Ground Fault Interrupter

Abstract

A ground fault interrupter is constructed with a single housing divided into two compartments. One compartment houses an automatic circuit breaker that is manually operable by successive depressions of a slidable operating member, and the other compartment houses a ground fault detector and an electromagnet that is actuated when a ground fault is detected. A lost motion means connects the electromagnet armature to the armature of the magnetic overload trip means of the circuit breaker in a manner such that movement of the electromagnet armature moves the overload armature to trip the circuit breaker, but movement of the overload armature will not move the electromagnet armature. In another embodiment a common magnetic frame and armature are used for the magnets in both compartments, and a permanent magnet is utilized to provide pre-excitation to the electromagnet structure.

Description

Conventional circuit breakers for home and light industrial applications usually have thermal and magnetic fault responsive trip means to automatically open the main contacts of the circuit breaker when excessively high current flows through the main contacts. The protection afforded prevents damage to load wiring and to the load. However, this does not insure that low magnitude fault currents caused by high resistance faults to ground will not result in injury to personnel or start fires.

In order to obtain protection against the aforesaid low magnitude faults, so-called ground fault interrupters have been provided to extend the protection afforded by conventional circuit breakers. A typical ground fault interrupter is described in U.S. Pat. No. 3,473,091, issued Oct. 14, 1959, to A. R. Morris et al. for a "Ground Leakage Differential Protective Apparatus."

In accordance with the instant invention, an insulated housing is divided into two compartments, one of which contains a conventional push-push type single-pole circuit breaker having thermal and magnetic means for automatic tripping under high current fault conditions. The other compartment houses the elements for detecting ground faults and generating a mechanical force to trip the circuit breaker when relatively low current ground faults are present. In one embodiment of the instant invention, the ground fault unit includes an electromagnet with an armature that is connected by an insulating link to the armature of the circuit breaker magnetic trip. This link provides a lost-motion connection constructed so that operation of the ground fault magnet moves the armature of the circuit breaker trip magnet, but energization of the trip magnet is ineffective to move the armature of the ground fault magnet so that calibration of the magnetic overload trip device is not effected by the ground tripping device.

In another embodiment of the instant invention the ground fault and circuit breaker magnet coils are mounted on a common magnetic frame extending into both compartments, with this frame including a single movable armature. The coils of the ground fault and overload magnets are wound so that the fluxes generated thereby are in aiding relationship. As an optional feature, one or more permanent magnets may be provided to aid the magnet fluxes.

Accordingly, a primary object of the instant invention is to provide a novel construction for a combination circuit breaker and ground fault protective device.

Another object is to provide a combination unit of this type in which the circuit breaker handle is of the push-push type.

Still another object is to provide a combination unit of this type having a lost motion connection between the overload magnet armature and the armature of the ground fault tripping magnet.

A further object is to provide a combination unit of this type in which there is a common magnetic frame and including a common armature for the overload tripping magnet and the ground fault magnet.

These objects as well as other objects of this invention will become readily apparent after reading the following description of the accompanying drawings in which:

FIG. 1 is a side elevation of a combination circuit breaker-ground fault detector constructed in accordance with teachings of the instant invention.

FIG. 2 is a plan view of the combination unit of FIG. 1.

FIG. 3 is a cross-section taken through line 3--3 of FIG. 2, looking in the direction of arrows 3--3.

FIG. 4 is a cross-section taken through line 4--4 of FIG. 3, looking in the direction of arrows 4--4.

FIG. 5 is a plan view of the armature for the ground fault tripping magnet.

FIG. 6 is an end view of the armature of FIG. 5, looking in the direction of arrows 6--6.

FIG. 7 is a plan view of the insulating link interconnecting the ground fault and overload current tripping armatures.

FIG. 8 is an end view link of FIG. 7, looking in the direction of arrows 8--8.

FIG. 9 is a plan view of the overload current armature.

FIG. 10 is an end view of the armature of FIG. 9, looking in the direction of arrows 10--10.

FIG. 11 is an electrical schematic showing the combination unit of FIG. 1, connected in circuit between a load and a source of electrical power.

FIG. 12 is a view similar to FIG. 3, illustrating another embodiment of the instant invention in which a common magnetic frame supports the operating coils for both the overload current and ground fault tripping electromagnets.

FIG. 13 is a side elevation of the electromagnets of FIG. 12, looking in the direction of arrows 13--13 of FIG. 12.

