FORM 2
THE PATENTS ACT, 1970
(39 of 1970)
&
THE PATENTS RULES, 2003
COMPLETE SPECIFICATION
[See section 10, Rule 13]
ARC CHUTE ASSEMBLY;
LARSEN & TOUBRO LIMITED, A COMPANY INCORPORATED UNDER THE COMPANIES ACT, 1956, WHOSE ADDRESS IS L&T HOUSE, BALLARD ESTATE, MUMBAI - 400 001, MAHARASHTRA, INDIA
THE FOLLOWING SPECIFICATION
PARTICULARLY DESCRIBES THE INVENTION AND THE MANNER IN WHICH IT IS TO BE PERFORMED.

FIELD OF THE INVENTION
The invention relates to circuit breakers and more particularly to arc quenching in circuit breakers. BACKGROUND OF THE INVENTION
Circuit breakers protect electrical circuits from damage by isolating the circuit, when there is an unusual current surge. However, when a circuit breaker isolates an electrical circuit from this unusual current surge, an uncontrolled arc may travel to the circuit breaker and damage it.
An arc basically is a discharge of electric current which results from the unusual current surge crossing between contacts of the circuit breaker, when these contacts are opened to isolate the electric circuit. The arc generated due to separation of contacts is then guided to an arc chute where it splits into several series of small arcs. However when the arc is guided into the arc chute, different forces, i.e. magnetic pull exerted by de-ion plates & forces generated due to gas dynamics inside the arc chute, acts on the arc. The forces generated due to gas dynamics are basically a result of pressure acting behind & in front of the arc column. The pressure behind arc column exerts force on the arc in forward direction i.e. towards de-ion plates, however the pressure in front of arc column exerts force on the arc in backward direction. When the pressure behind the arc column & in front of the arc column is same no gas dynamic force is exerted on the arc, and the arc takes long to penetrate the de-ion plates.

Arcs may vary in size and intensity depending on the amount of current surge, and minimizing the arc is important as the arc can damage the contacts and can also severely damage the circuit breaker and surrounding equipments.
The severity of arc current depends on how long the current flows, what's the level of fault current flowing. To protect the appliance from damage there is a requirement for circuit breaker to sense the fault in earlier stage and quench the arc in lesser time.
Furthermore, the available arc chutes comprises of de-ion plates which are permanently coupled to the arc chute. Hence maintenance of such arc-chutes wherein the assembly of deion plates and replacement of de-ion plates is required is complex.
In view of the above there is a need for an arc quenching device which quenches the arc in lesser time and is easy to assemble and maintain. SUMMARY OF THE INVENTION
Accordingly, the present invention in one aspect provides an arc chute assembly for a circuit breaker, the arc chute assembly comprising a cassette base having a plurality of slots at a first end of the cassette base, a plurality of de-ion plates adapted to the slots of the cassette base and a cassette cover accommodating the cassette base. BRIEF DESCRIPTION OF THE DRAWINGS
Reference will be made to embodiments of the invention, examples of which may be illustrated in the accompanying figures. These figures are intended to be illustrative, not limiting. Although the invention is generally described in the context of these embodiments, it should be understood that it is not intended to limit the scope of the invention to these particular embodiments.

Figure 1 shows an arc chute assembly for circuit breakers in accordance with an
embodiment of the invention.
Figure 2 shows a cassette base of the arc chute assembly in accordance with an
embodiment of the invention.
Figure 3 shows a cassette cover of the arc chute assembly in accordance with an
embodiment of the invention.
Figure 4 shows a stack of de-ion plates of the arc chute assembly in accordance
with an embodiment of the invention.
Figure 5 shows the arc chute assembly adapted to a molded case circuit breaker,
in accordance with an embodiment of the invention.
Figure 6 shows the arc chute assembly with lower contact.

DETAILED DESCRIPTION OF THE INVENTION
Various embodiments of the invention provide an arc chute assembly for a circuit breaker comprising a cassette base having a plurality of slots at a first end, a plurality of de-ion plates adapted to the slots of the cassette base and a cassette cover for accommodating the cassette base.
Figure 1 shows an arc chute assembly 100 in accordance with an embodiment of the invention. Arc chute assembly 100 includes a cassette base 102, a plurality of de-ion plates 104, and a cassette cover 106.
Cassette base 102 extends from a first end 102a to a second end 102b. In an embodiment cassette base 102 has a v-shape as shown in figure 2. In this regard, cassette base 102 diverges towards first end 102a. The v-shape of cassette base 102 generates a high pressure on the arc, penetrating the arc in arc chute assembly 100. At first end 102a, cassette base 102 has a plurality of slots 108. Slots 108 are capable of accommodating plurality of de-ion plates 104.
In an embodiment, de-ion plates 104 are disposed in slots 108 in a stacked configuration as shown in figure 4. In an embodiment of the invention, de-ion plates 104 are removably disposed in slots 108. Advantageously, de-ion plates 104 are easy to assemble and are not permanently coupled to slots 108 and can be replaced with new de-ion plates as per requirement. In an embodiment, de-ion plates 104 are made of a magnetic material. The magnetic material of de-ion plates 104 exerts a magnetic pull on the arc, thereby pulling the arc towards arc chute assembly 100.
In an embodiment of the invention, cassette base 102 has means for accommodating a slot motor at second end 102b.

