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 QUENCHING ASSEMBLY FOR CIRCUIT
INTERRUPTERS
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 systems. The present invention more particularly relates to a design of an arc chute assembly in an arch quenching device for circuit interrupters.
B) BACKGROUND OF THE INVENTION
[0002] Circuit interrupters are widely used in domestic, commercial and light industrial installations. Miniature circuit breakers (MCB) are used where the supply voltage exceeds 200 V AC and are used to protect circuits rated up to 100 A from overload and short circuit faults. During a short circuit fault, an electric arc is drawn between the opening contacts. The current through the conductors of the MCB generates a magnetic field in the arc chamber, which acts to force the arc to drive away from the contact region along the arc runners and into an arc stack provided with de-ion(de-ionizing) plates. The exchange spaces between the de-ion plates enhance the migration of the arc to the back of the arc chamber. The stack of de-ion plates further enables the arc to split into a number of series arcs which results in a high voltage across the circuit breaker. The high voltage counteracts the supply voltage and limits the peak fault current. Finally the emission of the arc is de-ionized and cooled avoiding damage to both the circuit and the circuit breaker is minimized.
[0003] Further, splitting of the arc is dependent on the formation of anode and cathode roots on the de-ion plates. The formation of cathode roots is governed by various factors such as surface temperature, effective work function and electric field at an emission spot of the arc. However, high thermal time constant of the de-ion plates inhibits the immediate splitting of the arc leading to an increase in total arcing time. During electrical faults, high arcing time can be detrimental to the installation of electrical distribution device.

[0004) Hence, there exists a need to provide an efficient arc quenching device to reduce the arcing time by generating conditions favourable for arc splitting and arc lengthening. Further, there is a need to improve arc quenching time to limit the let through energy in the current interrupting devices.
[0005] The above mentioned shortcomings, disadvantages and problems are addressed herein and which will be understood by reading and sstudying the following specification.
C) OBJECT OF THE INVENTION
[0006] These and other objects and advantages of the present invention wiJJ become readily apparent from the following detailed description taken in conjunction with the accompanying drawings.
[0007] The primary object of the present invention is to provide an arc quenching device for circuit interrupters to reduce the arcing time by generating conditions favourable for arc splitting and arc lengthening.
[0008] Another object of the present invention is to reduce thermal time delay of arc quenching device by coating arc entering face of each of de-ion plates with conductive materials of lesser work function value.
[0009] Another object of the present invention is to provide an arc quenching device for circuit interrupters to improve arc quenching time to limit the let through energy in the current interrupting device.
[0010] Yet another object of the present invention is to provide an arc quenching device for circuit interrupters to aid formation of cathode roots and anode roots

on the de-ion plates for faster splitting of the arc in arc chute of quenching device.
[0011] Yet another object of the present invention is to provide an arc quenching device for circuit interrupters to aid formation of cathode roots on de-ion plates to increase arc voltage across de-ion plates to efficiently quench the arc.
[0012] Yet another object of the present invention is to provide an arc quenching device for circuit interrupters for fast entering of arc to increase the arc mobility into arc chutes of the arc quenching device.
[0013] Yet another object of the present invention is to provide an arc quenching device for circuit interrupters to achieve desired direction of mobility of the arc in an arc chute.
[0014] Yet another object of the present invention is to provide an arc quenching device for circuit interrupter to de-ionize emissions of the arc.
[0015] Yet another object of the present invention is to provide an arc quenching device for circuit interrupter to minimize damage caused to internal parts within circuit interrupters and to move the arc away from the contacts to preserve integrity of the contacts for a longer service life.
D) SUMMARY OF THE INVENTION
[0016] The various embodiments of the present invention provide an arc quenching device for circuit interrupters. The device includes an arc chute, plurality of de-ion plates arranged in the arc chute, a first arc runner plate and a second arc runner plate. The first arc runner plate and the second arc runner plate are arranged adjacent to outer de-ion plates. Further the device includes a fixed contact and a moving contact. A top surface and bottom surface of each of the de-

