FORM2
THE PATENTS ACT, 1970
(39 of 1970)
&
The Patents Rules, 2003
COMPLETE SPECIFICATION
(See section 10; rule 13)
1. Title of the invention. -
ARC CHUTE ASSEMBLY FOR EXTINGUISHING ARC AND A METHOD THEREOF
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:

TECHNICAL FIELD OF THE INVENTION
This invention relates generally to arc quenching assembly and a method for arc quenching. More particularly the present invention relates to an arc chute assembly for electrical switching devices for extinguishing an electric arc and a method thereof.
BACKGROUND AND THE PRIOR ART
Switching devices like circuit breakers protect electrical circuits from damage by isolating the circuit, in the event of any abnormal condition i.e. overload and short circuit condition. During the process of isolating the circuit, the circuit breaker would see an arc between the opening contacts. This arc gets quenched inside the circuit breaker without damaging the other electrical systems.
The prior art circuit breakers consist of an arc chamber 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 attract the arc towards arcing chamber & cool it effectively during high fault conditions. There is a scope of improvement in existing arc chamber assemblies in terms of total arcing time and let through energy.
An arc basically is a discharge of electric current, flowing through the circuit in the event of any abnormal condition i.e. overload and short circuit condition, between contacts of a circuit breaker during the opening of contacts to isolate the electric circuit. Arcs may vary in size and intensity depending on the amount of fault current, and minimizing the arc is important as the arc can damage the contacts. Arc may further ionize gases inside the circuit breaker which could damage the circuit breaker casing. Arc can severely damage the circuit breaker and surrounding

equipment. Hence a circuit breaker must not only isolate electrical circuit but also control and quench the arc.
As a result, various arc control mechanisms like stretching the arc; breaking the arc into smaller segments; cooling the arc; blowing out the arc; vacuum interruption of the arc are used in the art.
Generally circuit breakers employ an arc chute to control and extinguish an electric arc. Arc chute confines, divides and cools an arc thereby resulting in quenching the arc. Arc chutes conventionally have arc dividers in the form of flat segments stacked one above the other preferably with an air gap between them. As an arc is developed the arc chute will pull the arc and divide it into smaller arcs. The division of arc into smaller segments increases the arc resistance. Also, before the arc enters the arc chute, it gets lengthened because of separation of contacts which increases its resistance. The increase in arc resistance due to lengthening and splitting in smaller arcs results in arc quenching.
The drawbacks of the above mentioned prior art it that the circuit breakers consist of an arc chamber 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 attract the arc towards arcing chamber & cool it effectively during high fault conditions. These arc chamber assemblies are inefficient in terms of total arcing time and let through energy.
The prior art circuit breakers do not consist of arc chutes wherein the arc is lengthened in a zigzag way during splitting increasing the arc length and hence arc resistance. These arc chamber assemblies are inefficient in terms of total arcing time and let through energy passed on to the downstream devices. If the arc is lengthened further when it is split in the arc chute, it will further increase arc resistance, increase arc voltage build up and will result in faster quenching of

the arc. The lesser arcing time will limit the current and reduce the let through energy to the downstream devices.
Thus there is a need to provide an improved arc quenching system for an electrical switching device with arc chute assembly, where the arc chute assembly is improved upon by means of splitter plate (de-ion plate) arrangement wherein the one corner of the splitter plate profile is chamfered and the splitter plates are arranged in way such that the chamfered profiles will fall in an alternate direction. In the present invention, conventional arc chute assembly is improved upon by means of splitter plate (de-ion plate) arrangement having alternate side chamfers in their profiles.
OBJECT OF THE INVENTION
A basic object of the present invention is to overcome the disadvantages/drawbacks of the known art.
Another object of the present invention is to provide an arc quenching assembly for use in switching devices.
Other object of the present invention is to provide an improved arc quenching system for an electrical switching device with an arc chute assembly adapted for zigzag splitting of the arc as it enters the arc chute which lengthens it further and increases the arc resistance along with splitting which helps in faster quenching of the arc.
Yet another object of the present invention is to provide an improved arc quenching system for an electrical switching device with an arc chute assembly adapted for reduction in arcing time let through energy of the circuit breaker due to faster arc quenching, reducing stresses on the electrical system on line.

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
There is provided an arc quenching assembly for use in switching devices.
According to one embodiment of the present invention, there is provided an arc chute assembly for electrical switching devices for extinguishing an electric arc, said arc chute assembly comprising a plurality of splitter plates stacked one above the other with one corner of said splitter plates chamfered, said splitter plates arranged such that said chamfered comer fall in alternate direction.
Other embodiment of the present invention provides a method for extinguishing an electric arc using an arc chute assembly for electrical switching devices comprising the steps of generating magnetic field in the splitter plates due to flow of fault current; said magnetic field driving said arc in the said arc chute; generation of gas pressure inside arcing chamber due to arc plasma pushing said arc further inside said arc chute; chamfered corner of said splitter plate generating magnetic force; said magnetic force and said gas pressure pushing said arc towards chamfered profile of said splitter plate causing lengthening of the arc in a zigzag way leading to splitting of said arc into a number of series arc.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
In the appended drawings:

