US3412349A - Current-limiting electric circuit breaker - Google Patents

Description

CURRENT-LIMITING ELECTRIC CIRCUIT BREAKER Filed NOV. 25, 1966 Nov. 19, 1968 R. w. LAUBENHEIMER 2 SheetsSheet l HTTDRNEY R. w. LAUBENHEIMER 3,412,349 CURRENT-LIMITING ELECTRIC CIRCUIT BREAKER Nov. 19,1968

2 Sheets-Sheet 2 Filed Nov 25, 1966 m \m mN A T7'0/ENE V United States "Patent 3,412,349 CURRENT-LIMITING ELECTRIC CIRCUIT BREAKER Robert W. Laubenheimer, Farmington, Conn., assignor to General Electric Company, a corporation of New York Filed Nov. 25, 1966, Ser. No. 597,119 4 Claims. (Cl. 335-9) ABSTRACT OF THE DISCLOSURE An electric circuit breaker including separable contacts and manually and automatically operable operating mechanism, the mechanism being connected to the contacts by means of an insulating member having oppositely directed threaded portions inter-engaging corresponding tubular portions of the mechanism and contact members respectively, to provide an adjustable mechanical connection between the mechanism and the contacts and also to electrically isolate the operating mechanism from the movable contacts. In another form, the insulating interconnection is non-adjustable, but also includes lostmotion means and compression spring means for which the insulating member acts as a stop, to provide contact pressure.

My invention relates to multi-pole electric circuit breakers and more particularly to multi-pole circuit breakers of the current-limiting type.

A multi-pole current-limiting electric circuit breaker is disclosed in application Ser. No. 596,637 filed Nov. 23, 1966, now Patent 3,384,845, May 21, 1968 by I. F. Johnson and R. W. Laubenheimer and assigned to the same assignee as the present invention. In accordance with the construction disclosed in the aforesaid application, a multi-pole circuit breaker is provided having means for controlling three separate electrical circuits, being provided with three line terminals, three load terminals and three electric current paths interconnecting these terminals respectively. Each of these current paths or poles includes the following components, disposed in the recited order: (a) contact and arc chute assembly, (b) high-speed opening solenoid, (c) manual and automatically openable operating mechanism, and ((1) overload and low short-circuit sensing trip unit.

Multi-pole circuit breakers, in accordance with the general prior art have included insulating barriers separating each pole chamber from the adjacent pole chambers, in order to prevent electrical flash-over or breakdown therebetween. The necessity for such insulation is particularly great in current-limiting type circuit breakers, since such circuit breakers, during the interruption develop arc voltages greatly in excess of the normal line voltage of the circuit breaker. Thus, for example, in a 600 volt circuit, the current-limiting circuit breaker as disclosed in the aforesaid application ordinarily develops arc voltages of over 1200 volts.

The use of insulating barriers between pole chambers to prevent electrical breakdowns is therefore not completely satisfactory in such current-limiting circuit breakers. Even in conventional circuit breakers, breakdowns occasionally occur by flash-over between poles. Thus for example it is not ordinarily possible to completely isolate each of the poles, since a multi-pole circuit breaker by its application requirements is required to operate all poles simultaneously. This necessity for simultaneous operation of the poles requires means interconnecting all of the pole chambers to cause automatic opening of all poles when one pole opens, such as a common contact cross-arm interconnecting the movable contact members of all three poles. In addition, it is necessary to provide means whereby an overload condition in any of the three poles can cause automatic opening. Since it is ordinarily more economical to provide only a single main operating mechanism, a common trip bar must be provided extending across all three poles to permit operation of a single latch member by any of the three poles. The necessity for these transversely extending interconnecting members, i.e., the contact cross-arm and common trip bar, makes it extremely diflicult to completely isolate the three poles of the circuit breaker.