ion plate is coated with conductive materials of predefined work function to reduce arc splitting time and to enhance an arc voltage to reduce the arc quenching time.
[0017] In various embodiments of the present invention the conductive materials are Silver having predefined work function value denoted as Wl throughout the detailed description, Iron (W2), Zinc (W3), Copper (W4), Tungsten (W5), and Nickel OR Osmium (W6). The relationship between the work functions values of the conductive materials are as follows, Wl < W2 < W3 < W4 < W5 < W6. Here the Silver has least work function value of Wl and the Nickel or Osmium has highest work function value of W6.
[0018] In various embodiments of the present invention, interrupting high short circuit currents leading to formation of anode to cathode voltage drop is functionality dependent on the work function of the conductive materials coated on the plurality of de-ion plates. The work function is defined as the minimum amount of energy needed to remove an electron from the metal. The effect of the work function can be analysed by given mathematical expression.

Where
Ac = Richardson constant. Tw = surface temperature (k). e = electron charge (coulombs). K = Boltzmann constant. eff = effective work function.

Ec = electric field intensity (V/m).

[0019] From the above equation the effective work function value is a function of electric field intensity. The electric field intensity is high for rough surface. The high electric field intensity further reduces the effective work function value of the conductive material.
[0020] The reduction in work function value of the conductive material at the arc entrance face of the de-ion plates results in less temperature formation and less time for splitting up the arc. The low work function of the conductive material ( θc) creates less temperature to ionize the conductive material surface. From the above equation it is shown that for the conductive materials of less work function, the number of electrons emitted from the conductive material surface indicating high conductivity of the conductive material.
[0021] The plurality of de-ion plates are arranged at right angles to each other in the arch chute. Top surface of the fixed contact has a smooth surface profile followed by a rough surface profile whereas bottom surface of the fixed contact has a smooth surface profile extended up to an arc exit face of the fixed contact. The smooth surface profile of the fixed contact is provided at an arc formation face of the fixed contact and extended along direction of propagation of the arc. The rough surface profile is formed after the smooth surface profile of the fixed contact and extended up to an arc exit face of the fixed contact. Top surface of the moving contact has a smooth surface profile at arc formation face and extended up to an arc exit face of the moving contact and the bottom surface of the moving contact has a smooth surface profile followed by a rough surface profile. The smooth surface profile of the moving contact is provided at an arc formation face of the moving contact and extended along a direction of propagation of the arc. The rough surface profile is formed after the smooth surface profile of the moving contact and extended up to an arc exit face of the moving contact. The two contacts meet at the smooth surface area. When they separate an arc is struck between the two contacts at this smooth surface and moves in to rough surface driven by the high electric field existing there.

[0022] The first arc runner plate and the second arc runner plate are provided with a first straight portion, a second bent portion, and a third elevated portion. The first straight portion is provided at arc entering face of the arc runner and extended along direction of propagation of the arc. The second bent portion is formed after the first straight portion of the arc runner and the third elevated portion is formed after the second bent portion of the arc runner and extended up to an arc exit face of the arc runner. The first straight portion, the second bent portion and the third elevated portion are coated with conductive materials of predefined work function values. The work function value of the conductive material coated on the first straight portion is lesser than the work function of the conductive material coated on the second bent portion. The work function value of the conductive material coated on the second bent portion is lesser than the work function value of the material coated on the third elevated portion of the arc runner. The first straight portion of the first arc runner plate and the second arc runner plate is coated with silver. The second bent portion of the first arc runner plate and the second arc runner plate is coated with Copper. The third elevated portion of the first arc runner plate and the second arc runner plate are coated with nickel respectively.
[0023] In one embodiment of the present invention, the third elevated portion of the first arc runner plate and the second arc runner plate are coated with Osmium.
[0024] In one embodiment of the present invention, the whole length of the top surface of each of the de-ion plate and the bottom surface of each of the de-ion plate are coated with two different materials of predefined work function values. The first surface of each of the de-ion plate is coated with conductive material of lesser work function value, and the second surface of each of the de-ion plate is coated with conductive material of higher work function value. The top surface of each of the de-ion plate is coated with one of silver, iron, zinc, copper, tungsten and nickel materials. The bottom surface of each of the de-ion plate is coated with one of copper, tungsten, nickel and osmium materials. The de-ion plates are

