FORM 2
THE PATENTS ACT, 1970 (39 of 1970)
&
THE PATENTS RULES, 2003
COMPLETE SPECIFICATION
[See section 10, Rule 13]
ARC CHUTE ASSEMBLY AND METHOD THEREOF;
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 THE INVENTION:
The present invention relates to switching device and preferably to an arc chute assembly for the switching devices. BACKGROUND OF THE INVENTION:
Switching devices like circuit breakers protect electrical circuits from damage by isolating the circuit, when there is an unusual current surge. However when a circuit breaker isolates an electrical circuit from this unusual surge, an uncontrolled arc may travel to the circuit breaker and damage it.
An arc basically is a discharge of electric current which results from the unusual surge crossing between contacts of a circuit breaker, when these contacts are opened to isolate the electric circuit. Arcs may vary in size and intensity depending on the amount of surge, and minimizing the arc is important as the arc can damage the contacts. Arc may further ionize gases inside the circuit breaker which could damage the circuit breaker casing. Arc can severely damage the circuit breaker and surrounding equipment. Hence a circuit breaker must not only isolate electrical circuit but also control and quench the arc.
As a result various arc control mechanisms like stretching arc, breaking arc into smaller pieces, blowing out arc, vacuum interrupter and arc chute are used in the art.
Generally circuit breakers employ an arc chute assembly to control and extinguish the arc. Arc chutes conventionally have arc dividers or arc plates in

the form of flat segments stacked one above the other preferably with an air gap between them. Configurations of these arc plates have majorly been varied to improve arc quenching. Though these arc plates in circuit breakers have improved arc quenching capabilities, there is still a need in the art for circuit breakers with improved performance at higher voltages and provide higher arc plate life without increasing the size or area occupied by arc plates. BRIEF DESCRIPTION OF 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.
Figure 1 shows perspective view of an arc chute assembly;
Figure 2 shows an arc plate according to the present invention;
Figure 3 shows another perspective view of an arc chute assembly;
Figure 4 illustrates how an arc achieves higher arc voltage using the arc chute assembly of the present invention. DETAILED DESCRIPTION OF THE INVENTION:
The invention described herein is explained using specific exemplary details for better understanding. However, the invention disclosed can be worked on by a person skilled in the art without the use of these specific details.

Hereinafter, the preferred embodiments of the present invention will be described in detail. For clear description of the present invention, known constructions and functions will be omitted.
The present invention provides a method and assembly for faster arc quenching in a switching device. Accordingly, the present invention provides an arc chute assembly which achieves higher arc length to achieve higher arc voltages which quenches the arc at a faster rate.
Generally switching devices comprise of a housing; contacts enclosed within the housing; operating mechanism to operate the contacts and an arc chute to attract an arc generated at the contacts.
Figure 1 shows a perspective view of an arc chute assembly (100) comprising of a plurality of arc plates/deion plates (10)(hereinafter referred to as arc plate) configured between two plates known as lining (20). This arc chute assembly is disposed in close proximity to the contacts of a circuit breaker (not shown) to attract an arc that may be generated at the contacts in response to an overload of short-circuit condition. Those skilled in the art will appreciate that the arrangement of the arc chute assembly in a circuit breaker is very well known in the art and hence is not discussed in detail.
As illustrated the arc plates (10) are incrementally configured in the arc chute i.e. length of each arc plate is different. The arc plates increase in length from a first arc plate (10a) to a last arc plate (10b) in the arc chute assembly (100). Thus the first arc plate (10a) is a shorter arc plate compared to the other arc plates, and the last arc plate (10b) is the longest arc plate. The

arc chute assembly (100) is adapted near the contacts of the circuit breaker so that the shorter arc plate is in close proximity to the contacts (not shown). This arrangement allows the gases in the contact zone to expand more than in conventional cases, where the arc plate heights are the same. Expansion of gases helps the arc move away from the contacts early, minimizing immobility time, and less erosion of contacts which enhances life of the switching device.
Further to arc pfates being incrementally configured in the arc chute assembly, each arc plate is differentially varied in a horizontal direction. The arc plates thus appear to have toothed or zigzag configuration at its lower end (2) as shown in Figure 2. Those skilled in the art will appreciate that the configuration of an arc plate is not limited to a zigzag configuration, and can also have an oval, toothed, rectangular configuration at its lower end (2).
Figure 3 shows another perspective view of the arc chute assembly as per a preferred embodiment of the present invention. The arc chute assembly comprises of a plurality of differentially varied arc plates of figure 2 which are incrementally configured in the assembly. The assembly helps in achieving higher arc lengths and higher arc voltage. Achieving higher arc voltage helps the arc to quench faster.
Figure 4 illustrates how an arc achieves higher arc voltage using the arc chute assembly of the present invention. From Figure 4 it is evident that arc length L2 entering the arc plate will always be greater than arc length L1. The arc length L1 is basically the distance between two arc plates and it would also be the arc length in a conventional arc chute assembly. The arc length are

taken from tip of one arc plate to another since there is a higher electric field concentration at tip of the arc plates.
The configuration of arc plates of the present invention thus achieves higher length arc as compared to conventional arc chute assembly where the arc plate length are not varied. The configuration facilitates faster and effective arc quenching as a high arc voltage is build up at an early stage. This arc voltage is of the order of phase voltage equivalent of the system voltage. So as the system voltage increases the corresponding arc voltage also increases. The present invention thus achieves effective arc quenching.
The present invention advantageously quenches the arc faster by achieving higher arc voltages without any increase in space. The invention also ensures less erosion of contacts, enhancing life of the circuit breaker.
While the present invention has been described with respect to certain preferred embodiments, it will be apparent to those skilled in the art that various changes and modification may be made without departing from the scope of the invention as defined in the following claims:

WE CLAIM:
1. A method for extinguishing an arc in an arc chute assembly, comprising
the steps of.
increasing length of the arc by providing arc plates with varying lengths arranged incrementally in the arc chute assembly so as to increase arc voltage to quench the arc faster.
2. An arc chute assembly for a switching device, comprising: a plurality of arc plates, each plate having varying length and arranged incrementally from a first arc plate to a last arc plate between two plates of the arc chute assembly.
3. An arc chute assembly as claimed in claim 2, wherein the arc plates can have zigzag, toothed oval, rectangular configuration etc. at its lower end.