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 FOR 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 I'T 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 a composite arc chamber assembly with a porous foam used as a heat sink in molded case circuit breakers.
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, an 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 techniques, the circuit breakers are extensively used in the power distribution systems to provide a 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 are with long arcing times. The long arcing times leads to

creating a stress on the downstream equipments due to a large amount of let through energy. Further the arcing time increases due to the inability to cool the arc effectively during the high fault conditions in the circuit breakers. These arc chamber assemblies are inefficient in terms of total arcing time and the let through energy which the circuit breaker passes to the downstream equipments.
[0005] Hence there exists a need to develop a circuit breaker with a mechanism for efficient cooling of the breaking gases ventilated from an arc extinguishing chamber. There also exists a need to provide a mechanism to reduce the let through energy of the circuit breaker..
[0006] 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
[0007J The primary object of the present invention is to provide a mechanism for effective cooling of the breaking gases ventilated from an arc extinguishing chamber in the molded case circuit breakers.
[0008] Another object of the present invention is to provide a mechanism to enable faster cooling of ionized gases.
[0009] Yet another object of the present invention is to provide a mechanism to reduce the total arcing time in moulded case circuit breakers.
[0010] Yet another object of the present invention is to provide a mechanism to reduce a let through energy of the moulded case circuit breakers.

[0011] Yet another object of the present invention is to provide a mechanism to reduce the stresses on the in line electric system.
D) SUMMARY OF THE INVENTION
[0012] The various embodiments of the present invention provide an arc chamber assembly with a deionization device in the circuit breaker. An arc chamber assembly of a molded case circuit breaker comprises a front vent, a back vent and the gas de-ionization device placed between the front vent and the back vent. The deionization device includes a structure to enable a cooling of a gas ventilated from the arc chamber. The de-ionization device comprises a porous foam formed from the agglomerated balls formed from a metallic base and it is adapted to function as a heat sink to enable faster cooling of the ionized gases. The porous foam includes a plurality of meshes with a gap between the pluralities of meshes for the passage of the ionized gases. The ionized gases are channelized in an efficient way through the porous foam between the front vent and the back vent during the short circuit conditions.
[0013] During short circuit conditions, the ionized gases are passed through the meshes formed between the porous metal foam. The gases are greatly disturbed in terms of direction and velocity. The heat is exchanged between the gases and the metallic foam. As a result the gases are de-ionized and cooled effectively.
[0014] The efficiency of a circuit breaker is measured in terms of total arcing time and let through energy. The present invention uses a metallic foam to enable a faster cooling of the ionized gases. This reduces the total arcing time as well as let through energy of the circuit breaker.

E) BRIEF DESCRIPTION OF THE DRAWINGS
[0015] The objects, features and advantages of the present invention will be understood by (hose skilled in the art from the following description of the preferred embodiments of the present invention and the accompanying drawings in which:
[0016] FIG. 1 illustrates a front view of the molded case circuit breaker with cover according to one embodiment of the present invention.
[0017] FIG, 2 illustrates a front view of the molded case circuit breaker without cover according to one embodiment of the present invention.
[0018] FIG.3 illustrates a sectional view of the molded case circuit breaker (Y
Pole) according to one embodiment of the present invention.
[0019] FIG.4 illustrates a perspective view of porous foam placed inside the arc chamber assembly of the molded case circuit breaker1 according to one embodiment of the present invention.
[0020] FIG.5 illustrates a schematic structure of the porous foam of the arc chamber assembly according to one embodiment of the present invention.
[0021] 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
[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 the present invention provide a composite arc chamber assembly with a foamed-ionization device used as a heat sink in a molded case circuit breaker. The present invention provides a gas deionization device (foam) suitably placed in the vicinity of an arcing chamber of a low voltage molded case circuit breaker. The deionization device provided in the arc chamber assembly is a metal foam or a ceramic foam placed between the front vent and the back vent and arranged adjacent to the outlet of the arc chamber. The gas deionization device comprises a foam material which is porous in nature. The porous foam is designed to be arranged adjacent to the outlet of the arc extinguishing chamber. The compact structure of the porous foam enables relatively efficient cooling of the breaking gases ventilated from the arc extinguishing chamber.
[0024] FIG. 1 illustrates a front view of the molded case circuit breaker with
cover according to one embodiment of the present invention and FIG. 2 illustrates a 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 chamber assembly 6, an upper contact assembly 4, a housing 1, a knob 3, a release assembly 2, a front vent 7, a back vent 8, a porous foam 9 and a cover 10. The arc chamber assembly 6 is provided with an