arranged in such a way that the coating materials having same predefined value face each other in the arc chute of the arc quenching device.
E) BRIEF DESCRIPTION OF THE DRAWINGS
|0025] 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:
[0026] FIG. 1 is a side view of a fixed contact button according to one embodiments of the present invention,
[0027] FIG. 2 is a side view of a moving contact button according to one embodiment of the present invention.
[0028] FIG. 3 is a side view of an arc runner of an arc quenching device according to one embodiment of the present invention.
[0029] FIG. 4 is a side view of a single de-ion plate of an arc chute with top surface and bottom surface of the de-ion plate coated with conductive materials of predefined work function according to one embodiment of the present invention.
[0030] FIG. 5 is a side view of an arc quenching assembly according to one embodiment of the present invention.
[0031] FIG. 6 is a side view of a single de-ion plate of arc chute with top surface and bottom surface of the de-ion plate coated with conductive materials of predefined work function values according to another embodiment of the present invention.

[0032] FIG. 7 is side view of an arc quenching device according to another embodiment of the present invention.
[0033] FIG. 8 is a graph illustrating variation in cathode voltage with respect to various conductive materials of predefined work function values according to various embodiments of the present invention.
[0034] 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
[0035] 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.
[0036] The various embodiments of the present invention provide an arc quenching device for circuit interrupters. The device includes an arc chute, a plurality of de-ion plates arranged in the arc chute, a first arc runner plate and a second arc runner plate. The first arc runner plate and the second arc runner plate are arranged adjacent to the de-ion plates placed at the end in the set of de-ion plates. Further the device includes a fixed contact which is functions as a cathode and a moving contact which functions as an anode. A. top surface and the bottom surface of each of the de-ion plate is coated with conductive materials of

predefined work function to reduce arc splitting time and to enhance an arc voltage to reduce the arc quenching time.
[003 7] In various embodiments of the present invention the conductive materials are Silver having predefined work function value denoted as Wl throughout the detailed description, Iron (W2), Zinc (W3), Copper (W4) Tungsten (W5), and Nickel OR Osmium (W6). The relationship between the work functions values of the conductive materials are as follows ,W1 < W2 < W3 < W4 < W5 < W6, where the Silver has least work function value of Wl and the Nickel OR Osmium has highest work function value of W6.
[0038] In various embodiments of the present invention while interrupting high short circuit currents formation of anode to cathode voltage drop is functionality dependent on the work function of the conductive materials coated on the plurality of de-ion plates. The work function is defined as the minimum amount of energy needed to remove an electron from the metal. The effect of the work function can be analysed by given mathematical expression, the number of electrons emitting per second per unit area from a cathode body which is given
by

Where
Ac = Richardson constant. Tw = surface temperature (k). e = electron charge (coulombs). K = Boltzmann constant. θeff = effective work function.


