FORM2
THE PATENTS ACT, 1970
(39 of 1970)
&
The Patents Rules, 2003
COMPLETE SPECIFICATION
(See section 10; rule 13)
1. Title of the invention. - IMPROVED CIRCUIT BREAKER ARRANGEMENT ENSURING LOWER TEMPERATURE RISE
2. Applicant(s)
(a) NAME : LARSEN A 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
The present invention relates generally to a circuit breaker arrangement. More particularly, the invention relates to an improved circuit breaker arrangement ensuring lower temperature rise.
BACKGROUND AND THE PRIOR ART
In the conventional circuit breakers, the current carrying path is manufactured out of copper with silver plating. As per IEC60947 standards, the breaker is required to exhibit only prescribed temperature limits. This calls for optimization of heat dissipation from the terminals. Conventional techniques are based on maximizing convection around the current paths to minimize this temperature rise.
Substantially large numbers of patents are available for temperature normalization using graphite as heat sinks. In circuit breaker, effective heat removal from current carrying path is critical for its healthy functioning. It is conventionally achieved by adjusting the construction of the copper path such that convective heat transfer coefficients are maximized in a given space constraint. A distinct inherent disadvantage is that copper itself has a exceptional thermal conductivity. As a result, design of heat sinks or use of other materials does not offer adequate improvement.
However, use of graphite for heat normalization around the copper conductors was not known in the prior art. Also, use of exfoliated

graphite sheets which are easy to fabricate in various shapes and also offer the desired flexibility of assembly contrary to common approach of using graphite in the form of sintered blocks or coatings was not known in the prior art.
Thus, there is a need to overcome the problems of the temperature normalization using graphite as heat sinks in the prior art. Therefore, the present inventors have developed an improved circuit breaker having a unique arrangement of exfoliated graphite sheets adapted to normalize the temperature rise of the circuit breaker terminals. It would lead to lower temperature rise in circuit breakers over prolonged flow of current through them.
OBJECTS OF THE INVENTION
The primary object of the present invention is to provide a mechanism and a method for temperature normalization in the circuit breakers.
Another object of the present invention is to provide a compact circuit breaker with reduction in copper volume at the breaker terminal.
Another object of the present invention is to provide a unique arrangement of exfoliated graphite sheets to extract excess heat from temperature hot spots in the circuit breaker and dissipating the heat to the atmosphere at a faster rate.

Yet another object of the present invention is to provide a method and mechanism to lower the temperature rise in the circuit breakers over prolonged flow of current through them.
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.
According to one embodiment of the present invention, there is provided an improved circuit breaker arrangement ensuring lower temperature rise, wherein said arrangement comprising plurality of graphite sheets adapted to provide thermal stabilization to said circuit breaker.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
In the appended drawings:

Fig 1 illustrates thermal conductivity (W/m.K) graph of copper versus graphite from OK to 400 K.
Fig 2 illustrates Conventional Pole arrangement.
Fig 3 illustrates Modified Pole arrangement with exfoliated graphite sheets.
DETAILED 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.
Reference is first invited to Fig 1 where the thermal conductivity (W/m.K) graph of copper versus graphite from OK to 400 K is shown.
Fig. 2 shows circuit breaker arrangement in accordance with the prior art.
Fig. 3 shows circuit breaker arrangement in accordance with the present invention.

The invented system is thus an improved circuit breaker arrangement ensuring lower temperature rise.
DETAILED DESCRIPTION OF THE INVENTION
Accordingly in the present invention there is provided an improved circuit breaker having a unique arrangement of exfoliated graphite sheets adapted to normalize the temperature rise of the circuit breaker terminals. From the graph of thermal conductivity, k vs. Tas shown in figure 1, one can observe that thermal conductivity of bulk graphite almost twice as that of bulk copper. These figures decline partially for exfoliated graphite to around 500-650 W/m.K as it is comprised of a culmination of compacted graphite flakes. The present invention intended operating range is from 300K to 400K. If a heated current carrying copper conductor is covered with flat sections of exfoliated graphite sheets, superior thermal conductivity is obtained along the copper conductor surface. It is also to be noted that heat dissipation by radiation also improves by virtue of increase in emissivity due to black form of graphite sheets.
Figure 2 shows one of the pole phases of a three phase current carrying circuit breaker. It comprises of two fixed contacts: Incoming and Outgoing terminals (1 and 2) and a moving contact (3) which is made of multiple copper fingers. The interconnection between moving and fixed contact is made through flexible copper braids crimped onto the bottom fixed terminal.

