DESC:TECHNICAL FIELD

[001] The present subject matter described herein, in general, relates to electrical switching devices specifically to a circuit breaker and more particularly to an arrangement of contact system of circuit breaker which enables the circuit breaker to make, carry and break current under normal circuit condition and also break during abnormal conditions.

BACKGROUND

[002] An electrical switching device may be defined as a unit designed to connect, carry and disconnect electrical supply so as to protect equipments connected in the electrical circuit from damage caused by overload, under-voltage or short circuit etc. Molded case circuit breakers (MCCB) are well-known electrical switching devices used to provide automatic circuit interruption, to a monitored circuit, when circuit fault conditions occur. Therefore the MCCB is designed in such a manner to interrupt the over current flow arising due to abnormal conditions in the network, as rapidly as possible so as to minimize damage caused by thermal and mechanical stresses to the equipment installed downstream.

[003] The molded case circuit breaker is operating on the current limiting principle typically have a pair of solid stationary electrical contacts joined by a solid moving electrical contact, which provides a path to carry the electrical current in the network. In case of a short circuit fault, the MCCB is capable of enabling the stationary and movable contacts to separate.

[004] Currently, all molded case circuit breaker have a rotor/drive shaft which rotates and switches the electrical circuit. Conventionally, the rotor construction uses an open rotor construction or partially closed construction. The rotary contact arrangement is rotatably arranged on a support shaft, and employs a rotor and a pair of rotor springs to maintain contact between the movable contact arms and the fixed contact arms, thus maintaining a good electrical connection between the contacts in a normal condition. During short circuit, the moving contact in the rotor starts rotating due to the repulsion forces produced by electromagnetic interaction during short circuit. Simultaneously, arc is produced between the fixed and moving contacts. Arcing between the contacts is usually extinguished by passing the arc through an arc dissipating means.

[005] The rotor construction in the rotary contact arrangement is designed in a double break arrangement that helps in the better make and break under normal and abnormal conditions involving very high over-currents. Thus the rotor or shaft of the molded case circuit breaker has to be robust as high electro dynamic repulsive forces are generated between the stationary and moving contacts in the over current conditions.

[006] The rotor is enabled to provide contact pressure so as to provide the intended repulsion threshold as well as to keep the temperature rise within allowable limit set by the relevant product standards under normal working condition. The moving contact is rotated by a certain angle or distance which is termed as over-travel for attaining the contact pressure. The springs that provide the contact pressure should not be exposed to the arcing, a phenomenon of electrical breakdown of gases which enables the passage of current during contact separation, to prevent the drop in spring force and ensure contact pressure. During the separation of contacts due to repulsion, very high energy is released due to arcing, which results in the erosion of the buttons on both moving contact as well as fixed contact. Thus the rotor should also have the provisions for compensating the erosion of the buttons resulting due to arcing faults, so as to maintain the contact pressure even after the erosion of buttons.

[007] Conventional techniques in circuit breakers with rotary mechanism provideno flipping action of moving contact with respect to the rotor/shaft of the rotor contact arrangement so that chances of high let through energy. Also, the prior art techniques does not provide any insulation cover on the moving contact due to which chances of standing arc increase because of lesser insulation between the contacts. Most prior arttechniques uses large number of components to assemble the shaft which further increases the size of the assembly due to large number of components used.

[008] Thus, in view the drawbacks of the existing contact arrangement of the circuit breaker, there exists a dire need to provide a circuit breaker with improved contact arrangement which is able to compensate for erosion generated due to arcing, on both moving contact as well as fixed contact and maintain the contact pressure.

SUMMARY OF THE INVENTION

[009] 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.

[0010] The main object of the present invention is to provide an improved contact assembly in circuit breaker that enables higher contact pressure for higher repulsion threshold.

[0011] Another object of the present invention is to provide a dead centre so as to reduce let through energy.

[0012] Yet another object of the present invention is to provide a higher size for moving contact to carry required current and also to provide a simpler assembly, high mechanical life and modular construction of the contact system.

[0013] Still another object of the present invention is to provide insulation means in moving contact as to protect the moving contact from arc particles and got gases generated during short circuit.

[0014] In one implementation, the present invention provides an improved contact assembly in a MCCB. For rotation of moving contact with respect to the rotor, there is an opening in the rotor with slot length depending on degree of rotation of moving contact. For erosion compensation, there a slot is provided on the moving contact aligned with the centre of the rotor thereby allowing the contact arm freedom of rotation to compensate for button erosion.

[0015] In one implementation, the present invention provides an arrangement of extension springs, U-shaped spring pins with moving contact so as obtain a dead centre in a shaft of which allows moving contact to flip with respect to shaft by reversing torque on moving contact.

[0016] In one implementation, the present invention provides a moving contact cover inner and moving contact cover outer so as to protect the moving contact from arc particles and hot gases generated during short circuit. These said covers also reduce chances of standing arc.