Ec = electric field intensity (V/m).
[0039] From the above equation the effective work function value is a function of electric field intensity. The electric field intensity is high for rough surface. The high electric field intensity further reduces the effective work function value of the conductive material.
[0040] The reduction in work function value of the conductive material at the arc entrance face of the de-ion plates results in less temperature formation and less time for splitting up the arc. The low work function of the conductive material (Θ C) creates less temperature to ionize the conductive material surface.
[0041] FIG. 1 is a side view of a fixed contact button 101 according to various embodiments of the present invention. With respect to FIG. 1, the fixed contact button 101 has a smooth surface 102 profile followed by a rough surface 103 profile at the top surface of the fixed contact. The smooth surface 102 profile of the fixed contact button 101 is provided at an arc formation face of the fixed contact and extended through the de-ion plate along a direction of propagation of the arc. The rough surface 103 profile is formed after the smooth surface 102 profile of the fixed contact button 101 and extended up to an arc exit face of the fixed contact. During a circuit interruption, an arc is formed between the contacts and the rough surface provided in the fixed contact button 101 eases fast movement of the arc away from the fixed contact button lOland preserves the integrity of the fixed contact button 101 for longer service life.
[0042] FIG. 2 is a side view of a moving contact button according to various embodiments of the present invention. With respect to FIG. 2, the moving contact button 201 has a smooth surface 202 profile followed by a rough surface profile 203. The smooth surface 202 profile of the moving contact button 201 is provided at an arc formation face of the moving contact and extended along a

direction of propagation of the arc. The rough surface 203 profile is formed after the smooth surface 202 profile of the moving contact button 201 and extended up to an arc exit face of the moving contact. During a circuit interruption, an arc is formed between the contacts and the rough surface provided in the moving contact button 201 eases fast propagation of the arc away from the moving contact button 201 and holds the integrity of the moving contact button 201 for a longer service life.
[0043] FIG. 3 is a side view of an arc runner of an arc quenching device according to various embodiments of the present invention. With respect to FIG. 3, the arc runner 301 is provided with a first straight portion, a second bent portion, and a third elevated portion. The first straight portion is provided at arc entering face of the arc runner and extended along direction of propagation of the arc. The second bent portion is formed after the first straight portion of the arc runner and the third elevated portion is formed after the second bent portion of the arc runner and extended up to an arc exit face of the arc runner as shown in the Fig.3. The first straight portion, the second bent portion and the third elevated portion are coated with conductive materials of predefined work function values of Wl, W4 and W6. During circuit interruption, an arc is formed between the contacts. The arc initiated at the point of separation of contact between the fixed and the moving contacts is transferred to an arc chute through the arc runners by an electromagnetic force causing body of arc to move towards the arc chute. In addition to the magnetic pull acting on the body of the arc, the coating of arc runners with conductive materials of predefined work function values aids in fast movement of the arc roots in the arc runner.
[0044] In one embodiment of the present invention, the first straight portion of the arc runner is coated with silver having a predefined work function value of Wl. The second bent portion of the arc runner is coated with copper having a predefined work function value of W4 and the third elevated portion of the arc runner is coated with nickel having a predefined work function value of W6. The

relationship between the work function values of the conductive materials coated on the arc runner is as follows Wl < W4 < W6. Thus the arc entering face of arc runner coated with silver having lower work function value of Wl eases the arc to easily enter in to the arc runner and takes less temperature for formation of arc roots on the arc runners. The second and third elevated portion of the arc runner 301 coated with conductive materials of higher work function values of W4 and W6 helps in build up of an arc voltage forcing the arc current to extinguish.
[0045] In one embodiment of the present invention, the first straight portion of the arc runner 301 is coated with silver having a predefined work function value of Wl. The second bent portion of the arc runner 301 is coated with copper having a predefined work function value of W4 and the third elevated portion of the arc runner 301 is coated with osmium having a predefined work function value of W6. The relationship between the work function values of the conductive materials coated on the arc runner 301 is as follows Wl < W4 < W6. Thus the arc entering face of arc runner 301 coated with silver having lower work function value of Wl eases the arc to easily enter in to the arc runner 301, and takes less temperature for formation of arc roots on the arc runner 301. The second and third elevated portion of the arc runner 301 coated with conductive materials of higher work function values of W4 and W6 helps in build up an arc voltage which forces the arc current to extinguish.
[0046] FIG. 4 is a side view of a single de-ion plate 400 of an arc chute with top surface and bottom surface of the de-ion plate coated with conductive materials of predefined work function values according to one embodiment of the present invention. With respect to FIG. 4, whole length of the top surface 401 of each of the de-ion plates 400 and the bottom surface of each of the de-ion plates 400 are coated with two different materials of predefined work function values. For example, in certain cases due to increase in cathode surface temperature, cathode voltage drop is decreased causing an increase in the density of electrons emitted from the cathode surface of the de-ion plate 400. The increase in the density of

