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: A COMPOSITE ARC CHAMBER ASSEMBLY WITH ROTATING
HEAT SINK
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 circuit breakers and particularly relates to an arc chamber assembly in molded case circuit breakers. More particularly the present invention relates to the arc chamber assembly with a rotating heat sink.
B) BACK GROUND OF THE INVENTION
[0002] Circuit breakers are the mechanical switching devices capable of making, carrying, and breaking currents under normal circuit conditions and also making, carrying for a specified time, and breaking currents under specified abnormal conditions. A circuit breaker basically consists of a pair of separable contacts and an interrupting medium. The function of the contacts is to conduct the electrical current when the breaker is closed and withstand the arcs while interrupting. Generally, the electrical contacts have a stationary part and a moving part. By bringing the moving contact to touch the stationary contact, electric current flows and the breaker is closed. By driving the moving contact away from the stationary contact, the electric arc develops and by quenching it the current stops flowing and the breaker is open.
[0003] In the existing technique, the circuit breakers are extensively used in the power distribution systems to provide protection for electrical equipment from electrical fault conditions such as current overloads, short circuits and abnormal level voltage conditions. Further the short circuit capacity of any circuit breaker is governed by the performance of an arc quenching chamber in the circuit breakers.
[0004] Further in the existing technique, the circuit breakers consist of the 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 leads to

creating a stress on the downstream equipments due to large amount of let through energy. Further the arcing time increases due to the inability to cool the arc effectively during high fault conditions in the circuit breakers.
[0005] Further in the existing technique, the insulation surrounding the arc is subjected to deposition of carbon material due to burning of the insulation during the arcing process. Further the carbonaceous material deposited forms tracking of the insulation which leads to flashover between one pole and another pole.
[0006] The prior art methods of arc chamber assemblies do not have heat sinks for effective arc cooling. The ionized hot gases generated during short circuit conditions are not demonized quickly. As a result, there is a possibility of external flashover out of the arc chamber. This increases total arcing time and ultimately increases let through energy passed on to the downstream equipments.
[0007] Hence there exists a need to develop a circuit breaker with composite arc chamber assembly with rotating heat sink for channelizing the hot gases.
[0008] 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 PRESENT INVENTION
[0009] The primary object of the present invention is to provide an arc chamber assembly with rotating heat sink in circuit breakers.

[0010] Another object of the present invention is to provide an arc chamber assembly with one or more heat sinks that reduces let through energy by faster cooling of the arc.
[0011] Yet another object of the present invention is to provide an arc chamber assembly with one or more heat sinks are free to rotate about their axis.
[0012] Yet another object of the present invention is to provide an arc chamber assembly with one or more heat sinks to dissipate the arc energy generated during short circuit conditions.
[0013] Yet another object of the present invention is to provide an arc chamber assembly with one or more heat sinks to reduce the arcing time by faster cooling of the arc.
[0014] Yet another object of the present invention is to provide an arc chamber assembly with heat sinks having highly thermally conductive materials.
I)) SUMMARY OF THE INVENTION
[0015] The various embodiments of the present invention provide a circuit breaker with an arc chamber assembly, a heat sink assembly, a front vent, a back vent, one or more heat sinks and one or more heat sink supports. One or more heat sinks are inserted into the one or more heat sink supports of the heat sink assembly for cooling arc effectively and the heat sink assembly is placed vertically between the front vent and the back vent in such a way that the direction of the one or more heat sink converges or diverts one or more hot gases towards an exit.

[0016] The heat sink supports are used for holding the heat sinks in their intended/respective positions. The heat sink supports have circular holes for inserting the heat sinks. The material of the heat sink support can be any insulating material with high arc resistance e.g. Glass polyester sheet, Glass melamine sheet etc. Pluralities of heat sinks and stopper pins are inserted in the circular holes of heat sink supports. The stopper pins are crimped or can be held by any other means and the heat sinks are free to rotate about their axis.
[0017] The hot gases generated in the circuit breakers are channelized behind the arc chamber between front vent and back vent through the heat sink assembly. A heat sink consists of vertical or horizontal cooling fins of highly thermally conductive material such as brass. In normal conditions, these fins rest one above the other such that the chamber is closed. During a short circuit condition, a very high pressure is built up to open up heat sinks (by rotational movement of heat sinks) and the hot gases are channelized through this opening and effectively cooled by a conduction process. This helps in faster dielectric built up and consequently reduces the total arcing time and the let through energy.
[0018] These and other objects and advantages of the present invention will become readily apparent from the following detailed description taken in conjunction with the accompanying drawings.
E) BRIEF DESCRIPTION OF THE DRAWINGS
[0019] 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:

