US3717792A - Leakage current interrupter device - Google Patents

Abstract

GROUND FAULT PROTECTIVE APPARATUS IS CONSTRUCTED AS A STACK OF THREE SIDE BY SIDE HOUSINGS, EACH HAVING SUBSTANTIALLY THE SAME OUTER DIMENSIONS AS A STANDARD 1" WIDE MOLDED CASE CIRCUIT BREAKER. ONE OF THE HOUSINGS CONTAINS A STANDARD CIRCUIT BREAKER MECHANISM INCLUDING THERMAL AND MAGNETIC TRIP MEANS, BUT DOES NOT CONTAIN AN EXTERNAL LINE TERMINAL. THE SECOND HOUSING CONTAINS STANDARD CIRCUIT BREAKER CONTACTS CONNECTED IN SERIES WITH THE CONTACTS OF THE CIRCUIT BREAKER IN THE FIRST HOUSING. ALSO IN THE SECOND HOUSING IS A CONTACT OPERATING MECHANISM AND ELECTROMAGNETIC MEANS FOR OPERATING THE MECHANISM IN RESPONSE TO A TRIGGER SIGNAL GENERATED BY A TRIGGER DEVICE IN THE THIRD HOUSING. THE OUTPUT OF A DIFFERENTIAL TRANSFORMER IN THE THIRD HOUSING IS MONITORED BY A SENSOR IN THE THIRD HOUSING AND WHEN A PREDETERMINED IMBALANCE IS PRESENT AT THE TRANSFORMERS THE SESOR CAUSES THE TRIGGER TO GENERATE A SIGNAL WHICH OPERATES THE ELECTROMAGNETIC TRIP MEANS IN THE SECOND HOUSING. THE THIRD HOUSING ALSO MOUNTS A PLUG-IN-TYPE LINE TERMINAL CONNECTED THROUGH ONE OF THE INPUTS OF THE DIFFERENTIAL TRANSFORMER TO THE SET OF CONTACTS IN THE SECOND HOUSING. THE OTHER INPUT CIRCUIT OF THE TRANSFORMER IS CONNECTED TO THE SECOND LOAD TERMINAL AND TO A NEUTRAL POINT EXTERNAL OF THE COMBINATION. THE SETS OF CIRCUIT BREAKER CONTACTS ARE TRIPPED OPEN INDEPENDENTLY OF EACH OTHER SO THAT OPENING OF ONE OF THE SETS OF CONTACTS DUE TO A LEAKAGE CURRENT PROBLEM WILL NOT REQUIRE TRIPPING OF THE OTHER SET OF CONTACTS, AND WEARING OF THE LATCH ASSOCIATED WITH THE LATTER.

D R A W I N G

Description

Feb. 20, 1973 c. E. GRYc'rKo 3,717,792

LEAKAGE CURRENT INTERBUPTER DEVICE Filed July 25, 1971 2 sheetsl's'ieet 1 Feb. 20, 1973 0.1:. GRYCTKO 3,717,792

LEAKAGE CURRENT ITERBUPTER DEVICE Filed July 23, 1971 2 sheetssheet 2 United States Patent Office 3,717,792 Patented Feb., 20, 1973 3,717,792 LEAKAGE CURRENT INTERRUPTER DEVICE Carl E. Gryctko, Haddon Heights, NJ., assignor to I-T-E Imperial Corporation, Philadelphia, Pa. Filed July 23, 1971, Ser. No. 165,678 Int. Cl. H02h 3/28 U.S. Cl. 317-18 D 3 Claims ABSTRACT F THE DISCLOSURE Ground fault protective apparatus is constructed as a stack of three side by side housings, each having substantially the same outer dimensions as a standard 1" wide molded case circuit breaker. One of the housings contains a standard circuit breaker mechanism including thermal and magnetic trip means, but does not contain an external line terminal. The second housing contains standard circuit breaker contacts connected in series with the contacts of the circuit breaker in the first housing. Also in the second housing is a contact operating mechanism and electromagnetic means for operating the mechanism in response to a trigger signal generated by a trigger device in the third housing. The output of a differential transformer in the third housing is monitored by a sensor in the third housing and when a predetermined imbalance is present at the transformers the sensor causes the trigger to generate a signal which operates the electromagnetic trip means in the second housing.

The third housing also mounts a plug-in type line terminal connected through one of the inputs of the diierential transformer to the set of contacts in the second housing. The other input circuit of the transformer is connected to the second load terminal and to a neutral point external of the combination. The sets of circuit breaker contacts are tripped open independently of each other, so that opening of one of the sets of contacts due to a leakage current problem will not require tripping of the other set of contacts, and wearing of the latch associated with the latter.

This invention relates to ground fault protective devices and more particularly relates to a device of this type which may readily be mounted in a standard panelboard.

