Claims:1. A moving terminal assembly for electrical switching apparatus, wherein said moving terminal assembly comprising: at least two conductive terminals with each having a C-shape at its one end, wherein said conductive terminals fixed to each other in a mirror image arrangement to form circular shape at termination end and a flat base at other end.

2. The moving terminal assembly as claimed in claim 1, wherein said conductive terminals are fixed to each other by plurality of fixing means to form said circular shape that projects outwards of a housing chamber of said switchgear unit.

3. The moving terminal assembly as claimed in claim 2, wherein said fixing means selected from current carrying rivets.

4. The moving terminal assembly as claimed in claim 1, wherein said flat base adapted to receive moving flexible current carrying wire strands which are further connected to current carrying metallic blades.

5. The moving terminal assembly as claimed in claim 1, wherein said circular shape of moving terminal assembly adapted to mount at least one current transformer for sensing current through a circuit.

6. An electrical switching apparatus comprising: at least one fixed terminal assembly and at least one moving terminal assembly as claimed in claims 1-5.
, Description:TECHNICAL FIELD OF THE INVENTION

[0001] The present subject matter described herein, in general, relates to electrical switching apparatus, and more particularly, to a moving terminal assembly of an electrical switching apparatus and a profile of the moving terminal assembly.

BACKGROUND OF THE INVENTION

[0002] Circuit breaker is an electrical switching device designed to make, carry and break the circuit. The main contact system of the circuit breaker consist of a moving terminal and a fixed terminal. Mechanism is the part of circuit breaker used for driving power contact system of the circuit breaker to close and open. Energy stored in the mechanism by means of spring is utilized to join the moving terminal with the fixed terminal and thereby close the circuit.

[0003] Under normal operating conditions i.e. in electrical current carrying state; circuit remains closed. Aforementioned mechanism is also associated with tripping linkages 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.

[0004] A protection Release is a device used in air circuit breakers to detect the abnormal conditions in the electrical circuit. A current transformer is placed on electrical circuits which senses the current through the circuit and gives appropriate signal to the protection device .The protection device thus disconnects the load from the system during fault conditions.

[0005] As mentioned, moving terminal and fixed terminal carry maximum up to rated operational current for which it can be designed during normal operating conditions. During operational life of the switching device, heat will be generated due to inherent losses. Necessary cross-section of the terminal limits the temperature rise in the circuit breaker.

[0006] Reference is made to US7655877 B2 which relates to an air circuit breaker, and particularly, to an air circuit breaker having mechanical trip indicating mechanism capable of mechanically reliably indicating the user of a trip operation of a circuit breaker when an overcurrent trip relay senses a fault current on a circuit. However, the prior art document is about horizontal terminals and cover entire circuit path of circuit breaker.

[0007] Reference is made to EP1471553 B1 which discloses Flat bar type terminal construction where the Intra phase Pitch is equal to distance between top & bottom terminal. It discloses an air circuit breaker capable of suppressing the temperature rise of a make and break contactor and energized bodies around the contact by a heat generation due to the energization of the contact, comprising, in a cabinet, a fixed conductor having a fixed contact fixed thereto, a movable element having a movable contact moving close to and apart from the fixed contact fixed thereto, and an arc-extinguishing device inductively extinguishing an arc generated between both contacts, a discharge window for discharging arc gas to the outside of the cabinet, vent holes opened at a position opposed to the discharge window and forming an air passage inside the cabinet, a valve member closing the vent holes when a pressure inside the cabinet rises, an arc block having a fixed side arc contactor extended from the fixed contact to allow an electricity and a heat to be transferred thereto, and the movable side arc contactor extended from the movable contact to allow an electricity and a heat to be transferred thereto.

[0008] Existing design of moving terminal assembly consist of current carrying metallic terminal generally made up from complex or specialized manufacturing process like hot forging or extrusion. Manufacturing cost of such terminals are generally high due to specialized manufacturing process like hot forging or extrusion

[0009] Further, in the existing design, the current transformers are inserted surrounding the conductor i.e. moving terminal assembly. Current transformer is mounted on mounting (bottom) surface of moving terminal on which it is fixed with switchgear housing. To position the current transformer on moving terminal; length of current path increases minimum by a value slightly more than thickness of current transformer. It calls for increase in current path length & provides additional resistance in the circuit.

[0010] Also, in existing practice, current transformer (CT) has rectangular core mounted on bottom terminal. The profile of the conducting terminal and the rectangular core has less flux linkage due to more air gap between the terminal and coil compared to the circular profile.

[0011] Thus, the following are the drawbacks of the existing design of moving terminal assembly:
• Requirement of specialized manufacturing processes like hot forging or extrusion for existing terminals.
• Higher material consumption in existing practices.
• Higher current path length to accommodate CT. This offers more resistance in circuit path.
• Existing terminal facilitates use of CT with Rectangular core.

[0012] Thus, in view of the drawbacks of the existing moving terminals of air circuit breakers, there is a need to provide an improved design of conductor profile in circuit breaker for suppressing rise in temperature of a current-carrying conductor at an opening and closing contact as well as in the vicinity of the contact in an air circuit breaker at the time of applying an electric current to the conductor under normal conditions.