the electrons emitted from the cathode surface of the de-ion plate 400 increases the magnitude of current. Further, the increase in the current magnitude decreases the cathode voltage drop across the de-ion plates 400 of the arc chute provided in an arc quenching device. The decrease in the cathode voltage drop causes a decrease in the total arc voltage thereby increasing an arc quenching time in the arc quenching device. Moreover, an anode spot at the back side of cathode spot causes an increase in the cathode surface temperature. Hence, the cathode spot and anode spot positions are separated on the de-ion plates 400 in order to limit the increase in the temperature at the cathode surface of the de-ion plate 400.
[0047] In one embodiment of the present invention, the cathode spot and anode spot positions on the de-ion plate 400 are separated by coating the first surface and the second surface of each of the de-ion plates 400 with conductive materials of predefined work function values. The first surface 401 of each of the de-ion plates 400 is coated with conductive material of lesser work function value, and the second surface 402 of each of the de-ion plates 400 is coated with conductive materials of higher work function value. For example, the first surface 401 of the de-ion plate 400 is coated with Silver of work function value Wl and the second surface 402 of the de-ion plate 400 is coated with Copper of work function value W4 , where the work function value Wl of silver is lesser than the work function value W4 of the Copper. The various possible combinations of selection of the conductive materials for coating on the de-ion plate 400 are as shown below in the table (Table. 1).

Combinations wa wb
1 Silver Copper
2 Silver Tungsten
3 Silver Nickel
4 Silver Osmium
5 Iron Copper
6 Iron Tungsten
7 Iron Nickel
8 Iron Osmium
9 Zinc tungsten
10 Zinc Nickel
11 Zinc Osmium
12 Copper Nickel
13 Copper Osmium
14 Tungsten Osmium
15 Nickel Osmium
Table 1
[0048] Further, during circuit interruption, the arc generated enters the arc chutes through the first surface 401 of the de-ion plate 400 coated with a conductive material of less work function value since less temperature is required to form anode and cathode spots on a conductive material with less work function value. Further, the arc moves faster on the area of the de-ion plate 400 coated with conductive material of less work function value, whereas the arc moves slower on the surface of the de-ion plate 400 coated with conductive material of high work function value. Hence, the difference in arc dynamics on the surfaces of the de-ion plate 400 leads to elongated conducting path of the arc across the de-ion plate 400 and finaJJy leads to increase in resistance of the arc path 400 for the arc to extinguish easily.

[0049] FIG. 5 is a side view of an arc quenching device 500 according to one embodiment of the present invention. With respect to FIG. 5, the arc quenching device 500 includes an arc chute 502 , a plurality of de-ion plates 400 arranged in the arc chute, a first arc runner plate 301a and a second arc runner plate 301b. The first arc runner plate 301a and the second arc runner plate 301b are arranged adjacent to de-ion plates arranged at the end portion of the de-ion plate set. The plurality of de-ion plates 400 are arranged at right angles to each other in the arc chute. The arrangement of the de-ion plates 400 in the arc chute 502 is in such a way that the conductive materials coated having similar predefined work function value faces each other in the arc chute. Further the device includes a fixed contact 101 which is a cathode and a moving contact 201 which is an anode. A top surface and bottom surface of each of the de-ion plate is coated with conductive materials of predefined work function values to reduce arc splitting time and to enhance an arc voltage to reduce the atc quenching time. The first surface of each of the de-ion plate is coated with conductive material of less work function value and the second surface of each of the de-ion plate is coated with conductive materials of higher work function value.
[0050] When an electric source 501 is interrupted, by separating the moving contact 201 from a fixed contact 101, an arc is generated between the moving and the fixed contacts. Further the arc is transferred into the arc chute by electromagnetic and thermal blowout forces causing the arc to move away from the contacts along the arc runners and finally into the de-ion plates. The spacers provided between the de-ion plates splits the arc into a series of small arcs, increases the resistance for the arc and extracts the heat from the arc. Since both surfaces of each of the de-ion plate have arc at two distinct locations (As shown in FIG. 5), the anode root does not provide for formation of cathode root and thus the cathode voltage drop obtained is higher. After the arc is completely transmitted into the de-ion plates, the higher work function value of the

