Claims:We Claim:

1. A contact system for a moulded case circuit breaker (MCCB)(1) comprising of:
a stationary contact (4);
a shaft assembly having a rotor (5) enclosing,
• plurality of moving contacts (6), each moving contact (6) of the plurality of moving contacts (6) having a first end and a second end, the plurality of moving contacts (6) adapted for removably engaging with the stationary contact (4) through the first end, each moving contact (6) of the plurality of moving contacts (6) having a slot (14) with a concave profile being configured thereon,
• a compression spring (12) disposed within the slot (14) and adapted for providing contact pressure to engage the plurality of moving contacts (6) with the stationary contact (4),
• a spring guiding pin (10) disposed within the slot (14) such that a first end rests within the slot (14) and a second end rests within a cavity (13) of the rotor (5), the spring guiding pin (10) having the compression spring (12) wrapped thereon and further adapted for preventing buckling of the compression spring (12), the spring guiding pin (10) being formed by bending a single pressed component (16) along a center surface (17) thereby fabricating the spring guiding pin (10) having a convex profile (15)at the first end thereof for facilitating frictionless engagement of the spring guiding pin (10) within the concave profile of the slot (14) of each moving contact (6) of the plurality of moving contacts (6);
• a moving contact cover (11) provided for each moving contact (6) of the plurality of moving contacts (6), the moving contact cover (11) adapted for securing the spring guiding pin (10) at desired position and thereinafter locking translational motion of the spring guiding pin (10), the moving contact cover (11) further adapted for maintaining equal spacing between the plurality of moving contacts (6);
plurality of electrical flexible conductors (7) operably connected with the plurality of moving contacts (6) through the second end thereof; and
a flexible conductor fixing block (8) operably connected with the plurality of electrical flexible conductors (7) and adapted for connecting the plurality of moving contacts (6) through the second end thereof with a terminal contact (9),
wherein the plurality of moving contacts (6) moves rapidly against force of the contact pressure of the compression spring (12) thereby repelling open the circuit by frictionless mating of the concave profile of the slot (14) of the plurality of moving contacts (6) with the convex profile (15) of the spring guiding pin (10) in response to a short circuit condition.

2. The contact system as claimed in claim 1, wherein the single pressed component (16) is made up of stainless steel.

3. The contact system as claimed in claim 1, wherein the first end of the spring guiding pin (10) having the convex profile (15) and the concave profile of the slot (14) of the plurality of moving contacts (6) enables frictionless engagement therebetween.

Dated this 27th day of March 2017

Prafulla Wange
(Agent for Applicant)
IN-PA/2058 , Description:CONTACT SYSTEM FOR MOULDED CASE CIRCUIT BREAKER

