FORM 2
THE PATENTS ACT, 1970 (39 of 1970)
&
THE PATENTS RULES, 2003
COMPLETE SPECIFICATION
[See section 10, Rule 13]
ARC RUNNER ASSEMBLY FOR MCCB;
LARSEN & TOUBRO LIMITED, A COMPANY INCORPORATED UNDER THE COMPANIES ACT, 1956, WHOSE ADDRESS IS L&T HOUSE, BALLARD ESTATE, MUMBAI - 400 001, MAHARASHTRA, INDIA
THE FOLLOWING SPECIFICATION
PARTICULARLY DESCRIBES THE INVENTION AND THE MANNER IN WHICH IT IS TO BE PERFORMED.

FIELD OF INVENTION
The present invention relates to circuit breakers and more particularly to arc chute structures for molded case circuit breakers.
BACKGROUND OF INVENTION
In an MCCB, the making and breaking of contacts happens by the movement of a moving contact connected to a first terminal by a flexible conductor. The fixed contact is connected to a second terminal. When moving contact is pressed against the fixed contact, current flow is established.
Current limiting property of the contact system may be established by ensuring that current through the fixed and moving contacts near the point of contact are in opposite directions. Thus opposite flow of current provides enough force during any fault for opening moving contact and hence limit the fault current.
Subsequent to this, an arc is formed which is quenched with the help of arc chutes. Actual contact between fixed and moving contact occurs through two silver buttons provided in the circuit breaker.
The making and breaking of current are through these buttons. During the initiation of the arc, arc root is on these silver buttons. To enhance the life of the button and hence the breaker, the arc root is pulled from button to an arc runner which is placed after the fixed contact button. Thus arc runner increases arc length and life of silver buttons.
Various arc runners are known in the art. One such arc runner is shown in Fig. 1 that is fixed to the stationary contact with the help of a screw. The screw restricts free movement of arc towards arc plates. This affects the performance and life of the circuit breaker.
Another arc runner is shown in Fig. 2 and as disclosed in US Patent-7830232. The said patented arc runner ensures easy assembly, however magnetic performance of the circuit breaker is not improved by the same.
A novel arc runner is therefore required and the same is disclosed as follows.

SUMMARY OF THE INVENTION
It is an object of the present invention to provide an arc runner assembly for a low voltage molded case current limiting circuit breaker that is easy to assemble and facilitates in improving the performance of the circuit breaker.
In one embodiment herein, the arc runner assembly comprises a runner element having a "C" shaped profile and a repulsive type fixed contact having reverse loop profile. The runner element is slide-fitted into the said fixed contact..
The inner curved surface of the C-shaped profile facilitates in interaction of magnetic flux lines in moving contact and fixed contact. This improves the magnetic performance of the circuit breaker and accelerates the opening of the circuit breaker under an arc.
During initiation of an arc, arc root is pulled by the runner element, thus facilitating in enhancing the life of the circuit breaker.
BRIEF DESCRIPTION OF THE DRAWINGS
Reference will be made to embodiments of the invention, examples of which may be illustrated in the accompanying figures. These figures are intended to be illustrative, not limiting. Although the invention is generally described in the context of these embodiments, it should be understood that it is not intended to limit the scope of the invention to these particular embodiments.
Fig. 1 is the prior art showing an arc runner
Fig. 2 is also a prior art showing an arc runner as disclosed in US Patent-7830232
Fig. 3 shows the arc runner element according to the present invention.
Fig. 4 shows a typical fixed contact for Cat-A MCCB with a silver button placed on it according to the present invention.
Fig. 5 shows the technique with which the arc runner element is assembled on the fixed contact according to the present invention.
Fig. 6 and Fig. 7 show the assembled arc runner according to the present invention.

DESCRIPTION OF THE INVENTION
Disclosed herein is an arc runner assembly for a low voltage molded case current limiting circuit breaker. The arc runner assembly comprises a runner element having a 'C-shaped profile and a repulsive type fixed contact having reverse loop profile. The said runner element can be slide-fitted into the said fixed contact.
Fig. 3 shows the arc runner element 300 according to the present invention. The runner element 300 has a 'C'-shaped profile that includes a top part 301 that acts as the arc runner and a bottom part 302 that act as a magnetic mass. The bottom part 302 is slide-fitted into the fixed contact. When inserted into the fixed contact, the inner curved surface of the C-shaped profile facilitates in interactions of magnetic flux lines in moving contact and fixed contact thereby improving the magnetic performance of the circuit breaker under an arc.
As mentioned above, the bottom part 302 of the runner element 300 allows placement of magnetic mass under the contact area of the circuit breaker. This enhances magnetic performance and also accelerates the opening of the circuit breaker under an arc.
It is known in the art that the actual contact between fixed and moving contact of the circuit breaker occurs through two silver buttons. The making and breaking of current are through these buttons. During initiation of an arc, arc root is present on these silver buttons.
Fig. 4 shows a typical fixed contact 401 for Cat-A MCCB with a silver button 402 placed on it. As per the present invention, the runner element 300 is slide-fitted into the said fixed contact 401 at a location located immediately after the button 402 provided on the fixed contact 401. To enhance the life of the button 402 and hence the breaker, the arc root is pulled from button 402 to the top part 301 {of the runner element) which is placed immediately after the fixed contact button 402. This increases arc length and life of silver buttons is enhanced.
Fig. 5 shows the technique with which the arc runner element 300 is assembled on the fixed contact 401 according to the present invention. The runner element 300 is placed on to the fixed contact 401 by slide fit. The 'C- shaped

runner element 300 is made by bending a metal sheet prepared by punching operation.
Fig. 6 and Fig. 7 show the arc runner assembly according to the present invention. The assembled arc runner allows placement of magnetic mass under the contact area. This facilitates in better interaction of magnetic flux lines in moving contact and fixed contact 401 thereby enhancing the magnetic performance and accelerating the opening of the circuit breaker.
Thus the present invention provides a simple arc runner assembly that eliminates the use of additional hardware or process for fixing (such as screwing, riveting, crimping etcetera). The improved design of the runner element facilitates in making simpler arc runner assembly, and in making it cost effective by eliminating the processes for fixing the same on the fixed contact. The design improves short-circuit performance by adding magnetic mass at a desired location.
While the foregoing is directed to embodiments of the present invention, other and further embodiments of the invention may be devised without departing from the basic scope thereof, and the scope thereof is determined by the claims that follow.

We Claim
1. An arc runner assembly for a circuit breaker comprising:
a runner element 300 having a 'C'-shaped profile;
a fixed contact 401 having reverse loop profile; wherein, the said runner element 300 is slide-fitted into the said fixed contact 401.
2. The arc runner assembly as in claim 1, wherein the runner element 300 is slide-fitted into the said fixed contact 401 at a location located immediately after a button 402 provided on the fixed contact 401.
3. The arc runner assembly as in claim 1, wherein the fixed contact 401 is a repulsive type fixed contact 401
4. The arc runner assembly as in claim 1, wherein the inner curved surface of the 'C'-shaped facilitates in interaction of magnetic flux lines in moving contact and fixed contact 401 thereby improving the magnetic performance of the circuit breaker under an arc.
5. The arc runner assembly as in claim 1, wherein upon initiation of an arc, the arc root is pulled by the runner element 300 thereby facilitating in enhancing the life of the circuit breaker.