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 QUENCHING SYSTEM FOR USE IN CIRCUIT
BREAKERS TO BLOCK BACKWARD FLOW OF GASES
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 an arc quenching system and more particularly to an improved arc quenching system for use in circuit breakers to block backward flow of gases produced during arcing.
BACKGROUND AND THE PRIOR ART
Electrical switching apparatus, such as circuit breakers, are employed in high range of 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 breaking capacity of any circuit breaker is totally governed by the performance of its arc quenching chamber. When the contacts separate in any electrical switching device, say a circuit breaker, arc is struck between fixed and moving contact. An arc basically is a discharge of electric current, which produce plasma between the contacts. Because of arc, there are rapid temperatures changes which develop a very high pressure inside the arcing chamber. Also the splitter plates of the arc chute in the circuit breaker exert a magnetic pull on the arc. The arc is blown towards the arc chute due to force exerted on it which is a balance of magnetic forces and the gas dynamics due to high pressure generated inside the arcing chamber. As the arc enters the arc chute, it is split & cooled and thereby effectively quenched.
The arc velocity during its movement towards the arc chute is dependent on balance of magnetic forces and gas dynamics. The gas flow towards the arc chute is because of the pressure difference between arc front and behind it. It is desirable to have high pressure behind the arc and lower pressure in front of it. Due to this, the gas dynamics aids the magnetic forces on the arc and helps the arc to move towards the arc chute. To achieve this, vents are provided behind the arc chute. However, there is some

vacant volume produced between the fixed contact and the moving contact when they separate from each other. Some of the pressure generated gets dissipated in this volume reducing the effective pressure behind the arc thereby lowering the arc velocity towards the arc chute. Also, due to this, hot gases may escape to the operating mechanism which may increase the chances of mechanism failure. Figure-1 & Figure-2 describes conventional contact system. In conventional contact system, when the contacts separate, the opening towards the mechanism side of the contact system between fixed contact and moving contact exists. This opening is shown in figure-2 with the help of arrows. The hot gasses and metallic globules produced during opening on short circuit can escape through this opening causing difficulty or sometimes failure of operation of the mechanism and other parts of the circuit breaker. At the same time due to presence of this opening, the hot gasses produced during opening on short circuit escape through the said opening between fixed and moving contact. Therefore the gases produced during short circuit flow in the unintended direction thereby lowering the pressure at exit of the contact system i.e. on the arc vent (6). These causes ultimately increase in short circuit time and let through energy of the circuit breaker. So the need was felt for a means by which the gases flowing in the reverse direction should be blocked.
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 certain arcing times. The energy dissipated during arcing and hence the stress developed during arcing depends on the total arcing time. Higher arcing times leads to severe stresses on the downstream equipments due to large amount of let through energy.
Therefore there is a need for equipment by which the backward flow of gases can be prevented during arcing resulting into slower movement of arc and long arching time. The present invention provides for an improved arc quenching system for use in circuit breakers which would prevent backward flow of gases produced during arcing.

OBJECTS 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 improved arc quenching system for use in circuit breakers.
Another object of the present invention is to increase the breaking capacity of the arc quenching chamber.
Another object of the present invention is to provide for high pressure behind the arc and lower pressure in front of it so the hot gases escape the arc vent with higher velocity.
Another object of the present invention is to block the gases flowing in the reverse
direction.
Another object of the present invention is to reduce the total arcing time.
Yet another object of the present invention is to protect the operating mechanism and other parts of the switching device from hot gases and globules generated in the arcing chamber thereby reducing the chances of potential failure due to the same.
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 improved arc quenching system for use in circuit breakers.
According to one embodiment of the present invention, there is provided an arc quenching system to increase the breaking capacity of the arc quenching chamber.
Other embodiment of the present invention provides for high pressure behind the arc and lower pressure in front of it so the hot gases escape the arc vent with higher
velocity.
Other embodiment of the present invention provides for blocking the gases flowing in
the reverse direction.
Other embodiment of the present invention provides for reduction in the total arcing
time.
Yet other embodiment of the present invention provides for protection of an operating mechanism and other parts of the switching device from hot gases and globules generated in the arcing chamber thereby reducing the chances of potential failure due to the same.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
In the appended drawings:
Fig 1 illustrates Conventional contact system in closed condition.
Fig 2 illustrates Conventional contact system in open condition.

Fig 3 illustrates Contact system (in closed condition) with flap for blocking gases.
Fig 4 illustrates Contact system (in open condition) with flap for blocking gasses.
Fig 5 illustrates cross section view of Contact system (in closed condition) with flap for blocking gasses.
Fig 6 illustrates cross section view of Contact system (in open condition) with flap for blocking gasses.
Fig 7 illustrates an exploded view of the components.
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 wherein Conventional contact system in closed condition is shown. It shows position of fixed contact and moving contact.
Fig 2 shows Conventional contact system in open condition and the corresponding position of the fixed and moving contact-Fig 3 shows Contact system (in closed condition) with flap for blocking gases. The flap (3) is made up of an insulating sheet which is able to sustain high pressure and temperatures produced in the arcing chamber.