Now referring to the figures. Combination circuit breaker ground fault detector 20, often referred to as a ground fault interrupter, includes molded housing 21 having a rear opening covered by insulating sheet 22 and metal plate 23 having mounting gears 24, 25 integrally formed therewith. Fasteners 26 received in three housing formations 27 fixedly secure sheet 22 and plate 23 to the rear of housing 21. Centrally located internal partition 28 divides housing 21 into side-by-side compartments. The left one of these compartments, as viewed in FIG. 3, contains the elements of a single pole so-called "push-push circuit breaker" constructed essentially the same as each pole of the circuit breaker illustrated in U.S. Pat. No. 3,075,058 issued Jan. 22, 1963, to E. P. Platz et al. for a "Push-Push Circuit Breaker." The right-hand compartment of housing 21, as viewed in FIG. 3, contains the elements of a ground fault protector. These elements (not shown) are mounted to printed circuit board 29 and are arranged, for example, in a circuit of the type illustrated in the aforesaid Morris et al. U.S. Pat. No. 3,473,091. Also mounted within the right-hand compartment is ground fault tripping magnet 30 that is actuated by signals generated in secondary winding 32 and fed through amplifier 35 of the ground fault detector.

Secondary winding 32 is part of transformer 31 which also includes identical primary windings 33, 34 connected in series with the neutral 37 and hot wires 38, respectively, connecting a.c. source 36 to electrical load 39. Primary 33 is connected through lead 41 to neutral line 37 that is grounded near source 36. The other end of primary 33 is connected through lead 42 and line 43 to one terminal of load 39. The other terminal of load 39 is connected through line 44 to circuit breaker load terminal 45. Hot line 38 is connected directly from source 36 to circuit breaker line terminal 46. The path between terminals 45, 46 internal of housing 21 includes load terminal 45 connected to one end of coil 47 of overload tripping magnet 50, through coil 47 and primary 34 to one end of overload tripping bimetal 58, through bimetal 58 and movable contact arm 48 engaged with stationary contact 49 mounted to line terminal 46 at a point thereof internal of housing 21.

Ground fault trip magnet 30 includes ground fault trip coil 84 and movable armature 52. The latter is connected by insulating link 53 to movable armature 51 of circuit breaker magnet 50 in a manner such that movement of armature 52 is transmitted by link 53 to cause movement of armature 51 downward with respect to FIG. 3, or in tripping direction, thereby moving armature latch formation 54 below and clear of latch tip 55 on movable contact arm 48 so that main operating spring 56 is effective to move contact arm 48 about its pivot pin 57, thereby separating the lower end of movable contact arm 48 from stationary contact 49. The circuit breaker automatic trip means also includes bimetal 58 which upon heating deflects downward with respect to FIG. 3, engaging insulating button 59 mounted to circuit breaker armature 51, causing the latter to move downward to unlatching position.

As fully explained in the aforesaid U.S. Pat. No. 3,075,058, operating button 61, slidably mounted to housing 21, is manually depressible and is constructed so that the circuit breaker main contacts 48, 49 will alternately open and close with successive depressing operations of button 61. In a manner well known to the art, button 62, upon being depressed, causes the engagement of spring contact 63 with spring contact 64 to generate a tripping signal in secondary winding 32 of transformer 31.

As best seen in FIGS. 7 and 8, insulating link 53 is a thin elongated member having rectangular cutouts 66, 67, with the latter being noticeably elongated in the direction of the longitudinal axis of link 53. Ground fault tripping armature 52 (FIG. 5) along one edge thereof is provided with spaced pivot extensions 71. Lateral extension 72 of armature 52 extends into the smaller aperture 66 of link 53. Elongated aperture 67 of link 53 receives lateral extension 73 of circuit breaker magnet armature 51 (FIG. 9). The latter is provided with pivot extensions 74 projecting from the edge thereof opposite plastic button 59. Thus, when coil 84 of ground fault magnet 30 is energized, the rear of armature 52 is moved downward against the force of coil spring 81, with armature extension 72 moving link 53 longitudinally downward. This causes the upper boundary wall of elongated aperture 67 to engage circuit breaker armature extension 73 thereby moving the rear end of armature 51 downward against the force of its coil biasing spring 82 to release latch tip 55 of movable contact arm 48. It is noted that energization of circuit breaker magnet 50 is ineffective to move ground fault armature 52 in that upon energization of magnet 50 causing downward movement of armature 51, extension 73 thereof is free to travel downward in elongated aperture 67 without causing movement of link 53. Thus, it is seen that ground fault armature biasing spring 81 does not influence the calibration of the magnetic trip for the circuit breaker section.

The first (FIGS. 1-10) and second (FIGS. 12 and 13) embodiments of this invention differ in that in the latter both circuit breaker trip coil 47, ground fault trip coil 84, and the magnetic cores for each are mounted to a common magnetic frame 85 which extends across both compartments of housing 86 for ground fault interrupter 100, and a common armature 87 extending across both compartments of housing 86 is utilized so that link 83 is eliminated. Naturally, because of the raised location of ground fault trip coil 84 in FIG. 12 as compared to the position thereof in FIG. 3, printed circuit board 88, carrying the electrical components (not shown) constituting the ground fault detector is of a different construction than printed circuit board 29, and most of the components mounted to board 88 are disposed below magnet coil 84. In the embodiment of FIGS. 12 and 13, since coils 47 and 84 are mounted to common frame 85, circuit breaker current flowing through coil 47 premagnetizes frame 85 to achieve very fast operation of armature 87 when coil 84 is energized. The magnetic fluxes generated by currents flowing in both coils 47 and 84 act in series on common armature 87. To accomplish even higher sensitivity and narrow the pickup range, additional magnetic flux is provided by permanent magnet 89 mounted to the vertical leg of magnetic frame 85. One or both of the cores for coils 47 and 84 may have permanent magnets. Any of the permanent magnets may be adjustable, by repositioning or otherwise, to control electromagnet sensitivity.