[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

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:

[0018] Figure 1 illustrates abasic view of the circuit breaker pole in ON condition, in accordance with the subject matter of the present invention.

[0019] Figure 2 illustrates abasic view of the circuit breaker pole in which moving contact is in repelled condition, in accordance with the subject matter of the present invention.

[0020] Figure3 illustrates anisometric view of moving contact assembly, in accordance with the subject matter of the present invention.

[0021] Figure 4 illustrates anisometric view of shaft assembly, in accordance with the subject matter of the present invention.

[0022] Figure 5 illustrates abasic cross-sectional view of shaft in normal condition, in accordance with the subject matter of the present invention.

[0023] Figure6 illustrates abasic cross-sectional view of shaft in repelled condition, in accordance with the subject matter of the present invention.

[0024] Figure7 illustrates anisometric view of the pole shaft, in accordance with the subject matter of the present invention.

[0025] Figure8 illustrates an isometric view of moving contact assembly with U-shaped spring pin, in accordance with the subject matter of the present invention.

[0026] 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

[0027] 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.

[0028] 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.

[0029] 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.

[0030] It is to be understood that the singular forms “a,” “an,” and “the” include plural referents unless the context clearly dictates otherwise.

[0031] 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.

[0032] 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.

[0033] 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.

[0034] In one implementation, the improved contact assembly in MCCB includes the following components:
1. Shaft
1a. Open space to accommodate components
1b. U-shaped slot
1c. Slot for spring pin
1d. Centre hole of rotor to accommodate centre pin
1e. Rib to lock spring pin in shaft
1f. Holes for coupling with the adjacent poles using through pin
2. Moving contact
2a. U-shaped slot 1
2b. U-shaped slot 2
2c. Oblong slot
2d. Buttons
2e. Slots to restrict axial movement of U-shaped spring pin
3. Moving contact cover Inner
3a. Oblong Slot
4. Moving contact cover outer
4a. Oblong Slot
5. U-Shaped spring pin
5a. Slot to restrict axial movement with respect to moving contact 2.
6. Spring pin
7. Centre pin
8. Springs

[0035] In one implementation, the improved contact assembly in MCCB includes the following components along with their material of manufacturing
1. Shaft: Material: Plastic, Size: Diameter: 49.5 mm,Width: 47.5 mm, Shape: Cylindrical
1a. Open space to accommodate components: Size: 39.5 mm
1b. U-shaped slot: Width: 4.1 mm, Depth: 3 mm
1c. Slot for spring pin: Width: 3.1 mm
1d. Centre hole of rotor to accommodate centre pin, Diameter: 3.1 mm
1e. Rib to lock spring pin in shaft, Thickness of Rib: 1 mm
1f. Holes for coupling with the adjacent poles using through pin, Dia : 5.1 mm
2. Moving contact: material: copper, thickness: 13 mm
2a. U-shaped slot 1, Size: 4.2 mm,
2b. U-shaped slot 2, Size: 4.2 mm
2c. Oblong slot, Height: 7.6 mm, Width: 3.1 mm,
2d. Buttons, Material: Silver, Size: 10 x 10 x 3 mm3
2e. Slots to restrict axial movement of U-shaped spring pin, Depth: 1.5 mm
3. Moving contact cover Inner: Material: Plastic
3a. Oblong Slot
4. Moving contact cover outer, Material: Plastic
4a. Oblong Slot
5. U-Shaped spring pin: Material: Steel (EN31)
5a. Slot to restrict axial movement with respect to moving contact 2, Diameter: 4 mm Width: 10.4 mm, Shape: Cylindrical
6. Spring pin: Material: Steel (EN31): Diameter: 3 mm: Height: 45.4 mm: Shape: Cylindrical
7. Centre pin: Material: Steel (EN31): Diameter: 3 mm: Height: 48.5 mm: Shape: Cylindrical
8. Springs: Material: IS 4454: (Part I): 2001: Patented & Cold Drawn Unalloyed: steel Wire: Grade III or DH or SH: Wire Diameter: 1.6 to 1.8 mm

[0036] Referring now to figure 1, abasic view of an improved MCCB contact system in ON condition is illustrated. In one implementation, the current conduction happens through a fixed contact onto a moving contact and again to a second fixed contact. In this condition contact pressure is provided by the springs assembled into a shaft.

[0037] Referring now to figure 2,abasic view of an improved MCCB in which moving contact is in repelled condition is illustrated. In one implementation, the contacts such as the fixed contacts and the moving contacts are designed (as in most of present MCCBs) in such a way that during short circuit conditions, an electromagnetic force acts between the moving contact and the fixed contacts. This force rotates the moving contact and brings it to repelled position.

