FORM 2
The Patents Act 1970
(39 of 1970)
&
The Patent Rules 2003
COMPLETE SPECIFICATION
(See Section 10 and rule 13)
TITLE OF THE INVENTION: CONTACT SYSTEM FOR A MOULDED CASE CIRCUIT BREAKER
APPLICANT: LARSEN & TOUBRO LIMITED
L&T House, Ballard Estate, P.O. Box No. 278,
Mumbai, 400 001, Maharashtra
INDIA.
PREAMBLE OF THE DESCRIPTION:
THE FOLLOWING SPECIFICATION PARTICULARLY DESCRIBES THE INVENTION AND THE MANNER IN WHICH IT IS TO BE PERFORMED

A) TECHNICAL FIELD
[0001] The present invention generally relates to Moulded Case Circuit Breakers (MCCB), particularly to contact systems in the MCCB. The present invention more particularly relates to a contact system for providing divergent type of contact buttons in a MCCB to increase the life of the MCCB.
B) BACKGROUND OF THE INVENTION
f0002] Circuit breakers are widely used in domestic, commercial and light industrial installations to provide a protection for the electrical systems from the electrical fault conditions such as current overloads, short circuits, and low level voltage conditions. The short circuit withstanding capacity of a circuit breaker is governed by a performance of an arc quenching chamber. A molded case circuit breaker generally comprises a terminal module which connects a power source or an electrical load of the circuit, a switching mechanism which switches the circuit by making a contact between a fixed contact and a movable contact or by separating the fixed contact and the moving contact from each other and a trip mechanism to sense a fault current to trip the switching mechanism to a circuit-broken position. The Moulded case circuit breaker (MCCB) is a circuit breaker assembled as an integral unit in a supportive and enclosed housing of an insulative material.
[0003] The currently available circuit breakers consist of an arc chamber assembly, which when subjected to a short circuit current of few kilo amperes. quenches the arc with a long arcing time. The long arcing time induces stresses on the downstream equipments due to a large amount of a let through energy. The large amount of the let through energy is due to the inability to move the arc roots from the contact buttons to an arc runner efficiently. These arc chamber assemblies are inefficient in terms of a total arcing time and the let through energy which is passed to the downstream equipment from the circuit breaker.

[0004] Hence, there exists a need to provide a contact system for a MCCB for a fast movement of the arc from the contact buttons towards the arc runner for reducing an arcing time. Also there exists a need to reduce a let through energy in the MCCB during a short circuit condition.
[0005] The above mentioned shortcomings, disadvantages and problems are addressed herein and which will be understood by reading and studying the following specification.
C) OBJECT OF THE INVENTION
[0006] These and other objects and advantages of the present invention will become readily apparent from the following detailed description taken in conjuction with the accompanying drawnigs.
[0007] The primary object of the present invention is to provide a contact system for a MCCB for a fast movement of an arc from the contact buttons towards an arc runner for reducing an arcing time.
[0008] Another object of the present invention is to provide contact system for a MCCB to reduce a let through energy in the MCCB during a short circuit condition,
[0009] Yet another object of the present invention is to provide a contact system for a MCCB to prevent an erosion of the contact buttons.
(0010] Yet another object of the present invention is to provide a contact system in a MCCB to increase an electrical life of the MCCB.
D) SUMMARY OF THE INVENTION

[0011] The various embodiments of present invention provide a contact system for a Moulded Case Circuit Breaker (MCCB). The contact system includes a fixed contact, a fixed contact button attached to the fixed contact, a moving contact and a moving contact button attached to the moving contact. The system also includes an arc chamber, a plurality of arc runners provided within the arc-chamber, a plurality of de-ion plates adapted to extinguish an arc formed between the fixed contact button and the moving contact button. Further, chamfers are formed on both the fixed contact button and the moving contact button to form a divergent type contact buttons for the fast movement of the arc from the contact buttons towards the arc runner for reducing the arcing time.
[0012] According to one embodiment of present invention, the divergent type contact buttons are adapted to shift the arc from the contact buttons to the plurality of arc runners to prevent an erosion of the contact buttons. A diverging angle is formed between the fixed contact button and the moving contact button for a smooth movement of an arc from the contact buttons towards the arc runner. The diverging angle ranges between 50° to 90°. The chamfers are formed on a tip of the moving contact button and the fixed contact button and are projected towards the arc chamber. The chamfers are formed on the tip of the fixed contact button and the moving contact button by one of an extrusion process or a die compacting process.
[0013] In one embodiment of the present invention, the diverging angle is formed between the fixed contact tip and the moving contact tip for a smooth movement of an arc from the contact buttons towards the arc runner. The diverging angle ranges within 50°to 90 °.
[0014] The contact system provides a fast movement of the arc from the contact buttons towards the arc runner for reducing the arcing time. The contact system also reduces the let through energy in the MCCB during a short circuit

