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 a 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 (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 a 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 moving contact assembly disconnects from the stationary contact assembly. 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). However, having a scissor arrangement entails movement of both the contact assemblies, and as the contact assemblies are bulky, such circuit breakers are difficult to manufacture. The complicated design further reduces the reliability of the circuit breaker. Further, such designs consume considerable amount of energy to achieve the movement of the contact assemblies. As the arc contacts do not move relative to corresponding main contacts, electrical stresses on the arc contacts are not optimized. This limits the dielectric withstand capability of the circuit breaker during fault condition, thereby limiting the circuit breaker to be used for breaking circuits operating at a certain voltage level.

Therefore, it would be advantageous to have a circuit breaker that achieves a fast switching operation by providing movement to an arc contact of a contact assembly and a main contact of the contact assembly, achieves relative motion between the arc contact and the main contact, increases reliability and dielectric withstand capability of the circuit breaker, and that 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 and a scissor arrangement. The first contact assembly includes a movable first main contact and a movable first arc contact. The second contact assembly includes a movable second main contact and a movable second arc contact. A first end of the scissor arrangement is connected to a second end of a nozzle of the first contact assembly, and a second end of the scissor arrangement is connected to the second arc contact. The scissor arrangement is hinged to a fixed tube of the circuit breaker and the second main contact. The scissor arrangement provides movement to the second main contact and the second arc contact such that there is relative motion of the second arc contact relative to the second main contact, thereby increasing dielectric withstand capability of the circuit breaker and achieving fast switching operation.

Another 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 and a movable first arc contact. The second contact assembly includes a movable second main contact and a movable second arc contact. The circuit breaker further includes a scissor arrangement. A first end of the scissor arrangement is connected to a second end of a nozzle of the first contact assembly and a second end of the scissor arrangement is connected to the second arc contact. The scissor arrangement is hinged to a fixed tube of the circuit breaker and the second main contact. During opening operation, the first arc contact moves away from the second arc contact. The scissor arrangement provides movement to the second arc contact and the second main contact such that there is relative motion between the second arc contact and the second main contact. The relative velocity of separation of the first arc contact from the second arc contact is adjustable by changing the position at which the scissor arrangement is hinged to the fixed tube. The relative velocity of the second arc contact with respect to the second main contact is adjustable by changing the position at which the scissor arrangement is hinged to the second main contact.

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:

FIGS. 1A and 1B show a cross-sectional view and a top view of a circuit breaker, respectively, in a closed position in accordance with an embodiment of the present invention;

FIGS. 1C and 1D show a cross-sectional view and a top view of the circuit breaker, respectively in an open position in accordance with another embodiment of the present invention; and

FIG. 1E shows a scissor arrangement 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 in 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 achieving a fast switching operation and high dielectric withstand capability. 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.

FIGS. 1A and 1B show a cross-sectional view and a top view of a circuit breaker 100, respectively, in a closed position in accordance with an embodiment of the present invention. FIGS. 1C and 1D show a cross-sectional view of the circuit breaker 100, respectively in an open position in accordance with an embodiment of the present invention. In an embodiment, the circuit breaker 100 is a gas circuit breaker. The circuit breaker 100 includes first and second contact assemblies 102 and 104. The first contact assembly 102 includes a first main contact 106 and a first arc contact 108. The second contact assembly 104 includes a second main contact 110 and a second arc contact 112. 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 110 and the second arc contact 112 are also arranged concentrically such that the second main contact 110 encloses the second arc contact 112. The first and second main contacts 106 and 110 are movable. The first and second arc contacts 108 and 112 are also movable.

The first contact assembly 102 includes a nozzle 114 that is connected to the first main contact 106. The nozzle 114 has first and second ends (not shown). In an embodiment of the present invention, the second end of the nozzle 114 has first and second plates 116 and 118. The second end of the nozzle 114 is further connected to a scissor arrangement 120 by way of the first and second plates 116 and 118 and a shaft (not shown). FIG. 1E shows the scissor arrangement 120 in accordance with an embodiment of the present invention. The scissor arrangement 120 is hinged to a fixed tube 121 using first and second anchor pins 122a and 122b. The scissor arrangement 120 is hinged to the second main contact 110 using a first pin 123. The scissor arrangement 120 has first and second ends 124a and 124b. The second end of the nozzle 114 is connected to the scissor arrangement 120 at the first end 124a by way of the first and second plates 116 and 118 and the shaft (not shown). The second arc contact 112 is connected to the scissor arrangement 120 at the second end 124b by way of a bar 126. The scissor arrangement 120 is hinged to the bar 126 by using a second pin 128. The bar 126 has a slot which allows the free movement of the first pin 123 along with the scissor arrangement 120. The scissor arrangement 120 provides movement to the second main contact 110 and the second arc contact 112 along an X-axis. The first pin 123 hinges at a contact point 130 of the scissor arrangement 120 to the second main contact 110. The contact point 130 is in between the first end 124a and the second end 124b of the scissor arrangement 120.Thus, for a given movement of the first main contact 106, the amount of relative movement achieved between the first main contact 106 and the second arc contact 112 is greater than the amount of relative movement achieved between the first main contact 106 and the second main contact 110. In an embodiment, the circuit breaker 100 is enclosed in a tubular chamber 131. The first anchor pin 122a, the first and second ends 124a and 124b of the scissor arrangement 120, first and second pins 123 and 128, and the contact point 130 are visible in the FIG. 1E.

