FORM2
THE PATENTS ACT, 1970
(39 of 1970)
&
The Patents Rules, 2003
COMPLETE SPECIFICATION
(See section 10; rule 13)
1. Title of the Invention. - ENHANCED ARC RUNNER ARRANGEMENT FOR
MCCB
2. Applicant(s)
(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:

TECHNICAL FIELD OF THE INVENTION
This invention relates generally to a circuit breaker. More particularly the present invention relates to an improved arc runner arrangement for a circuit breaker providing low contact erosion.
BACKGROUND AND THE PRIOR ART
A circuit breaker is equipped with a current limiting arc runner for effective overcurrent interruption without additional heating under problematic operating conditions. Upon contact separation, an arc is drawn with the endpoints of the arc being initially rooted on the set of open contacts.
Some of the prior arts in the present field of invention are as follows:
KR20090020394 provides an air circuit breaker to reduce the number of component and the assembly time by reducing the screw clamping portion and to suppress the damage of the main contact by quickly moving the arc. The air circuit breaker comprises a fixed contact, an arc runner, a fixed protrusion and a fixed protrusion fixing unit. The fixed contact includes the main contact point and an arcing contact point. One end of the arc runner is arranged to be faced with the main contact. The other end of the arc runner end is extended to the arc extinguishing unit. The fixed protrusion is formed in one of the fixed contact and the arc runner. The fixed protrusion fixing unit is geared with the fixed protrusion and fixes the fixed protrusion. The fixed protrusion fixing unit is a calking part formed by calking the arc contact point.
KR100832329 provides an arc runner of an air circuit breaker is provided to maximize a breaking performance of the circuit breaker by promptly extinguishing an arc in an arc chamber. An arc runner of an air circuit breaker includes an arc discharge promotion member on one side to promote discharge of an arc induced into the arc runner to an arch chamber side. The arc discharge promotion member is an arc discharge promotion guide projected from a plate surface of the arc runner. The arc discharge promotion guide is not thicker than

the arc runner. An outer surface of the arc discharge promotion member is embossed with a plurality of projections.
JP2006059758 improve arc-extinguishing capacity of an arc-extinguishing device for a circuit breaker by changing a part of a conventional structure. In this arc-extinguishing device for the circuit breaker, an arc-extinguishing grid constructed with several grid plates is arranged in an opening moving passage of a movable contact making a pair with a fixed contact, and an arc runner extended from a contact member to the arc-extinguishing grid is provided in the fixed contact. An insulating material (resin) juxtaposed to the arc runner and receiving heat of the arc having moved from the fixed contact point la to the arc runner when a current is cut off for generating pyrolysis gas is provided near the arc runner for effectively functioning an arc cooling effect by the pyrolysis gas of the insulating material in addition to arc division effects by the arc-extinguishing grid. Thereby, arc voltage is quickly increased to improve arc-extinguishing performance.
JP2005216807 increase arc driving force after an arc commutates onto an arc runner, in a circuit breaker provided with the arc runner at the tip of a stationary contact. In this circuit breaker wherein an arc-extinguishing device provided with a plurality of grids having V-shaped notches while being laminated through gaps is disposed so as to face the stationary contact and a movable contact, and the arc runner to move an arc generated between the stationary contact and the movable contact toward the arc extinguishing device side is mounted on the stationary contact, an arc driving body formed of a U-shaped magnetic plate is provided, the arc driving body is combined with the arc runner from the back side through a gap, and the leg parts are up righted on the both sides of the arc runner. After the arc commutates to the arc runner, the magnetic flux of a current passing through the arc runner is gathered in the arc driving body, and powerfully drives the arc toward the arc extinguishing device.
In a typical conventional breaker, the arc runner is extended only from the fixed contact and the moving contact do not have any such arc runner in its vicinity. The end result is that, in convetional arrangement erosion is more in moving contacts compared to low erosion in the fixed contacts. Therefore there is a need to provide an arc runner assembly for an improved arc runner arrangement for a circuit breaker providing low contact erosion.

In the present invention, the arc runner is provided both in the fixed contact and moving contact zone. It ultimately leads to low erosion in both the contacts. Here, the runner in the moving contact zone is extended from the terminal of the braid and the one in fixed contact zone is made out of magnetic shield.
OBJECTS OF THE INVENTION
A basic object of the present invention is to overcome the disadvantages/drawbacks of the known art.
Another object of the present invention is to provide an improved arc runner arrangement for a circuit breaker providing low contact erosion.
Another object of the present invention is to provide an integrated runner cum magnetic shield that eliminates the additional component requirement.
These and other advantages of the present invention will become readily apparent from the following detailed description read in conjunction with the accompanying drawings.
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.
There is provided an enhanced arc runner arrangement for MCCB.

