FORM 2
THE PATENT ACT 1970
&
The Patents Rules, 2003
COMPLETE SPECIFICATION (See section 10 and rule 13)
1. TITLE OF THE INVENTION:
"Double Break Circuit Breaker with Improved Arc Quenching"
2. APPLICANT:
(a) NAME: Larsen & Toubro Limited
(b) NATIONALITY: Indian Company registered under the
provisions of the Companies Act-1956.
(c) ADDRESS: LARSEN & TOUBRO LIMITED,
L&T House, Ballard Estate, P. O. Box: 278, Mumbai 400 001, India
3. PREAMBLE TO THE DESCRIPTION:
COMPLETE
The following specification particularly describes the invention and the manner in which it is to be performed.

Double Break Circuit Breaker with Improved Arc Quenching
Field of the invention
The present invention relates to circuit breakers, and more particularly, to a double break circuit breaker with improved arc quenching having with current limitation and reduced heat losses.
Background of the invention
In the case circuit breaker device, it is of critical importance for the life and the switching power that an arc produced when a fixed contact and a moving contacts are opened, does not remain on the contact pieces. The arc should be guided as quickly as possible to a quenching chamber region where the arc is cooled and quenched. Every time the arc remains in an arc chute assembly, even in the millisecond range, the wear and erosion of de-ion plate is increased.
The circuit breaker has a contact point which is formed from the fixed contact and the moving contacts. The contact point is located in a so-called contact region, to which a quenching chamber having an arc splitter stack is connected. The base points of the arc are guided from the fixed contact and the moveable contact via arc guide rails to the arc splitter stack. In this case, the arc broadens directly after contact opening, and the speed at which the arc runs into the arc splitter stack is dependent on the self-blowing of the arc. Once the arc moves inside the splitter plates, it gets elongated and splitted.
The design of the arc guide rails is such that resistance in the quenching circuit is lower, with the result that the quenching circuit can be interrupted, but with increased let through energy and heat losses.
Accordingly, there exists a need to provide an arc quenching device which overcomes the drawbacks of the prior art.

Objects of the invention
An object of the present invention is to introduce additional resistance only during fault conditions, to limit the fault current and to quench the arc effectively.
Summary of the invention
Accordingly, the present invention provides a double break circuit breaker device with improved arc quenching. The device comprises a first fixed contact assembly, a second fixed contact assembly, a quenching chamber, and arc chute. The first fixed contact assembly includes a first fixed contact, and a first arc runner joined to a jumper. The joined first arc runner and the jumper acts as a connecting link between two arc chambers and completes the current path which makes the two arcs in series and through which no current flows in the closed state, for the purpose of taking over an arc which forms on the tip of a moving contact when the fixed contact and the moving contacts are open. The second fixed contact assembly includes a second fixed contact, and a second arc runner positioned near the second fixed contact, and a third arc runner. The second arc runner is connected to the first fixed contact through which no current flows in the closed state, for the purpose of taking over an arc which forms on the tip of the first fixed contact and a contact button thereof. The third arc runner is positioned near the second fixed contact. The third arc runner is connected to the second fixed contact assembly through which no current flows in the closed state of the breaker, for the purpose of taking over an arc which forms on the tip of the second fixed contact and a contact button thereof. The quenching chamber is provided for quenching the arcs. The quenching chamber includes a first slot motor and a second slot motor assembled with an ablative to intensify the magnetic fields in the region of the arc. The arc chute includes a stack of deion plates connected together to receive the arc therethrough. A insulating middle support is provided for electrically isolating the two arc chambers.

