FORM2
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
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 an arc chute assembly. More, particularly it is an improved arc chute assembly having an ablative gassing material for faster cooling of the arc and helps to break electric current faster.
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. This is because of their inability to cool the arc effectively during high fault conditions. These arc chamber assemblies are inefficient in terms of total arcing time and let through energy with a circuit breaker passes to the downstream equipments.
Normally during arcing process, the insulation surrounding the arc is subjected to deposition of carbon material due to burning of the insulation. This carbonaceous material forms tracking of the insulation thereby leading to flashover between poles to pole. This problem is addressed in the present invention by using a sheet of ablative gassing material.
US 4,609,797 document discloses that an arc splitter plate made of steel includes a pair of spaced parallel limbs which merge together at one end into a block forming a notch there between. Toward an end portion of the block remote from the notch is an insulated region which extends across a portion of a first face of the block, over a leading edge of the block, and onto a second face of the block. The insulated region is formed from an insulating means which is made from a tape including combined layers of an insulating material and an adhesive. The arc splitter plates are for use in arc chutes and more especially for use in cold cathode arc chutes. However, the present invention uses a self adhesive Polytetrafluoroethylene (PTFE) sheet having rectangular

slots is placed on inner surfaces of supporting structures and not on splitter plates and only one sheet is stuck on inner sides of two supporting structures.
Thus, the present invention is provided with an arc chute assembly with a sheet of ablative gassing material to overcome the disadvantages in the prior art. So, the present invention enhances the circuit breaker's breaking capacity by generating insulating gases during current interruption.
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 arc chute assembly with a sheet of ablative gassing material.
Another object of the present invention is to provide an arc chute assembly for faster cooling of the arc.
Another object of the present invention is to provide splitter plates and ablative material in single assembly.
Another object of the present invention is to provide an arc chute assembly to enhance the circuit breaker's breaking capacity by generating insulating gases during current interruption.
SUMMARY OF THE INVENTION
According to one aspect of the present invention there is provided an improved arc chute assembly comprising :
(i) plurality of de-ion plate means;
(ii) support structure means holding said de-ion plates; and
(iii) ablative material sheet means being lamellarly provided on inner side of said support structure means; wherein said support structure means being provided with unique slot profiles such that said plurality of de-ion plate means and said ablative material sheet means are accommodated in said

slot profile to make said assembly rigid and providing decomposition of said ablative gassing material sheet due to thermal stress during arcing process resulting in enhanced release of gases having high thermal conductivity resulting in faster cooling of the arc thus reducing let through energy of circuit breaker and reducing stress on electric system.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
Figure 1 illustrates front view of the arc chute assembly
Figure 2 illustrates side view of the arc chute assembly
Figure 3 illustrates top view of the arc chute assembly
Figure 4 illustrates isometric view of the arc chute assembly
Figure 5 illustrates the arc chute assembly in a molded case circuit breaker
DETAILED DESCRIPTION OF THE ACCOMPANYING DRAWINGS
According to the present invention there is provided with an arc chute assembly is an arrangement comprising of components namely splitter plates 1, side insulating walls known as support structure 2 and a sheet of ablative material 3 comprising PTFE (Poly tetra flouro ethylene) sheet in a single assembly as shown in figure 1.
According to one embodiment of the present invention, the arc chute assembly is provided with a sheet of ablative gassing material. The ablative material in the invention is a combination of PTFE plus glass fiber with silicon adhesive having overall thickness of 0.25 mm. Glass cloth contribute excellent strength and dimensional stability, exhibit essentially zero flow under heat and pressure and are highly resistant to cut-through.
In another embodiment of the present invention, the support structure comprises of rectangular slots which fits both the splitter plates and the sheet of gassing material. The gassing material is placed on the inner sides of both the support structures. During arc quenching process the gassing material emits insulating gases which rapidly cool the arc and finally breaks the electric current.

