F O R M 2

THE PATENTS ACT, 1970
(39 of 1970)
&
The Patents Rules, 2003
COMPLETE SPECIFICATION
(See section 10; rule 13)

1. Title of the invention: AN IMPROVED ARC CHUTE ASSEMBLY IN A MOULDED CASE CIRCUIT BREAKER

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:


FIELD OF THE INVENTION

The present invention relates to a contact system with arc chute assembly in a moulded case circuit breaker. More particularly the present invention relates to an improved arc chute assembly with an inbuilt arc energy extractor means of a moulded case circuit breaker adapted to enhance the circuit breakers breaking capacity by increasing power dissipation inside arc chamber, thereby reducing total arcing time and let through energy.

BACKGROUND OF THE INVENTION

Electrical switching apparatus, such as circuit breakers, are employed in diverse capacities in power distribution systems such as, for example, to provide protection for electrical equipment from electrical fault conditions (e.g. without limitation, current overloads, short circuits, abnormal level voltage conditions). Therefore the short circuit capacity of any circuit breaker is totally governed by the performance of its arc quenching chamber.

The prior art circuit breakers consist of an arc chamber assembly which when subjected to a short circuit current of few kilo amperes quench the arc with long arcing times. The long arcing times lead to severe stresses on the downstream equipments due to large amount of let through energy. The prior art circuit breakers do not have efficient arc cooling mechanisms to reduce the arcing time.

The prior art circuit breakers do not have any efficient arc energy extracting mechanisms. They have conventional arc chamber assemblies, which under short circuit conditions, do not dissipate arc energy efficiently. They are inefficient in terms of faster arc cooling. These prior art circuit breakers, when subjected to a short circuit currents, quench the arc with long arcing times. The long arcing times lead to severe stresses on the downstream equipments due to large amount of let through energy. This is because of their inability to cool the arc efficiently during high fault conditions.

The drawbacks of the prior art methods are no / inefficient arc energy extracting mechanism, long arcing times, higher let through energy.
Thus there is a need to provide an improved arc chute assembly with an inbuilt arc energy extractor means of a moulded case circuit breaker adapted to enhance the circuit breakers breaking capacity by increasing power dissipation inside arc chamber.

OBJECTS OF THE INVENTION

An object of the present invention is to overcome the problems/disadvantages of the prior art.

Another object of the present invention is to provide an improved arc chute assembly for a moulded case circuit breaker.
Yet another object of the present invention is to provide an inbuilt arc energy extractor means of a moulded case circuit breaker adapted to enhance the circuit breakers breaking capacity by increasing power dissipation inside arc chamber thereby reducing total arcing time and let through energy.

These and advantages of the present invention will become readily apparent from the following detailed description taken in conjunction with the accompanying drawings.

SUMMARY OF THE INVENTION
According to another aspect of the present invention there is provided an improved arc chute assembly in a moulded case circuit breaker, said assembly comprising:
a front vent ;
plurality of lining means enclosing the said arc chute assembly, said lining means comprising plurality of slots;
plurality of plate means substantially aligned with said slots of plate means and
plurality of extractor means substantially aligned with said slots of plate means;
wherein said extractor means are placed substantially after/behind the plates means and in proximity with said front vent, said extractor means in line with plate plane.

BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWING

Other features as well as the advantages of the invention will be clear from the following description.
In the appended drawings:
Fig 1 illustrates RHS view of MCCB.
Fig 2 illustrates Front view of MCCB.
Fig 3 illustrates Front view of MCCB without cover.
Fig 4 illustrates Sectional view of MCCB (Y pole).
Fig 5 illustrates Front, Top & sectional view of arc energy extractor assembly.
Fig 6 illustrates Exploded view of arc energy extractor assembly.

DETAILED DESCRIPTION OF THE INVENTION

The present invention relates to an improved arc chute assembly for use in moulded case circuit breakers. The prime feature of present invention is the way arc energy extractor mechanism is designed to maximize arc power dissipation inside an arc chamber as a single assembly.

In the following detailed description, reference is made to the accompanying drawings that form a part hereof, and illustrate the best mode presently contemplated for carrying out the invention. Further functioning of the mechanism has been discussed below to describe the way the mechanism operates. However, such description should not be considered as any limitation of scope of the present unit. The structure thus conceived is susceptible of numerous modifications and variations, all the details may furthermore be replaced with elements having technical equivalence. In practice the materials and dimensions may be any according to the requirements, which will still be comprised within its true spirit.

List of components:

1. Housing
2. Release assembly
3. Knob
4. Upper contact assembly
5. Lower contact assembly
6. Arc chute assembly
7. Front vent
8. Back vent
9. Arc chute lining
10. Deion plate
11. Arc energy extractor
12. Cover

Construction of arc chute assembly:

In the present invention arc chute assembly is inserted inside the arc chamber. It consists of three components viz. arc chute linings, deion plates & arc energy extractors. The arc energy extractors are of highly thermally conductive material like copper, brass etc.

The arc chute assembly is as explained below.

The deion plates are aligned along with the rectangular slots of arc chute linings. The slots can also be of any shape and the rectangular shaped slots should not be considered as restricting scope of the present invention. Similarly the rectangular shaped arc energy extractors are aligned with the respective slots of arc chute lining as shown in fig 6. The arc chute assembly is then made rigid by any mechanical means like crimping from both ends.

In the present invention, the cross-section of arc energy extractor is square. However, it can be of any shape depending upon ease of manufacturability, any regular / irregular shape.

In the present invention, arc energy extractor are placed immediately after the deion plates (towards front vent) in line with deion plate plane. The extractors are placed anywhere in the vicinity of arc chamber but only in the direction of front vent and after the deion plates & in the same plane. However arc energy extractors can also be placed with any given inclination as well as anywhere in the vicinity of arc chamber.

During short circuit conditions, heavy arcing takes place between upper & lower contacts. Because of the magnetic pull generated by the deion plates, arc is pulled inside the spacing of deion plates. However, the mass of deion plates is not sufficient to effectively dissipate the arc energy. This increases the total arcing time.

In the present invention, arc energy extractors are placed just behind the deion plates. At the time of short circuit, hot ionized column of arc enters the deion plates, thereby splitting the arc into multiple arcs. The hot ionized column of arc is efficiently cooled by highly thermally conductive material of arc energy extractors.

This significantly takes away the heat and thereby improves built up of dielectric strength. This ultimately results in faster fault clearance, low arcing time, low cut off current and let through energy.

WE CLAIM

1. An improved arc chute assembly in a moulded case circuit breaker , said assembly comprising:
a front vent ;
plurality of lining means enclosing the said arc chute assembly, said lining means comprising plurality of slots;
plurality of plate means substantially aligned with said slots of plate means and
plurality of extractor means substantially aligned with said slots of plate means;
wherein said extractor means are placed substantially after/behind the plates means and in proximity with said front vent, said extractor means in line with plate plane.

2. Assembly as claimed in claim 1 wherein said extractor means are thermally conductive material.

3. Assembly as claimed in claim 2 wherein said thermally conductive material selectively comprising copper, brass and the like.

4. Assembly as claimed in claim 4 wherein said extractor means is optionally having cross sectional area of any regular or irregular shape.

5. Assembly as claimed in claim 1 wherein said arc chute assembly further comprising mechanical means like crimping from both ends adapted to make it rigid.

6. Assembly as claimed in claim 1 wherein said plate means comprising plurality of deion plates.

7. An improved arc chute assembly in a moulded case circuit breaker as herein substantially described and illustrated with the accompanying drawings.