According to one embodiment of the present invention, there is provided an improved arc
runner arrangement for use in a circuit breaker, said arrangement comprising:
a moving contact means defining a moving contact zone, said moving contact having a braid
terminal;
a fixed contact means defining a fixed contact zone;
a magnetic shield located at the said fixed contact zone and extended towards a de-ion plate
stack provided in the said arrangement for arc quenching;
wherein said braid terminal comprising an extended portion and said magnetic shield along
with said extended portion forming said arc runner arrangement so that burning arc shifts its
root from the contact buttons to said runner arrangement thereby leading to low erosion in
said contact buttons.
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 I illustrates the arc runner, fixed contact and flexible conductor.
Fig 2 illustrates the arc position displacement in conventional breaker.
Fig 3 illustrates the magnetic shield.
Fig 4 illustrates the fixed contact.
Fig 5 illustrates the conventional circuit breaker arrangement.
Fig 6 illustrates the breaker arrangement as per the present invention.
Fig 7 illustrates the magnetic shield.

Fig 8 illustrates insulation wall between runner and moving contacts.
Fig 9 illustrates initial position of arc between the contact buttons.
Fig 10 illustrates the shifted arc from the contact buttons to the runner assembly.
DETAILED DESCRIPTION OF THE INVENTION
Accordingly in the present invention the enhanced arc runner and slot motor assembly for a low voltage molded case current limiting circuit breaker. In MCCB making and breaking of contact happens by the movement of a contact connected to the terminal by a flexible conductor. When moving contact is held against the fixed contact current flow is established. Current limiting property of the contact system is established by ensuring that current through U-type fixed and flexible contact forms a near opposite current flow path. This diametrically opposite current paths provide enough force between them during over current for opening moving contact and hence limit the over current by phenomena of arc quenching.
The different components shown in the figure along with their reference numerals are as follows: Arc runner (1); Fixed contact (2); Flexible conductor (3); Arc position (4); Magnetic shield (5); Extension from braid terminal (6); Insulation wall (7); Contact buttons (8).
The forces developed are primarily due to interaction of fluxes of the above said opposite current paths. Another dimension of flux interaction takes place between lower arm of fixed contact and its upper arm, which at large is unacceptable due to its negative role in the contact opening. Hence, a magnetic shield is used between the arms of the U-type fixed contact to prevent the interactions from taking place.
The buttons of the contacts, particularly fixed contact, have arc runners adjacent to it, whose role is to facilitate arc movement from button to runner. The present invention is of an enhanced runner assembly for moving contact seldom provided with arc runners. Once the moving contact reaches its final destination, the burning arc will shift its root from moving contact button to runner contact, which is the extended component of braid terminal. The said

root displacement is carried out by the magnetic and gas dynamic forces acting on the arc. This results in minimal erosion of moving contact buttons.
In the present invention an extended component of the braid terminal serves as the arc runner of the moving contact. Cassette construction is such that creates barrier between moving contact and arc runner. It acts as insulation wall between runner and moving contact. Also it provides a simple integrated magnetic shield and runner assembly, attached to the fixed contact by rivet less joints. Braid terminal serving purpose of arc runner in the moving contact zone.
By rendering the arc runner in this fashion, the life of the breaker improves since the lengthy dwell time of the arc on the buttons is subsided. Other feature of making integrated runner cum magnetic shield-eliminates the additional component requirement.
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 arc runner arrangement for use in a circuit breaker, said arrangement
comprising:
a moving contact means defining a moving contact zone, said moving contact having
a braid terminal;
a fixed contact means defining a fixed contact zone;
a magnetic shield located at the said fixed contact zone and extended towards a de-ion
plate stack provided in the said arrangement for arc quenching;
wherein said braid terminal comprising an extended portion and said magnetic shield
along with said extended portion forming said arc runner arrangement so that burning
arc shifts its root from the contact buttons to said runner arrangement thereby leading
to low erosion in said contact buttons.
2. Arrangement as claimed in claim 1 wherein said fixed contact housing said magnetic shield in its substantially U-bend.
3. Arrangement as claimed in claim 1 wherein said magnetic shield is integrated to the fixed contact preventing interaction between the arms of said fixed contact.
4. Arrangement as claimed in claim 1 wherein said arc runner being configured to facilitate arc root displacement by channelizing magnetic and gas dynamic forces towards the arc.
5. Arrangement as claimed in claim 1 further comprising a cassette means adapted to create barrier between said moving contact and said extension from a braid terminal at moving contact zone

6. An improved arc runner arrangement for a circuit breaker providing low contact erosion as herein described and illustrated with reference to accompanying drawings.