Recently, it has become more apparent that serious damage may result from even very low values of so-called leakage or ground fault currents. The instant invention provides a modular construction tor a ground fault interrupter. This interrupter includes three units, each substantially the size of a single pole standard 1" wide molded case circuit breaker, so that a stack of these units may readily be mounted in existing panelboards.

Two of these units are essentially circuit breakers of equal current carrying ratings having their contacts connected in series. The first unit is provided with thermal and magnetic trip means for tripping under fault conditions in the load circuit, and the second unit is adapted to be tripped automatically upon an indication from the third unit that leakage current has reached a predetermined level. The trip and operating mechanisms of the rst and second units operating independently of one another so that separation of the contacts in the second unit, indicating excessive leakage current, will not bring about tripping of the rst unit, thereby saving Wear and tear on the relatively delicate cooperating latch surfaces of the first unit. In addition, the first and second units are provided with independent handles, each movable to a trip position when its respective unit is tripped rather than to the oil position assumed when manually operated to open position. This indicates whether tripping is due to a fault in the load circuit or to excessive leakage current.

Accordingly, a primary object of the instant invention is to provide a novel construction for a combination load and leakage current interrupter.

Another object is to provide an interrupter of this type that is adapted to be mounted in existing panelboards.

Still another object is to provide an interrupter of this type in which the unit for detecting faults in the load circuit does not trip when the leakage current interrupter unit is tripped.

A further object is to provide an interrupter of this type having means to indicate whether tripping is caused by excessive leakage current or fault conditions in the load circuit.

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 an end View of interrupter apparatus constructed in accordance with teachings of the instant invention.

FIGS. 2 and 3 are cross-sections taken through lines 2-2 and 3-3 respectively of FIG. l.

FIG. 4 is a schematic showing the electrical elements of the apparatus of FIG. l connected to energize a load circuit and detect leakage currents.

Now referring to the gures. Interrupter apparatus 10 consits of three units 11, 12, 13, each having a molded insulating housing of substantially the same size as the l wide single pole circuit breaker illustrated in ULS. Pat.`

ble braid 21 bimetal 22 iluexible braid 23,. movable con- I tact arm 24, movable contact 18, to stationary contact 17 and then out the side of interruptor housing 27 through lead 28 (FIG. 4).

In a manner well known to the art, movable contact 18 is operated into and out of engagement with stationary contact by an operating mechanism including spring 31 connected at its lower end to a mid-point of contact arm l24. The upper end of spring 31 is connected to a midpoint of releasable Cradle 32 so as to bias the upper end of contact arm 24 into engagement with suitable formations of pivotable operating member 33, Whose upper extension 34 constitutes a manual operating member. Cradle 32 is pivoted at one end to housing protrusion 36, and at the other end is provided with latch tip 37 engageable by latch 38 mounted to bimetal 22 just above magnet armature 39. The latter is attracted to the right to stationary yoke 41 when current through bimetal 22 exceeds predetermined limits. The operating mechanism for contact arm 24 is so constructed that manual operation of handle 34 between its extreme positions indicated in FIG. 2 as On and Ott will operate contact 18 into and out of engagement with contact 17 when cradle tip 37 is in the latched position shown in FIG. 2. When cradle tip 37 is released by latch 38, either through deflection or bodily movement of bimetal 22, the operating mechanism separates contact 17, 18 and moves handle 34 to the intermediate or Trip position indicated in FIG. 2.

The contacts and contact operating mechanisms of units 11 and 12 are identical. However, the terminal 22 and magnetic 39, 41 trip devices of unit 11 are replaced by magnetic shunt trip device 46 in unit 12. Trip device 46 includes multi-turn coil 47 having one end thereof connected externally of housing 48 through the side thereof by lead 49. The other end of coil 47 is connected through braid 51 to movable contact arm 52 with the latter being connected by conductor 2-8 to stationary contact 17 of unit 11. When sufficient current flows through coil 47, armature 53 is moved to the right with respect to FIG. 3 with extension 55 thereof engaging the lower end of pivoted member 56 to bodily move the latter, thereby moving latch 57 to the right to free latch tip 58 of cradle 59 and permit operating spring -65'to separate movable contact 62 from stationary contact 61 and to operate handle 54 to its intermediate or trip position.

Disposed Within housing 66 of unit 13 is differential transformer 67 which, as will be hereinafter seen, is used to monitor load current. Transformer 67 includes input windings 68 and 69, and output winding 71 all wound about toroidal core 70. One end of input Winding is connected through the sides of housings 48 and 66 by means of lead 72 to stationary contact 61. The other end of input winding -68 is connected to female-type plug-in terminal 73, intended to engage a line voltage connected stab of a `panelboard.