The pole chamber insulation and isolation problems are, moreover, intensified in the current-limiting circuit breaker construction as shown in the aforementioned patent application by the physical structure involved. This is because each pole chamber of the three-pole circuit breaker is required to contain more operating mechanisms than would ordinarily be contained in a conventional or non-current-limiting type three-pole circuit breaker. Thus, as mentioned above, in a conventional three-pole circuit breaker, the operating mechanism is ordinarily positioned in the center pole and is used to operate all three poles of the breaker. Thus there is-no adjacent mechanism containing metallic parts which require shielding from the center pole mechanism.

In the current-limiting type circuit breaker referred to, however, in addition to the main operating mechanism which is contained in the center pole, additional mechanism or linkages comprising a defeatable or breakaway contact operating member connecting means, as will be more fully described hereinafter, is required for each of the outer poles. This means that there is additional metallic mechanism positioned relatively closely adjacent the main operating mechanism on either side, which requires electrical isolation therefrom.

It is an object of the present invention to provide a multi-pole type electric circuit breaker including a plurality of side-by-side pole chambers and a plurality of pairs of side-by-side relatively separable contact members and means whereby the relatively separable contact members are electrically insulated from the corresponding operating mechanisms, whereby the operating mechanism in each pole chamber are at the same potential, and are not at a potential substantially elevated above ground potential, thus obviating the need for electrical insulation or barriers between pole chambers in the mechanism area.

It is another object of the invention to provide a multipole electric circuit breaker of the type including a plurality of pairs of separable contact members and side-byside operating mechanism operably related to each of the pairs of movable contacts and a contact operating member interconnecting the operating mechanism and the relatively movable contacts which operating member includes at least a portion of insulating material thereby insulating the movable contacts from the mechanism.

It is another object of the invention to provide a multipole current-limiting type electric circuit breaker of the type including a plurality of pairs of contacts and a plurality of side-by-side contact operating mechanisms, and means interconnecting the contacts and the mechanisms respectively, said connecting means including two relatively movable portions and insulating means interconnecting the relatively movable portions, and electrically isolating the movable contacts from the operating mechanism, whereby the insulating member also serves to provide contact pressure adjustment.

In accordance with the invention in one form. an electric circuit breaker is provided of the type including a plurality of electrical poles disposed in side-by-side relation and including a plurality of pairs of relatively separable electrical contacts disposed in generally side-by-si de relation and a plurality of contact operating members also disposed in :side-by-side relation and means interconnecting the operating members to the movable contacts which means comprises a connecting member of insulating material.

In accordance with one form of the invention, the connecting member which is provided of insulating material engages two adjacent portions of the contact operating member with a threaded type engagement, whereby the insulating connecting member may be utilized to provide contact pressure adjustment.

The invention will be more fully understood from the following detailed description, and its scope will be pointed out in the appended claims.

In the drawings,

FIGURE 1 is a perspective view of an electric circuit breaker incorporating the invention;

FIGURE 2 is a perspective view similar to FIGURE 1, the cover of the breaker being shown in exploded relation and partly :broken away;

FIGURE 3 is a side elevation view of the circuit breaker of FIGURE 1, the enclosing casing being shown in section;

FIGURE 4 is a schematic representation of the circuit breaker of FIGURE 1, showing particularly the electrical current paths therethrough;

FIGURE 5 is a detail view of one of the contact operating rod assemblies partly in section of the circuit breaker of FIGURE 1, and

FIGURE 6 is a view similar to FIGURE 5, showing a modified form of contact arm construction.

Referring to the figures, the invention is shown as inconporated in an electric circuit breaker including a generally U-shaped cross-sectioned metallic sheet metal cover 10 and a generally planar back plate 11 of insulating material. Supported on the back plate 11 are a plurality of spaced insulating block support members comprising a load terminal support block 12, a mechanism and trip unit support block 13 including a trip unit support portion 13A, a stationary contact and arc chute support block 14, and a combination line terminal and supplementary are chute support block 15. The blocks 12-15 inclusive are fixedly mounted on the back plate 11 by suitable means, such as by means of screws, not shown.

The insulating block 12 serves to support a plurality of load terminals 16, there being one provided for each of the pole chambers of the circuit breeaker. The embodiment illustrated is a three-pole circuit breaker and therefore there are three sets of line and load terminals.

