FORM 2
THE PATENTS ACT, 1970 (39 of 1970)
COMPLETE SPECIFICATION
(See section 10 and rule 13)
TITLE OF THE INVENTION
Double break arc quenching circuit breaker with improved current limitation
2. APPLICANT(S)
(a) NAME : Larsen and Toubro Ltd.
(b) NATIONALITY: Indian
(c)ADDRESS : L&T House, Ballard Estate, Mumbai-400 001, India.
3. PREAMBLE TO THE DESCRITION
COMPLETE
The following specification particularly describes the invention and the manner in which it is to be performed
4. DESCRIPTION (Description shall start from next page)
5. CLAIMS (not applicable for provisional specification. Claims should start with the preamble -"I/We claim" on separate page)
6. DATE AND SIGNATURE (to be given on the last page of specification)
7. ABSTRACT OF THE INVENTION (to be given along with complete specification on the separate page)
Note:
*Repeat boxes in case of more than one entry
*To be signed by the applicant(s)or the authorized registered patent agent
*Name of the applicant should be given in full, family name in the beginning
*Complete address of the applicant should be given stating with postal index no. / code, state and
country
*Strike out the column which is/are not applicable

Double break arc quenching circuit breaker with improved current limitation
Field of the invention
The present invention relates to the circuit breakers for low-voltage distribution systems. More particularly it relates to an arc-quenching or arc-extinguishing device for circuit breakers having double-break contacts.
Background of the invention
A normal circuit breaker has a contact point which is formed from a fixed and a moveable contact piece. 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 piece and the moveable contact piece 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 so-called self-blowing, i.e. the magnetic blowing field induced by the arc itself, the pressure ratios in the arc, the formation of the guide rails and the selection of the contact material. Owing to such design of guide rails, the 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.
In the case of switching devices, it is important for the life and the switching power that the arc produced when the contacts are opened does not remain on the contact pieces but is guided as quickly as possible to a quenching chamber region where the arc is cooled and quenched. Every time the arc remains on the contact pieces, even in the millisecond range, the wear and erosion of the contact pieces is increased. What is required is an arc quenching device having improved current limitation and reduced heat losses where a moving contact and fixed contact are not subject to increased erosion and wear.

Object of the invention:
The object of the present invention is to provide an additional resistance only during fault conditions to limit the fault current in a circuit breaker having double-break contacts.
Another object of present invention is to provide first arc runner loop in an arc-quenching circuit, through which current flows only during the disconnection process of the circuit breaker.
Yet another object of the present invention is to provide an arc-runner assembly connected to neighbouring arc runner that offer more resistance and effective arc quenching.
Further object of the present invention is to reduce the cut-off current (peak current seen by the load) and limit the let-through energy. Summary of the invention:
An arc runner arrangement with a loop is provided to add an extra resistance in the current path only during short circuit. This causes an increase in circuit breaker resistance. Such increase in the breaker resistance comes into the circuit only during fault conditions when the arc roots move from the contact button and moving contact region to the arc runner. First arc runner assembly consists of first arc runner welded with arc runner jumper. This arc runner jumper acts as a connecting link between the two arc chambers and competes the current path which makes the two arcs in series. Additional bent provided in arc loop improves resistance offered by the arc chamber.
Description of the Drawings:
Fig. 1: shows front view of the arc quenching arrangement Fig. 2: shows right hand side view of the arc quenching arrangement Fig. 3: shows exploded view of the arc quenching arrangement Fig. 4: shows first arc runner assembly
Fig. 5: shows another type of first arc runner assembly

List of components:
1. First arc runner assembly
2. First arc runner
3. Arc runner jumper
4. Arc chute
5. Lining
6. Deion plate
7. Slot motor assembly
8. Slot motor
9. Ablative
10. First fixed contact assembly
11. First fixed contact
12. Second arc runner
13. Contact button
14. Second fixed contact assembly
15. Second fixed contact
16. Middle support
17. Moving contact
18. First arc runner of second type
Detailed Description:
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 specifies an arc quenching device having improved current limitation and reduced heat losses, in the case of which a moving contact and fixed contact are not subject to increased erosion and wear. For this purpose, a quenching path according to the invention is provided which takes over an arc from said contacts and comprises two arc runners, a quenching chamber consisting of arc chute, slot motor and ablative. Based on circuit breakers with double

