FORM 2
The Patents Act 1970
(39 of 1970)
&
The Patent Rules 2003
COMPLETE SPECIFICATION
(See Section 10 and rule 13)
TITLE OF THE INVENTION:
ARC CHUTE ASSEMBLY FOR CIRCUIT BREAKER
APPLICANT:
LARSEN & TOUBRO LIMITED
L&T House, Ballard Estate, P.O. Box No. 278,
Mumbai, 400 001, Maharashtra,
INDIA.
PREAMBLE OF THE DESCRIPTION:
THE FOLLOWING SPECIFICATION PARTICULARLY DESCRIBES THE INVENTION AND THE MANNER IN WHICH IT IS TO BE PERFORMED

A) TECHNICAL FIELD
[0001] The present invention generally relates to electrical distribution devices, and particularly to circuit interrupting devices. The invention more particularly relates to design of arc chutes in circuit interrupting devices.
B) BACKGROUND OF THE INVENTION
[0002] Circuit interrupting devices such as circuit breakers typically include a set of . stationary electrical contacts and a set of movable electrical contacts. The stationary and movable contacts are actuated to be in contact with one another when the circuit breaker needs to provide electricity through a load. However when it is desired to interrupt the circuit, the movable contacts is moved away from the stationary contacts, thereby creating a space between the stationary contacts and the movable contacts.
[0003] The movement of the movable Contacts away from the stationary contacts results in the formation of an electrical arc in the space between the contacts. Such an arc must be extinguished quickly to prevent damage of the electrical wiring and the load, as well as the circuit interrupting device itself. Additionally, the electrical arc between the contacts often results in vaporization or sublimation of the contact material itself, eventually resulting in deformation of the movable and stationary contacts. It is thus desired to eliminate any such arcs as soon as possible upon their propagation.
[0004] A general requirement of circuit interrupting device is that the electric arc has to be split into multiple series arcs for efficient quenching. This is achieved by introducing multiple plates (here after referred as de-ion plates) in the path transverse to the arc column. The movable electrical contacts typically are mounted on arms that are contained in a pivoting assembly which pivots the movable contacts away from the stationary contacts. An arc chute is provided along the path of each arm to break up and dissipate such arcs. The arc chutes typically include a plurality of spaced apart de-ion arc plates. As the movable contact is moved away from the stationary contact;

the movable contact moves past the ends of the de-ion arc plates with the arc being magnetically urged towards and between the arc plates. The arc plates are electrically insulated from one another such that the arc is broken up and extinguished by the arc plates.
[0005] In addition to splitting the arc into multiple smaller arcs, the arc-chute also serves to extract heat from the high temperature arc, thereby cooling the arc which assists further in quenching the same. The size and number of de-ion plates would decide the effectiveness of the arc-chute. However, due to limited space available in the circuit breaker, it becomes imperative to improve the efficiency of each plate and thereby improve the effectiveness of the entire arc-chute.
[0006] Conventional methods of arc-chute design of de-ion plates was having normal V-cut profile and square cut profile. A normal V-cut also provides a force of attraction to the arc but then this modification is not sufficient if breaking at higher voltages and currents is desired. The square cut leaves very less amount of thermal mass as most of the plate is cut off to impart the profile. This reduction in thermal mass significantly hampers the performance of the arc chute, and restricts its utilization for higher breaking capacities.
[0007] The existing profile of the de-ion plate increases the force of attraction on the arc thereby pulling it faster into the arc-chute and also elongating the arc significantly, thereby increasing the arc voltage During electrical faults, the high arcing time can be detrimental to the installation.
[0008] Hence there is a requirement for a de-ion plate design which increases the force of attraction on the arc thereby pulling the arc faster into the arc-chute and also elongating the arc significantly, thereby increasing the arc voltage. Further there exists a need to provide sufficient thermal mass to the de-ion plates to maximize force on the arc.