Brief description of the drawings
Figure 1 shows a front view of a double break circuit breaker with improved arc quenching, in accordance with the present invention;
Figure 2 shows a right hand side view of the double break circuit breaker of figure 1;
Figure 3 shows an exploded view the double break circuit breaker of figure 1; and
Figure 4 shows left hand side view of the double break circuit breaker of figure 1 showing arc elongation.
Detailed description of the invention
The foregoing objects of the present invention are accomplished and the problems and shortcomings associated with the prior art, techniques and approaches are overcome by the present invention as described below in the preferred embodiments.
The present invention provides an arc quenching device having improved current limitation and reduced heat losses, in the case of which the de-ion plates are prevented to increased erosion and wear. For this purpose, a quenching path according is provided which takes over an arc from runner rails to an arc chute. Based on circuit breakers with double interruption, the looped arc runners with specific profile, adds resistance to the short circuit current in order to limit the fault current.
Referring now to figure 1 to 4, there is shown a the double break circuit breaker device (100) (hereinafter, the device (100)) with improved arc quenching. The device (100) includes a first fixed contact assembly (20), a second fixed contact assembly (40), a quenching chamber (50), an arc chute (60) and an insulating middle support (70).

The first fixed contact assembly (20) includes a first fixed contact (10), a first arc runner (12) joined to a jumper (14). In an embodiment, the first arc runner (12) is joined to the jumper (14) by welding.
The joined first arc runner (12) and the jumper (14) acts as a connecting link between two arc chambers and completes the current path which makes the two arcs in series and through which no current flows in the closed state, for the purpose of taking over an arc (72) which forms on the tip of a moving contact (80) when the fixed contact (10) and the moving contacts (80) are open. The first arc runner (12) is having a specific profile on base thereof, so as to increase the circuit breaker resistance only during fault conditions. The specific profile of first arc runner (12) helps in lengthening of arc (72) as shown in the figure 4. Specifically, in the first arc runner (12) and the second arc runner (34), the profile is arranged in transverse manner that is mirror image to each other, which helps in lengthening and splitting of the arc (72) diagonally as shown in figure 4. Accordingly, when the arc (72) jumps from running phase to splitting phase, short circuit current gets more resistance due to geometry, to complete the circuit. So, high arc voltage builds up in the circuit which in turn helps in extinguishing the arc (72) effectively.
In an embodiment, the first arc runner (12) is preferably provided in terms of its geometry or material with current-limiting properties such as steel which is having high electrical resistivity.
The second fixed contact assembly (40) includes a second fixed contact (32), a second arc runner (34) and a third arc runner (36).
The second arc runner (34) is positioned near the second fixed contact (32). Specifically, the second arc runner (34) is connected to the first fixed contact (10) through which no current flows in the closed state of the circuit breaker. This is for the purpose of taking over the arc (72) which forms on the tip of the first fixed contact (10) and a contact button thereof (10a).

Since the first arc runner (12) as well as the second arc runner (34) does not carry any current during rated operation, i.e. when the switching contact is closed, this does not influence the intrinsic impedance of the circuit breaker and, as a result of its low starting or cold resistance of a few mΩ, also does not impede the commutation of the arc to the corresponding arc runners (12) and (34). Once commutation of the two arcs has taken place, the arc runner (12) also has current flowing through it, as a result of which its impedance increases and the fault current is limited.
The third arc runner (36) is positioned near the second fixed contact (32). Specifically, the third arc runner (36) is connected to the second fixed contact (32) through which no current flows in the closed state of the circuit breaker. This for the purpose of taking over the arc (72) which forms on the tip of the second fixed contact (32) and a contact button thereof (32a). The third arc runner (36) is connected with the fixed contact (32) in transverse manner to increase the circuit breaker resistance in faulty condition so as to lengthen the arc (72) and to quench the arc more effectively.
The quenching chamber (50) is provided for quenching the arc (72). The quenching chamber (50) includes a first slot motor (42) and a second slot motor (44) assembled with an ablatives (46, 46a) to intensify the magnetic fields in the region of the arcs (72). The magnetic shield produced, by the first slot motor (42) and the second slot motor (44) , being turned over first arc runner (12), such that the arc area or the pre-chamber is sealed off on three sides by the ablative (46, 46a).
Specifically, the first slot motor (42) which is an upper L-shaped slot motor and the second slot motor (44) which is a base I-shaped slot motor is used to intensify the magnetic fields in the region of the arc along with the help of the first arc runner (12). The first arc runner (12) is also known as a looped arc runner. Thus, the Lorentz force acting on the arc drives the arc in the direction of the arc chute (60). This causes the arc to move more rapidly, the contact wear to be reduced and current is limited in running phase.