[0038] Referring now to figure3, anisometric view of moving contact assembly in an improved MCCB is illustrated.

[0039] Referring now to figure 4, anisometric view of shaft assembly in an improved MCCB is illustrated.

[0040] Referring now to figure 5, a basic cross-sectional view of shaft in normal condition is illustrated.

[0041] Referring now to figure 6, a basic cross-sectional view of shaft in repelled condition is illustrated.

[0042] Referring now to figure 7, anisometric view of the pole shaft is illustrated.

[0043] Referring now to figure 8, an isometric view of moving contact assembly with U-shaped spring pin is illustrated.

[0044] In one implementation, a rotor or shaft 1, carries at least one contact arm 2, alternately called a moving member or moving contact in open space 1a, assembled together to form a rotary actuating structure. While the moving contact 2 moves to the repelled position as shown in figure 6 from its normal position shown in figure 5, arcing occurs as a result of which arc particles and hot gases are produced.

[0045] In one implementation, the moving contact covers 3 and 4 shown as shown in figure 3 provide insulation for moving contact 2 from arcing produced between the contacts. The moving contact 2 is anchored at centre of the rotor. The location of the contact arm is secured through insertion of the central anchor pin 7 through an oblong slot 2c on the moving contact 2 aligned with the centre hole of the rotor 1d thereby allowing the contact arm 2 freedom of rotation within a predetermined locus about the said central anchor pin 7 as shown in figure 4 and in figure 5.

[0046] In one implementation, rotor 1 construction includes holes 1f to give the provision of coupling with the adjacent poles using a through pin. U-shaped slots 1b are provided, enables the movement of U-shaped spring pins 5 by cam action and thereby the movement of moving contact 2. As illustrated in figure 8, slot 5a on U-shaped spring pins 5 are assembled with U-shaped slot 2a and 2b on moving contact 2 which gives pin connection between U-shaped spring pins 5 and moving contact 2 and at the same time slot 5a on U-shaped spring pin and slots 2e on moving contact 2 restrict axial movement of U-shaped spring pins 5 with respect to moving contact 2. Spring pin 6 is rested in the slot 1c as shown in figure 4, and small ribs 1e on shaft 1 are provided to stop axial movement of spring pin 6 as shown in figure 7.

[0047] In one implementation, as shown in figure 4 and figure 5, extension springs 8 that provide the contact pressure, are assembled between U-shaped spring pin 5 and spring pin 6, so direction of forces on the moving contact is in anti-clockwise direction in case of normal condition as shown in figure 5 and in clockwise direction in case of repelled condition as shown in figure 6. Slots 1g on shaft 1 are provided for mounting of springs 8 on spring pins 6 which also helps in maintaining clearance between springs and other components of shaft shown in figure 4 and figure 7.

[0048] In one implementation, the moving contact 2 consists of two buttons 2d which makes contact with the respective fixed contact buttons. The U-shaped slots 2a and 2b accommodate the U-shaped spring pins 6 to support the spring 8. The moving contact covers 3 and 4 ensure the insulation of moving contact 2. For erosion compensation, there is an oblong slot 2c is provided on moving contact 2 shown in figure 5 aligned with the centre hole 1d of the drive shaft 1 thereby allowing the contact arm freedom of rotation to compensate for button erosion.

[0049] In one implementation, a modified circuit breaker is disclosed. The modified circuit breaker comprises a shaft 1, a moving contact 2, a U-shaped spring pin 5, and at least one spring 8, wherein the U-shaped spring pin 5 is coupled to the moving contact 2 to form a pin connection, and the shaft 1 to provide a cam connection; and the spring 8, the U-shaped spring pin 5, and the moving contact 2, are coupled to form a dead centre in the shaft 1, thereby allowing the moving contact 2 to flip with respect to the shaft 1 by reversing torque on the moving contact 2.

[0050] In one implementation, the modified circuit breaker further comprises a moving contact inner cover 3, a moving contact outer cover 4, a spring pin 6, a center pin 7, wherein the moving contact inner cover 3 comprises an oblong slot 3a; and the moving contact outer cover 4 comprises an oblong slot 4a.

[0051] In one implementation, the shaft 1 comprises an open space to accommodate components 1a;a shaped slot 1b;a slot for spring pin 1c;a centre hole of rotor to accommodate centre pin 1d;a rib to lock spring pin in shaft 1e; and holes for coupling with the adjacent poles using through pin 1f.

[0052] In one implementation, the moving contact 2 comprises a U-shaped slot 1 2a;a U-shaped slot 2 2b;an oblong slot 2c; at least one button 2d; and at least one slots to restrict axial movement of U-shaped spring pin 2e.