[0009] The abovementioned shortcomings, disadvantages and problems are addressed herein and which will be understood by reading and studying the following specification.
C) OBJECTS OF THE INVENTION
[0010] The primary object of the present invention is to provide an improved arc chute assembly to provide a higher force on the arc to lead to a higher elongation of the arc.
[0011] Another object of the present invention is to provide a method of reducing the arcing time by generating conditions favourable for arc splitting.
[0012] Yet another object of the present invention is to improve the design profile of the de-ion plates so has to improve the force of attraction to putt the arc faster.
[0013] Yet another object of the present invention is to improve the design profile of the de-ion plates so has to elongate the arc significantly and increase the arc voltage.
[0014] Yet another object of the present invention is to provide a significant thermal mass on the de-ion plates.
[0015] These and other objects and advantages of the present invention will become readily apparent from the following detailed description taken in conjunction with the accompanying drawings.
D) SUMMARY OF THE INVENTION
[0016] The various embodiments of the present invention provide an arc-chute assembly in a circuit interrupting device comprising an arc chute, a plurality of de-ion plates arranged in the arc chute; wherein each de-ion plate has a preset design profile to distribute a arc within the arc chute to and to enhance the arc voltage to reduce the arc quenching time.

[0017] The arc chute assembly comprising of de-ion plates arranged in parallel to each other with a preset design profile, wherein the preset design profile on each de-ion plate has a ladder like stepped construction cut profile. The stepped construction cut profile narrows towards the inside portion of the de-ion plate where each step is termed as notch. Further the first stepped cut profile is larger in width than compared to the following stepped construction cut profile and contains at least one subsequent lower step cut construction. The final step construction can be of either rectangle or triangle in shape.
E) BRIEF DESCRIPTION OF THE DRAWINGS:
[0018] The other objects, features and advantages will occur to those skilled in the art from the following description of the preferred embodiment and the accompanying drawings in which:
[0019] FIG. 1 illustrates a schematic front view of the de-ion plate according to one embodiment of the present invention.
[0020] FIG. 2 illustrates a schematic front view of the de-ion plate with different design profile according to one embodiment of the present invention.
[0021 ] FIG. 3 shows a perspective top view of the arc-chute stack formed by a multiplicity of the de-ion plates according to one embodiment of the present invention.
[0022] Although specific features of the present invention are shown in some drawings and not in others. This is done for convenience only as each feature may be combined with any or all of the other features in accordance with the present invention.

F) DETAILED DESCRIPTION OF THE INVENTION
[0023] In the following detailed description, reference is made to the accompanying drawings that form a part hereof, and in which the specific embodiments that may be practiced is shown by way of illustration. These embodiments are described in sufficient detail to enable those skilled in the art to practice the embodiments and it is to be understood that the logical, mechanical and other changes may be made without departing from the scope of the embodiments. The following detailed description is therefore not to be taken in a limiting sense.
[0024] The various embodiments of the present invention provide an arc-chute assembly in a circuit interrupting device comprising an arc chute, a plurality of de-ion plates arranged in the arc chute. Each de-ion plate has a preset design profile to distribute an arc within the arc chute to and to enhance the arc voltage to reduce the arc quenching time.
[0025] The unique profile of the de-ion plate diverts the magnetic flux thorough the plate in a manner which results in a high force on the arc. The profile has been devised such that as the arc moves forward and penetrates into the arc-chute. The force of attraction is maintained at a high value at different positions of the arc as it penetrates into the arc-chute.
[0026] The number, size and thickness of the de-ion plates varies depending upon the breaker rating and the short-circuit capacity of the same. The typical thickness varies from 1 to 3 mm. The profile of the de-ion plate is cut in as ladder like stepped construction. The notch 'A' provides space for the contact to be placed such that there is a suitable overlap between de-ion plates and the contact, thereby linking most of the magnetic flux produced by the arc during its initiation at the contact. The notch 'B' further has a smaller width compared to notch 'A', which will result in a higher force as the arc moves towards the same.
[0027] Finally, the notch 'C' which is comparatively smaller in width produces a
higher force upon the arc as the arc travels further. The narrow cut of notch 'C also
« i .