conductive materials coated on the de-ion plates cause rapid buildup of cathode voltage, leading to a fast quenching of the arc and a reduced quenching time.
[0051] In one embodiment of the present invention, the plurality of de-ion plates 400 are arranged in a partially divergent assembly in the arc chute. Arrangement of the de-ion plates in the arc chute is in such a way that the part of the de-ion plates coated with conductive materials having same predefined work function values face each other in the arc chute.
[0052] FIG. 6 is a side view of a single de-ion plate 600 of arc chute with top surface and bottom surface of the de-ion plate 600 coated with conductive materials of predefined work function according to another embodiment of the present invention. With respect to FIG. 6, the top surface and the bottom surface of each de-ion plate 600 is coated with materials of predefined work function values to reduce arc splitting time and to enhance an arc voltage and to reduce arc quenching time. The top surface of each of the de-ion plates is coated with three materials of predefined work function values denoted by Wl, W2 and W3 in an order of increasing work functionality (Wl < W2 < W3) starting from arc entering face of each of the de-ion plate 600 and extending up to an arc exit face of each of the de-ion plate 600 (as indicated on the top surface of the FIG. 6). The bottom surface of each of the de-ion plates is coated with three materials of predefined work function values denoted by W6, W5, and W4 (W6 > W5 > W4) (as indicated on the bottom surface of the FIG. 6) in order of lesser work functionality starting from arc entering face and extending up to arc exit face of each of the de-ion plate 600. Formation of anode to cathode voltage drop is functionality dependent on the work function of the conductive materials coated on the plurality of de-ion plates 600.
[0053] During circuit interruption, the arc generated between the contacts enters through the top surface of the de-ion plate 600 coated with conductive material of less work function value, since less temperature is required to form anode and

cathode spots on the conductive material with lesser work function value. Further, the arc moves faster on the top surface area of the de-ion plate 600 coated with conductive material of lesser work function value, whereas the arc moves slower at the bottom surface of the de-ion plate 600 coated with conductive material of higher work function value. The difference in arc dynamics on the surfaces of the de-ion plate 600 leads to elongated conducting path of the arc across the de-ion plate and finally leads to increase in resistance of the arc path 600 for the arc to extinguish easily.
[0054] In one embodiment of the present invention, a first portion, a second portion and a third portion at the top surface of each de-ion plate 600 is coated with silver (Wl), iron (W2) and zinc (W3) conductive materials as shown in the FIG. 6. The first portion, the second portion, and the third portion of the de-ion plate is taken in equal proportions corresponding to one-third of the length of the de-ion plate. Also, a first portion, a second portion and a third portion on the bottom surface corresponding to the portions on the top surface are coated with conductive materials such as nickel (W6), tungsten (W5) and copper (W4) as shown in the FIG. 6.
[0055] In one embodiment of the present invention, the first portion, second portion and third portion at the top surface corresponding to one third of the length of each of the de-ion plate is coated with conductive materials such as silver (Wl) , iron (W2) and zinc (W3). Further, the bottom surface of each of the de-ion plate is coated with conductive materials such as Osmium (W6), tungsten (W5) and copper (W4) in an equal proportion corresponding to one third of the length of the de-ion plate.
[0056] FIG. 7 is a side view of an arc quenching device 700 with various elements according to another embodiment of the present invention. With respect to FIG. 7, the arc quenching device includes an arc chute 702,a plurality of de-ion plates 600 arranged in the arc chute 702, a first arc runner plate 301a and a

