Claims:1. An electrical switching apparatus comprising:
at least one load conductor assembly;
at least line conductor assembly:
at least one pair of separable contacts electrically connected between said load conductor assembly and said line conductor assembly, wherein said separable contacts comprises a pair of separable arcing contacts;
at least one operating mechanism adapted for movement between an open and/or close position of said separable pair of contacts to enable opening and/or closing of said separable pair of contact;
at least one arc chute assembly provided adjacent to said separable contact; and
at least one arc runner comprising at least one electrically conductive member having a base surface in contact with said line conductor assembly, and a surface in said arc runner leading towards said arc chute, wherein said arc runner provide a path for an arc struck between said separable pair of arcing contacts as said separable pair of arcing contacts open with movement of said moving conductor assembly from said closed position to said open position.
2. The electrical switching apparatus as claimed in claim 1, wherein said pair of separable contacts comprises a pair of main contacts having a movable main contact and a stationary main contact, and said separable pair of arcing contacts having a movable arcing contact and a stationary arcing contact.

3. The electrical switching apparatus as claimed in claim 2, further comprising at least one contact finger means, pivotally mounted on said contact carrier and having the movable arcing contact positioned adjacent to a free end of said contact finger means and the movable main contact spaced from the free end of said contact finger means.

4. The electrical switching apparatus as claimed in claim 3, further comprising at least one contact spring means pivotally biasing said contact finger means to move from closure of said pair of main contacts with said contact carrier in the closed position, to closure of both said pair of main contacts and said separable pair of arcing contacts, to closure of only said separable pair of arcing contacts while said pair of main contacts remains open, to opening of said separable pair of arcing contacts as said contact carrier moves to said open position.

5. The electrical switching apparatus as claimed in claim 1, wherein said separable pair of contacts is encompassed in a pole cage by means of fulcrum pin, wherein said fulcrum pin adapted to join said separable pair of contact with said load conductor.

6. An electrical switching apparatus comprising:
a housing;
a load conductor;
a line conductor mounted in the housing;
a pair of main contacts comprising a movable main contact and a stationary main contact, and a separable pair of arcing contacts, comprising a movable arcing contact and a stationary arcing contact;
a moving conductor assembly electrically connecting said movable main contact and the movable arcing contact to said load conductor, wherein said moving conductor assembly comprising a contact carrier for movement between an open position and a closed position to open and close said main contacts and/or said arcing contacts;
at least one contact finger means, pivotally mounted on said contact carrier and having said movable arcing contact adjacent to a free end and the movable main contact spaced from said free end;
a contact spring means pivotally biasing said contact finger to move from closure of said pair of main contacts with said contact carrier in the closed position, to closure of said pair of main contacts and said separable pair of arcing contacts, to closure of only said separable pair of arcing contacts while said pair of main contacts remains open, to opening of said separable pair of arcing contacts as said contact carrier moves to said open position;
at least arc chute assembly positioned adjacent said moving conductor assembly; and
at least arc runner electrically connected to the stationary arcing contact and extending toward the arc chute to provide a path for an arc struck between the separable pair of arcing contacts as the separable pair of arcing contacts open with movement of the moving conductor assembly from the closed position.
, Description:TECHNICAL FIELD

[001] The present subject matter described herein, in general, relates to electrical switching devices such as circuit breaker, and more particularly, to an operating mechanism incorporated in said circuit breaker for increasing making capacity on faults.

BACKGROUND

[002] Air circuit breaker is a switching device designed to make, carry and break the circuit. The main contact system of the air circuit breaker consists of a moving terminal and a fixed terminal. Mechanism is the part of the circuit breaker used for closing and opening and contact system of the circuit breaker. Energy stored in the mechanism by means of springs is utilized to join the moving terminal with the fixed terminal and thereby close the circuit. Under normal operating conditions the circuit will remain closed. Circuit breaker also has a tripping mechanism to open the circuit. Opening of the circuit can be done intentionally by the operator or can happen automatically during an abnormal electrical condition like overload, under voltage or short circuit.

