring 91 is secured to the field adjustment cam 86 as by staking.

Adjustment of the trip device 10 to an initial setting is accomplished by first rotating the cam member 80 so that the planar lower edge face 82 thereof is parallel to the planular upper edge face 76 of the slidable member 66. In this position, the eccentric portion 85 of the cam member 86 biases the upper extension 66 of the armature 53 clockwise about the pivotal support 55 thereof thus rotating the lower extension 61 of the armature 53 to the smallest air gap position with respect to the pole faces 44 on the magnetic core 41. Further, the slidable member 66 is permitted to fully retract into the trip frame 70 under the bias of the spring 59 thereby reducing the effective force of the spring 59 on the armature 53. The adjustment screw 62 is then advanced until a desired minimum value of current develops a flux in the magnet core 41 sufficient to attract the lower extension 61 of the armature to the pole faces 46 thereof against the bias of the trip spring 59. The initial positioning of the adjustment screw 62 takes care of variances between trip units due to manufacturing tolerances.

After rotation of the initial adjustment screw 62 to an initial setting, the insulating knob 86 is placed over the cam member 80 in interlocking relationship. If it is desired to increase the amount of current required to energize the trip device 10, the insulating cap 86 and cam member 86, which rotates therewith, are turned with respect to the housing 12. Rotation of the cam member 80 forces the tubular member 66 downwardly because the lowermost area of the planular face 82 of the cam member 8t bears upon the upper face 76 of the slidable member 66. The maximum adjustment of the trip device 10 is achieved when the lowermost area of the planar lower edge face 82 is turned to the point where it contacts the uppermost area of the planar upper edge face 76 of the tubular member 66 (Fig. 4). Upon rotation of the cam member 86, and at the same time that it is moving the tubular member 66 downwardly, the eccentric portion 85 thereof rotates to reduce the radial distance between the outer edge face thereof and the rotative axis of the cam 80, thereby permitting the upper extension 60 of the armature 53 to rotate counter-clockwise about its pivotal support 50 under the bias of the spring 59. Counter-clockwise rotation of the armature 53 increases the air gap between the lower extension 61 of the armature and the pole faces 46 of the magnetic core 41. In this manner a wide range of adjustment is achieved for the trip device 10 because the armature 54 is biased more strongly to the unattracted position simultaneously as the air gap between the lower extension 61 of the armature 54 and the pole faces 44 of the magnetic core 41 is increased. The effect of this simultaneous adjustment of air gap and armature spring bias is to change the magnetic flux required within the magnetic core to attract the armature and trip the circuit breaker.

Upon excessive current flow through the coil 48, a magnetic flux is established in the core 41 and the lower extension 61 of the armature 53 is attracted toward the pole faces 46 thereof (Fig. 5). As the armature 53 rotates in the clockwise direction, the upper extension 60 thereof biases the cross bar 39 in a clockwise direction thereby retracting the cross bar from engagement with the latching portion 38 of the releasable member 31 and allowing the releasable member 34 to rotate about the pin 32 thereby opening the contacts 15 and 16 with a snap action.

Upon rotation of the manual operator 24 to the open and closed positions, the operating member 20 is biased alternately in opposite directions about the pin 19. Movement of the operating member carries the link 28 across the line of action of the spring 35 to open and close the contacts 15 and 16 with a snap action, selectively.

