FORM 2
THE PATENTS ACT, 1970
(39 of 1970)
&
The Patents Rules, 2003
COMPLETE SPECIFICATION
(See section 10; rule 13)
1. Title of the invention - IMPROVED ARC QUENCHING ARRANGEMENT FOR FASTER ARC QUENCHING IN CIRCUIT BREAKERS
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
The present invention relates generally to circuit breakers. More particularly, the invention relates to an improved arc quenching arrangement for faster arc quenching in circuit breakers.
BACKGROUND AND THE PRIOR ART
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 contact system and arc quenching chamber.
In conventional arc quenching mechanism when the two contacts separate, an electric arc struck in between them. The arc is then moved by the arc runners to the arc chute where it splits into several small arcs and cools down, raising the arc voltage and thus quenching the arc. However when the arc is guided by the arc runners into the arc chute, a portion of arc still remains in between the moving and fixed contact.
Although moving and fixed contact are spaced from each other by a determined distance, very hot and conductive arc present in between may damage the contacts. Also, the hot ionized gases present in between the moving and fixed contact after arc extinction may cause

re strike, if the dielectric strength of the gap becomes less than the applied system voltage. These arc quenching mechanisms are inefficient in terms of total arcing time and let through energy.
The movable arc barrier mechanism consists of a fixed and moving barrier arranged in the contact system above the level of fixed contact in such a way that the movable barrier moves forward with the opening of contacts and goes inside the fixed barrier with some overlap between the two barriers. The moving arc barrier is connected to the drive shaft through rack and pinion gear mechanism and moves with respect to rotation of drive shaft.
As a result the fixed contact button becomes fully blocked from any other current conducting path to moving contact. Due to this electrical blocking phenomenon there is no path for the arc to conduct and hence it is quenched very fast. The total arcing time is substantially reduced which reduces heat generation in the device and also lowers the stresses on the downstream devices. Also less number of de-ion plates are required for quenching the arc by splitting and cooling since the arc energy is limited because of insulation of contacts by the arc barrier mechanism. This facilitates in making a higher rating breaker of smaller size and weight.
At the time of fault, the contacts start separating due to current repulsion and simultaneously the mechanism is triggered by tripping signal rotating the drive shaft of the device. The moving arc barrier arrangement can also be attached to the moving contacts directly

instead of drive shaft to achieve faster insulation of contacts as the same will start moving as soon as the contacts start repelling.
The arc barrier is preferably made up of an ablative material which can produce electronegative gases in high temperature. These electronegative gases absorb the electrons produced during arcing and increase the resistivity and limit the current flowing through the breaker. So, less amount of let through energy is allowed to downstream equipments.
Also since the arc barrier mechanism in this case insulates the fixed and moving contact completely, there are no chances of a re-strike of the arc once it is extinguished.
The prior art circuit breakers consist of an contact systems 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 and also this long arcing time results in higher erosion of contact button which ultimately lowers the life of breaker. This is because of their inability to rapidly move the arc, to limit the current and to cool it effectively during high fault conditions. These arc chamber assemblies are inefficient in terms of total arcing time and let through energy passed on to the downstream devices.
GB2450809 describes a similar arc barrier mechanism. However, there are certain limitations and advantages over it in the present

invention, which are listed below. It relates to an arc barrier mechanism which comes in between the fixed and moving contact to extinguish the arc between the two. However the same does not completely insulate fixed and moving contacts. There are chances that the arc may re-strike from some other path whenever the dielectric strength of that path will be less than the applied system voltage. The present invention however insulates the fixed and moving contacts completely thus having no possibilities of arc re-strike. The arc barrier material does not produce electronegative gases in high temperature which absorb the electrons produced during arcing helping in faster quenching of the arc.
Thus there is need to provide with an arc barrier which is preferably made up of a material which can produce electronegative gases in high temperature. The present invention accordingly provides an improved arc quenching arrangement for faster arc quenching in circuit breakers. In the present invention electronegative gases absorb the electrons produced during arcing and increase the resistivity of the medium and limit the current flowing through the breaker. This helps further for rapid quenching of the arc. In the present invention, Conventional contact system is improved upon by addition of movable arc barrier mechanism which insulates the fixed and moving contact completely when the moving contact separate from the fixed contact.
OBJECTS OF THE INVENTION
A basic object of the present invention is to overcome the disadvantages/drawbacks of the known art.