The magnetic field, acting on the arc, of the disconnection current flowing in the arc runners (12, 34, and 36) is thus intensified due to the blow-out field. The first slot motor (42) is electrically isolated for the arc chamber by means of the insulating material ablative (46) and the assembly is referred to as slot motor assembly (48). Similarly, the second slot motor (44) is electrically isolated for the arc chamber by means of the insulating material ablative (46a) and the assembly is referred to as slot motor assembly (48a). In an embodiment, four such slot motor assemblies (48) are provided, two in each arc chamber.
The arc chute (60) is provided to receive the arc (72) therethrough. The arc chute (60) includes a stack of deion plates (52) connected together by means of crimping with lining (52a) or any other mechanical means so as to hold the plates together. The arc moves from the first arc runner (12) through the arc chute (60) to the second arc runner (34). The arc chute (60) is alternatively called as an arc splitter. The insulating middle support (70) provides for electrically isolating the two arc chambers. There are two arcs which are formed in the two arc chambers which are electrically in series which result into adding arc voltages.
Advantages of the invention
1. The device (100) adds resistance into the breaker, only during fault conditions, so as to limit the fault current
2. The device (100) reduces the cut-off current (peak current seen by the load) and hence the let-through energy is limited.
3. The device (100) helps in further elongation and splitting of arc in turn improves in arc quenching capability.
4. The device (100) provides a faster current limitation and arc quenching improves the reliability thereof.
The foregoing descriptions of specific embodiments of the present invention have been presented for purposes of illustration and description. They are not intended to be exhaustive or to limit the present invention to the precise forms disclosed, and

obviously many modifications and variations are possible in light of the above teaching. The embodiments were chosen and described in order to best explain the principles of the present invention and its practical application, to thereby enable others skilled in the art to best utilize the present invention and various embodiments with various modifications as are suited to the particular use contemplated. It is understood that various omission and substitutions of equivalents are contemplated as circumstance may suggest or render expedient, but such are intended to cover the application or implementation without departing from the spirit or scope of the present invention.

We claim
1. A double break circuit breaker device with improved arc quenching
comprising:
a first fixed contact assembly comprising, a first fixed contact, and
a first arc runner joined to a jumper, wherein the joined arc runner and the jumper acts as a connecting link between two arc chambers and completes the current path which makes the two arcs in series and through which no current flows in the closed state, for the purpose of taking over an arc which forms on the tip of a moving contact when the fixed contact and the moving contacts are open; a second fixed contact assembly comprising, a second fixed contact,
a second arc runner positioned near the second fixed contact, the second arc runner connected to the first fixed contact through which no current flows in the closed state, for the purpose of taking over an arc which forms on the tip of the first fixed contact and a contact button thereof; and
a third arc runner positioned near the second fixed contact, the third arc runner connected to the second fixed contact through which no current flows in the closed state of the breaker, for the purpose of taking over an arc which forms on the tip of the second fixed contact and a contact button thereof;
a quenching chamber for quenching the arcs, the quenching chamber having a first slot motor and a second slot motor assembled with an ablative to intensify the magnetic fields in the region of the arc;
an arc chute comprising a stack of deion plates connected together, wherein the arc moves from the first arc runner through the arc chute to the second arc runner; and an insulating middle support for electrically isolating the two arc chambers.
2. The device as claimed in claim 1, wherein a first arc runner is having, a .
particular profile given on base thereof.

3. The device as claimed in claim 1, wherein the third arc runner is connected with the fixed contact in a transverse manner to increase the circuit breaker resistance in faulty condition so as to lengthen arc and quench it more effectively.