DESC:BACKGROUND

FIELD OF THE INVENTION

The invention relates to switching circuits, and, more particularly to a circuit breaker in a switching circuit.

DESCRIPTION OF THE RELATED ART

A circuit breaker is often connected in a circuit for breaking the flow of current in the circuit and includes a stationary contact assembly and a moving contact assembly. The stationary contact assembly includes a stationary arc contact and a stationary main contact. The stationary main contact and the stationary arc contact are concentric, where the stationary main contact encloses the stationary arc contact. The moving contact assembly includes a moving arc contact, a moving main contact, and a nozzle. The moving main contact and the moving arc contact are concentric, where the moving main contact encloses the moving arc contact. For breaking the circuit, i.e., during an opening operation of the circuit breaker, the moving main contact moves away from the stationary main contact. When the moving main contact is physically disconnected from the stationary main contact, the current in the circuit flows through the moving and stationary arc contacts. During separation of the moving and stationary arc contacts, an arc is formed in a space between the moving and stationary arc contacts (hereinafter referred to as an “interacting space”). Compressed gas flows inside the interacting space from a puffer chamber of the circuit breaker by way of the nozzle when the moving arc contact is physically disconnected from the stationary arc contact. For a high voltage across the circuit breaker, the moving contact assembly needs to move at fast speed with respect to the stationary contact assembly for quenching the arc. Such circuit breakers involve movement of only one contact assembly and hence, do not achieve the desired speed of operation for breaking circuits operating at high voltages. Thus, such circuit breakers are not effective for breaking circuits that operate at high voltages.
A known technique to overcome the aforementioned problem is to increase the speed at which the two contact assemblies separate from each other. Circuit breakers employing this technique involve movement of both the contact assemblies. Thus, the relative velocity of separation of both the contact assemblies increases. Such circuit breakers include a scissor arrangement, one end of which is connected to one contact assembly (the moving contact assembly) and the other end connected to the other contact assembly (the stationary contact assembly). Thus, the stationary arc contact and the stationary main contact move together. When the moving arc contact separates from the stationary arc contact, the arc formed in the interacting space generates a large amount of heat. However, the distance between the stationary and moving arc contacts may increase to an extent that the pressure of the compressed gas may not be sufficient to drive the heat away from the interacting space, thereby not quenching the arc effectively.
Therefore, it would be advantageous to have a circuit breaker that has a distance between arc contacts within a desired range, and overcomes the aforementioned problems of the conventional circuit breakers.

OBJECTS OF THE INVENTION

An object of the present invention is to provide a circuit breaker that includes first and second contact assemblies. The first contact assembly includes a movable first main contact, a movable first arc contact, and a nozzle. The second contact assembly includes a stationary second main contact, a stationary second arc contact, and a transfer contact. An end of the nozzle is connected to the first main contact. Each of the first main contact, the first arc contact, and the nozzle is movable between first and second positions. The transfer contact is electrically connected to the second arc contact and mechanically connected to the nozzle. In the first position, the first arc contact is connected to the second arc contact, and in the second position, the first arc contact is disconnected from the second arc contact by way of movement of the first main contact, the first arc contact, and the nozzle in a first direction. The transfer contact moves in the first direction when the first main contact, the first arc contact, and the nozzle move in the first direction. A distance between the first arc contact and the transfer contact is constant.
Another object of the present invention is to provide a circuit breaker that includes first and second contact assemblies and a linkage arrangement. The first contact assembly includes a movable first main contact, a movable first arc contact, and a nozzle. The second contact assembly includes a movable second main contact, a second arc contact, and a transfer contact. Each of the first main contact, the first arc contact, and the nozzle is movable between first and second positions. The linkage arrangement is hinged to a fixed tube of the circuit breaker. A first end of the nozzle is connected to the first main contact. A second end of the nozzle is connected to a first end of the linkage arrangement. The second arc contact is connected to a second end of the linkage arrangement. The transfer contact is connected to the linkage arrangement. The second arc contact moves in a second direction when the first main contact, the first arc contact, and the nozzle move in the first direction. The transfer contact moves in the first direction when the first main contact, the first arc contact, and the nozzle move in the first direction. The ratio of speed of movement of the transfer contact in the first direction to the movement of the first main contact, the first arc contact, and the nozzle in the first direction depends upon the points of the linkage arrangement at which the transfer contact and the nozzle are connected to the linkage arrangement.

