F0RM2
THE PATENTS ACT, 1970
(39 of 1970)
&
The Patents Rules, 2003
COMPLETE SPECIFICATION
(See section 10; rule 13)
l. Title of the invention. - LINEAR REPULSION TYPE CONTACT SYSTEM
2. Applicant
(a) NAME : LARSEN & TOUBRO LIMITED
(b) NATIONALITY : An Indian company
(c) ADDRESS : L& T House, Ballard Estate, Mumbai 400 001,
State of Maharashtra, India
3.PREAMBLE TO THE DESCRIPTION
The following specification particularly describes the invention and the manner in which it is to be performed:

FIELD OF THE INVENTION
The present invention generally relates to the field of circuit breaking devices. More particularly the invention relates to an improved contact arrangement for circuit breakers. It provides a linear repulsion type contact system to provide enhanced arcing performance in circuit breakers.
BACKGROUND AND THE PRIOR ART
Circuit breaker is a device employed to protect the equipments in an installation in case of over currents rising out of fault conditions. An electric circuit breaker contact system is provided including at least one stationary contact member and at least one movable contact member and biasing means between the movable contact member and a normally stationary support member to provide contact closing pressure during normal condition. It is also required to interrupt the fault current rapidly in one or more circuit's paths upon the occurrence of an over current in any one circuit path so as to minimize damage to the installation resulting from thermal and mechanical stresses.
In order to minimize damage to the downstream devices, circuit breakers are intended to be fast acting. While conventional circuit breakers have a rotary motion of the moving contacts, a linear movement in the construction proposed by US3483343 has several benefits like arc transferring to the runners from the contact buttons, thereby reducing the contact erosion. However, separation of the contacts is driven by a solenoid which has an inherent delay. The present invention separates the contact due the interaction of magnetic forces due to the special current path configuration. The same is derived by means of contact geometry of the set of contacts.

Some of the prior art in the field of invention are as follows:
US3483343 have two extended limbs attached to the fixed contacts in a direction which aids the arc movement during short-circuit conditions. The present invention however, has a relative simpler shape of the fixed contact and the arc quenching is made effective by virtue of quick separation of the moving contact under high fault currents. In this invention, a mechanism drives the moving contact which results in an inherent delay in mechanism actuation.
US4276526 pertain to an MCB which is supposed to be fast acting. It has been achieved using a solenoid. However in case of present invention, the contact separation is due to the electromagnetic forces between the two set of contacts.
USRE35507 pertain to a repulsion type circuit breaker movable contact device comprising a first movable contact, an opening/closing mechanism which drives the first movable contact for opening and closing, a second movable contact for contacting the first movable contact, the second movable contact being freely pivotable and adapted to receive an electromagnetic repulsion force from said first movable contact, and a contact spring comprising a twisted coil spring disposed with its twisting fulcrum displaced from the rotational pivot of the second movable contact, the contact spring urging the second movable contact into contact with the first movable contact, whereby upon flow of a predetermined mount of electric current through the first and second movable contacts, the electromagnetic repulsion force moves the second movable contact apart from the first movable contact.
US2010170875 provides a circuit breaker that includes a conductor, a fixed contact connected to the conductor, and an arc runner disposed on the conductor adjacent the fixed contact. The arc runner includes a first portion

abutting the fixed contact and a second portion disposed in a recess of the circuit breaker housing. The arc runner is adapted to draw an arc from the fixed contact. A circuit breaker operating mechanism cooperates with a movable contact for opening and closing the fixed contact and the movable contact. An arc chute is adjacent the arc runner. A trip unit cooperates with the operating mechanism to trip open the fixed and movable contacts.
US2005279734 provides a circuit breaker that includes a line terminal conductor, a fixed contact electrically and mechanically connected to the line terminal conductor, and an arc runner disposed on the line terminal conductor adjacent the fixed contact. The arc runner includes a first flat portion abutting a flat portion of the fixed contact, a second elongated and rounded portion adapted to draw an arc from the fixed contact, and a pair of legs clinching the conductor. A circuit breaker operating mechanism cooperates with a movable contact for opening and closing the fixed contact and the movable contact. An arc chute is adjacent the second elongated and rounded portion of the arc runner. A trip unit cooperates with the operating mechanism to trip open the fixed and movable contacts.
In the prior arts, the runner is disposed on to the conductor which is attached to the fixed contact. The present invention provides an improved contact arrangement for circuit breakers. It provides a linear repulsion type contact system to provide enhanced arcing performance in circuit breakers. In the present invention the fixed runners can be fixed to the contact either by two screws or by brazing, which gives a better electrical and mechanical joint. Use of two screws for fixing, allows using of fastening means on either side of arc running path. This avoids stalling of arc on the screw slot and ensuring a smooth arc running.