interruption, the arc runners, arc runner with a loop in particular, adds resistance to the short circuit current in order to limit the fault current.
The essence of the invention is to use an arc runner with a loop 1 to add an extra resistance in the current path only during short circuit. This causes an increase in circuit breaker resistance. Such increase in the breaker resistance comes into the circuit only during fault conditions when the arc roots move from the contact button 13 & moving contact 17 region to the arc runner 1,18.
A suitable magnetic shield slot motor 8 is used to intensify the magnetic fields in the region of the arc and thus the Lorentz force acting on the arc and driving said arc in the direction of the stack of deion plates 6 i.e. arc chute 4. This causes the arc to move more rapidly, the contact wear to be reduced and current is limited.
The magnetic shield produced, for example, from steel is preferably realized by an integral shaped part, which is open at one end and has a U profile called slot motor 8, being turned over first arc runner 1, such that the arc area or the pre-chamber is sealed off on three sides by the ablative 9. The magnetic field, acting on the arc, of the disconnection current flowing in the arc runners is thus intensified due to the blow-out field. The slot motor 8 is electrically isolated for the arc chamber by means of an insulating material ablative 9 and this assembly is referred to as slot motor assembly 7. Two such slot motor assemblies 7 are provided, one in each arc chamber.
The object of present invention is, first arc runner 1 loop is introduced in an arc-quenching circuit, through which current flows only during the disconnection process of the circuit breaker and which comprises the two arcs. Said arc runner loop 1 is arranged in such a way that it has a current flowing through it only when the arc roots move from contact region consisting of contact button 13 and moving contact 17 to the arc runner 1,18.
The first arc runner 1 loop is preferably provided in terms of its geometry or material with current-limiting properties such as steel which is having high electrical resistivity.
Since the first arc runner loop 1 as well as the second arc runner 12 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 switch 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 1, 12. Once commutation of the two arcs has taken place, the arc runner loop 1 also has current flowing through it, as a result of which its impedance increases and the fault current is limited.
There are two arcs which are formed in the two arc chambers which are electrically in series which result into adding arc voltages. The two arcs are electrically isolated by means of an insulating material called middle support 16.
The present invention relates to such an arc runner which is easy to manufacture. The first arc runner assembly 1 consists of first arc runner 2 welded with arc runner jumper 3. This arc runner jumper 3 acts as a connecting link between the two arc chambers and competes the current path which makes the two arcs in series.
Another way of adding resistance into the arcing circuit is also the objective of this invention. In this case the profile of the first arc runner of second type 18 is made in such a way that the cut-out section of the arc runner is bent such that the two faces are in parallel. Even in this case the arcs formed on this runner configuration in the two arc chambers are in series. The fault current is limited by virtue of this additional resistance of arc runner 18. This additional resistance is due to decreased cross-section of the current carrying element of arc runner 18 as well as due to increased current path length of cut-out section.
Arc chute 4 is made up of stack of de-ion plates 6 held together by means of crimping with lining 5 or any other mechanical means so as to hold the plates together. First fixed contact assembly 10 comprises of first fixed contact 11, contact button 13 and second arc runner 12. They can be joined by any process of welding. Second fixed contact assembly 14 comprises of second fixed contact 15, contact button 13 and second arc runner 12. They can be joined by any process of welding.

We claim,
1) An arc quenching arrangement for double break circuit breaker comprising;
double break contact system consisting of two fixed contacts connected to two
corresponding moving contacts for carrying rated current.
two arc chambers positioned around each of the said contact points, the arc chamber
having an arc chute made up of stack of de-ion plates held together by means of crimping
with lining;
an arc runner provided in each of the said arc chamber, one end of the arc runner
mounted below the said arc chute and another end of the arc runner having a bent loop
profile forming parallel face;
an arc jumper, the arc jumper connecting ends of the said arc runners to move the arc
generated at any of the fixed contact due to opening of contacts due to fault current.
2) An arc quenching arrangement for double break circuit breaker of the claim 1 wherein, the arc runners are mounted in electrically non conducting ablatives and the ablative is surrounded by slot motor.
3) An arc quenching arrangement for double break circuit breaker of the claim 1, wherein the arc runner can be a cut-out section to be punched out of the same material having its surfaces parallel to each other adding its resistance to the fault current path.
4) An arc quenching arrangement for double break circuit breaker of the claim 1, wherein first and second arc runners are made up of any metal having high electrical resistivity.
5) An arc quenching arrangement for double break circuit breaker of the claim 1, wherein first arc runner is having a particular loop so as to increase the breaker resistance only during fault conditions.