The main portion of the insulating block 13 serves to support 'a manual and automatic operating mechanism designated generally by the numeral 18 and having an insulating handle portion 19. The insulating block portion 13A serves to support a conventional trip unit 17 which will be described in more detail later. The insulating block 14 serves to support and position the 3-pole stationary contact and arc chute and mufile assembly designated generally by the numeral 20.

The insulating block 15 supports and positions a plurality of line terminals 21 and includes upstanding barrier portions comprising outside barrier portions 22 at each side of the circuit breaker and intermediate barrier portions 23.

The operating mechanism 18 may be of any suitable type adapted to perform the required functions, including (1) the manual opening and closing of the contacts, (2) the automatic opening of the contacts in response to mechanism release by the conventional trip unit 17, and (3) automatic opening of the contacts despite the nonrelease of the mechanism 18 upon the actuation of a highspeed tripping means such for example as the high-speed trip solenoid shown at 25. The solenoids 25 of each of the poles are separated from each other by insulating barrier plates 27, see FIGURE 2. A mechanism of the type described is disclosed and described in detail in copending application Serial No. 596,637 filed Nov. 23, 1966, now Patent 3,384,845, May 21, 1968 and assigned to the same assignee as the present invention. The operating mechanism 18 includes a central pole assembly 18A which provides the manually actuated means for controlling all three poles, and for automatically operating them on the occurrence of certain predetermined current conditions. In addition, means is provided including part of the mechanism 18A and the mechanisms 18B and 18C, for permitting high-speed opening independently of the main mechanism.

The trip unit 17 includes means for causing release of a latch normally holding the operating mechanism 18 in latched position, comprising inverse current-time sensing means such for example as a bimetallic strip, and magnetic sensing means such as a solenoid (not shown). A trip unit of the type described is disclosed for example in Patent No. 3,264,435, K. W. Klein et al., issued Aug. 2. 1966, and assigned to the same assignee as the present invention.

The outer enclosure 10 is preferably constructed of metallic material such, for example, as steel and includes an insulating coating 10A on all surfaces.

The cover member 10 also has an opening 10B in the top wall thereof which is partially closed by an insulating shield member 29 rigidly afiixed to the top wall of the cover by suitable means, such as by screws or rivets 30. If desired, other means of attaching the shield 29, may be utilized, such for example as chemical bonding. The shield 29 includes an aperture 31 of smaller size, through which the insulating handle 19 projects, the opening 31 being otherwise closed by the enlarged inner portion 19A of the handle 19. The insulating shield 29 also serves to support an identification plate 32 suitably attached thereto. The insulating plate includes a plurality of generally circular apertures 33 providing access to adjusting members 34 of the trip unit 17.

The various insulating blocks and the insulating shield 29 are preferably formed by molding, facilitating high production at relatively low cost. Since these parts are individually not of execessive dimension in any one direction, molding by conventional techniques is economically feasible.

The current path through one pole of the circuit breaker will be described with reference to FIGURES 3 and 4. The current enters at the line terminal 21, passes through the elongated conductor 21A passing underneath the arc chute and mufile assembly 20, to stationary contact 24A, thru bridging contact 24B to stationary contact 24C to terminal 25A; from the terminal 25A to the solenoid 25 and to a conductor strap 25B passing under the mechanism 18 to the trip unit terminal 17A. The current then passes through the thermal trip device 17B and the magnetic trip device 17C of the trip unit 17, to the load terminals 16. Upon the occurrence of predetermined current conditions, the current sensitive means 17B and/ or 17C within the trip unit 17 is actuated, causing release of the latched mechanism 18A and automatic opening of the circuit breaker contacts. Likewise the occurrence of excessive current conditions causes actuation of any of the solenoids 25 before the conventional trip unit 17 can respond and opens the movable contacts independently of the corresponding mechanism 18A, 18B, 18C.