Based on the above construction, there can be in total, two main regions of heat generation.
a) At the interface of moving fingers with fixed contact
To redistribute heat generated at this place, the graphite sheets (on both sides of the incoming conductor) and on top of the incoming conductor are used.
b) At the copper braid crimping region.
To redistribute heat generated at this place, the graphite sheet on the back side of braided junction. Also, note that it is placed vertically to improve vertical convective heat transfer coefficient at this place.
c) Along the braid conductor as it is one of the least cross
section of current path in the whole link.
To redistribute heat generated at this place, the graphite sheets (4) on both sides of the bottom conductor and on top of the bottom conductor are used.
The present invention brings about an improvement in over 5 K in the overall temperature rise conducted at continuous current of 1600 A till thermal stabilization. Depending on the copper volume used in the product, this amounts to substantial savings that can be generated through reduction of copper volume. As stated earlier, new product can be made more compact using this scheme.
Another advantage of this principle is that graphite sheets (4) ensure thermal normalization across the copper cross section. This also

amounts to better utilization of conductor cross section for current flow especially in ac systems where current densities vary due to skin effect and proximity effects.
Also note that while exfoliated graphite sheets (4) have been arranged in the present invention to harp on the advantages of graphite in simplified manner. A more refined approach would be applying graphite coatings on the conductor surface to achieve similar performance characteristics. However, such deposition processes are expensive and might offset the benefit accrued from copper volume reduction. As a result, such processes may only gain precedence in bulk manufacturing. On the contrary, exfoliated graphite (4) is commonly available and can also easily be crafted in various shapes into above proposed assemblies.
The exfoliated graphite sheets (4) which have very high through plane thermal conductivity are found to be highly effective in this application. They are also light, flexible and inexpensive which facilitates the implementation of such concepts in existing device configurations. Unique arrangement of exfoliated graphite sheets which help in excess heat extraction from the temperature hot spots and dissipating in the atmosphere at a faster rate. This leads to lower temperature rise in circuit breakers over prolonged flow of current through them. This opens up prospects for partially reducing the volume of copper used for current flow. This not only leads to savings in material costs but also leads to design of more compact devices.

ADVANTAGES:
1 Reduced temperature rise at circuit breaker terminals.
2. Compact size of breaker.
3. Reduction in copper volume used for manufacturing of the circuit breakers.
4. The exfoliated graphite sheets used around the current carrying path achieves better heat dissipation.
5. The exfoliated graphite sheets of the present invention are in the form of sintered blocks or coatings
6. The exfoliated graphite sheets proposed in the present invention is easy to fabricate in various shapes and also offer the desired flexibility of the assembly.
7. The present invention offers easy and cost effective assembly of the exfoliated graphite sheets on the current carrying conductors.
8. The exfoliated graphite sheets of the present invention are light weight, flexible and inexpensive which facilitates the implementation of such concepts in the existing device configurations.
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 circuit breaker arrangement ensuring lower temperature rise, wherein said arrangement comprising plurality of graphite sheets (4) adapted to provide thermal stabilization to said circuit breaker.
2. Arrangement as claimed in claim 1 wherein said graphite sheets (4) are substantially exfoliated graphite sheets adapted to normalize temperature rise in said circuit breaker.
3. Arrangement as claimed in claim 1 wherein said graphite sheets (4) providing improved thermal conductivity along said conductor surface.
4. Arrangement as claimed in claim 1 wherein said graphite sheets (4) providing improved heat dissipation due to increase in emissivity.
5. Arrangement as claimed in claim 1 wherein said plurality of graphite sheets (4) placed at interface of moving fingers with the fixed contact (1) of the circuit breaker thereby improving heat dissipation.

6. Arrangement as claimed in claim 1 wherein said graphite sheets (4) placed vertically at copper braid crimping region thereby improving vertical convective heat transfer coefficient.
7. Arrangement as claimed in claim 1 wherein said graphite sheets (4) placed along braid conductor providing improved heat distribution.
8. An improved circuit breaker arrangement ensuring lower temperature rise as herein described and illustrated with reference to accompanying drawings.