Field of the invention
The present invention relates to contact system for circuit breaker, mainly moulded case circuit breakers (MCCBs). More particularly, the present invention provides a contact system comprising of a spring arrangement for enabling smooth opening of the moving current carrying contacts during short circuit condition.
Background of the invention
A circuit breaker is an electrical protection device which can make, break & carry current in normal condition. When there is a fault in the system due to overload, short circuit etc. circuit breaker can break and clear the fault.
Circuit breaker typically consists of at least one stationary contact and at least one movable contact in each pole. When circuit breaker is switched ON by means of an operating mechanism movable contact mates with the stationary contact. To hold the movable contact at the mating position high contact pressure is applied on the movable contact using springs. Different arrangements of springs are followed currently for maintaining contact pressure. Lorentz force and Holm’s force between stationary contact and movable contact act against the applied contact pressure. Higher the current, higher are the Lorentz Force and Holm’s Force. So, when there is a fault in the system both Lorentz force and Holm’s force increase. When the combined force due to Lorentz force and Holm’s force goes higher than the applied contact pressure, the movable contact repels open. Faster the movable contact repels open, lesser fault interruption time.
During ON condition, a set of springs provide contact force to maintain the moving contact in ON condition. Any type of spring can be used for applying contact pressure on the moving contact. When compression spring is used, buckling of the spring must be avoided. One of the ways to avoid buckling of compression spring is to provide guiding pin inside the spring. One end of the guiding pin along with compression spring rests on a surface of the moving contact. To enable faster opening of the movable contact there should be less frictional force between the mating surfaces of the guiding pin and the moving contact. The guiding pin has to be robust to enable multiple opening of the moving contacts. Further, it has to be ensured that the guiding pins are placed properly on the moving contacts and don’t get displaced during opening of the moving contacts.
In existing arrangements, most of the configurations have a continuously opposing spring force against the repulsion force thereby giving less opening speed in event of a short circuit. Further, the contact pressure for most of the configurations is provided by extension springs which are comparatively complex in construction and less accurate. Even if compression springs are used, they face a common problem of buckling of the compression spring and displacement of the guiding pin. Even in existing systems, the arrangement of springs gives rise to instability in plurality of moving contacts and increased friction resulting in more time to open the contacts during faulty conditions.
All the above drawbacks of conventional arrangements also translate into lesser contact opening during a fault which makes clearing higher faults difficult. (If the contacts open more, more arc voltage is obtained which helps in easier fault clearance).
Therefore, there exists a need to provide an improved contact system comprising of a spring arrangement which overcomes the above mentioned drawbacks of the existing systems. Further there exists a need to provide an improved contact system where the moving contacts repels open faster thereby reducing the fault interruption time during short circuit conditions.
Objects of the invention
The primary object of present invention is to provide an improved contact system for moulded case circuit breaker.
Another object of present invention is to provide higher stability and lesser friction effect to the moving contacts during opening the moving contacts in faulty condition.
Yet another object of the present invention is to increase the moving contacts opening speed thereby reducing the fault interruption time during short circuit conditions.
Summary of the invention
The present invention provides a contact system for a moulded case circuit breaker (MCCB). The contact system comprises of a stationary contact, a shaft assembly, plurality of electrical flexible conductors, a flexible conductor fixing block and a terminal contact. The shaft assembly further encloses a plurality of moving contacts, plurality of compression spring, plurality of spring guiding pin, and plurality of moving contact cover.
The plurality of moving contacts having a first end and a second end, are adapted for removably engaging with the stationary contact through the first end. Further, each moving contact of the plurality of moving contacts is provided with a slot configured thereon. The slot includes a concave profile configured thereon. Particularly, the surface of the slot is concave in shape.
The compression spring is disposed within the slot and provides contact pressure for engaging/mating the plurality of moving contacts with the stationary contact and to induce no return force for opening thereof in closed position of the circuit breaker.
The spring guiding pin, having a first end and a second end, is disposed within the slot such that the first end rests within the slot and the second end rests within a cavity of the rotor. The spring guiding pin is provided with the compression spring being wrapped thereon. Particularly, the spring guiding pin helps in preventing buckling of the compression spring. The spring guiding pin is fabricated using minimum cat numbers and components numbers thereby ensuring frictionless opening of the plurality of moving contacts during faulty condition. Particularly, fabricating the spring guiding pin involves bending of a single pressed component along center surface to form a convex profile at the first end of the spring guiding pin. The convex profile of the spring guiding pin engages frictionlessly with the concave profile of the plurality of moving contacts resulting into a strong mating therebetween.