It will be observed by reference to the schematic diagram of FIGURE 4, that since the contact operating rods 42, 43, 44, are each at the potential of the corresponding movable contacts, this would ordinarily place the mechanisms 18A, 18B, 18C at the same potential as the movable contacts 24B. The contact cross-arm 18D which interconnects the main mechanism 18A with the outer poles 18B, and 18C would accordingly have to be provided with insulation to prevent short-circuiting between poles. Thus in accordance with prior art circuit breaker construction, such cross-arms have ordinarily been constructed of insulating material or have been coated with insulating material.

In addition, even if the contact cross-arm 18D is insulated so as to electrically separate the center pole mechanism 18A from the outer pole mechanisms, the outer pole mechanisms 18B and 18C would each nevertheless be at a different electrical potential from the mechanism of the center pole 18A. Thus insulating barriers would be required between the mechanisms 18A- 18B and ISA-18C. Moreover, precautions would have to be taken to guard against strikeovers from any one of the mechanisms to the metallic enclosing casing. Such electrical insulation and clearance problems are particularly severe in current-limiting type circuit breakers because of the high'voltages which are generated during the interruption process.

In accordance with the present invention however, a construction is provided which places these mechanisms all substantially at the same potential and eliminates not only the need for barriers between the mechanism sections, but in'fact there also eliminates the need for insulating the cross-arm 18D from each of the mechanisms in each of the poles. The construction by means of which this is accomplished is illustrated particularly in FIGURES 5 and 6.

As shown in FIGURE 5, a movable contact rod assembly is provided including a metallic rod portion 43 having a solenoid armature member 45 afiixed to the outer end thereof. The movable contact member 24B is supported by a rod section 46 which is connected by a lost motion pin and slot connection including pin 47 carried by the rod 46 and a slot (not shown) in the tube 43. A compression spring 48 is positioned between the end of the rod 46 and a stop pin 49 carried by the rod 43. The rod 43 extends in slidable manner through a stationary magnetic core piece 50 having a flange 51 by which it is trapped and retained in place between the insulating block portion 13 and portion 13B which are held together by screws 13D.

An insulating connecting member 52 is provided comprising an enlarged central portion 53 and oppositely directed threaded stern portions 54 and 55 respectively. The stem portion 54 is threadedly engaged in the tube 43, while the threaded stem portion 55 is threadedly engaged in one end of metallic connecting link 56, which carries a bifurcated portion 57 at its free end for connection '00 the operating mechanism.

The solenoid winding 25 surrounds the magnetic core 50 and at least a portion of the magnetic armature 45, and when energized draws these two members together, drawing the movable contact to the right as viewed in FIGURE 3, to open position.

It will be observed that because of the insulating connector member 52, the right hand portion of the assembly shown in FIGURE 5 is electrically insulated from the left hand portion, and from the movable contact 24. Because of this construction, each of the mechanisms 18A, 18B, and 180 is electrically isolated and there is no need for extra insulating barriers, etc.

In accordance with a modified form of the invention shown in FIGURE 6, an elongated insulating tube 60 is provided, carrying the movable contact stem 46 at one end thereof connected thereto by pin 47. In this form, the contact pressure spring 48 is positioned between a stop pin 49 carried by the tube 60 and the end of the connecting link 56 which is connected to the tube 60 by a lost motion pin and slot connection comprising the pin 61 carried by the member 56 and slot 62 in the tube 60.

While the invention has been described in only two specific embodiments, it will be readily apparent that many modifications thereof may be made without departing from the spirit and scope of the invention. It is therefore intended by the appended claims to cover all such modifications as fall within the true spirit and scope of the invention.

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

1. A multi-pole electric circuit breaker comprising:

(a) a support;

(b) at least two pairs of relatively separable contacts supported on said support in side-by-side relation;

(0) operating mechanism supported on said support;

(d) means interconnecting said operating mechanism to said relatively separable contacts to move said separable contacts between open and closed circuit positions in response to movement of said operating mechanism between open and closed circuit conditions;

(e) current responsive means supported on said support for each of said pairs of relatively separable contacts, means electrically connecting said current responsive means each in series with one of said pairs of relatively separable contacts;

(f) said operating mechanism including latch means operated by each of said current responsive means to cause automatic opening of said mechanism in response to predetermined current conditions in each of said poles of said circuit breaker;

(g) said interconnecting means comprising a tubular member having one of said contacts attached to one end thereof and having a first stop member spaced inwardly from the other end thereof;

(h) an insulating member having a first end portion connected to said operating mechanism and having a second cylindrically shaped end portion extending into said other end of said tubular member and connected to said tubular member by lost-motion connecting means, and

(i) a compression spring within said tubular member between said first stop member and said end of said tubular portion of said insulating member, whereby force in contact closing direction is exerted by said operating member on said contact member through the agency of said compression spring.