second arc runner plate 301b. The first arc runner plate 301a and the second arc runner plate 301b are arranged adjacent to outer de-ion plates. The plurality of de-ion plates 600 are arranged at right angles to each other in the arch chute. Further the device includes a fixed contact 101 which is a cathode and a moving contact 201 which is an anode. A top surface and bottom surface of each of the de-ion plate is coated with three conductive materials of predefined work function values to reduce arc splitting time and to enhance an arc voltage to reduce the arc quenching time. The top surface of each of the de-ion plates is coated with three materials of predefined work function values denoted by Wl, W2 and W3 in order of higher work functionality (Wl < W2 < W3) starting from arc entering face of each of the de-ion plate 600 and extended up to arc exit face of each of the de-ion plate 600 as shown in FIG. 6. The bottom surface of each of the de-ion pistes is coated with three materials of predefined work function values denoted by W6, W5, and W4 (W6 > W5 > W4) in order of less work functionality starting from arc entering face and extended up to arc exit face of each of the de-ion plate.
[0057] When an electric source 501 is interrupted by separating the moving contact 201 from a fixed contact, an arc is generated between the moving 201 and the fixed contacts 101. Further the arc is transferred into the chute by electromagnetic and thermal blowout forces causing the arc to move away from the contacts along the arc runners 301a, 301b and finally into the de-ion plates 600. The spacers provided between the de-ion plates splits the arc into a series of small arcs, thereby increasing the resistance for the arc and extracts heat from the arc. Since both surfaces of each of the de-ion plates have arc at two distinct locations as shown in FIG. 5, the anode root no longer aids in the formation of a cathode root and thus the cathode voltage drop obtained is higher. After the arc has completely entered into de-ion plates, the higher work function value of the conductive materials coated on the de-ion plates 600 causes rapid buildup of cathode voltage, leading to a fast quenching of the arc and a reduced quenching time.

[0058] In one embodiment of the present invention, the plurality of de-ion plates 600 are arranged in a partially divergent assembly in the arc chute.
[0059] FIG. 8 is a graph illustrating variation in cathode voltage with respect to predefined work function values of various conductive materials according to embodiments of the present invention. With respect to FIG. 8, substantial measurements of "Work function" values and "Cathode voltage" values are taken along abscissa and ordinate of the two dimensional graph respectively. The cathode voltage increases with increase in work function values. For example, by increasing the work function value from 4.9ev to 5.9ev the cathode voltage increases by 2V. The increment in cathode voltage is for one cathode de-ion plate, if the number of de-ion plates are 10, then there exists a cathode voltage boost of (10*2=20V). The additional 20V cathode voltage leads to faster quenching of the arc and reduces quenching time required in quenching of the arc.
G) ADVANTAGES OF THE INVENTION
|0060] The various embodiments of the invention provide an arc quenching device for circuit interrupters. The quenching device reduces the arcing time by generating conditions favourable for arc splitting and arc lengthening. The arc quenching device improves arc quenching time to limit the let through energy in the current interrupting device. Further, fast splitting of the arc in arc chute of quenching device is achieved. The device de-ionizes emissions of the arc and cools down the arc. Furthermore, the device minimizes damage caused to internal parts within circuit interrupters and to moves the arc away from the contacts to preserve integrity of the contacts for a longer service life.
[0061] 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.
[0062] 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 quenching assembly for a circuit interrupting device, the assembly
comprising:
an arc chute;
a plurality of de-ion plates arranged in the arc chute; a first arc runner provided at one end of the arc chute; a second arc runner provided at another end of the arc chute; a fixed contact; and a moving contact;
wherein a top surface and a bottom surface of each of the plurality of the de-ion plates is provided with a plurality of conductive material coating having a predefined work function to reduce an arc splitting time and to enhance an arc voltage to reduce the arc quenching time.
2. The assembly of claim 1, wherein the top surface of each of the de-ion
plate is coated with a plurality of conducting materials of the predefined
work function.
3. The assembly of claim 2, wherein the conductive material is selected
from a group comprising of silver, iron, zinc, copper, tungsten and nickel.
4. The assembly of claim 2, wherein the conductive material is coated in an order of decreasing work function starting from an arc entering face and extending up to an arc exit face of each of the de-ion plate.
5. The assembly of claim 1, wherein the bottom surface of each of the de-ion plate is coated with a plurality of conducting materials of the predefined work function.