What is claimed is:

l. A circuit breaker comprising relatively movable contacts, means releasable to eifect opening of said contacts, and a trip device operable to release said releasable means in response to predetermined electrical conditions in an electrical circuit containing said circuit breaker, said trip device comprising a magnetic core, means connected in said electrical circuit to develop a magnetic flux in said core upon the occurrence of said condition, a magnetic armature operatively related with said magnetic core so as to be attracted thereto upon the occurrence of said condition, a first member mounted for movement with respect to said magnetic core, an initial adjustment screw movable by and with respect to said first member, an armature spring extending between said initial adjustment screw and said armature and biasing said armature to an unattracted position with respect to said magnetic core, the bias of said armature spring on said armature being variableupon movement of said initial adjustment screw with respect to said first member and upon movement of said first member with respect to said magnetic core, a second member disposed for movement with respect to said first member and said magnetic core and engageable with said first member, movement of said second member effecting movement of said first member with respect to said magnetic core, and an armatu re positioning portion on said second member, engageable with said armature for movement of said armature against the bias of said armature spring thereby to determine said unattracted position of said armature with respect to said magnetic core.

2. A circuit breaker comprising relatively movable contacts, means releasable to effect opening of said contacts, and a trip device operable to release said releasable means in response to predetermined electrical conditions in an electrical circuit containing said circuit breaker, said trip device comprising a magnetic core, means connected in said electrical circuit to develop a magnetic flux in said core upon the occurrence of said condition, a magnetic armature operatively related with said magnetic core so as to be attracted thereto upon the occurrence of said condition, a first member mounted for slidable translation with respect to said magnetic core, an initial adjustment screw threadably engaged with said first member, an armature spring extending between said initial adjustment screw and said armature and biasing said armature to an unattracted position with respect to said magnetic core, the bias of said armature spring on said armature being variable upon rotation of said initial adjustment screw with respect to said first member and upon movement of said first member with respect to said magnetic core, and a second member disposed for rotation with respect to said first member and said magnetic core and engageable with said first member, rotation of said second member effecting translation of said first member with respect to said magnetic core, and an armature positioning cam on said second member engageable with said armature for movement of said armature against the bias of said armature spring thereby to determine said unattracted position of said armature with respect to said magnetic core.

3. A circuit breaker comprising relatively movable contacts, means releasable to efiect opening of said contacts, and a trip device operable to release said releasable means in response to predetermined electrical conditions in an electrical circuit containing said circuit breaker, said trip device comprising a magnetic core, means connected in said electrical circuit to develop a magnetic flux in said core upon the occurrence of said condition, a magnetic armature operatively related with said magnetic core so as to be attracted thereto upon the occurrence of said condition, a first member mounted for slidable translation with respect to said magnetic core and having a planar edge face disposed at an angle other than an angle normal to the direction of translation thereof, an armature spring extending between said first member and said armature and biasing said armature to an unattracted position with respect to said magnetic core, the bias of said armature spring on said armature being variable upon movement of said first member with respect to said magnetic core, and a second member disposed for rotation with respect to said first member, said magnetic core having a surface engageable with said edge face of said first member, and rotation of said second member eifecting translation of said first member with respect to said magnetic core.

4. A circuit breaker comprising relatively movable contacts, means releasable to effect opening of said contacts, and a trip device operable to release said releasable means in response to predetermined electrical conditions in an electrical circuit containing said circuit breaker, said trip device comprising a magnetic core, means connected in said electrical circuit to develop a magnetic flux in said core upon the occurrence of said condition, a magnetic armature operatively related with said magetic core so as to be attracted thereto upon the occurrence of said condition, a first member mounted for translation with respect to said magnetic core having an edge face disposed other than normally to the direction of translation thereof, an armature spring extending between said first member and said armature and biasing said armature to an unattracted position with respect to said magnetic core, the bias of said armature spring on said armature being variable upon movement of said first member with respect to said magnetic core, a second member disposed for movement with respect to said first member and said magnetic core and engageable with said edge face of said first member, movement of said second member effecting movement of said first member with respect to said magnetic core, and an armature positioning portion on said second member engageable with said armature for movement of said armature against the bias of said armature spring thereby to determine said unattracted position of said armature with respect to said magnetic core.

5. A circuit breaker in accordance with claim 1 characterized in that the magnetic armature of the trip device is mounted on a pivot and turns about the pivot upon said attraction to the magnetic core.

No references cited.