OBJECT OF THE INVENTION
A prime object of the invention is to overcome the drawbacks / disadvantages of the prior art.
Another object of the invention is to enable fast opening of contacts during short-circuiting for linear type of contact system.
Another object of the present invention is to provide the geometry of runners that enables quick transfer of the arc from between the fixed and moving buttons to the fixed runners resulting in faster arc quenching.
Yet another object of the invention is to eliminate the use of external mechanism for opening of the contacts.
SUMMARY OF THE INVENTION
The following presents a simplified summary of the invention in order to provide a basic understanding of some aspects of the invention. This summary is not an extensive overview of the present invention. It is not intended to identify the key/critical elements of the invention or to delineate the scope of the invention. Its sole purpose is to present some concept of the invention in a simplified form as a prelude to a more detailed description of the invention presented later.
In accordance with a present embodiment of the invention there is provided a contact arrangement of circuit breakers to achieve linear opening to improve the durability of contact system and to provide enhanced arcing performance.

In accordance with another embodiment, the invention provides a fixed contact assembly and moving contact assembly comprising moving contact link and moving contact arm.
In accordance with another embodiment, the invention provides flow of current from fixed contacts to fixed contact button, to moving contact button, to moving contact link to moving contact arm and flows out in a similar sequence through other fixed contact.
In accordance with another embodiment, the invention provides, in vicinity of contact buttons the current in corresponding limb of fixed and moving contact are opposite resulting in repulsive force.
In accordance with another embodiment of the invention there is provided each half of moving contact link is attached to a moving contact arm.
In accordance with another embodiment, the invention provides the current in moving contact arm and corresponding fixed contact are in same direction resulting in attractive force.
In accordance with another embodiment, the invention provides Semi-circular slots on the corners of moving contact link, which result in redistribution of current density thereby enhancing the repulsive force between the said pair of contacts.
In accordance with another embodiment, the invention provides the difference in the widths of the moving contact arm and moving contact link of the moving contact helps in increasing the repulsive force and reducing the attractive force between the said pair of contacts. By varying the said widths, the current at which the contacts begin to separate can be tuned.

Other aspects, advantages, and salient features of the invention will become apparent to those skilled in the art from the following detailed description, which, taken in conjunction with the annexed drawings, discloses exemplary embodiments of the invention.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
The following drawings are illustrative of particular examples for enabling methods of the present invention, are descriptive of some of the methods, and are not intended to limit the scope of the invention. The drawings are not to scale (unless so stated) and are intended for use in conjunction with the explanations in the following detailed description.
Fig. 1 shows the Side view of the moving contact arrangement along with the fixed contacts in OFF condition
Fig. 2 shows the Side view of the moving contact arrangement along with the fixed contacts in ON condition
Fig. 3 shows the Side view of the moving contact arrangement along with the fixed contacts in ON condition with current directions.
Fig. 4 shows the Side view of the moving contact arrangement with current directions
Fig. 5 shows Isometric view of the moving contact arrangement.
Fig. 6 shows the sectional view of the moving contact arrangement.
Fig. 7 Shows the Isometric view of the contacts arrangement along with fixed runners fastening screws.

Fig. 8 Shows the Side view of the contacts arrangement along with arc with two distinct arc positions.
Persons skilled in the art will appreciate that elements in the figures are illustrated for simplicity and clarity and may have not been drawn to scale. For example, the dimensions of some of the elements in the figure may be exaggerated relative to other elements to help to improve understanding of various exemplary embodiments of the present disclosure.
Throughout the drawings, it should be noted that like reference numbers are used to depict the same or similar elements, features, and structures.
DETAILED DESCRIPTION OF THE INVENTION
The following description with reference to the accompanying drawings is provided to assist in a comprehensive understanding of exemplary embodiments of the invention as defined by the claims and their equivalents. It includes various specific details to assist in that understanding but these are to be regarded as merely exemplary. Accordingly, those of ordinary skill in the art will recognize that various changes and modifications of the embodiments described herein can be made without departing from the scope and spirit of the invention. In addition, descriptions of well-known functions and constructions are omitted for clarity and conciseness.
The terms and words used in the following description and claims are not limited to the bibliographical meanings, but, are merely used by the inventor to enable a clear and consistent understanding of the invention. Accordingly, it should be apparent to those skilled in the art that the following description of exemplary embodiments of the present invention are provided for illustration

purpose only and not for the purpose of limiting the invention as defined by the appended claims and their equivalents.
It is to be understood that the singular forms "a," "an," and "the" include plural referents unless the context clearly dictates otherwise.
By the term "substantially" it is meant that the recited characteristic, parameter, or value need not be achieved exactly, but that deviations or variations, including for example, tolerances, measurement error, measurement accuracy limitations and other factors known to those of skill in the art, may occur in amounts that do not preclude the effect the characteristic was intended to provide.
Accordingly, in the present invention an improved contact arrangement for circuit breakers is provided.
Figures 2 and 3 show the details of Contact arrangement. The position with the fixed contact (1) and the moving contact assembly comprising Moving contact -link (7) and moving contact arm (6) shown corresponds to the contacts in ON state.
As shown in figure 3, the current flows from fixed contact to fixed contact button, to moving contact button, to moving contact-link to moving contact arm and flows out following a similar sequence through the other fixed contact. In the vicinity of the contact buttons, the current in the corresponding limb of the fixed contacts(1) and the moving contact -link (7) are in opposite direction which results in a net repulsive force between the two. Each half of moving contact-link (7) attached to a moving contact arm (6), having a shape as shown in the figure.
The relative direction of the currents in the above said arm and those in the corresponding fixed contact (1) arms are in same direction, which results in