condition. Further the contact system helps in shifting the arc from the contact buttons to the plurality of arc runners provided in the arc chamber to prevent the erosion of the contact buttons.
E) BRIEF DESCRIPTION OF THE DRAWINGS
[0015] The other objects, features and advantages will occur to those skilled in the art from the following description of the preferred embodiment and the accompanying drawings in which:
[0016] FIG. 1 illustrates a side view of a Moulded Case Circuit Breaker (MCCB) according to one embodiment of the present invention.
[0017] FIG. 2 illustrates a top view of a Moulded Case Circuit Breaker (MCCB) according to one embodiment of the present invention.
[0018] FIG. 3 illustrates a top view of a Moulded Case Circuit Breaker (MCCB) without casing according to one embodiment of the present invention.
[0019] FIG. 4 illustrates a side sectional view of a contact system in a MCCB according to one embodiment of the present invention.
[0020] FIG. 5 illustrates an expanded view of a contact system in a MCCB according to one embodiment of the present invention.
[0021] Although specific features of the present invention are shown in some drawings and not in others. This is done for convenience only as each feature may be combined with any or all of the other features in accordance with the present invention.
F) DETAILED DESCRIPTION OF THE INVENTION

[0022] In the following detailed description, a reference is made to the accompanying drawings that form a part hereof, and in which the specific embodiments that may be practiced is shown by way of illustration. These embodiments are described in sufficient detail to enable those skilled in the art to practice the embodiments and it is to be understood that the logical, mechanical and other changes may be made without departing from the scope of the embodiments. The following detailed description is therefore not to be taken in a limiting sense.
[0023] The various embodiments of present invention provide a contact system for a Moulded Case Circuit Breaker (MCCB). The system includes a fixed contact, a fixed contact button attached to the fixed contact, a moving contact, and a moving contact button attached to the moving contact. The system also includes an arc chamber, plurality of arc runners provided within the arc-chamber, a plurality of de-ion plates to extinguish the arc formed between the fixed contact button and the moving contact button. Further, the chamfers are formed both on the fixed contact button and the moving contact button at the tip of the fixed contact and the moving contact which extends towards the arc chamber. The chamfers create a diverging angle between the fixed contact button and the moving contact button for the fast movement of the arc from the contact buttons towards the arc runner for reducing the arcing time.
[0024] FIG. I illustrates a side view of a Moulded Case Circuit Breaker (MCCB) 100 according to one embodiment of the present invention. With respect to FIG. I, a contact system is provided in the MCCB 100.
[0025] FIG. 2 illustrates a top view of a Moulded Case Circuit Breaker (MCCB) 100 according to one embodiment of the present invention. With respect to FIG. 2, a contact system is provided in the MCCB 100.

[0026] FIG. 3 illustrates a top view of a Moulded Case Circuit Breaker (MCCB) without a casing according to one embodiment of the present invention. With respect to FIG. 3, a contact system is provided in the MCCB 100. With respect to the FIG.l, F1G.2, and FlG.3, the molded case circuit breaker includes an upper contact assembly, housing, a knob, a release, a cover and an arc chamber. The arc chamber is provided with an improved arc puller to pull the arc efficiently from the contact buttons.
[0027] FIG. 4 illustrates a side sectional view of a contact system in a MCCB according to one embodiment of the present invention. With respect to FIG. 4, the contact system includes a fixed contact 401, a Fixed contact button 402 attached to the fixed contact 401, a moving contact 403 and a moving contact button 404 attached to the moving contact. The contact system also includes an are chamber, a plurality of are runners 405 provided within the are-chamber plurality of de-ion plates 406 adapted in the arc runners to extinguish an arc formed between the fixed contact button 401 arid the moving contact button 404. Further, the chamfers are formed on both the fixed contact button and the moving contact button 404 to form the divergent type contact buttons for a fast movement of the arc from the contact buttons towards the arc runner for reducing the arcing time.
[0028] The divergent type contact buttons 401, 404 are adapted to shift the arc from the contact buttons to the plurality of arc runners 405 to prevent the erosion of the contact buttons. A diverging angle is formed between the fixed contact button and the moving contact button for the smooth movement of the arc from the contact buttons towards the arc runner. The diverging angle ranges between 50° and 90°. The diverging angle formed between the fixed contact button and the moving contact button depends on the speed of opening of the moving contact 403 during a short circuit condition.

