CLIAMS:
1. An arc chute assembly for use within a change over switch disconnector (COSD), said assembly comprising:
a moving bridge means;
plural arc chutes assembled on said moving bridge means
wherein said arc chutes are placed in line with fixed and moving contacts of the said change over switch disconnector such that during breaking operation at the time of a short circuit or fault scenario when the arc is drawn between the fixed and moving contacts, the current through conductors of the change over switch disconnector generates a magnetic field forcing the arc away from the contact region into the said arc chutes whereby said arc is being split into number of series arcs thereby limiting the peak fault current thus quenching the arc.

2. Assembly as claimed in claim 1 wherein said arc chutes being located on said moving bridge means such that the said arc chutes move corresponding to the movement of the moving bridge means.

3. Assembly as claimed in claim 1 wherein said arc chutes comprising arc holder means located on said moving bridge.

4. Assembly as claimed in claim 3 wherein said arc chute holder means is made of SMC material.

5. Assembly as claimed in claim 3 wherein said holder means comprising rib means so as to guide deion plate means.

6. Assembly as claimed in claim 5 wherein said rib means having parallel configuration.

7. Assembly as claimed in claims 5 and 6 wherein said rib means having parallel configuration adapted to lengthen the arc to quench it immediately without affecting the contacts.

8. Assembly as claimed in claim 1 wherein said moving bridge means comprising a sliding mechanism for sliding over the fixed contact.

9. Assembly as claimed in claim 1 wherein the fixed and moving contacts comprising chamfer means.

10. Assembly as claimed in any of the preceding claims adapted to be used for COSD having voltage rating of 690 volts and above.
,TagSPECI:
FIELD OF THE INVENTION
The present invention relates to arc chute assembly for change over switch disconnector (COSD). More particularly, the present invention relates to an arc chute assembly for use in a change over switch disconnector (COSD) that helps in reduction of contact erosion due to arcing. The arc chute assembly is provided on the moving Bridge.

BACKGROUND OF THE INVENTION AND PRIOR ART

In Change over switch Disconnector, the current path includes:-
1) Terminals (Fixed Contacts)
2) Moving contacts (Bridge Assembly)

While switching (i.e. making & breaking of contacts) Change over Switch Disconnector, certain amount of arcing takes place between the moving & fixed terminals. For the sliding mechanism where the moving contact slides over to the fixed terminals in order to complete the circuit, chamfers given on both the contacts need to be there for entire operating life. As a consequence of arcing, erosion of the moving & fixed contacts takes place which further leads to locking of moving bridge rendering the unit inoperable.
The present invention involves an arc chute assembly within the changeover switch which is currently being used for a 415V application. At present in Changeover switch Disconnector no such arrangement (arc chute assembly) is present, air gap present is sufficient to extinguish the arc. But in order to use same COSD for higher voltages (i.e.690 V), this air gap (dielectric) is not sufficient enough to extinguish the arc generated due to contact repulsion.
The aforementioned change can enhance operational performance capability.
The present invention has been conceived keeping in mind the reduction of contact erosion due to arching, that can be accrued by using the arc chute assembly in the moving Bridge. An Arc chute Assembly is beneficial to extinguish the arc without affecting the performance of the switch.

OBJECTS OF THE INVENTION
One object of the present invention is to overcome the disadvantages / drawbacks of the prior art.

A basic object of the present invention is to provide an arc chute assembly for change over switch disconnector (COSD) in moving bridge.
Another object of the present invention is to provide an arc chute assembly for change over switch disconnector (COSD) in moving bridge that helps in reduction of contact erosion due to arching, that can be accrued by using the arc chute assembly in the moving Bridge.
Another object of the present invention is to provide an Arc chute Assembly to extinguish the arc without affecting the performance of the switch.
These and other advantages of the present invention will become readily apparent from the following detailed description taken in conjunction with the accompanying drawings.