assists in considerable heat extraction from the arc as the arc progressively penetrates the region forming the same. This shall result in cooling the arc and squeezing the arc as the temperature around the hot plasma core comes down due to heat transfer to the metal in the de-ion plate.
[0028] The arc movement is heavily influenced by the magnetic forces, the pressure drag due to the surrounding gases and obstructions in the path of the arc travel. A wider notch compared to notch 'C while being narrower than notch 'A' accelerates the propagation of the arc towards the narrow notch 'C'
[0029] Thus, the introduction of a step in between the initial wide notch and the final narrow notch results in an effective movement of the arc towards the notch 'C\ This leads to effective splitting and cooling of the arc. In the process, there is a considerable elongation in the arc length, which further assists in a better arc quenching performance.
[0030] Another embodiment of the present invention is depicted in figure 2, wherein the notch 'C' is triangular shaped instead of a rectangle. Both the profiles shown in Figure 1 and Figure 2 match in terms of the characteristics.
[0031] FIG. 1 illustrates a top view of the de-ion plate according to one embodiment of the present invention. With respect to FIG. 1, the circuit interrupting device includes an arc chute assembly comprising of a plurality of de-ion 106 plates arranged parallel to each other. Each of the de-ion plate 106 has a ladder like stepped construction of the profile. The notch 'A' 101 provides space for the contact to be placed such that there is a suitable overlap between de-ion 106 plates and the contact, thereby linking most of the magnetic flux produced by the arc during its initiation at the contact. The notch 'B' 102 shown here has a smaller width compared to notch 'A' 101, which shall result in a higher force as the arc moves towards the same. The notch 107 is used to place and hold each deion plate by means of crimping to a side liner (not shown) such as to form the arc-chute by stacking a multiplicity of plates one above another.

[0032] Finally, notch 'C' 103 which is much smaller in width will produce a still higher force upon the arc 104 as it travels further. The narrow cut of notch 'C' 103 will also assist in considerable heat extraction from the arc 104 as the arc 104 progressively penetrates the region forming the same. This shall result in cooling the arc 104 and squeezing the same as the temperature around the hot plasma core comes down due to heat transfer to the metal in the de-ion plate.
[0033] The creation of a narrow cut as in notch 'C' 103, right after notch 'A' 101 has a disadvantage of sluggish entry of the arc 104 into the chute. This has a bearing upon the rate of rise of arc voltage and also on the effective penetration of the arc 104 into the arc chute. The arc 104 movement is heavily influenced by the magnetic forces and the pressure drag due to the surrounding gases and obstructions in the path of the arc 104 travel.
[0034] A wider notch compared to notch 'C' 103 while being narrower than notch 'A' 101 helps in the acceleration of the arc. 104 towards the narrow notch 'C- 103. Thus, the introduction of a step in between the initial wide notch and the final narrow notch results in an effective movement of the arc 104 towards the notch 'C' 103. This leads to effective splitting and cooling of the arc 104. In the process, there is a considerable elongation in the arc 104 length, which further assists in a better arc quenching performance,
[0035] FIG. 2 illustrates a top view of the de-ion plate with different design profile according to one embodiment of the present invention. With respect to FIG. 2, the de-ion plate has a preset design profile, wherein the preset design profile on each de-ion 106 plate has a triangle shaped 105 notch 'C. The triangle shaped 105 notch 'C' which is much smaller in width will produce a still higher force upon the arc 104 as it travels further. The triangle cut 105 of notch 'C' will also assist in considerable heat extraction from the arc 104 as the arc progressively penetrates the region forming the same. This shall result in cooling the arc 104 and squeezing the same as the temperature around the hot plasma core comes down due to heat transfer to the metal in the de-ion plate 106. Creation of a triangle cut as in notch C 105, right after notch