One end of the other input winding 69 is connected to load terminal 74, and the other end of winding 69 is connected externally of housing 66 to neutral bar 75 by means of lead 76. The ends of output winding 71 are connected to the input of solid state sensor 81, whose output is connected through lead 82 to the input of trigger device 183. Elements 81, 83 are both connected to lead 76 by lead `84, and the output of trigger 83 is connected to tripping coil 4'/ by lead 49.

In FIG. 4 the load current path consists of neutral Ibar 75, conductor 76, input winding 69, load terminal 74, load y85, load terminal 19, the current path through unit 11 including separable cooperating contacts 17, 18, lead 28, contact arm 52, separable cooperating contacts 61, 62, lead 72, input winding 68 and line terminal 73 which is connected to source 86. Under normal conditions, equal currents flow in input coils 68, 69 of differential transformer 67. However, when ground fault or leakage current is present, the currents in input coils 68, 69 are unequal so that the net ux in core 70 rises above the zero level and causes a signal to be induced in output coil 71. The signal is detected by sensor 81.

When `the signal induced in output winding 71 is of sufficient magnitude, sensor 81 generates a signal of suicient magnitude so that trigger 83 produces an output which energizes shunt Winding 47, causing the contacts of unit 12 to separate, thereby interrupting the load circuit. At this time handle 54 assumes its intermediate or Trip position, but handle 34 remains in the On position. This provides a visual indication that tripping has resulted from excessive leakage current. Under these circumstances, there is no need to trip unit 11 and cause wear of its latch 38.

When tripping is caused by excessive currents in the load circuit, either magnetic 39, 41 or thermal 22 trip means will cause automatic operation of unit 11 to separate contact 17, 18 and operate handle 34 to its intermediate or Trip position, while handle 54 of unit 12 remains in its On position, thereby providing a visual indication that tripping has been caused by a fault in the load circuit rather than by excessive leakage current.

While tie means 91 has been illustrated as interconnecting handles 34 and 54, it is noted that apparatus 10` will function in its intended manner, even without this handle connection. Handle tie 91 is of the type illustrated in U.S. Pat. No. 3,040,140, issued June 19, 1962 to O. Nimylowycz for a Handle Tie. Another suitable haudle tie is illustrated in the W. H. Edmunds |U.S. Pat. No; 2,773,949 issued Dec. 11, 1956 for a Circuit Breaker Tie Bar.

Although in the foregoing this invention has been described in conjunction with preferred embodiments, many variations and modifications will now become apparent to those skilled in the' art, and it is therefore preferred that this invention not be limited by the foregoing disclosure but only by the appending claims.

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

1. Load and leakage current protective apparatus including a first interrupter means, a second interrupter means, and leakage current responsive means; said first interrupter means including a first set of cooperating contacts, a first operating mechanism for opening and closing said first set'of contacts, and first means for tripping said first operatingmechanism to automatically open said first set of cooperating contacts when overload fault conditions exist in a load circuit being protected by said apparatus; said second interrupter means including a second set of cooperating contacts connected in said load circuit in electrical series with said first set of contacts whereby opening either said first or said second set of contacts is effective to deenergize said load circuit, a second operating mechanism for opening and closing said second set of contacts, and second means for tripping said second operating mechanism to automatically open said second set of contacts; said leakage current responsive means including third means for monitoring said leakage current; fourth means fed by said third means for sensing when said leakage current reaches a predetermined level and generating a signal which actuates said second means to trip said second operating mechanism when said leakage current reaches said predetermined level; said first operating mechanism being isolated from said second interrupter means whereby said first set of contacts remains closed during automatic opening of said second set of contacts; said first `and second interrupter means being provided with respective first and second trip indicator means movable independently of each other to trip indicating positions to indicate whether tripping resulted from overload fault conditions in said load circuit or excessive leakage current.

2. Protective apparatus as set forth in claim 1 in which the first and second trip indicator means comprise respective rst and second manual operating handles for said first and second operating mechanisms respectively.

3. Protective apparatus as set forth in claim 2 in which said first interrupter means includes a first housing, said second interrupter means includes a second housing, and said leakage current responsive means includes a third housing; said housings stacked side by side and secured together in an assembly; each of said housings being of essentially the same overall dimensions; said first and second handles extending from the respective first and second housings; and tie means interconnecting said handles externally of said housings.

References Cited UNITED STATES PATENTS 3,525,903 8/ 1970 Morris et al. 317-18 D 3,256,407 6/1966 Klein 335-173 3,436,695 4/ 1969 Dessert 335-13 X 3,369,202 2/ 1968 Gryctko 335-9 3,426,301 2/ 1969 Bodge 335-8 3,611,038 10/1971 Benham 317-18 D JAMES D. TRAMMELL, Primary Examiner U.S. Cl. X.R.

Images