improved gas deionization device to enable relatively efficient cooling of the gases ventilated from an arc extinguishing chamber. The arrangement of the components in the molded case circuit breaker is as shown in FIG. 1 and FIG. 2. The efficiency of the circuit breaker is measured in terms of total arcing time and let through energy. The gas de-ionization device used herein is a porous foam with a compact structure and functions as a heat sink to absorb the heat from the breaking gas ventilated from the arc extinguishing chamber. The porous foam used herein is a metallic foam or a cermaic foam to enable faster cooling of ionized gases. This reduces a total arcing time as well as a let through energy of the circuit breaker.
[0025] FIG. 3 illustrates the sectional view of the molded case circuit breaker (Y Pole) according to one embodiment of the present invention. With respect to FIG. 3, the arc chamber assembly includes a lower contact assembly 5. The deionization device preferably made of metal or ceramic foam 9 is placed between the front vent 7 and the back vent 8. The porous foam 9 comprises a porous shield designed to be arranged near to the outlet of the arc extinguishing chamber as shown in FIG. 3. The porous foam has a compact structure which enables relatively efficient cooling of the breaking gases ventilated from an arc extinguishing chamber with a high breaking capacity.
[0026] FIG.4 illustrates a porous foam placed inside the arc chamber assembly of the molded case circuit breaker and FIG.5 illustrates the structure of the porous foam of the arc chamber assembly according to one embodiment of the present invention. The porous foam is a compact structure which functions as a heat sink to absorb the heat from the breaking gas ventilated from the arc extinguishing chamber. Meshes 11 are formed between the porous foam. During short circuit conditions, the ionized gases pass through the meshes 11 formed between the porous foam as shown in FIG. 4. The gases are disturbed in terms of direction and velocity. FIG. 5 illustrates the

path of the hot ionized gas 12. The heat exchanges between the gases and the foam and therefore their deionization by cooling is enhanced.
(0027] The gas deionization device comprises a porous foam formed from agglomerated balls made from metallic base. Gaps are arranged between the balls to enable the hot ionized gases 12 to pass to the outside environment as shown in FIG. 4 and FIG. 5. The ceramic foams or metallic foam 9 can be of any metallic material which is heat conducting and corrosion resistant such as silicon carbide (15000°C), Alumna (11000°C), Zirconia (17000QC) etc. Figures in the bracket show the withstand temperatures of foams 9. The metallic material can be chosen based on their maximum withstand temperatures.
[0028] The foam 9 keeps certain porosity in order to enable an outflow of gases thus limiting the overpressure occurring in the arc chamber 6. It will therefore be necessary to find a compromise between the exhaust cross section and the heat exchange surface. The porosity can vary from 50 to 95 % depending upon the arc energy to be dissipated.
G) ADVANTAGES OF THE INVENTION
[0029] The arc chamber assembly of the present invention provides faster
cooling of the arc using porous foam thereby reducing let through energy of the circuit breaker. The arc energy generated during short circuit conditions is efficiently dissipated by the porous foam. The hot gases are channelized in an efficient way through the porous foam arranged between front and back vents. The porous foam can be easily inserted between the front vent and the back vent which makes the assembly easier. 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 a burden on the downstream equipments by virtue of a low let through energy.
[0030] 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.
[0031] 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. An arc chamber assembly of a molded case circuit breaker comprising:
a front vent;
a back vent: and
a de-ionization device placed between the front vent and the back vent; wherein the de-ionization device includes a structure to enable a cooling of gas ventilated from the arc chamber.
2. The arc chamber assembly of a molded case circuit breaker of claim 1. wherein the de-ionization device is adapted to function as a heat sink to enable faster cooling of ionized gases.
3. The arc chamber assembly of a molded case circuit breaker of claim I, wherein the deionization device comprises porous foam formed from agglomerated balls formed from a metallic base.
4. The arc chamber assembly of a molded case circuit breaker of claim 3, wherein the porous foam includes a plurality of meshes with a gap between the plurlaity of meshes for the passage of ionized gases.
5. The arc chamber assembly of a molded case circuit breaker of claim 1. " wherein the porous foam is at least one of a ceramic foam and a metal foam.
6. The arc chamber assembly of a molded case circuit breaker of claim 1, wherein the porous foam is arranged adjacent to an outlet of an arc extinguishing chamber.
7. The arc chamber assembly of a molded case circuit breaker of claim 4, wherein the ceramic foams is made of at least one of silicon carbide (15000°C), Alumna (11000°C), or Zirconia (17000°C).
8. The arc chamber assembly of a molded case circuit breaker of claim 1, wherein the ionized gases are channelized in an efficient way through

the porous foam between the front vent and the back vent during short circuit conditions.
9. The arc chamber assembly of a molded case circuit breaker of claim 1, wherein the porosity of the porous foam varies from 50% to 95 % depending upon arc energy to be dissipated.
10. The arc chamber assembly of a molded case circuit breaker of claim 1, wherein the ionized gases are disturbed in terms of direction and velocity in the porous foam.
11. The arc chamber assembly of a molded case circuit breaker of claim 1, wherein the heat exchanges between the gases and the porous foam causes cooling of hot gases thereby enhancing the de-ionization of the hot gases.