Although there have been described preferred embodiments of this novel invention, many variations and modifications will now become apparent to those skilled in the art. Therefore, this invention is to be limited not by the specific disclosure herein, but only by the appending claims.

Claims

The embodiments of the invention in which an exclusive privilege or property is claimed are defined as follows.

1. A ground fault protective device including a single housing having a partition separating first and second side-by-side compartments within said housing; an automatic circuit breaker within said first compartment; a ground fault detector in said second compartment; said circuit breaker including a stationary contact, a movable contact means, latch means for maintaining said movable contact means in an operating position, automatic trip means to release said latch upon predetermined overload conditions in the circuit being protected by said circuit breaker, an operating means for moving said movable contact means to a circuit breaker closed position when said movable contact means is in said operating position and for moving said movable contact means to a circuit breaker open position when said latch means releases said movable contact means; said operating means including an operating member biased to normally protrude outward from said first compartment; said operating member being mounted for linear movement and being manually depressible so that upon successive manual operations thereof in the same direction, said operating member will actuate said operating means to alternately open and close said circuit breaker; said ground fault detector including a releasing portion connected to said circuit breaker to release said latch means when a ground fault is detected by said ground fault detector; said automatic trip means including a first electromagnet having a first armature and the releasing portion of the ground fault detector including a second electromagnet having a second armature connected to said first armature for moving the latter to release said latch means when said second electromagnet is energized; a link interconnecting the armatures and movable linearly in a plane generally parallel to said partition and generally parallel to movement of said operating member.

2. A device as set forth in claim 1 in which there is a lost motion connection between said first and second armatures whereby movement of said second armature is effective to move said first armature and movement of said first armature is ineffective to move said second armature.

3. A device as set forth in claim 1 in which the link is adjacent the partition.

4. A ground fault protective device including housing means defining first and second side-by-side compartments; an automatic circuit breaker within said first compartment; a ground fault detector in said second compartment; said circuit breaker including a stationary contact, a movable contact means, latch means for maintaining said movable contact means in an operating position, automatic trip means to release said latch upon predetermined overload conditions in the circuit being protected by said circuit breaker, an operating means for moving said movable contact means to a circuit breaker closed position when said movable contact means is in said operating position and for moving said movable contact means to a circuit breaker open position when said latch means releases said movable contact means; said operating means including an operating member biased to normally protrude outward from said first compartment; said operating member being mounted for linear movement and being manually depressible so that upon successive manual operations thereof in the same direction, said operating member will actuate said operating means to alternately open and close said circuit breaker; said ground fault detector including a releasing portion connected to said circuit breaker to release said latch means when a ground fault is detected by said ground fault detector; said first and second armatures constituting different portions of a single armature member; said first and second electromagnets including a common stationary frame to which said armature member is mounted; said first and second electromagnets including respective first and second operating coils mounted to said stationary frame and arranged so that aiding fluxes are generated in said frame by currents flowing in said operating coils.

5. A device as set forth in claim 4 in which there is a permanent magnet means positioned to generate flux in said core to said those fluxes generated by currents flowing in said operating coils of said electromagnets.

6. A ground fault protective device including housing means defining first and second side-by-side compartments; an automatic circuit breaker within said first compartment; a ground fault detector in said second compartment; said circuit breaker including a stationary contact, a movable contact, latch means for maintaining said movable contact means in an operating position, automatic trip means to release said latch upon the occurrence of predetermined overload conditions in the circuit being protected by said circuit breaker, an operating means for moving said movable contact means to a circuit breaker closed position when said movable contact means is in said operating position and for moving said movable contact to a circuit breaker open position when said latch means releases said movable contact means; said operating means including an operating member pretruding outward from said first compartment; said operating member being manually operable so that successive manual operations of said operating member will actuate said operating means to alternately open and close said circuit breaker; said ground fault detector including a portion connected to said circuit breaker to release said latch means when a ground fault is detected by said ground fault detector; said automatic trip means including a first electromagnet having a first armature and the portion of the ground fault detector including a second electromagnet having a second armature connected to said first armature for moving the latter to release said latch means when said second electromagnet is energized; said first and second armatures constituting different portions of a single armature member; said first and second electromagnets including a common stationary frame to which said armature member is mounted; said first and second electromagnets including respective first and second operating coils mounted to said stationary frame and arranged so that aiding fluxes are generated in said frame by current flow in said operating coils.

7. A device as set forth in claim 6 in which there is an adjustable permanent magnet means positioned to generate flux in said core to aid those fluxes generated by currents flowing in said operating coils and thereby control sensitivity.