attraction between them. To minimize this attractive force width of the moving contact arm (6) is reduced and a slot is created at the edge of the moving contact link (7) as shown in the figure.
Elements and Construction:
1: Fixed contact: It is current carrying element of the circuit which remains fixed during the operation.
2: Fixed Runner: It is connected to the fixed contact for efficient movement of the electric arc formed during fault condition in the circuit breaker.
3. Link Pin: It is connected the link to the moving contact.
4. Fixed Contact Button: It is the button on the fixed contact.
5: Moving Contact Button: It is the button on the moving contact
6: Moving Contact Arm: It is one of the current carrying part of the moving contact
7: Moving Contact Link: It is one of the current carrying part of the moving contact in which the direction of current is opposite to that of the fixed contact.
8: Link: It connects the mechanism with the moving contact.
9. Pivot Pin: It is the pivot pin of the moving contact. About this pin the
moving contact can rotate so as to make proper contact at both the contact
buttons.
10. Slider Pin: It is the slider pin of the moving contact. About this pin the moving contact will slide when the operating mechanism operates it.
11. Fixed runner fixing fasteners: These are Screws used to dispose fixed runner to the contact.

In case of linear opening of contacts during faults, in general the contacts are opened by an external mechanism. There is a delay in sensing and actuation which might cause the current to rise to significantly high values. There are other means, like opening by a solenoid coil; however that results in a bulky coil in order for it to withstand the short circuit forces.
In the present invention, the very geometry of the contacts enables the separation under high fault currents. The difference in the widths of the limbs (moving contact arm and moving contact link) of the moving contact helps in increasing the repulsive force and reducing the attractive force between the fixed and moving contact. The width of the moving contact link is greater than that of moving contact arm in the present embodiment. However, alternatively moving contact arm can have a greater width than the moving contact link and still increased repulsive force can be obtained. By varying the said widths, the current at which the contacts begin to separate can be tuned hence the invention allows adjustment of the opening current as per the need of the application where the circuit-breaker is installed.
In the present invention, fixed runners are disposed on to the fixed contact either by fastening through two screws or by brazing. This gives a better electrical and mechanical joint. Use of two screws for fixing, allows using of fastening means on either side of arc running path. This avoids stalling of arc on the screw slot and ensuring a smooth arc running. Orientation of the runners with respect to arc disposition creates additional magnetic blow-out on the arc. This helps in faster arc movement and effective elongation of arc, thereby quenching the arc efficiently.
Although the embodiments herein are described with various specific embodiments, it will be obvious for a person skilled in the art to practice the

embodiments herein with modifications. However, all such modifications are deemed to be within the scope of the claims.
It is also to be understood that the following claims are intended to cover all of the generic and specific features of the embodiments described herein and all the statements of the scope of the embodiments which as a matter of language might be said to fall there between.

WE CLAIM
1. An improved contact arrangement for circuit breakers, said arrangement comprising:
at least one fixed contact having a fixed contact button attached thereto;
at least one moving contact having a moving contact button attached thereto, said moving contact having a moving contact arm for carrying current and a moving contact link having current direction opposite to that of said fixed contact;
a fixed runner fastened to said fixed contact to facilitate movement of an arc formed during fault condition in the circuit breaker;
a link connected to said moving contact using a link pin;
wherein said moving contact arm having a width different from said moving contact link so as to increase repulsive force between said fixed contacts and said moving contacts;
wherein said runner attached to said fixed contact configured to facilitate separation of said fixed and moving contact and enabling transfer of arc between said fixed and moving buttons to said fixed runners thereby resulting in arc quenching.
wherein orientation of said runners with respect to arc disposition creates additional magnetic blow-out force on the arc thereby enabling substantial arc movement and elongation of the arc.

2. Arrangement as claimed in claim 1 wherein said moving contact link width is greater than said moving contact arm.
3. Arrangement as claimed in claims 1 and 2 wherein optionally said moving contact arm width is greater moving contact link.
4. Arrangement as claimed in claim 1 is a linear repulsion type contact system.
5. Arrangement as claimed in claim 1 wherein said fixed runner connected to said fixed contact optionally by means of brazing.
6. Arrangement as claimed in claim 1 and 2 wherein by varying said widths, the current at which the contacts begin to separate is tuned.
7. Arrangement as claimed in claim 1 wherein said moving contact link comprising a semi-circular slot providing for redistribution of current density that builds repulsive force between said pair of contacts.
8. Arrangement as claimed in claim 1 further comprising pivot pin means about which said moving contact rotate thereby making contact at said contact buttons.
9. Arrangement as claimed in claim 1 further comprising slider pin means about which said moving contact is slideable during operation.

10. An improved contact arrangement for circuit breakers as herein described and illustrated with reference to accompanying drawings.