[003] The process of joining contacts using stored energy in the mechanism is termed as making. A circuit breaker should be capable of making the contacts under normal conditions and separating the contacts under fault condition. During normal condition electrical system operates the way it is designed to and current flowing through the contacts will be rated operating current or less than that. Energy stored in the mechanism is capable enough to make the contacts under normal conditions. If energy provided by mechanism is much more required than to make the contacts under normal conditions then there is a possibility for contacts to chatter and this adversely affect the quality of the contact and should be avoided, so possibility of chatter under normal making is a factor that limits the quantum of stored energy.

[004] During a fault condition higher current will be flowing through the contact system of the circuit and while making the contacts, higher repulsion forces will be generated at the contact and the energy provided by mechanism must be higher than the repulsion force generated by the fault current.

[005] While making the contacts ON, mechanism delivers energy through a series of linkages, these linkages are designed in a specific way as to move from an unlocked condition to locked condition. The point at which the linkages transition from unlocked to locked condition is termed as toggle point. Significance of the locked condition is that when contact are in closed condition and fault occurs then the repulsive forces generated by fault current will not be able to open the contacts through mechanism, only an explicit open command given by trip unit of the circuit breaker or by end user can make the contacts open. While making the contacts during the fault current starts flowing through the system when the contacts make the first touch and the energy delivered by the mechanism should always be higher than the repulsive energy generated fault current till toggle point or else the contacts will open up and undesired consequences such as arcing, material erosion will happen.

[006] As opposed to normal load current, fault current is not sinusoidal and has an asymmetrical component that exists in the initial phase of the fault, fault current will rise exponentially and it will try to push open the contacts. Time difference between first contact touch and toggle point determines the time for which mechanism has to directly oppose the electrodynamic forces at the contact. Making capacity of a circuit breaker depends on the ability of the mechanism to reach the toggle point successfully by overcoming the repulsion force generated at the contact.

[007] Reference is made to prior art document US 8859916 B2, wherein an electrical cut-off device with high making capacity is provided with a control module associated with at least one cut-off module corresponding to a phase of an electrical network, this cut-off module including at least one moving contact associated with at least one pair of fixed contacts, said moving contact being coupled with an actuator mechanism controlled by said control module so as to be moved between at least one switched-off position in which the moving contact is distant from the pair of fixed contacts and the electrical circuit is open, and a switched-on position in which the moving contact is resting on the pair of fixed contacts and the electrical circuit is closed.

[008] Reference is made to prior art document, US20100026427 A1, which discloses electromagnetic switches and contact systems and, in particular, electromagnetic switches which can operate under high current conditions.

[009] Thus, in view of the electrical switching mechanism, there is a necessity for an improved mechanism that enhances the making capacity of the circuit breaker by adjusting the time difference between first contact touch and toggle point so as to minimize the repulsion forces generated at the contact.

SUMMARY OF THE INVENTION

[0010] 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.

[0011] An object of the present invention is to provide a mechanism for increase making capacity of the electrical switching device.

[0012] Another object of the present invention is to reduce energy storage requirement of operating mechanism thus reducing mechanical stresses and improving mechanical life.

[0013] Yet another object of the present invention is to reduce energy storage requirement so as to optimize use of energy storage and eliminate any chance of contact bounce during contact making under normal condition.

[0014] Still another object of the present invention is to increase the making capacity by minimizing toggle time between contact touch and toggle point.

[0015] According to one aspect, the present invention provides an electrical switching apparatus comprising: at least one load conductor assembly; at least line conductor assembly; at least one pair of separable contacts electrically connected between said load conductor assembly and said line conductor assembly, wherein said separable contacts comprises a pair of separable arcing contacts; at least one operating mechanism adapted for movement between an open and/or close position of said separable pair of contacts to enable opening and/or closing of said separable pair of contact; at least one arc chute assembly provided adjacent to said separable contact; and at least one arc runner comprising at least one electrically conductive member having a base surface in contact with said line conductor assembly, and a surface in said arc runner leading towards said arc chute, wherein said arc runner provide a path for an arc struck between said separable pair of arcing contacts as said separable pair of arcing contacts open with movement of said moving conductor assembly from said closed position to said open position.