6. The assembly of claim 6, wherein the conductive material is selected
from a group comprising of osmium, nickel, tungsten and copper.
7. The assembly of claim 6, wherein the conductive material is coated in an order of increasing work function starting from an arc entering face and extending up to an arc exit face of each of the de-ion plate.
8. The assembly of claim 1, wherein the plurality of de-ion plates in the arc chute is arranged in such a way that the similar conductive material coating having predefined work function faces each other.
9. The assembly of claim 1, wherein a combination of the coating having low work function and high work function material provides for building up an arc voltage to extinguish the arc.
10. The assembly of claim 1, wherein the plurality of de-ion plates are arranged at right angles to each other in the arch chute.
11. The assembly of claim 1, wherein the plurality of de-ion plates are arranged in a partially divergent assembly in the arc chute.
12. The assembly of claim 1, wherein top surface of the fixed contact has a smooth surface profile followed by a rough surface profile.
13. The assembly of claim 1, wherein bottom surface of the fixed contact has a smooth surface profile extended up to an arc exit face of the fixed contact.
14. The assembly of claim 1, wherein the smooth surface profile of the fixed contact is provided at an arc formation face of the fixed contact and extended along a direction of propagation of the arc.

15. The assembly of claim 1, wherein the rough surface profile is formed after the smooth surface profile of the fixed contact and extended up to an arc exit face of the fixed contact.
16. The assembly of claim 1, wherein top surface of the moving contact has a smooth surface profile at arc formation face and extended up to an arc exit face of the moving contact.
17. The assembly of claim 1, wherein bottom surface of the moving contact has a smooth surface profile followed by a rough surface profile.
18. The assembly of claim 1, wherein the smooth surface profile of the moving contact is provided at an arc formation face of the moving contact and extended along a direction of propagation of the arc.
19. The assembly of claim 1, wherein the rough surface profile is formed after the smooth surface profile of the moving contact and extended up to an arc exit face of the moving contact.
20. The assembly of claim 1, wherein the first arc runner plate and the second arc runner plate are provided with a first straight portion, a second bent portion, and a third elevated portion.
21. The assembly of claim 1, wherein the first straight portion is provided at arc entering face of the arc runner and extended along direction of propagation of the arc.
22. The assembly of claim 1, wherein the second bent portion is formed after the first straight portion of the arc runner and the third elevated portion is formed after the second bent portion of the arc runner and extended up to an arc exit face of the arc runner.

23. The assembly of claim 1, wherein the first straight portion, the second bent portion and the third elevated portion is provided with a conductive material coating of a predefined work function.
24. The assembly of claim 1, wherein work function of the material coated on the first straight portion is lesser than the work function of the material coated on the second bent portion.
25. The assembly of claim 1, wherein work function of the material coated on the second bent portion is lesser than the work function of the material coated on the third elevated portion.
26. The assembly of claim 1, wherein the first straight portion of the first arc runner plate and the second arc runner plate is coated with silver.
27. The assembly of claim 1, wherein the second bent portion of the first arc runner plate and the second arc runner plate is coated with copper.
28. The assembly of claim 1, wherein the third elevated portion of the first arc runner plate and the second arc runner plate is coated with nickel and osmium.
29. The assembly of claim 1, wherein the third elevated portion of the first arc runner plate and the second arc runner plate are coated with osmium,