A basic object of the present invention is to provide an improved arc quenching mechanism in a contact system having a movable arc barrier mechanism for faster arc quenching.
Another object of the present invention is to provide an improved arc quenching mechanism with less erosion of contacts due to insulating arc barrier coming in between the moving contact and fixed contact as they separate.
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
The following presents a simplified summary of the invention in order to provide a basic understanding of some aspects of the invention. This summary is not an extensive overview of the present invention. It is not intended to identify the key/critical elements of the invention or to delineate the scope of the invention. Its sole purpose is to present some concept of the invention in a simplified form as a prelude to a more detailed description of the invention presented later.
There is provided an improved arc quenching system.
According to one embodiment of the present invention, there is provided improved arc quenching arrangement for faster arc

quenching in circuit breakers; said arrangement comprising at least one cover means (1); at least one knob means (2) in operative engagement with said cover (1); at least one housing means (3) covered the said cover means (1) thereby securing other components/parts inside the said housing (3); at least one release means (4); at least one driveshaft (6) in operative connection with said knob means; at least one driver gear means (7) mounted on said driveshaft (6), whereby movement of said driver gear (7) corresponds to the movement of said driveshaft (6); at least one driven gear means (8) in operation driven by said driver gear means (7); an arc chute (15); plurality of arc barriers comprising fixed arc barrier (10) and moving arc barriers (9A) for insulating fixed and moving contact, wherein said moving arc barrier being coupled to said driven gear such that in operation said moving arc barrier is movable in between main contacts during separation of said contacts and move out during closing of said contacts.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
In the appended drawings:
Fig 1 illustrates RHS view of MCCB.
Fig 2 illustrates Top view of MCCB.
Fig 3 illustrates Different components of arc barrier assembly describing their position in breaker.

Fig 4 illustrates Sectional view of MCCB showing arc barrier mechanism assembly at contact closed.
Fig 5 illustrates Sectional view of MCCB showing arc barrier mechanism assembly at contact open condition.
Fig 6 illustrates 3D sectional view of MCCB showing arc barrier mechanism assembly at contact closed condition.
Fig 7 illustrates 3D sectional view of MCCB showing arc barrier mechanism assembly at contact open condition.
Fig 8 illustrates Sectional view of MCCB showing arc barrier mechanism assembly at contact closed condition in which both of the barriers are movable.
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 RHS view of MCCB is shown. It shows cover, knob and housing.

Fig 2 shows Top view of MCCB. In addition to knob and housing it shows release means.
Fig 3 shows Different components of arc barrier assembly describing their position in breaker.
Fig 4 shows Sectional view of MCCB showing arc barrier mechanism assembly at contact closed.
Fig 5 shows Sectional view of MCCB showing arc barrier mechanism assembly at contact open condition.
Fig 6 shows 3D sectional view of MCCB showing arc barrier mechanism assembly at contact closed condition.
Fig 7 shows 3D sectional view of MCCB showing arc barrier
mechanism assembly at contact open condition.
Fig. 8 shows the moving and fixed arc barriers as component 9A and 10. The movable arc barrier is preferably made of ablative material which assists in arc quenching and current limiting by producing electronegative gases. The moving arc barrier is placed just behind the lower (fixed) contact button
The invented system is thus an improved arc quenching arrangement for faster arc quenching in circuit breakers.

DETAILED DESCRIPTION OF THE INVENTION
Accordingly in the present invention relates to an improved contact system of an electrical switching device with a movable arc barrier mechanism for arc quenching. The prime feature of present invention is the way arc is pushed away from the contact buttons and quenched by electrical insulation of fixed and moving contacts.
The arc barrier mechanism is designed such that it moves in between the main contacts when they get separated and moves out when main contacts get closed. This invention enhances the circuit breakers breaking capacity by faster recovery of dielectric strength of arcing zone and lesser erosion of main contacts by faster transition of arc from contact buttons to arc chute, thereby increasing electrical life of circuit breaker as well as enhancing its performance during fault conditions by eliminating the chances of re-strike.
The arc barriers in the present invention are made up of insulating material with high temperature withstand capability and high dielectric strength comparable to those required in the arcing chamber. As soon as the drive shaft starts rotating the movable barrier starts moving forward and gets in between the fixed and moving contact. This decreases the arc running time. This reduces the contact button erosion and improves the electrical life of MCCB.
List of components: Cover (1)

Knob (2)
Housing (3)
Release (4)
Mechanism (5)
Driveshaft (6)
Wheel gear (7)
Linear gear (8)
9A and 9B: Moving arc barrier (9)
Fixed arc barrier (In Fig. 9 it is also moving) (10)
Lower (Fixed) contact (11)
Upper (Moving) contact (12)
Upper (Moving) contact button (13)
Lower (Fixed) contact button (14)
Arc chute (15)
Linear gear for double moving barrier (16)
The present invention consists of improved contact system by addition of arc barrier mechanism which consists of fixed and movable arc barriers of insulating material with ability to withstand high temperature and has a high dielectric strength. The moving and fixed arc barriers are shown in Fig. 3 as component (9A) and (10). The movable arc barrier is preferably made of ablative material which assists in arc quenching and current limiting by producing electronegative gases. The moving arc barrier is placed just behind the lower (fixed) contact button as shown in Fig. 3. The moving arc barrier is attached to a linear gear shown in Fig. 3 as component (8) and moves with the movement of the same.