The sheets 3 are provided with rectangular slots same as those provided in supporting structure 2 for supporting splitter plates. The adhesive side of the PTFE plus glass fiber sheet is stuck on the inner side walls of the supporting structure. Then the splitter plates 1 are stacked one by one. The entire arc chute assembly 4 is then crimped from both ends of the supporting structure to make it a rigid body. This assembly 4 is then placed in the circuit breaker assembly 5
In the present invention, arc cooling is enhanced by the use of a gassing material within an arc chute assembly having a support structure for the stack of arc plates also known as de-ion plates. This invention enhances the circuit breaker's breaking capacity by generating insulating gases during current interruption.
In most of the switching devices the insulated housing and that of the moving insulated contact carrier are meant for resting the contact of the system. Similarly the side insulated walls of the de-ion plates are meant for supporting the stacks of U plates one above the other which is known as arc chamber or arc chute assembly. But apart from this during arcing process, the insulated material coming in its vicinity is subjected to thermal stress, which results in decomposition of the insulated material above their respective boiling point. Decomposition of the insulated material results in release of gas at a very high pressure. The gases released by the ablative material are of high thermal conductivity, resulting into faster cooling of the ionized plasma. This results in reduction of the conductivity of the plasma material. The jet of high pressure gases released increases the overall dielectric strength of the medium, which is sufficient to overcome the transient recovery voltage of the system. Also due to high electron electronegativity of the gases released, they attract electrons to neutralize the plasma at a faster rate. This reduces the rate of rise of the electron combination.
During any short circuit fault the sensing unit of the circuit breaker gives a tripping command to the mechanism and an electric arc consisting of negative and positive ions is struck between the contacts of the circuit breaker. The ionized arc is very high temperature plasma of few thousands of °C. The decomposition temperature of PTFE sheet 3 is about 525°C and hence it vaporizes.
Normally during arcing process, the insulation surrounding the arc is subjected to deposition oi" carbon material due to burning of the insulation. This carbonaceous material forms tracking of the insulation thereby leading to flashover between poles to pole. However the present invention

is provided with ablative material releases gases, which normally does not burns by itself but in turn leads to cooling of the plasma. Hence the residue formed by it does not create any carbon composition, which forbids any formation of conductive tracking upon the insulation.
Gases released by insulator PTFE with binder is H2, CF4 Be F in large percentage. Due to polymeric chain like construction, the percentage of F released is very high. Also the covaient bond HF compound has high dielectric constant as compared to ammonia. These gases being inflammable & inert in nature does not burn by itself even at the arcing temperature of 6000°C to 10,000°C.
The present invention also relates to the effortless cooling property of PTFE sheet 3 by emitting inert gases with high thermal conductivities. Typical thermal conductivities are H2 (0.1684), F (0.0279), CF2 (0.1415),CO(0.0232) in W/m/K. Faster cooling of the arc reduces the electrical conductivity of the arc by a large amount there by limits the fault current and increases the arc voltage. The arc time and hence the energy of the arc reduces considerably as compared to standard arc chute assembly.
ADVANTAGES OF THE INVENTION
1. Faster cooling of the arc.
2. Making hybrid assembly (containing splitter plates, support structures & ablative sheet) as a
single unit.
The invention has been described in a preferred form only and many variations may be made in the invention which will still be comprised within its spirit. The invention is not limited to the details cited above. The splitter plates, supporting structure, PTFE (Poly tetra flouro ethylene), ablative material as stated do not limit the scope of the present invention. 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.

WE CLAIM
1. An improved arc chute assembly comprising:
(i) plurality of de-ion plate means;
(ii) support structure means holding said de-ion plates; and
(iii) ablative material sheet means being lamellarly provided on inner side of said
support structure means; wherein said support structure means being provided with unique slot profiles such that said plurality of de-ion plate means and said ablative material sheet means are accommodated in said slot profile to make said assembly rigid and providing decomposition of said ablative gassing material sheet due to thermal stress during arcing process resulting in enhanced release of gases having high thermal conductivity resulting in faster cooling of the arc thus reducing let through energy of circuit breaker and reducing stress on electric system.
2. Assembly as claimed in claim 1 wherein said slot profiles are rectangular slots.
3. Assembly as claimed in claim 1 wherein said ablative material comprises selectively polytetraflouro ethylene (PTFE), glass fiber and silicon and combination thereof.
4. Assembly as claimed in claims 1 to 3 wherein said ablative material sheet having thickness about 0.25 mm.
5. Assembly as claimed in claims 1 to 4 wherein said ablative material sheet having temperature of decomposition of about 525°C.
6. Assembly as claimed in any of the preceding claims wherein said de-ion plates having substantially U shaped profile.
7. An improved arc chute assembly as herein substantially described and illustrated with the accompanying drawings.