SUMMARY OF THE INVENTION

[0013] 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.

[0014] An object of the present invention is to provide a moving terminal structure in circuit breaker that can provide at least rise in temperature of a current-carrying conductor when rated current is conducted through it under normal conditions.

[0015] Another object of the present invention is to provide a moving terminal assembly of two identical conductor components which are fixed to each other in a mirror image fashion and facilitates circular termination surface.

[0016] Yet another object of the present invention is to provide a design of the moving terminal assembly that reduces depth of switch gear for rated current as compared to other switchgears as current transformer CT is placed on circular termination surface of terminal assembly.

[0017] Still another object of the present invention to provide a moving terminal assembly and the joining and fixing methods along with simplified manufacturing process that facilitates optimum material usage with reduced cost.

[0018] Accordingly, in one aspect, the present invention provides a moving terminal assembly for electrical switching apparatus, wherein said moving terminal assembly comprising: at least two conductive terminals with each having a C-shape at its one end, wherein said conductive terminals fixed to each other in a mirror image arrangement to form circular shape at termination end and a flat base at other end.

[0019] In another aspect, the present invention provides an electrical switching apparatus comprising: at least one fixed terminal assembly and at least one moving terminal assembly as mentioned above.

[0020] 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

[0021] 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:

[0022] Figure 1 illustrates the moving terminal assembly with two identical conductive terminals, in accordance with an embodiment of the present invention.

[0023] Figure 2 illustrates the plularity of fixing means that enable the two conductive terminals to remain attached together permanently, in accordance with an embodiment of the present invention.

[0024] Figure 3 illustrates the assembled condition of two identical metallic components, in accordance with an embodiment the present invention.

[0025] Figure 4 illustrates the bottom terminal assembly which further constitutes pole assembly, in accordance with an embodiment the present invention.

[0026] Figure 5 shows the sectional view of the pole assembly made up of bottom terminal assembly mounted inside the housing of the switchgear, in accordance with an embodiment of the present invention.

[0027] Figure 6 shows the sectional isometric view of the pole assembly, with an embodiment of the present invention.

[0028] 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

[0029] 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.

[0030] 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.

[0031] 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.

[0032] It is to be understood that the singular forms “a,” “an,” and “the” include plural referents unless the context clearly dictates otherwise.

[0033] 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.

[0034] 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.

[0035] 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.

[0036] The present invention refers to a design of conductor profile in circuit breaker. It relates to a structure for suppressing rise in temperature of a current-carrying conductor at an opening and closing contact as well as in the vicinity of the contact in an air circuit breaker at the time of applying an electric current to the conductor under normal conditions.

[0037] Disclosed invention describes moving terminal assembly which facilitates use of optimum mass of current carrying element manufactured with simplified process. Profile of the assembly improves current metering accuracy and improves current transformer (CT) accuracy. Rated current is carried in smaller depth of switchgear apparatus. Termination is improved on account of increase in top-bottom clearance within a phase and thus provides ease of bus-bar termination from terminating end of switchgear

[0038] In one implementation, an electrical switching apparatus comprises: a fixed terminal (19) and a moving terminal (14) for each electrical phase. Generally one terminal remains fixed and another moving. Moving terminal when connected to fixed terminal completes the circuit and current conduction takes place. Disclosed invention talks about design arrangement moving terminal assembly (21).

[0039] In one implementation, the present invention consists of a moving terminal (14), plurality of flexible metallic wire strands (braids) (18), current carrying blades (16) and contact tips or buttons (17) attached to blades (16).

[0040] In one implementation, figure 1 shows two identical components (11). These two metallic conductors (11) can be made up of simplified process that can include but not limited to sheet metal, and can be joined together by fixing means. When they are joined together such that their individual C-shaped surfaces (12) at terminating end form a circular shape in assembled condition. The C-shaped surfaces may be generally having a semicircular terminating shape or even approximately semi-circular shape. The "C-shaped" cover even minor shape variations and ensure that the scope is not limited to any of such variation.

[0041] In one implementation, figure 2 shows plurality of fixing means (13) with metallic properties that enable two components displayed in figure 1 to remain attached together permanently. Fixing means can include but not limited to rivet, screw, brazing process or any other metal joining process.

[0042] In one implementation, figure 3 refers to assembled condition (14) of two identical metallic components (11). Post assembly, this offers different thickness as mentioned in 14 and 15. Circular shape (15) formed by two individual C-shape (12) facilitate mounting surface for current transformer.

[0043] In one implementation, figure 4 describes assembly of bottom terminal (14), plurality of braids (18) connected to bottom terminal (14) at one end and plurality metallic blades (16) at another end. Plurality of power contact tips (17) can be fixed to blades (16) as shown. Entire assembly can be referred as bottom terminal assembly which further constitutes pole assembly.