The linear gear is assembled to a wheel gear shown in fig. 3 as component (7) by means of gear arrangement so that the linear gear can move the movable barrier linearly due to the rotation of wheel gear with the rotation of drive shaft. This wheel gear also can be accommodated with the rotation of moving contact instead of with respect to driveshaft. In this case the arc barrier moves with the rotation of moving contact and helps in further decreasing the immobility time than in the case where it is attached to the drive shaft as shown here This is because of the fact that it will move with the repulsion of contacts which happens before the rotation of drive shaft due to a tripping signal to the mechanism.
There is another barrier which is fixed in nature placed just in front of the lower contact as shown in fig. 3 as component (10). The moving arc barrier goes in a cavity in the fixed arc barrier similar to a table drawer mechanism. This ensures an overlap of the two arc barriers and completely blocks the fixed and moving contacts from each other. This barrier can also be made moving instead of fixed for faster blocking of the contacts. The same can be done by using another linear gear moved by the same wheel gear to which the front arc barrier is attached as shown in fig. 8 or any different arrangement of such kind could be employed.
When the contacts start separating during fault conditions, arc is struck between contact buttons. The moving barrier comes forward as the barrier moves with the rotation of driveshaft (or by the movement of moving contact in case where it is attached to it) and gets in between the fixed and moving contacts. The fixed contact button is

blocked by the barrier as shown in the Fig. 5 and 7. This helps in extinguishing the arc in very initial stages. In case of lower fault currents this electrical blocking itself extinguishes the arc rapidly. Also since the fixed contact is completely insulated, it eliminates the chance of arc re-strikes.
The barrier is preferably made by ablative material which produces electronegative gases in high temperature conditions as in contact with the arc. These gases help in absorbing the ionized particles in the medium. This helps in faster quenching of the arc with the movement of the arc barrier. This limits the current and lowers the amount of let through energy to the downstream devices.
Advantages and features:
• Less erosion of contact Buttons due to insulating arc barrier coming in between the moving contact and fixed contact as they separate.
• The quenching of the arc in case of lower fault current will only be because of complete electrical insulation of fixed and moving contacts during separation. This increases the electrical life of the MCCB substantially.
• For high fault current as it blocks the current path fully when contacts open. The chance of re-strike of arc between the contacts is eliminated.

• Use of arc barrier lowers the requirement of de-ion plates for splitting and cooling the arc which helps in designing a lower weight and smaller size switching device.
• The barrier is preferably made up of an ablative material which produces electronegative gases during arcing absorbing the ionized particles exactly near the region where they are produced. This helps in faster quenching of the arc when arc barrier is insulating fixed and moving contact. This limits the current and lowers the amount of let through energy 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 improved arc quenching arrangement for faster arc quenching in circuit breakers; said arrangement comprising:
at least one cover means (1);
at least one knob means (2) in operative engagement with said cover (1);
at least one housing means (3) covered the said cover means (1) thereby securing other components/parts inside the said housing (3);
at least one release means (4);
at least one driveshaft (6) in operative connection with said
knob means;
at least one driver gear means (7) mounted on said driveshaft (6), whereby movement of said driver gear (7) corresponds to the movement of said driveshaft (6);
at least one driven gear means (8) in operation driven by said driver gear means (7);
an arc chute (15);
plurality of arc barriers comprising fixed arc barrier (10) and moving arc barriers (9A) for insulating fixed and moving contact,

wherein said moving arc barrier being coupled to said driven gear such that in operation said moving arc barrier is movable in between main contacts during separation of said contacts and move out during closing of said contacts.
2. Arrangement as claimed in claim 1 wherein said arc barrier having high temperature withstanding capacity.
3. Arrangement as claimed in claim 1 wherein said arc barrier having high dielectric strength.
4. Arrangement as claimed in claim 1 wherein said arc barrier adapted to block current path completely thereby preventing re-strike of arc.
5. Arrangement as claimed in claim 1 wherein said arc barrier made of substantially ablative material.
6. Arrangement as claimed in claim 1 wherein said arc barrier during arcing producing substantially electronegative gases thereby limiting current flowing through said circuit breaker.
7. Arrangement as claimed in claim 1 wherein said driver gear means is a wheel gear.

8. Arrangement as claimed in claim 1 wherein said driven gear means is a linear gear.
9. Arrangement as claimed in claim 1 wherein said arc barrier further comprising a cavity for completely blocking arc between contacts.
10. An improved arc quenching arrangement for faster arc quenching in circuit breakers as herein described and illustrated with reference to accompanying drawings.