[0029] During a short circuit condition in the MCCB, the arc is formed between the moving contact button and the fixed contact button. The arc stays across the two contact buttons for some time until the moving contact starts opening. Due to an electromagnetic pull on the arc by the de-ion plates and pressure differentials across the arc, the arc starts moving towards the de-ion plates by virtue of the divergent contact buttons. Further, the arc smoothly moves from the contact buttons to the arc runner, thereby reducing the erosion of the contact buttons. The effective arc root movement from the contact buttons to the arc runner reduces the erosion of the contact buttons and hence increases the electrical life of the MCCB.
[0030] FIG. 5 illustrates an expanded view of the contact system in a MCCB according to one embodiment of the present invention. With respect to FIG. 5, the expanded view of the contact system includes a fixed contact 401, a fixed contact button 402 is attached to the fixed contact 401, a moving contact 403, and a moving contact button 404 is attached to the moving contact. The chamfers 501 are formed on both the fixed contact button 402 and the moving contact button 404 to form the divergent type contact buttons for a fast movement of the arc from the contact buttons 402, 404 towards the arc runner for reducing the arcing time.
[0031] The divergent type contact buttons 401, 404 are adapted to shift the arc from the contact buttons to the plurality of arc runners 405 to prevent the erosion of the contact buttons. A diverging angle 502 is formed between the fixed contact button 402 and the moving contact button 404 for the smooth movement of the arc from the contact buttons towards the arc runner. The diverging angle ranges within 50° to 90°. The diverging angle 502 formed depends on the speed of opening of the moving contact 403 during a short circuit condition in the MCCB. The chamfers 501 are formed on the tip of the moving contact button 404 and the fixed contact button 402 towards the arc chamber. The chamfers 501 are formed on the tip of the fixed contact button

402 and the moving contact button 404 by an extrusion process or a die compacting process.
[0032] During a short circuit condition in the MCCB, the arc is formed between the moving contact button and the fixed contact button. The arc stays across the two contact buttons for some time until the moving contact starts opening. Due to an electromagnetic pull on the arc by the de-ion plates and pressure differentials across the arc, the arc starts moving towards the de-ion plates, by virtue of the divergent contact buttons. Further, the arc smoothly moves from the contact buttons to the arc runner thereby reducing the erosion of the contact buttons. The effective arc root movement from the contact buttons to the arc runner reduces the erosion of the contact buttons and hence increases the electrical life of the MCCB.
G) ADVANTAGES OF THE INVENTION
[0033] The various embodiments of the present invention provide a divergent type contact system for a Moulded Case Circuit Breaker (MCCB). The contact system provides a fast movement of the arc from the contact buttons towards the arc runner for reducing the arcing time. The contact system also reduces the let through energy in the MCCB during a short circuit condition. Further the contact system helps in shifting the arc from contact buttons to the plurality of arc runners provided in the arc chamber to prevent the erosion of the contact buttons.
[0034] Although the invention is described with various specific embodiments, it will be obvious for a person skilled in the art to practice the invention with modifications. However, all such modifications are deemed to be within the scope of the claims.

[0035] It is also to be understood that the following claims are intended to cover all of the generic and specific features of the present invention described herein and all the statements of the scope of the invention which as a matter of language might be said to fall there between.

CLAIMS
What is claimed is:
1. A contact system for a moulded case circuit breaker , the system
comprising:
a fixed contact;
a fixed contact button attached to the fixed contact;
a moving contact;
a moving contact button attached to the moving contact;
an arc chamber;
a plurality of arc runners provided within the arc-chamber;
a plurality of de-ion plates adapted in the arc runners to extinguish an arc
formed between the fixed contact button and the moving contact button;
Wherein a chamfer is formed on both the fixed contact button and the
moving contact button to form a divergent type contact button for a fast
movement of the arc from the contact buttons towards the arc runner for
reducing an arcing time.
2. The system of claim I, wherein the divergent type contact button is adapted to shift the arc from the contact buttons to the plurality of arc runners to prevent an erosion of the contact buttons.
3. The system of claim I, wherein a diverging angle is formed between the fixed contact button and the moving contact button for a smooth movement of the arc from the contact buttons towards the arc runner.
4. The system of claim 1, wherein a diverging angle is formed between the fixed contact tip and the moving contact tip for the smooth movement of the arc from the contact buttons towards the arc runner.
5. The system of claim 3 and 4, wherein the diverging angle ranges between 50" and 90°.

6. The system of claim 1, wherein the chamfers are formed on a tip of the moving contact button and the fixed contact button extending towards the arc chamber.
7. The system of claim 1, wherein the chamfers are formed on the tip of the fixed contact button and the moving contact button by an extrusion process.
8. The system of claim 1, wherein the chamfers are formed on the tip of the fixed contact button and the moving contact button by a die compacting process.