Fig 4 shows position of fixed contact, Moving contact, Flap and Slit, The slit (4) is the part of housing or a separate component assembled to form slit used to assemble flap with the fixed contact.
Fig 5 shows cross section view of Contact system (in closed condition) with flap for blocking gasses. The flap seals the vacant volume between the moving contact and the fixed contact which else while would have been produced in absence of the same.
Fig 6 shows cross section view of Contact system (in open condition) with flap for blooking gasses. This increases the pressure build up behind the arc which increases the difference in pressures between the front of the arc and behind it.
Fig 7 shows an exploded view of the components. The assembly of the flap (3) along with moving contact (2) in the slit (4) provided in the housing is shown
The invented system is thus an improved arc quenching system for use in circuit breakers.
DETAILED DESCRIPTION OF THE INVENTION
According to the present invention there is provided an improved arc quenching system for use in circuit breakers. In the present invention, conventional arc quenching chamber is improved upon by means of an insulated sheet henceforth referred as flap attached to the moving contact of circuit breaker. The insulating sheet is connected to the moving contact of the circuit breaker in such a manner that the area' offered behind the contact system towards mechanism is covered forming a very narrow gap (almost negligible). This narrow gap results into the gas pressure build up and arc movement towards the desired position i.e. the arc chute side. The said

arrangement increases the pressure to a great extent compared to the pressure in front of it and moves it faster towards the arc chute reducing the total arcing time. Also, it protects the mechanism and other parts of the electrical switching device from hot gases & globules produced during arcing.
In the present invention, an arrangement of insulating sheet (called flap) is assembled in such a way that it helps in increasing the pressure of arc chamber and enhances the movement of arc towards arc chute under short circuit conditions. The faster movement of the arc reduces the arc quenching time and hence reduction in the let through energy.
The present invention relates to an arc quenching system which prevents backward flow of gases (from arc chamber towards mechanism) produced during arcing by means of flap attached to the moving contact and placed inside the housing of the circuit breaker. This invention enhances the circuit breakers breaking capacity by faster movement of arc towards arc chute because of high pressure generation behind the arc. Also it protects the operating mechanism and other parts of the switching device from hot gases and globules generated in the arcing chamber thereby reducing the chances of potential failure due to the same.
In the following detailed description, reference is made to the accompanying drawings that form a part hereof, and illustrate the best mode presently contemplated for carrying out the invention. Further functioning of the mechanism has been discussed below to describe the way the mechanism operates. However, such description should not be considered as any limitation of scope of the present unit. 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.

According to a preferred embodiment of the invention, there is provided an improved arc quenching system for use in circuit breakers. The present invention enhances the pressure build up behind the arc by sealing the vacant volume produced between the moving and fixed contact by means of a flap (3) attached to the moving contact (2) as shown in fig. 3. The flap (3) is made up of an insulating sheet. This sheet can be able to sustain high pressure and temperatures produced in the arcing chamber. The flap has a slot in which moving contact is inserted. The flap (3) along with the moving contact is then inserted in a slit (4). The slit (4) is the part of housing or a separate component assembled to form slit used to assemble flap with the fixed contact can have this provision as shown in figures 3 and 4.
The assembly of the flap (3) along with moving contact (2) in the slit (4) provided in the housing is shown in figure 7. The location of the slit is such that it creates a gap between the flap (3), moving contact (2) and the base of the housing. When the moving contact (2) and fixed contact (1) close, the flap (3) covers the vacant portion between fixed contact (1) and moving contact (2). As the moving contact separate from the fixed contact, the flap travels with the moving contact, the location of the slit in the housing is chosen in such a way that flap covers the vacant space between the fixed and moving contact completely. Thus the flap seals the vacant volume between the moving contact and the fixed contact which else while would have been produced in absence of the same. This is shown in figure-4 as well as in figure-6 in two different views. This increases the pressure build up behind the arc which increases the difference in pressures between the front of the arc and behind it. The greater pressure differential enhances the gas dynamics inside the arc chamber and the hot gases produced rapidly flow towards the arc chute (5). This aids the magnetic forces exerted on the arc due to splitter plates of the arc chute to a great extent and thereby increases the arc velocity towards arc chute. The increased arc velocity enhances faster movement of the arc and faster entrance of the arc in the splitter plates where it is split, cooled and effectively quenched reducing total arcing time.

The reduction in total arcing time reduces the let through energy of the circuit breaker and thereby the stresses on the downstream devices.
Also, since the flap seals the vacant volume between the moving contact and the fixed contact produced when they separate, it prevents the backward flow of hot gases towards the mechanism and other parts of the switching device preventing them from any potential failure due to the same during arcing.
The material of the flap can also be of a material capable of producing gases (under high temperature) which assist in arc quenching. The production of electronegative gases rapidly de-ionizes the ionized hot gases produced and increases the arc voltage. This helps to quench the arc rapidly and further reduce the arcing time. Also, the production of electronegative gases reduces the possibility of arc re-strike after fault clearance by the arc chute. Constructional components:
1. Fixed contact
2. Moving contact
3. Flap
4. Slit
5. Arc chute
6. Arc vent
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 ail 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 arc quenching system for use in circuit breakers for blocking backward flow of gases produced during arcing comprising a flap attached to the moving contact of circuit breaker.
2. System as claimed in claim 1 wherein the flap is provided such that the vacant volume between the fixed and moving contact is sealed to build up gas pressure.
3. System as claimed in claim 1 wherein the flap is assembled such that pressure is built up towards the arc chute side under short circuit conditions.
4. System as claimed in claim 1 wherein the flap further comprises a slot to insert the moving contact.
5. System as claimed in claim 4 further comprises a slit to assemble the flap along with the moving contact.
6. System as claimed in claim 5 wherein the slit is provided such that it creates a gap between the flap (3), moving contact (2) and the base of the housing.
7. System as claimed in claim 5 further comprises a housing to accommodate the assembly of the flap (3) along with moving contact (2) in the slit (4).
8. An improved arc quenching system for use in circuit breakers for blocking backward flow of gases as herein substantially described and illustrated with reference to the accompanying drawings.