A 101 has a disadvantage of sluggish entry of the arc 104 into the chute. This has a bearing upon the rate of rise of arc voltage and also on the effective penetration of the arc 104 into the arc chute. The arc movement is heavily influenced by the magnetic forces and the pressure drag due to the surrounding gases and obstructions in the path of the arc travel. A wider notch compared to notch 'C 105 while being narrower than notch 'A' 101 helps in the acceleration of the arc 104 towards the narrow notch 'C 105. Thus, the introduction of a step in between the initial wide notch and the final narrow notch results in an effective movement of the arc towards the notch 'C 105. This leads to effective splitting and cooling of the arc 104. In the process, there is a considerable elongation in the arc length, which further assists in a better arc quenching performance.
[0036] FIG. 3 shows an elaborate view of the arc-chute stack formed by a multiplicity of the de-ion plates according to one embodiment of the present invention. With respect to FIG. 3, the de-ion plates 106 with preset design cut are stacked in series and above each other. Each de-ion plates 106 has a ladder like stepped construction profile and the number, size and thickness of each de-ion 106 plate varies depending upon the breaker rating and the short-circuit capacity of the same. The typical thickness shall vary from 1mm to 3 mm. The notch 'A' 101 provides space for the contact to be placed such that there is a suitable overlap between de-ion plates 106 and the contact, thereby linking most of the magnetic flux produced by the arc during its initiation at the contact The notch 'B'102 shown has a smaller width compared to notch 'A'101, which shall result in a higher force as the arc moves towards the same. Finally, notch 'C 103 which is much smaller in width will produce a still higher force upon the arc as it travels further.
G) ADVANTAGES OF THE INVENTION
[0037] The various embodiments of the present invention provide an arc-chute assembly in a circuit interrupting device comprising an arc chute, a plurality of de-ion plates arranged in the arc chute; wherein each de-ion plate has a preset design profile to split the arc into multiple series of arc and to enhance the arc voltage to reduce the arc quenching time.

[0038] The present invention proposes the method where a ladder like stepped construction of the profile of de-ion plates are used for quenching arc effectively and quickly. The de-ion plates consists of notch 'A' cutting which provides space for the contact to be placed such that there is a suitable overlap between de-ion plates and the contact, thereby linking most of the magnetic flux produced by the arc during its initiation at the contacts.
[0039] Although the invention is described with various specific embodiments, it will be obvious for a person skilled in the art to practice the invention with modifications. However, all such modifications are deemed to be within the scope of the claims.
[0040] It is also to be understood that the following claims are intended to cover all of the generic and specific features of the present invention described herein and all the statements of the scope of the invention which as a matter of language might be said to fall there between.

CLAIMS
What is claimed is:
1. An arc-chute assembly in a circuit interrupting device, the assembly comprising:
an arc chute; and
a plurality of de-ion plates arranged in the arc chute;
wherein each de-ion plate has a preset design profile to split the arc into multiple
series of arc so as to enhance the arc voltage thereby reducing the arc quenching
time.
2. The assembly according to claim 1, wherein the preset design profile on each de-ion plate includes a ladder like stepped construction cut profile.
3. The assembly according to claim 1, wherein the preset design profile includes at least three notches to provides for a stepped edge on the de-ion plates.
4. The assembly according to claim 1, wherein the stepped construction cut profile narrows towards the inside portion of the de-ion plate.
5. The assembly according to claim 1, wherein a first stepped cut profile is larger in width than compared to the following stepped construction cut profile.
6. The assembly according to claim 1, wherein a first stepped cut profile provides space for the contact to be placed so as to provide an overlap between the de-ion plates and the contact.
7. The assembly according to claim 1, wherein the de-ion plate consists of at least one step cut construction following the first step cut construction.
8. The assembly according to claim 1, wherein the last step construction cut profile is rectangle in shape.

9. The assembly according to claim 1, wherein the last step construction cut profile is also triangle in shape.