[0016] In second aspect, the present invention provides an electrical switching apparatus comprising:
a housing;
a load conductor;
a line conductor mounted in the housing;
a pair of main contacts comprising a movable main contact and a stationary main contact, and a separable pair of arcing contacts, comprising a movable arcing contact and a stationary arcing contact;
a moving conductor assembly electrically connecting said movable main contact and the movable arcing contact to said load conductor, wherein said moving conductor assembly comprising a contact carrier for movement between an open position and a closed position to open and close said main contacts and/or said arcing contacts;
at least one contact finger means, pivotally mounted on said contact carrier and having said movable arcing contact adjacent to a free end and the movable main contact spaced from said free end;
a contact spring means pivotally biasing said contact finger to move from closure of said pair of main contacts with said contact carrier in the closed position, to closure of said pair of main contacts and said separable pair of arcing contacts, to closure of only said separable pair of arcing contacts while said pair of main contacts remains open, to opening of said separable pair of arcing contacts as said contact carrier moves to said open position;
at least arc chute assembly positioned adjacent said moving conductor assembly; and
at least arc runner electrically connected to the stationary arcing contact and extending toward the arc chute to provide a path for an arc struck between the separable pair of arcing contacts as the separable pair of arcing contacts open with movement of the moving conductor assembly from the closed position

[0017] 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 DRAWINGS

[0018] The above and other aspects, features, and advantages of certain exemplary embodiments of the present invention will be more apparent from the following description taken in conjunction with the accompanying drawings in which:

[0019] Figure 1 illustrates Cross sectional view of switching device consisting of current housings which encompass the current carrying path, according to one embodiment of the present invention.

[0020] Figure 2 illustrates Current carrying path consisting of fixed terminal and moving terminal assemblies in open condition, according to one embodiment of the present invention.

[0021] Figure 3 illustrates Current carrying path consisting of fixed terminal and moving terminal assemblies in closed condition, according to one embodiment of the present invention.

[0022] 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 PRESENT INVENTION

[0023] The following description with reference to the accompanying drawings is provided to assist in a comprehensive understanding of exemplary embodiments of the invention. It includes various specific details to assist in that understanding but these are to be regarded as merely exemplary.

[0024] Accordingly, those of ordinary skill in the art will recognize that various changes and modifications of the embodiments described herein can be made without departing from the scope of the invention. In addition, descriptions of well-known functions and constructions are omitted for clarity and conciseness.

[0025] The terms and words used in the following description and claims are not limited to the bibliographical meanings, but, are merely used by the inventor to enable a clear and consistent understanding of the invention. Accordingly, it should be apparent to those skilled in the art that the following description of exemplary embodiments of the present invention are provided for illustration purpose only and not for the purpose of limiting the invention as defined by the appended claims and their equivalents.

[0026] It is to be understood that the singular forms “a,” “an,” and “the” include plural referents unless the context clearly dictates otherwise.

[0027] By the term “substantially” it is meant that the recited characteristic, parameter, or value need not be achieved exactly, but that deviations or variations, including for example, tolerances, measurement error, measurement accuracy limitations and other factors known to those of skill in the art, may occur in amounts that do not preclude the effect the characteristic was intended to provide.

[0028] Features that are described and/or illustrated with respect to one embodiment may be used in the same way or in a similar way in one or more other embodiments and/or in combination with or instead of the features of the other embodiments.

[0029] It should be emphasized that the term “comprises/comprising” when used in this specification is taken to specify the presence of stated features, integers, steps or components but does not preclude the presence or addition of one or more other features, integers, steps, components or groups thereof.

[0030] It is also to be understood that the term “module” is used in the specification to indicate an apparatus, unit, component and the like. The term “means” when used in the specification is taken to specify the mode by which desired result is achieved.

[0031] The present invention can be implemented with an electrical switching system that may include but not limited to, circuit breakers or thermo-magnetic breaker, molded case circuit breaker (MCCB) residual circuit breaker (RCB), earth leakage circuit breaker (ELCB) and the like.

[0032] In switching device for increasing making capacity 2 factors need to be considered: Arcing to toggle time and Capacity of spring in operating mechanism. In the invention arcing to toggle time will be reduced and spring in mechanism will remain same. So for similar spring value a switching device with present invention will have higher making capacity. Existing mechanism for making capacities in the switching device would not require operating spring capacities as used in the present invention. In one embodiment of the present invention, lower value of spring can be used to achieve making current values.

