DYNAMIC ARC CHUTE WITH ARCING CONTACT IN MOLDED CASE
CIRCUIT BREAKERS
Field of the Invention:
The invention relates to molded case circuit breakers (MCCB), and more particularly to an arc chute in circuit breakers.
Prior Art: A variety of over current protective devices are known in the art for circuit protection and isolation. These current protecting devices generally include contactors, fuses and circuit breakers that are typically used for electrical distribution and control. For more than 30 years in high-voltage circuitbreakers in power plants, substations etcetera, 'arc chutes' are used to insulate and protect circuits from shorting. A typical arc chute acts like an insulator, is nonconductive, and its function is to quench the arc or the plasma state wherein the air breaks down and current continues to flow through the circuit.
Circuit breakers are designed to make, carry and break current during normal and abnormal conditions. An arc is formed under all circumstances (except for carrying) though the intensity of it varies in each case. Arc may also be formed during bouncing of contacts. Abnormal conditions such as overload and short circuit conditions generally occur during service conditions.
Of these, condition of 'short circuit' affects more adversely than that of the overload. This is due to the fact that in short circuit condition, the fault current level is quite high (of an order of 50 kilo amperes or even more), whereas flow of the overload current is usually in the range of 3 to 6 times the rated current.
In the abnormal conditions, when the contact of a circuit breaker initially separates for some distance in order to prevent the fault or overload current, during Off or during trip, the dielectric strength or breakdown voltage of air is conquered by the high order fault currents, and these currents start flowing through the circuit. This momentary conduction of currents may cause damage to the circuit. So the arc must be quenched as soon as possible to save the system.

Further, arc intensity can be very high at the initial stage of opening of contacts when compared to the final stage. Intense arc at the initial stage produces more heat, which may melt the contact buttons. So it is very important to remove the arc from the contact buttons as soon as possible.
Therefore, arc chutes are used to (1) increase the voltage formed between two open contacts, which is called as arc voltage; and (2) to absorb the arc as soon as possible from the main contacts button so that life of the button can be increased which in turn increases the life of the breaker.
A typical arc chute comprises of a number of plates stacked in columns, without any conducting path between each plate, for the formation of anode and cathodes.
When the contact completely opens, the plates produce arc voltage equal to or little greater than the system voltage.
Arc chute contributes to the arc voltage through anode and cathode drop and through the voltage drop in air between its plates. Arc is basically current which produces flux lines. These flux lines always chooses a low reluctance flux path to flow. Reluctance in magnetic circuit is analogous to resistance in electrical circuit. So, by reducing the reluctance in arc chute and providing a relatively low reluctance path than between contacts, arc can be attracted towards the arc chute.
It is a well-known fact that air has very high reluctance when compared to mild steel (material of those stacked plates). So if air in a flux path is reduced, much of the reluctance can also be reduced.
If the arc chute is fully a solid block then it has low reluctance and can attract the arc quickly but it has a disadvantage of not producing the anode cathode drop. If the plates are stacked as in conventional type, the advantage is that we get anode cathode drop but the disadvantage is reluctance of the arc chute at all times will be constantly high so that pulling of the arc from the contact button is delayed.
Hence there is a need for an improved arc chute for molded case circuit breakers (MCCB) that eliminates the drawbacks of existing arc chutes,

Summary of the Invention:
It is therefore an object of the present invention to provide the phenomenon of arc chute and arcing contact.
Another object of the present invention is to save the contact buttons in the main contacts of the circuit breaker in order to increase the life of the circuit breaker.
The above-mentioned objects may be achieved by the embodiments of the present invention. In one embodiment herein, an improved dynamic arc chute of a contact system is described. The contact system comprises a cup for holding a stack of plates of a circuit breaker, and two main contacts, each having a contact button. An arcing contact is adapted in the improved dynamic arc chute for allowing a minimum flow of current through said arcing contact when the main contacts are closed. Also the arcing contact quenches the arc formed between the plates by providing required isolation between the plates thereby saving each of the contact buttons and increasing the life of the circuit breaker.
According to one embodiment of the present invention, the arc may be formed between the plates after the main contacts are opened apart for 16mm; whereas, the required isolation between the main contacts may be around 30mm to quench the arc.
Other objects, features and advantages of the invention will be apparent from the drawings, and from the detailed description that follows below.
Brief Description of Drawings:
Figure 1 shows the three-dimensional schematic of the improved dynamic arc chute with arcing contact arrangement according to an embodiment herein.
Figure 2 illustrates shows the two-dimensional schematic of the improved dynamic arc chute with arcing contact arrangement according to an embodiment herein.
Detailed Description of the Invention:
The invention is described below in the context of various embodiments. It should

be understood that it is not intended to limit the scope of the invention to these particular embodiments.
The embodiments of the invention described herein provides an improved dynamic arc chute that advantageously utilize the stacking of plates to yield a low reluctance and to produce the desired anode cathode drop required for an arc to traverse through the chute.
Referring now to the figures including Figure 1 and Figure 2, the like numerals assigned to the parts shown in various figures indicate the like parts.
Figure 1 shows the three-dimensional schematic of the improved dynamic arc chute with arcing contact arrangement according to an embodiment herein. The improved dynamic arc chute with arcing contact comprises a stack of plates 101 arranged in a stack holder 103. Contact buttons 102 and a special spring 105 can be seen in the figure that holds the foremost plate 104 of the stack 10L
Figure 2 illustrates shows the two-dimensional schematic of the improved dynamic arc chute with arcing contact arrangement according to an embodiment herein. In one embodiment herein, the improved dynamic arc chute comprises a cup 201 for holding the upper contact 203 of a circuit breaker, and two main contacts (203, 207), each having a contact button 102. The two main contacts comprise of an upper main contact 203 and a lower main contact 207.
An arcing contact (not shown) is adapted in the improved dynamic arc chute for allowing a minimum flow of current through said arcing contact when the main contacts 203, 207 are closed. Also the arcing contact quenches the arc formed between the plates 101 by providing required isolation between the main contacts 203,207 thereby saving each of the contact buttons 102 and increasing the life of the circuit breaker.
Projections protruding out from the cup 201 are provided. These projections may be called as stoppers 202. There may be two stoppers, one at the top and another at the bottom of the cup 201. The lower stopper is used to carry the foremost plate 104 upwards when the upper main contact 203 opens. The upper stopper is used to

We claim:
1. An improved dynamic arc chute comprising:
a stack of plates;
at least two main contacts including an upper main contact and a lower main contact, each main contact having a contact button; a cup for holding the upper main contact of a circuit breaker; characterized in that an arcing contact is adapted for:
allowing a minimum flow of current through said arcing
contact when the main contacts are closed, and quenching an arc formed between the plates by providing required isolation between the main contacts thereby saving each of the contact buttons.
2. The arc chute according to claim 1 wherein a movable handle is riveted to the foremost plate of the stack,
3. The arc chute according to claim 2 wherein the cup is having an outward projection to carry the foremost plate.
4. The arc chute according to claim 2 wherein a spring is provided for providing a contact pressure to the movable handle.
5. The arc chute according to claim 1 wherein a guide way is provided at sides of the plates to ensure linear movement of the plates.
6. The arc chute according to claim 1 wherein a small projection is made on top of the cup for pushing downwards the plates that are being de-ionized when the main contacts are closed.

7. The arc chute according to claim 1 wherein the contact buttons are
harder and have more resistance than the main contacts.
8. The arc chute according to claim 1 wherein the movable handle moves
sideways with respect to the stack of the plates.