It will be understood by those of skill in the art that the length and/or number of scissor linkages of the scissor arrangement 120 may be varied based on the design requirements of the circuit breaker 100 for achieving a desired relative velocity of the second arc contact 112 with respect to the first arc contact 108 and a desired relative velocity of the second arc contact 112 with respect to the second main contact 110. It will be further understood by those of skill in the art that the circuit breaker 100 may include multiple scissor arrangements for achieving the desired results.

Referring now to FIGS. 1C and 1D, the circuit breaker 100 is shown in the open position. The first main contact 106 is physically disconnected from the second main contact 110 and the first arc contact 108 is physically disconnected from the second arc contact 112. The scissor arrangement 120 is in a stretched position. A distance between the first end 124a of the scissor arrangement 120 and the second end 124b of the scissor arrangement 120 in the closed position is less than a distance between the first end 124a of the scissor arrangement 120 and the second end 124b of the scissor arrangement 120 in the open position. In the open position, relative positions of the second main contact 110 and the second arc contact 112 with respect to a position of the fixed tube 121 are changed as compared to relative positions of the second main contact 110 and the second arc contact 112 with respect to a position of the fixed tube 121 in the closed position.

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 by way of a drive rod 132. 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 the X-axis away from the second main contact 110. As the second end of the nozzle 114 is connected to the scissor arrangement 120 at the first end 124a, the first end 124a of the scissor arrangement 120 moves towards the nozzle 114. The contact point 130 is hinged to the second main contact 110 by way of the first pin 123. Thus, the movements of the first end 124a of the scissor arrangement 120 along the X-axis towards the nozzle 114 causes the movement of the second end 124b of the scissor arrangement 120 along the X-axis away from the nozzle 114. Hence, the second main contact 110 moves along the X-axis away from the first main contact 106 and the second arc contact 112 moves along the X-axis away from the first arc contact 108. When the first main contact 106 is physical disconnected from the second main contact 110, a current flows through the first and second arc contacts 108 and 112. When the first arc contact 108 is physically disconnected from the second arc contact 112, an arc is produced in a space between the first and second arc contacts 108 and 112 (referred to as an “interacting space”). Compressed gas flows inside the interacting space from a puffer chamber (not shown) of the circuit breaker 100 by way of the nozzle 114 for quenching the arc. In an embodiment, the compressed gas may be an inert gas.

During the opening operation of the circuit breaker 100, the first main contact 106 moves along the X-axis away from the second main contact 110 and the first arc contact 108 moves along the X-axis away from the second arc contact 112. The scissor arrangement 120 provides movement to the second main contact 110 and the second arc contact 112, along the X-axis. Thus, the time required for achieving a desired distance between the first and second arc contacts 108 and 112 is reduced; thereby achieving fast switching operation and increasing a dielectric withstand capability of the circuit breaker 100. As the scissor arrangement 120 provides movement to the second main contact 110, a relative velocity of separation of the first main contact 106 from the second main contact 110 increases. This further increases the dielectric withstand capability of the circuit breaker 100. Thus, for given size, the circuit breaker 100 can withstand large voltages as compared to the conventional circuit breakers. The contact point 130 that is hinged to the fixed tube 121 can be changed for changing the relative velocity at which the first arc contact 108 disconnects from the second arc contact 112. Further, the contact point 130 that is hinged to the second main contact 110 can be changed for changing the relative velocity of the second arc contact 112 with respect to the second main contact 110. Thus, it is possible to change the velocity of separation of the first arc contact 108 from the second arc contact 112 and the relative velocity of the second arc contact 112 with respect to the second main contact 110 by changing positions of the first and second anchor pins 122a and 122b. Thus, it is not necessary to change the design of the circuit breaker 100. Due to the motion of the second arc contact 112 relative to the second main contact 110, an electrical stress on the second arc contact 112 is optimized, thereby providing a reliable operation and increasing operational life of the second arc 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 the first main contact, the first arc contact, and the nozzle each is movable between first and second positions;

a second contact assembly including a second main contact and a second arc contact, wherein the second main contact and the second arc contact are movable contacts; and

a scissor arrangement having a first end connected to a second end of the nozzle, a second end connected to the second arc contact, and a contact point connected to the second main contact, 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 movement of the second arc contact and the second main contact by way of the scissor arrangement in a second direction that is opposite to the first direction.

2. The circuit breaker of claim 1, wherein the second main contact is hinged to the scissor arrangement of the circuit breaker at the contact point by way of a pin.

3. The circuit breaker of claim 1, wherein the scissor arrangement is hinged to a fixed tube of the circuit breaker by way of an anchor pin.

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

5. 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.

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

7. The circuit breaker of claim 1, wherein the second end of the nozzle is connected to the first end of the scissor arrangement by way of first and second plates and a shaft, and the second arc contact is connected to the second end of the scissor arrangement by way of a bar, and wherein the first and second ends of the scissor arrangement are proximal and distal ends, respectively.

8. The circuit breaker of claim 1, wherein a distance between the first end of the scissor arrangement and the second end of the scissor arrangement in the first position is less than a distance between the first end of the scissor arrangement and the second end of the scissor arrangement in the second position, respectively.

9. The circuit breaker of claim 1, further comprising a puffer chamber for releasing an inert gas inside the nozzle in the second position.