SUMMARY OF THE INVENTION
The following presents a simplified summary of the invention in order to provide a basic understanding of some aspects of the invention. This summary is not an extensive overview of the present invention. It is not intended to identify the key/critical elements of the invention or to delineate the scope of the invention. Its sole purpose is to present some concept of the invention in a simplified form as a prelude to a more detailed description of the invention presented later.

According to one of the aspect of the present invention there is provided an arc chute assembly for use within a change over switch disconnector, said assembly comprising:
a moving bridge means;
plural arc chutes assembled on said moving bridge means
wherein said arc chutes are placed in line with fixed and moving contacts of the said change over switch disconnector such that during breaking operation at the time of a short circuit or fault scenario when the arc is drawn between the fixed and moving contacts, the current through conductors of the change over switch disconnector generates a magnetic field forcing the arc away from the contact region into the said arc chutes whereby said arc is being split into number of series arcs thereby limiting the peak fault current thus quenching the arc.

Other aspects, advantages, and salient features of the invention will become apparent to those skilled in the art from the following detailed description, which, taken in conjunction with the annexed drawings, discloses exemplary embodiments of the invention.

BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWING

The following drawings are illustrative of particular examples for enabling methods of the present invention, are descriptive of some of the methods, and are not intended to limit the scope of the invention. The drawings are not to scale (unless so stated) and are intended for use in conjunction with the explanations in the following detailed description.

Figures 1a and 1b illustrate different views of Arc Chute Assembly in the present invention.
Figure 2 illustrates Moving Bridge on the arc chute assembly is assembled in the present invention.
Figure 3 illustrates Entire Assembly of the present invention
Figure 4 illustrates characteristics of re-striking voltage.
Figures 5a to 5c illustrate different views of the arc chute.
Figure 6 illustrates schematic view of the whole assembly.
Persons skilled in the art will appreciate that elements in the figures are illustrated for simplicity and clarity and may have not been drawn to scale. For example, the dimensions of some of the elements in the figure may be exaggerated relative to other elements to help to improve understanding of various exemplary embodiments of the present disclosure.

Throughout the drawings, it should be noted that like reference numbers are used to depict the same or similar elements, features, and structures.

DETAILED DESCRIPTION OF THE INVENTION

Referring to figures 1a and 1b arc chute assembly (1) have arc dividers in the form of flat segments (2) stacked one above the other, with an air gap between them. When the arc occurs, it is expelled into the arc chute and into the arc dividers, such that it wraps back and further between the arc dividers. The wrapping back and forth around the arc dividers effectively stretches the length of the arc until it is just too long for the voltage to keep it going. When this happens, the arcing stops. The arc has been extinguished.

Arc chute holder (3) is made of SMC material, the same composition as used for the moving Bridge (4) shown in figure 2 (Sheet Mould compound) and de-ion plate (5) is of MS material (Mild steel).At the time of switching (i.e. making & breaking of contacts) Change over Switch Disconnector (6), arcing takes place between the moving & fixed terminals (7 and 8) as shown in figure 3. For the sliding mechanism, where the moving contact slides over to the fixed terminals, chamfers given on both the contacts need to be there for entire operating life. Arcing, led to erosion of the moving & fixed contacts (7 and 8). This could lead to bridge lock (due to the formation of globules) or no continuity in few of the cases rendering the unit inoperable. Hence this entire assembly helps to quench the arc in an appropriate time without affecting the Switch.
The new bridge assembly with arc chute helps in Extinguish the arc as in case of higher voltage (i.e. 690V), Enhance the operational performance capability and Enhancing product performance by reducing arcing.
Challenges of arc quenching at 690 Vac
I. Higher system voltage results in higher:
— Peak current
— Arcing time
— Arc energy ( ?vi dt )
II. As a result, di-electric strength in the contact gap is deteriorated