Fig 1 illustrates RHS view of MCCB.
Fig 2 illustrates front view of MCCB.
Fig 3 illustrates sectional view of MCCB showing contact assembly.
Fig 4 illustrates conventional splitter plate (de-ion plate) 3d view.
Fig 5 illustrates splitter plate with chamfer on one of its side 3d view.
Fig 6 illustrates arrangement of splitter plates.
Fig 7 illustrates arc chute assembly.
Fig 8 illustrates magnetic flux linkages and direction of force on arc.
Fig 9 illustrates the gas flow because of chamfer on one of the sides of splitter plates.
Fig 10 illustrates splitting and zig zag lengthening of arc in present invention.
Fig 11 illustrates splitting of arc in conventional splitter plate arrangement without chamfer on one of its side.
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 molded case circuit breaker comprising arc chute assembly is shown.
Fig. 2 and 3 shows front view and cross sectional view of the MCCB.
Fig. 4 shows the conventional splitter plates without any chamfer.
Fig. 5 shows the splitter plate in accordance with the present invention. It shows chamfer on one corner of the splitter plate.
Fig. 6 shows the arrangement of the splitter plates with alternate chamfers.
Fig. 7 shows the arrangement of splitter plate in the arc chute assembly.
Fig. 8 shows magnetic flux linkages and direction of force on arc. It shows high density of magnetic flux lines near the chamfer.
Fig. 9 shows flow of gas from the splitter plate.
Fig. 10 shows splitting and zig zag lengthening of arc in accordance with the present invention.
Fig. 10 shows splitting of arc in the conventional splitter plates.
The invented system is thus an arc chute assembly for electrical switching devices for extinguishing an electric arc.

DETAILED DESCRIPTION OF THE INVENTION
Accordingly in the present invention the arc chute assembly is improved upon by means of splitter plate (de-ion plate) arrangement wherein the one corner of the splitter plate profile is chamfered and the splitter plates are arranged in way such that the chamfered profiles will fall in an alternate direction. This results in a zigzag splitting of the arc as it enters the arc chute which lengthens it further and increases the arc resistance along with splitting which helps in faster quenching of the arc. The phenomenon is explained in detail description. Faster quenching of the arc results in lower arcing times which limits the fault current and lowers the let through energy/stresses passed on to the downstream devices.
List of components:
1. Moving (upper) contact assembly (1)
2. Arc chute assembly (2)
3. Fixed (lower) contact assembly (3)
4. Splitter plate with chamfer on one side (4)
5. Arc (5)
The prime feature of the present invention is the way arc is lengthened in a zig-zag manner and split in smaller arcs as it enters the arc chute increasing the arc resistance and thus quenching the arc faster.
In the present invention, conventional arc chute assembly is improved upon by means of splitter plate (de-ion plate) arrangement having alternate side chamfers in their profiles. The splitter plate is as shown in fig. 5 against the conventional one in fig 4. The arrangement of the splitter plates is done such that the side chamfers on their profiles fall in an alternate manner as shown in fig. 6. The arc chute assembly of the same is as shown in fig 7.

After entering the arc inside the arc chute, it splits in no of smaller series arcs. The fault current flowing through the circuit produces a magnetic field in splitter plates. Magnetic field lines passing through splitter plates produces a pulling force (attraction force) on the arc which drives it further inside the arc chute. The magnitude and direction of the pulling force acting on the arc depends on the magnetic flux density and its distribution in the splitter plates. The force acting on arc due to the gas pressure generated inside the arcing chamber also pushes the arc further inside the arc chute.
The splitter plates have a chamfer on one side which results in crowded magnetic flux lines in that region. This result in higher magnetic flux density in that region compared to any other region of the splitter plate. This is depicted in fig 8. The arc thus experiences maximum magnetic force in the direction of chamfered profile of splitter plate. Also the hot gases produced due to arc plasma experience lesser opposition while escaping out from the chamfered profile which increases the gas flow in that region as shown in fig 9. Thus the force acting on the arc due to gas dynamics pushes arc towards the chamfered profile of the splitter plate.
The splitter plates are arranged such that the chamfered profile of the splitter plate falls in an alternate direction. The combined effect of magnetic force and gas dynamic force pushes the arc root towards chamfered profile of the splitter plate and thus causing lengthening of the arc inside the splitter plates in a zig-zag way as shown in fig. 10. This also helps in faster cooling of arc.
Due to increase of arc resistance by zig-zag lengthening, it is quenched faster compared to the case where it is only split and cooled in the conventional arc chute as in fig 11. This reduces the total arcing time and limits the current which reduces the let through energy passed on to the downstream devices.

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 arc chute assembly for electrical switching devices for extinguishing electric arc, said
arc chute assembly comprising:
plurality of splitter plates stacked one above the other having predetermined air gap in between each of said splitter plates and having one corner of each of the said splitter plates being chamfered, wherein said chamfered corner adapted to produced maximum magnetic flux lines, and
wherein said splitter plates arranged such that said chamfered corner fall in alternate direction.
2. Arc chute assembly as claimed in claim 1 wherein said splitter plates are substantially flat segments with corner chamfered.
3. Arc chute assembly as claimed in claim 1 wherein said splitter plates are de-ion plates.
4. A method for extinguishing electric arc using an arc chute assembly for electrical switching devices comprising steps of:
generating magnetic field in the splitter plates due to flow of fault current; said magnetic field driving said arc in the said arc chute; generation of gas pressure inside arcing chamber due to arc plasma pushing said arc further inside said arc chute; chamfered corner of said splitter plate generating magnetic force; said magnetic force and said gas pressure pushing said arc towards chamfered profile of said splitter plate causing lengthening of the arc in a zig zag way leading to splitting of said arc into a number of series arc.
5. Method as claimed in claim 5 wherein said chamfer provides a high magnetic density
thus generating very high magnetic force.

6. Method as claimed in claim 5 wherein said magnetic force and said gas pressure confine said arc in said arc chute assembly.
7. Method as claimed in claim 5 wherein said splitter plates facilitates cooling of said arc.
8. An arc chute assembly for electrical switching devices for extinguishing an electric arc as herein described and illustrated with respect to the accompanying drawings.
9. A method for extinguishing an electric arc using an arc chute assembly for electrical switching devices as herein described and illustrated with respect to the accompanying drawings.