BRIEF DESCRIPTION OF DRAWINGS

The features of the present invention, which are believed to be novel, are set forth with particularity in the appended claims. Embodiments of the present invention will hereinafter be described in conjunction with the appended drawings provided to illustrate and not to limit the scope of the claims, wherein like designations denote like elements, and in which:
FIG. 1 shows a cross-sectional view of a circuit breaker in a closed position in accordance with an embodiment of the present invention;
FIG. 2 shows a cross-sectional view of the circuit breaker of FIG. 1 in an open position in accordance with an embodiment of the present invention; and
FIG. 3 shows an enlarged view of a section of the circuit breaker of FIG. 2 in accordance with an embodiment of the present invention.
DETAILED DESCRIPTION OF EMBODIMENTS

As used in the specification and claims, the singular forms “a”, “an” and “the” include plural references unless the context clearly dictates otherwise. For example, the term “an article” may include a plurality of articles unless the context clearly dictates otherwise. Those with ordinary skill in the art will appreciate that the elements in the Figures are illustrated for simplicity and clarity and are not necessarily drawn to scale. For example, the dimensions of some of the elements in the Figures may be exaggerated, relative to other elements, in order to improve the understanding of the present invention.
There may be additional components described in the foregoing application that are not depicted on one of the described drawings. In the event such a component is described, but not depicted in a drawing, the absence of such a drawing should not be considered as an omission of such design from the specification.
Before describing the present invention in detail, it should be observed that the present invention utilizes a combination of system components which constitutes a circuit breaker for maintaining a distance between arc contacts in a desired range during arc quenching. Accordingly, the components have been represented, showing only specific details that are pertinent for an understanding of the present invention so as not to obscure the disclosure with details that will be readily apparent to those with ordinary skill in the art having the benefit of the description herein.
As required, detailed embodiments of the present invention are disclosed herein; however, it is to be understood that the disclosed embodiments are merely exemplary of the invention, which can be embodied in various forms. Therefore, specific structural and functional details disclosed herein are not to be interpreted as limiting, but merely as a basis for the claims and as a representative basis for teaching one skilled in the art to variously employ the present invention in virtually any appropriately detailed structure. Further, the terms and phrases used herein are not intended to be limiting but rather to provide an understandable description of the invention.

FIG. 1 illustrates a cross-sectional view of a circuit breaker 100 in accordance with an embodiment of the present invention. In an example, the circuit breaker 100 is a gas circuit breaker. The circuit breaker 100 includes a first contact assembly 102 and a second contact assembly 104. The first contact assembly 102 includes a first main contact 106, a first arc contact 108 and a nozzle 110. The second contact assembly 104 includes a second main contact 112, a second arc contact 114 and a transfer contact 116. The circuit breaker 100 is enclosed in a tubular chamber 118.
In an embodiment, the first main contact 106 and the first arc contact 108 are arranged concentrically such that the first main contact 106 encloses the first arc contact 108. The second main contact 112 and the second arc contact 114 are also arranged concentrically such that the second main contact 112 encloses the second arc contact 114. The first main contact 106 and the first arc contact 108 are movable. The second main contact 112 and the second arc contact 114 are stationary.
The transfer contact 116 is positioned between the second main contact 112 and the second arc contact 114. The transfer contact 116 is electrically connected to the second arc contact 114. In an example, the transfer contact 116 is mechanically connected to the nozzle 110. In the closed position, the first main contact 106 is connected to the second main contact 112 and the first arc contact 108 is connected to the second arc contact 114.
FIG. 2 shows a cross-sectional view of the circuit breaker 100 in an open position in accordance with an embodiment of the present invention. FIG. 3 shows an enlarged view of a section of the circuit breaker 100 of FIG. 2 between lines A and A’ in accordance with an embodiment of the present invention. In the open position, the first main contact 106 is disconnected from the second main contact 112 and the first arc contact 108 is disconnected from the second arc contact 114.
In operation, the circuit breaker 100 is in the closed position. During a fault condition, a relay (not shown) detects the fault condition and provides a control signal to a driving mechanism (not shown). The control signal is indicative of opening the circuit breaker 100. In an embodiment of the present invention, the driving mechanism is connected to the first contact assembly 102. When the driving mechanism receives the control signal from the relay, the driving mechanism provides a pull force to the first contact assembly 102 for disconnecting the first contact assembly 102 from the second contact assembly 104. During the opening operation, the first main contact 106 moves along X-axis away from the second main contact 112. The nozzle 110 moves along the X axis away from the second main contact 112 as the nozzle 110 is connected to the first main contact 106. As the transfer contact 116 is mechanically connected to the nozzle 110, the transfer contact 116 also moves along the X axis away from the second main contact 112. Thus, a distance between the transfer contact 116 and the first arc contact 108 remains constant.

When the first main contact 106 is disconnected from the second main contact 112 and the first arc contact 108 is connected to the second arc contact 114, electric current flows in a circuit (not shown), which includes the circuit breaker 100, by way of the first arc contact 108 and the second arc contact 114. Electric current does not flow through the transfer contact 116. During the opening operation, when the first main contact 106 continues to move away from the second main contact 112 and the second arc contact 114 is disconnected from the first arc contact 108, an arc is produced in a space between the first and second arc contacts 108 and 114 (hereinafter referred to as “interacting space”). Thus, electric current flows in the circuit by way of the first and second arc contacts 108 and 114.