[0044] In one implementation, figure 5 shows sectional view of pole assembly made up of bottom terminal assembly (of figure 4) mounted inside housing (20) of a switchgear unit. Moving terminal pole assembly (21) connects with top terminal (19) in closed position under normal operating conditions. The figure 5 shows open condition of pole assembly.

[0045] In one implementation, figure 6 shows sectional isometric view of pole assembly which on terminating side shows circular shaped terminating surface. Lower half of Circular shape is below base level of pole mounting surface of housing. This facilitates increase in Top-Bottom clearance within a phase as shown.

[0046] In the implementation, moving terminal (14) is an assembly consisting of two identical conductive terminals (11) made out of conductive material sheets through simplified process. These two conductive terminals are identical and are fixed to each other by any suitable fixing means (13) so as to form circular shape (15) that projects outside the housing chamber (20) of switchgear. For instance, they are riveted together using current carrying rivets (13) of suitable material. Two identical components (11) can be held together such that one component remains mirror image of another and can be fixed. Individual component has C-shaped terminating face (12) outside housing chamber (20) which may be approximately semicircular in geometry. When these terminals (11) are joined using connecting rivets (13), circular profile (15) will be achieved.

[0047] In the implementation, as shown in figure 4, flat end (11) of moving terminal assembly (14) is designed such that moving flexible current carrying wire strands (braids) (18) can be attached to it. Wire strands (18) present in plurality of bundles will be fixed with terminal assembly’s flat base (11) and can be connected to current carrying blade (16) at another end. When moving terminal assembly is closed by energy stored in mechanism (not shown), current gets conducted through top terminal (19) (as shown in figure 5) then through fixed contact strip connected to fixed terminal further through contact tip (button) (17) attached to blades (16) followed by braids (18) and then through bottom positioned moving terminal assembly (14).

[0048] Current transformer (CT) is used for current sensing, metering and protection. In the implementation, current transformer can be mounted on circular profile (15) of moving terminal assembly (21). CT senses the current through the circuit. In abnormal current condition, it provides signal to the protection release which in turn disconnects the load from the power supply. Accuracy of this signal depends on the location of current transformer, gap with respect to the terminal and profile of the terminal for same design of the current transformer.

[0049] Switching device carries current up to rated electrical current under normal operating conditions for which current path is designed for; subjects to production of thermal heat while in operation. Heat is generated due to inherent losses. Adequate cross section depending upon the current carrying metallic properties of terminals limit the temperature rise in circuit breakers.

[0050] In one implementation, the present invention relates to the use of simplified manufacturing process like sheet metal process for manufacturing the moving terminal assembly and still achieving variable thickness at different surfaces of moving terminal.

[0051] Some of the noteworthy features of the present invention, considered to be noteworthy are mentioned below:
1. Disclosed invention is a moving terminal assembly wherein metallic conductor consists of two identical components which are fixed to each other in mirror image fashion. This facilitates circular terminating surface.
2. Circular terminating profile of bottom terminal contributes to increase in Top-bottom clearance within a phase than existing system. It also facilitates for improved metering accuracy on account of CT mounting and its orientation.
3. Current transformers can be mounted on circular terminating surface of bottom terminal. This facilitates to use CT with circular core which provides better flux linkage.
4. Moving assembly and its fixation with flexible plurality of wire strand bundles and their connection to metallic blades at another end.
5. Circular profile of assembly that facilitates improvement in flux path of CT when mounted on circular profile and increase in top-bottom clearance within an individual phase arising due to circular geometry.
6. Lowest l/A ratio of assembly that is achieved on account of reduced current path length due to depth reduction of terminal assembly and maintaining adequate cross section at both flat rectangular and circular cross section; limiting heating losses for switchgears or circuit breakers.

[0052] Some of the non-limiting advantages of the present invention are mentioned below:
• Circular terminating profile of bottom terminal contributes to increase in Top-bottom clearance within a phase than existing system. It also facilitates for improved metering accuracy on account of CT mounting and its orientation and preciseness in signal given to protection release is achieved.
• As current transformer can be mounted on circular profile, extra space for accommodating CT gets eliminated & results in reduced current path & lower overall resistance of circuit path.
• Present invention refers to improvement in design that provides more pitch (Figure 6) between top (19) and bottom terminals (14) when compared to previous circuit breaker main circuit designs. Thus, there is an improvement in intra-phase pitch between top and bottom terminal and ease of bus-bar termination.
• Disclosed invention refers to variable thickness (11 & 15) even if simplified manufacturing processes are used. Variable thickness (11 & 15) facilitates use of optimum mass of conducting metal and meeting required cross section to carry rated electrical current.
• Metallic components are manufactured using simplified processes like sheet metal resulting in lower manufacturing costs.
• Low heating losses; lesser temperature rise during current conduction.
• Reduction in depth of the terminals.
• Improved convection.

[0053] Although the moving terminal assembly and design of conductor profile in electrical switching devices 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 herein. Rather, the specific features are disclosed as examples of implementations of moving terminal assembly which suppresses rise in temperature of a current-carrying conductor at an opening and closing contact as well as in the vicinity of the contact in an air circuit breaker at the time of applying an electric current to the conductor under normal conditions.