[0020] FIG. 1 illustrates the front view of the molded case circuit breaker with cover according to one embodiment of the present invention.
[0021] FIG. 2 illustrates the front view of the molded case circuit breaker without cover according to one embodiment of the present invention.
[0022] FIG.3 illustrates the sectional view of the molded case circuit breaker with heat sink closed (Y Pole) according to one embodiment of the present invention.
[0023] FIG.4 illustrates the heat sink assembly in closed condition according to one embodiment of the present invention.
[0024] FIG.5 illustrates the sectional view of the molded case circuit breaker with heat sink open (Y Pole) according to one embodiment of the present invention.
[0025] FIG.6 illustrates the heat sink assembly in open condition according to one embodiment of the present invention.
[0026] Although the 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
[0027] 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.
[0028] The various embodiments of the present invention provide a circuit breaker with an arc chamber assembly, a heat sink assembly, a front vent, a back vent, one or more heat sinks and one or more heat sink supports. The one or more heat sinks are inserted into the one or more heat sink supports of the heat sink assembly for cooling an arc effectively and the heat sink assembly is placed between the front vent and the back vent in such a way that the direction of the one or more heat sink converges or diverts one or more hot gases towards an exit.
[0029] According to one embodiment of the present invention, the one or more hot gases are channelized behind the arc chamber assembly between the front vent and the back vent through the heat sink assembly.
[0030] According to one embodiment of the present invention, an area inside the arc chamber assembly is completely de-ionized and dielectric strength is increased due to the channelizing of the one or more hot gases.
[0031] According to one embodiment of the present invention, the one or more heat sinks reduces let through energy by faster cooling of the arc.
[0032] According to one embodiment of the present invention, the one or more heat sinks reduce stress on the one or more downstream equipments by virtue of the low let through energy.

[0033] According to one embodiment of the present invention, the one or more heat sinks dissipate the arc energy generated during the short circuit conditions.
[0034] According to one embodiment of the present invention, the one or more heat sinks reduce an arcing time by cooling the arc quickly and rapidly.
[0035] FIG. 1 illustrates the front view of the molded case circuit breaker with cover according to one embodiment of the present invention while FIG. 2 illustrates the front view of the molded case circuit breaker without cover according to one embodiment of the present invention. With respect to the FIG.l and FIG.2, the molded case circuit breaker includes an arc chute assembly 1, a front vent 2, a back vent 3, a heat sink assembly 4, a housing 10, a knob 12 and a release 13. The hot gases generated in the circuit breakers are channelized behind the arc chamber assembly 1 between the front vent 2 and the back vent 3 through the heat sink assembly 4. The Heat sink assembly 4 includes one or more heat sinks which are placed in the assembly either horizontally or vertically. The one or more heat sinks are made up of highly thermally conductive material such as brass. Further a ferrous or non ferrous material with good thermal conductivity is also used such as brass, stainless steel, mild steel and copper.
[0036] FIG.3 illustrates the sectional view of the molded case circuit breaker with heat sink in closed condition (Y Pole) according to one embodiment of the present invention while FIG.4 illustrates the side view, front view and the perspective view of a heat sink assembly in closed condition according to one embodiment of the present invention. With respect to FIG.3 and FIG.4, the molded case circuit breaker includes an upper contact assembly 5, a lower contact assembly 6, heat sinks 7, heat sink supports 8 and the stopper pins 9. The heat sink assembly 4 of the present invention consists of heat sink supports 8 and plurality of heat sinks 7. The heat sink