2. A multi-pole electric circuit breaker comprising:

(a) a support;

(b) at least two pairs of relatively separable contacts supported on said support in side-by-side relation; (0) operating mechanism supported on said support; ((1) means interconnecting said operating mechanism to said relatively separable contacts to move said separable contacts between open and closed circuit positions in response to movement of said operating mechanism between open and closed circuit conditions;

(e) current responsive means supported on said support for each of said pairs of relatively separable contacts, means electrically connecting said current responsive means each in series with one of said pairs of relatively separable contacts;

(f) said operating mechanism including latch means operated by each of said current responsive means to cause automatic opening of said mechanism in response to predetermined current conditions in each of said poles of said circuit breaker;

(g) said interconnecting means including means electrically insulating said separable contacts from said operating mechanism;

(h) each of said connecting means comprising a tubular member connected to one of said relatively separable contacts and a second tubular member connected to said operating mechanism and an elongated interconnecting member of insulating material having the opposite ends thereof threaded and threadedly received in corresponding end portions of said tubular members to mechanically connect said movable contact to said operating mechanism while electrically isolating said movable contact from said operating mechanism and providing means for adjusting the positioning of said movable contact with respect to said operating mechanism.

3. A multi-pole electric circuit breaker comprising:

(a) a support;

(b) at least two pairs of relatively separable contacts supported on said support in side-by-side relation;

(c) operating mechanism supported on said support;

(d) means interconnecting said operating mechanism to said relatively separable contacts to move said separable contacts between open and closed circuit positions in response to movement of said operating mechanism between open and closed circuit conditions;

(e) current responsive means supported on said support for each of said pairs of relatively separable contacts, means electrically connecting said current responsive means each in series with one of said pairs of relatively separable contacts;

(f) said operating mechanism including latch means operated by each of said current responsive means to cause automatic opening of said mechanism in response to predetermined current conditions in each of said poles of said circuit breaker;

(g) said interconnecting means including means electrically insulating said separable contacts from said operating mechanism;

(h) each of said pairs of relatively movable contacts comprising a reciprocally movable contact movable along a straight-line path between open and closed circuit positions;

(i) a plurality of elongated contact operating members each attached to one of said movable contacts;

(j) a plurality of magnetic armatures each attached to one of said elongated contact operating members;

(k) a plurality of stationary magnetic field pieces each fixedly mounted on said support in juxaposed spaced relation to one one of said magnetic armatures, said elongated contact operating members each extending through the corresponding magnetic armature and through the corresponding magnetic field piece and terminating in a generally tubular internally threaded end portion;

(1) said operating means including a plurality of contact operating link members each having a generally tubular internally threaded portion disposed in alignment with said internally threaded portion of a corresponding one of said contact operating members, and

(m) a plurality of elongated insulating members each having a first portion in threaded engagement with said threaded portion of one of said contact operating members and a second portion in threaded engagement with said threaded portion of one of said operating links.

4. An electric circuit breaker as set forth in claim 3, wherein each of said elongated insulating members also includes an enlarged intermediate portion manually accessible for rotation and wherein said threaded portions of said contact operating members and said insulating members are threaded in opposite sense whereby rotation of said interconnecting member serves to move said contact operating members and said insulating members in opposite directions.

References Cited UNITED STATES PATENTS 2,844,689 7/ 1958 Middendorf 200-1 16 3,012,118 12/1961 Edmunds 200-116 3,043,934 7/ 1962 Bodenschatz 200-416 BERNARD A. GILHEANY, Primary Examiner.

H. BROOME, Assistant Examiner.

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