[0033] In one implementation, reference is made to figures 1-3, wherein the electrical switching apparatus comprises of load conductor (5), line conductor (3) assembly comprises of the fixed terminal & arcing contact, which is connected to arc runner (2) using connecting screws. The associated separable contacts (8) is encompassed in the pole cage (6) made of plastic material with the help of fulcrum pin (7) which in turn is joined to the load conductor (5). The electrical switching device essentially would consist of: Deion plates (1), arc runner (2), line conductor (3), breaker housing (4), load conductor (5), pole cage (6), fulcrum pin (7) ,separable contact (8) & arc chute (9).

[0034] In one implementation, the electrical switching apparatus comprises: a load terminal and a line terminal; at least one pair of separable contacts(8) electrically connected between the load conductor(5) and the line conductor(3); an operating mechanism adapted for movement between an open position and a closed position to open and close the separable contacts; an arc chute(9) positioned adjacent the separable contacts(8) and an arc runner(2) electrically connected to one of the separable contacts and extending toward the arc chute to provide a path for an arc struck between the separable contacts(8) as the separable contacts open with movement of the operating assembly from the closed position. The stationary arcing contact and the arc runner comprise of an electrically conductive member (2) having a base surface in contact with the line terminal, a stationary contact surface forming the stationary arcing contact, and a runner(2) surface leading toward the arc chute.

[0035] In one embodiment, the conductive member (2) as shown in the figure1 adapted to guide the arc which gets initiated during contact separation towards arc chutes.

[0036] In one implementation, the electrical switching apparatus comprises: a housing(4); a load conductor(5) and a line conductor(3) mounted in the housing(4); a pair of main contacts including a movable main contact and a stationary main contact, and a separable pair of arcing contacts, including a movable arcing contact and a stationary arcing contact, the stationary main contact and the stationary arcing contact being in electrical contact with the line conductor(3); a moving conductor assembly electrically connecting the movable main contact and the movable arcing contact to the load conductor(5) and comprising a contact carrier mounted for movement between an open position and a closed position to open and close the separable pairs of contacts(8), at least one contact finger pivotally mounted on the contact carrier and having the movable arcing contact adjacent a free end and the movable main contact spaced from the free end, and contact spring means pivotally biasing the at least one contact finger to move from closure of only the pair of main contacts with the carrier in the closed position, to closure of both the pair of main contacts and the separable pair of arcing contacts, to closure of only the separable pair of arcing contacts while the pair of main contacts are opened, to opening of the separable pair of arcing contacts as the carrier moves to the open position; an arc chute(9) positioned adjacent the moving conductor assembly; and an arc runner(2) electrically connected to the stationary arcing contact and extending toward the arc chute(9) to provide a path for an arc struck between the separable pair of arcing contacts as the separable pair of arcing contacts open with movement of the moving conductor assembly from the closed position.

[0037] In one embodiment, that moving arcing contact has to be at one of the free end of the moving finger and it has to be adjacent to the end. By the term “Free end” it means the end part of the contact finger.

[0038] In one implementation, under normal operating condition the separable contacts (8) will be in contact with the line conductor (3) creating a joint through which electric current flows. When switching apparatus need to be tripped intentionally or when the switching device trips due to an abnormal electrical condition moving terminal moves away from line conductor(3). The joint which was created between separable arcing contacts (8) and the line conductor (3) will break. This will lead to ionization of medium which exist between line conductor (3) and separable contacts (8) resulting in an arc. The arc runner(2) electrically connected to the stationary arcing contact and extending toward the arc chute(9) to provide a path for an arc struck between the separable pair of arcing contacts as the separable pair of arcing contacts open with movement of the moving conductor assembly from the closed position.

[0039] Some of the advantages of the present invention, are as follows:
• Higher making capacity on faults;
• Energy storage requirement of operating mechanism in existing ratings are reduced;
• Increased operating mechanism life;
• Elimination of chances of contact bounce.

[0040] Although an electrical switching device with high making capacity have been described in language specific to structural features and/or methods, it is to be understood that the embodiments disclosed in the above section are not necessarily limited to the specific features or methods or devices described. Rather, the specific features are disclosed as examples of implementations of the electrical switching device with high making capacity.