supports 8 are used for holding heat sinks 7 in their intended positions. The heat sink supports 8 have circular holes for inserting heat sinks 7. The material of heat sink support can be any insulating material with high arc resistance e.g. Glass polyester sheet, Glass melamine sheet etc. Heat sink 7 and stopper pins 9 are inserted into the circular holes of heat sink supports 8. The stopper pins 9 are crimped or can be held by any other means and the heat sinks 7 are free to rotate.
[0037] FIG. 5 illustrates the sectional view of the molded case circuit breaker with heat sink in open condition (Y Pole) according to one embodiment of the present invention while FIG. 6 illustrates a front view, a side view and a perspective view of the heat sink assembly in open condition according to one embodiment of the present invention. With respect to FIG. 5 and FIG. 6, the molded case circuit breaker includes an upper contact assembly 5, a lower contact assembly 6, heat sinks 7, heat sink supports 8 and the stopper pins 9. The hot gases are first channelized between the front vent 2 and the back vent 3 during a short circuit condition. The hot gases are then passed through the one or more heat sinks 7 for effectively cooling the arc. The process of passing the hot gases through the vents ( 2 and 3) and then through the one or more heat sinks 7 helps in faster dielectric built up and also reduces the total arcing time and let through energy.
[0038] The faster cooling of the arc reduces the let through energy of the circuit breakers. The reduction of the let through energy in turn reduces the stress on the one or more equipments in the electric system. The one or more heat sinks 7 are inserted into the one or more heat sink supports 8 of the heat sink assembly 4 for effectively cooling the arc and the heat sink assembly 4 is placed between the front vent 2 and the back vent 3 in such a way that the direction of the one or more heat sinks 7 converges the hot gases towards an exit. The one or more heat sinks 7 consist of a highly thermally conductive material and are placed in such a way that the maximum

surface area is exposed of the one or more heat sinks 7 to the hot ionized gases. The one or more heat sinks 7 also channelize the path for the hot gases towards an exit.
[0039] The heat sink assembly 7 includes nine horizontal heat sinks that are inserted in to the circular holes of the heat sink supports 8 and hinged as shown in FIG. 4 and FIG. 6. The heat sinks 7 are free to rotate about their axis. However their rotation is restricted by two stopper pins 9 placed at the top and bottom on the heat sink supports 8. The positions of these stopper pins 9 are such that the heat sinks 7 align themselves one above the other thereby closing the arc chamber as shown in FIG. 3 and FIG, 4, when the heat sink assembly 4 is inserted between the two vents (2 and 3) and the circuit breaker is mounted vertically.
[0040] During a short circuit condition, a very high pressure is built up due to the enclosed chamber. High velocity ionized gases force the heat sinks 7 to rotate about their axis thereby allowing the gases to exit. At the same time, the gases are cooled by these heat sinks 7 by convection. This condition is shown in FIG. 5 and FIG. 6. The velocity of an arc is directly proportional to the pressure inside the arc chamber. Thus a high pressure developed at the start of the arcing process greatly increases the arc velocity thereby reducing the arcing time and the let through energy.
G) ADVANTAGES OF THE INVENTION
[0041] The various advantages of the present invention are low splitting time, low total arching time and low let through energy. The arc energy generated during short circuit conditions is efficiently dissipated by heat sinks. The hot gases are channelized in an efficient way through the heat sink between the front vent and the back vent and thus the area inside the arc chamber is completely de-ionized and dielectric strength is built up rapidly which enhances post short circuit performance.

The present invention substantially reduces the burden on the downstream side equipments by virtue of the low let through energy.
[0042] 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.
[0043] 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 circuit breaker comprising:
an arc chamber assembly;
a heat sink assembly;
a front vent;
a back vent;
one or more heat sinks; and
one or more heat sink supports;
Wherein one or more heat sinks are inserted into the one or more heat sink
supports of the heat sink assembly for effective arc cooling and the heat sink
assembly is placed vertically between the front vent and the back vent in
such a way that the direction of the one or more heat sinks converges or
diverts a hot gas towards an exit from the arc chamber assembly.
2. The circuit breaker of claim 1, wherein one or more heat sinks and a plurality of the stopper pins are inserted in to the circular holes of the heat sink supports.
3. The circuit breaker of claim 1, wherein the plurality of stopper pins are crimped or held in place by a suitable means on the heat sink supports and the heat sinks are made free to rotate.
4. The circuit breaker of claim 1, wherein the axis of rotation of heat sink is perpendicular to a flow of the hot gas.
5. The circuit breaker of claim 1, wherein the heat sink is an inclined rotating type heat sink in which a rotation of the heat sink assembly is inclined to the flow of the hot gas.
6. The circuit breaker of claim 1, wherein the hot gas is channelized behind the arc chamber assembly between the front vent and the back vent through the heat sink assembly.

7. The circuit breaker of claim ], wherein an area inside the arc chamber assembly is completely de-ionized and dielectric strength is increased due to the channelizing of the hot gas.
8. The circuit breaker of claim 1, wherein the one or more heat sinks reduces a let through energy by faster cooling of the arc.
9. The circuit breaker of claim 4, wherein one or more heat sinks reduces a stress on the one or more downstream side equipments by virtue of the low let through energy.
10. The circuit breaker of claim 1, further the heat sinks includes horizontal or vertical cooling fins of a thermally conductive material.