[0053] In one implementation, the slot 5a on U-shaped spring pins 5 is adapted to rest on the U-shaped slots 2a and 2b of the moving contact 2 thereby forming the pin connection between the U-shaped spring pin 5 and the moving contact 2; and simultaneously, the U-shaped spring pin 5 is adapted to be inserted in the U-shaped slots 1b of the shaft 1 to achieve the cam connection between the U-shaped spring pin 5 and the U-shaped slots 1b in shaft 1.

[0054] In one implementation, the location of the moving contact 2 is secured by an insertion of the centre pin 7 through the oblong slot 2c on the moving contact 2 aligned with the centre hole 1d of the shaft 1.

[0055] In one implementation, the spring pin 6 is adapted to be inserted in the slot 1c on the shaft 1 to hold the spring 8.

[0056] In one implementation, preferably, four springs 8 are mounted on the U-shaped spring pins 5 and the spring pins 6 to provide force on moving contact 2.

[0057] In one implementation, the U-shaped spring pin 5 comprises at least one slot 5a to restrict axial movement with respect to moving contact 2.

[0058] In one implementation, the spring 8 is mounted on the spring pin 6 using the spring slot 1g in the shaft 1 thereby allowing a clearance between the spring 8 and restricting movement the spring 8.

[0059] As compared to the convention techniques, the operational philosophy of shaft assembly as well as components used in shaft assembly are new. The U-shaped pin, shaft with U-shaped slot and the moving contact with U-slot enables to achieve technical advantages.

[0060] Some of the important features of the present invention, considered to be noteworthy are mentioned below:
1. The present invention provides a flipping action of moving contact so as to reduce the high let through energy.
2. The present invention provides the use of extension springs in such a way that it gives higher contact pressure within a small space.
3. The present invention provides a moving contact cover which gives better insulation between contacts so there are less chances of standing arc.
4. The present invention provides lesser number of components in a shaft assembly.
5. Assembly is easy as lesser number of components is used.
6. The present invention provides a compact design.
,CLAIMS:1. A circuit breaker comprising:
a shaft 1, a moving contact 2, a U-shaped spring pin 5, and at least one spring 8; and WHEREIN
the U-shaped spring pin 5is coupled to:
the moving contact 2 to form a pin connection, and
the shaft 1 to provide a cam connection;
the spring 8, the U-shaped spring pin 5, and the moving contact 2, are coupled to form a dead centre in the shaft 1,thereby allowing the moving contact 2 to flip with respect to the shaft 1 by reversing torque on the moving contact 2.
2. The circuit breaker as claimed in claim 1, further comprises a moving contact inner cover 3, a moving contact outer cover 4, a spring pin 6, a center pin 7, wherein:
the moving contact inner cover 3 comprises an oblong slot 3a; and
the moving contact outer cover 4 comprises an oblong slot 4a.
3. The circuit breaker as claimed in claim 1, wherein the shaft 1 comprises:
an open space to accommodate components 1a;
a U-shaped slot 1b;
a slot for spring pin 1c;
a centre hole of rotor to accommodate centre pin 1d;
a rib to lock spring pin in shaft 1e; and
holes for coupling with the adjacent poles using through pin 1f.
4. The circuit breaker as claimed in claim 1, wherein moving contact 2 comprises:
a U-shaped slot 1 2a;
a U-shaped slot 2 2b;
an oblong slot 2c;
at least one button 2d; and
at least one slots to restrict axial movement of U-shaped spring pin 2e.
5. The circuit breaker as claimed in any of the preceding claims, wherein:
the slot 5a on U-shaped spring pins 5 is adapted to rest on the U-shaped slots 2a and 2b of the moving contact 2 thereby forming the pin connection between the U-shaped spring pin 5 and the moving contact 2; and simultaneously,
the U-shaped spring pin 5 is adapted to be inserted in the U-shaped slots 1b of the shaft 1 to achieve the cam connection between the U-shaped spring pin 5 and the U-shaped slots 1b in shaft 1.
6. The circuit breaker as claimed in any of the preceding claims, wherein the location of the moving contact 2 is secured by an insertion of the centre pin 7 through the oblong slot 2c on the moving contact 2 aligned with the centre hole 1d of the shaft 1.
7. The circuit breaker as claimed in any of the preceding claims, wherein the spring pin 6 is adapted to be inserted in the slot 1c on the shaft 1 to hold the spring 8.
8. The circuit breaker as claimed in any of the preceding claims, wherein preferably, four springs 8 are mounted on the U-shaped spring pins 5 and the spring pins 6 to provide force on moving contact 2.
9. The circuit breaker as claimed in any of the preceding claims, wherein the U-shaped spring pin 5 comprises at least one slot 5a to restrict axial movement with respect to moving contact 2.
10. The circuit breaker as claimed in any of the preceding claims, wherein the spring 8 is mounted on the spring pin 6 using the spring slot 1g in the shaft 1 thereby allowing a clearance between the spring 8and restricting movement the spring 8.