III. Stronger electric field in the gap then may lead to re-strike resulting in standing arc

-To attain the recovery voltage faster during switching operation.
Referring to figure 2 the arc chute assembly (1) is shown to be located within the changeover switch (6) which is currently being used for a 415V application. At present in Changeover switch Disconnector no such arrangement (arc chute assembly) is there and the design margin is sufficient to extinguish the arc at such voltage. In order to use same COSD for higher voltages (i.e.690 V and above), this air gap (dielectric strength) is not sufficient enough to extinguish the arc generated due to contact repulsion. While using this assembly in a moving bridge (as shown in fig) the same switch can be use for higher voltage.
Figures 3 and 6 show the moving bridge (4) in which arc chutes are assembled (1) and the fixed contacts (8) (terminals). These arc chutes are placed directly in line with fixed and the moving contact (7 & 8), at the time of breaking an electric arc is drawn between opening contacts, the current through the conductors generates a magnetic field in the arc chamber. This forces the arc (elliptical cloud) away from the contact region into an arc stack where the arc is split into a number of series arcs. This result in a high arc voltage which counteracts the supply Voltage to limit the peak fault current in this way arc gets quenched. Arc chutes forms the part of moving system which moves along with the moving bridge assembly (contact system). Usually Arc breaking system is the stationary arrangement. The arc chamber & the plates need to create a pull to run the arc through splitter plates. New arrangement helps to reduce the arcing time. In the existing moving bridge an area is provided to insert the arc holder. In holder (3) the ribs (9) (as shown in Figure 5(b)) are provided to guide the de-ion plates (5) these ribs are arranged in a parallel construction. The purpose of providing the parallel path is to lengthening the arc so that arc can quench immediately without affecting the contacts.
Fig 4: As soon as the contact separate out an arc is formed.The voltage across the contact during the arcing period is known as the arc voltage and is relatively low with heavy current arcs of short length. At current zero it rises rapidly to a peak value since a short circuit current is almost 90º lagging. The translate voltage appearing across the contact at current zero during arc period is called restriking voltage.This restrike the arc so that it persists for another half cycle. The voltage is given by the expression
V = V (1-cos 1/vLC)
The normal frequency rms voltage that appears across the breaker contacts after final arc extinction has occurred is called the recovery voltage.
The average RRRV= (peak value of restriking voltage)/(time taken in attending peak value) =(2Vm)/(µvLC)
Characteristics of restriking voltage:
The important characteristics of restriking voltage which affect the circuit breaker performance are: (a) amplitude factor (b) Rate of rise of restriking voltage
(a)Amplitude factor-Amplitude factor is defined as the ratio of the peak of transient voltage to the peak system frequency voltage.
(b)R.R.R.V-It is the rate of increase of restriking voltage and is abbreviated by R.R.R.V. its unit is kV/m sec.Consider the fig below showing the opening of circuit breaker under fault conditions. Before current interruption, the capacitance C is short circuited by the fault and the short circuit current through the breaker is limited by inductance L of the system as shown in figure 5.
The short circuit current will lag the voltage by 90° as shown in fig 4, where i represent the short circuit current and ea represents the arc voltage. Under short circuit condition the entire generator voltage appears across inductance L. when the contacts are opened and the arc finally extinguishes at some current zero, the generator voltage e is suddenly applied to the inductance and capacitance in series. This L-C combination forms an oscillatory circuit produces a transient of frequency; fn= 1/ [2p (LC) 1/2], which appears across the capacitor and hence across the contacts of the circuit breaker. This transient voltage is known as restriking voltage and may reach an instantaneous peak value twice the peak phase neutral voltage i.e. 2 Em.
It is R.R.R.V, which decides whether the arc will re-strike. If R.R.R.V is greater than the rate of rise of dielectric strength between the contacts, the arc will re-strike. The arc will fail to re-strike if R.R.R.V is less than the rate of increase of dielectric strength between the contacts of the breaker. The value of R.R.R.V depends on:
1. Recovery voltage
2. Natural frequency of oscillations

Features:
· Enhance the short circuit breaking capacity of the switch.
· To increase the Electrical & mechanical life of COSD (Change over switch Disconnector).
· Arc path along with the moving bridge.