When the first main contact 106 still continues to move away from the second main contact 112, at one instant, a first end 120 of the transfer contact 116 is in line with a first end 122 of the first arc contact 108. At this instant, electric current flows in the circuit by way of the first arc contact 108, the transfer contact 116, and the second arc contact 114. The distance between the first end 120 of the transfer contact 116 and the first end 120 of the first arc contact 108 remains contact, thereby not increasing the interacting space. This confines the arc within a space that is fixed and hence, the pressure of compressed gas that flows inside the interacting space from a puffer chamber (not shown) of the circuit breaker 100, by way of the nozzle 110, is sufficient to move away the heat in the interaction space away from the interacting space, thereby quenching the arc effectively. In an embodiment of the present invention, the compressed gas is an inert gas and the distance between the first end 120 of the transfer contact 116 and the first end 122 of the first arc contact 108 required for effective quenching of the arc is between 100-200 millimetres (mm).

In another embodiment of the present invention, the circuit breaker 100 includes a linkage arrangement (now shown). The linkage arrangement comprises a mechanical actuator such as, but not limited to, a scissor arrangement, a rack and pinion arrangement, a level arrangement, and a sprocket arrangement. The linkage arrangement is hinged to a fixed tube 124 of the circuit breaker 100. One end of the linkage arrangement is connected to the second arc contact 114 and other end is connected to the nozzle 110. The linkage arrangement provides movement to the second arc contact 114 along the X axis in a direction opposite to the direction of the movement of the nozzle 110. In this embodiment, the transfer contact 116 is mechanically connected to an end of the linkage arrangement instead of the nozzle 110 such that the transfer contact 116 moves in the direction of the movement of the nozzle 110 when the first main contact 106 moves away from the second main contact 112. Thus, the time required for achieving a desired distance between the first and second arc contacts 108 and 114 is reduced, thereby providing fast switching operation and further improving dielectric properties of the circuit breaker 100. The distance between the first end 120 of the transfer contact 116 and the first end 122 of the first arc contact 108 is within the desired range during quenching of the arc.

The speed at which the first arc contact 108 disconnects from the second arc contact 114 can be changed by changing the point at which the linkage arrangement is hinged to the fixed tube 124. The speed at which the second arc contact 114 moves relative to the second main contact 112 can be changed by changing the point at which the second arc contact 114 is connected to the linkage arrangement. The ratio of speed of movement of the transfer contact 116 in the first direction to the movement of the nozzle 110 in the first direction depends upon the points of the linkage arrangement at which the transfer contact 116 and the nozzle 110 are connected to the linkage arrangement.

In an embodiment, the second main contact 112 is connected to the linkage arrangement and hence, is movable. The second main contact 112 moves in a direction opposite to the direction of the movement of the nozzle 110 when the first main contact 106 moves away from the second main contact 112.

The present invention has been described herein with reference to a particular embodiment for a particular application. Although selected embodiments have been illustrated and described in detail, it may be understood that various substitutions and alterations are possible. Those having ordinary skill in the art and access to the present teachings may recognize additional various substitutions and alterations are also possible without departing from the spirit and scope of the present invention.
,CLAIMS:1. A circuit breaker, comprising:

a first contact assembly including a first main contact, a first arc contact, and a nozzle, wherein the first main contact and the first arc contact are movable contacts, and wherein a first end of the nozzle is connected to the first main contact, and wherein each of the first main contact, the first arc contact, and the nozzle is movable between first and second positions; and

a second contact assembly including a second main contact, a second arc contact and a transfer contact, wherein the transfer contact is connected to the second arc contact, and wherein in the first position, the first arc contact is connected to the second arc contact, and wherein in the second position, the first arc contact is disconnected from the second arc contact by way of movement of the first main contact, the first arc contact, and the nozzle in a first direction, and wherein the transfer contact moves in the first direction when the first main contact, the first arc contact, and the nozzle move in the first direction.

2. The circuit breaker of claim 1, further comprising a linkage arrangement having a first end connected to a second end of the nozzle and a second end connected to the second arc contact, wherein the second arc contact moves in a second direction when the first main contact, the first arc contact, and the nozzle move in the first direction.

3. The circuit breaker of claim 2, wherein the linkage arrangement is hinged to a fixed tube of the circuit breaker by way of an anchor pin.

4. The circuit breaker of claim 2, wherein the linkage arrangement comprise a mechanical actuator.

5. The circuit breaker of claim 2, wherein the transfer contact is connected to the linkage arrangement.

6. The circuit breaker of claim 1, wherein the transfer contact is connected to the nozzle, and wherein a distance between the first arc contact and the transfer contact is constant.

7. The circuit breaker of claim 1, wherein the first and second positions comprise closed and open positions, respectively.

8. The circuit breaker of claim 1, wherein the first main contact encloses the first arc contact and the second main contact encloses the second arc contact, and wherein the transfer contact is positioned between the second main contact and the second arc contact.

9. The circuit breaker of claim 1, wherein the first main contact, the first arc contact, and the nozzle move in the first direction by way of an external driving mechanism.

10. The circuit breaker of claim 1, wherein an electric current flows from the first arc contact to the second arc contact by way of the transfer contact when the transfer contact is in a third position.