In an embodiment of the invention, cassette base 102 is accommodated in cassette cover 106 shown in figure 3. Cassette cover 106 encloses cassette base 102 and forms a closed-type of assembly as shown in figure 1, wherein such an assembly withstands high pressure generated during arcing. Advantageously, cassette cover 106 protects the circuit breaker housing and cover from impact of high pressure gases produced due to arc during short-circuit fault.
In an embodiment of the invention, cassette base 102 and cassette cover have means for ventilation. Means for ventilation is provided near first end 102a of cassette base. Means for ventilation allows hot and ionized gases produced during arcing during short-circuit fault to escape from arc chute assembly 100 and the circuit breaker.
In an embodiment of the invention, cassette base 102 and cassette cover 106 are made of a thermoset material. The thermoset material can be selected from a group comprising of epoxy, phenol formaldehyde, polyester moulding compound, SMC, DMC and the like. The thermoset material enables cassette base 102 and cassette cover 106 to withstand high pressure and minimizes stresses induced on the circuit breaker housing and cover. The thermoset material reduces weight of arc chute assembly 100 and is also cost efficient.
When an arc is formed during short-circuit condition in a circuit breaker, undesired hot and ionized gases also get generated. In accordance with an embodiment of the invention, the v-shape of the cassette base generates a high pressure behind an arc column and the hot and ionized gases flow with a high velocity from the second end of the cassette base to the first end due to the high pressure created behind the arc column by the v-shape of the cassette base. These gases

escape through means for ventilation provided at the second end of the cassette base. As the gases flow with a high velocity from the second end to the first end, they, in turn, push the arc towards the de-ion plates, and help in faster cooling of the arc. Besides, the arc experiences a magnetic pull towards the de-ion plates due to high magnetic field of the de-ion plates.
Once the arc is pulled inside the arc chute assembly, the arc splits into series of small arcs and creates a number of arc roots. Also, the cassette base exerts more pressure on the arc because of its v-shape. Thus, the resultant force on the arc generated due to gas pressure and magnetic pull, pulls the arc towards the de-ion plates, helping the arc to penetrate faster and deeper inside the de-ion plates of the arc chute assembly. The arc chute assembly thus reduces total arcing time.
In an embodiment of the invention, arc chute assembly 100 is adapted to a molded case circuit breaker as shown in figure 5.
Figure 6 shows arc chute assembly 100 with a lower contact 110.
Advantageously the present invention provides an arc chute assembly which quenches the arc in lesser time; the assembly is cost-effective, and facilitates ease of assembling and maintenance since the de-ion plates are removably disposed in the assembly resulting in higher productivity. Also, the arc chute assembly can be adapted to existing circuit breaker without major modification.
While the present invention has been described with respect to certain embodiments, it will be apparent to those skilled in the art that various changes and modification may be made without departing from the scope of the invention as defined in the following claims.

We Claim :
1. An arc chute assembly for a circuit breaker, the arc chute assembly comprising:
a. a cassette base, the cassette base having a plurality of slots at a first end of
the cassette base;
b. a plurality of de-ion plates, the de-ion plates being adapted to the slots of the
cassette base; and
c. a cassette cover, the cassette cover accommodating the cassette base.
2. The arc chute assembly as claimed in claim 1, wherein the cassette base has a v-shape for creating a high pressure zone behind an arc column, wherein the cassette base diverges towards the first end of the cassette base.
3. The arc chute assembly as claimed in claim 1, wherein the cassette base and the cassette cover are made of a thermoset material, the thermoset material enabling the cassette base and the cassette cover to withstand high pressure generated by the arc.
4. The arc chute assembly as claimed in claim 1, wherein the de-ion plates are made of a magnetic material.
5. The arc chute assembly as claimed in claim 1, wherein the de-ion plates are removably disposed in the slots.
6. The arc chute assembly as claimed in claim 1, wherein the cassette base and cassette cover have means for ventilation of the arc chute assembly.

7. The arc chute assembly as claimed in claim 1, wherein the cassette base has means for accommodating a slot motor.