The moving contact cover helps in securing the spring guiding pin at desired position and thereinafter locking translational motion of the spring guiding pin. Furthermore, the moving contact cover is adapted for maintaining equal spacing between the plurality of moving contacts. Thus, the moving contact cover serves a dual purpose.
The plurality of electrical flexible conductors is operably connected with the plurality of moving contacts through the second end thereof.
The flexible conductor fixing block is operably connected with the plurality of electrical flexible conductors. The flexible conductor fixing block helps in connecting the plurality of moving contacts through the second end thereof with the terminal contact.
The contact system enables smooth and faster opening of the plurality of moving contacts during faulty conditions.
Brief description of the drawings
Figure 1 shows an isometric view of the 4 pole Circuit Breaker cassette embodying the contact system of the present invention;
Figure 2 shows an isometric view of the contact system, in accordance with the present invention, in ON condition of MCCB;
Figure 3 shows a cross-sectional view of the shaft assembly, in accordance with the present invention;
Figure 4 shows an isometric view of the moving contact, in accordance with the present invention;
Figure 5 shows an isometric view of the single pressed component used in fabricating the spring guiding pin, in accordance with the present invention;
Figure 6 shows an isometric view of the spring guiding pin, in accordance with the present invention;
Figure 7 shows a detailed view of the spring guiding pin resting on the moving contact, in accordance with the present invention;
Figure 8 shows a detailed view of section A of figure 7, in accordance with the present invention, in ON condition of MCCB;
Figure 9 shows a detailed view of section A of figure 7, in accordance with the present invention, in OFF condition of MCCB;
Figure 10 shows a detailed view of the moving contact cover, in accordance with the present invention.
Detailed description of the invention
The foregoing objects of the invention are accomplished and the problems and shortcomings associated with the prior art techniques and approaches are overcome by the present invention as described below in the preferred embodiment.
The present invention provides a contact system for a moulded case circuit breaker (MCCB). The contact system comprises of spring guiding pin that is fabricated using minimum cat numbers and components. The contact system enables smooth and faster frictionless opening of the plurality of moving contacts during faulty condition.
This present invention is illustrated with reference to the accompanying drawings, throughout which reference numbers indicate corresponding parts in the various figures. These reference numbers are shown in bracket in the following description.
Referring to figures 1 to 10, disclosed is a contact system, hereinafter referred to as “the system” for a circuit breaker (1), particularly for a moulded case circuit breaker (1) (MCCB). In an embodiment, the system is used for a 4 pole circuit breaker cassette (1) as shown in figure 1. The 4 pole circuit breaker cassette (1) consists of a top cover (2) and a bottom cover (3) enclosing therebetween the system of the present invention.
Referring to figure 2, an isometric view of the system, in ON condition of the circuit breaker (1) is shown. In accordance with the present invention, and referring to figure 2, the system comprises of: a stationary contact (4), a shaft assembly, plurality of electrical flexible conductors (7), a flexible conductor fixing block (8) and a terminal contact (9). The shaft assembly, as shown in figure 3, further includes a rotor (5). The rotor (5) encloses a plurality of moving contacts (6), with each moving contact (6) having a compression spring (12), a spring guiding pin (10) and a moving contact cover (11) configured thereon. Current conducts through the stationary contact (4) and the plurality of moving contacts (6), the plurality of electrical flexible conductors (7), and through the flexible conductor fixing block (8) connecting the plurality of moving contacts (6) to the terminal contact (9) and vice versa.
Each moving contact (6) of the plurality of moving contacts (6) includes a first end (not numbered) and a second end (not numbered), and is adapted for removably engaging with the stationary contact (4) through the first end. Further, each moving contacts (6) of the plurality of moving contacts (6) is provided with a slot (14) configured thereon. In a preferred embodiment, the slot (14) includes a concave profile configured thereon.
The compression spring (12) is disposed within the slot (14) and provides contact pressure for engaging/mating the plurality of moving contacts (6) with the stationary contact (4) and to induce no return force for opening thereof in closed position of the circuit breaker (1).
The spring guiding pin (10) is disposed within the slot (14) configured on each moving contact (6) of the plurality of moving contacts (6). The spring guiding pin (10) further includes the compression spring (12) being wrapped thereon. In an embodiment, the spring guiding pin (10) is used to avoid buckling of the compression spring (12) which is provided to apply contact pressure on the plurality of moving contacts (6). The spring guiding pin (10) is fabricated using a single pressed component (16). In an embodiment, the single pressed component is made up of stainless steel. More particularly, as shown in figure 5, the single pressed component (16) is bend along a center surface (17) forming the spring guiding pin (10) having a convex profile (15) at a first end thereof as shown in figure 6. In an embodiment, fabricating the spring guiding pin (10) requires least possible component numbers thereby reducing on the manufacturing costs. The spring guiding pin (10) is fabricated using minimum cat numbers and components numbers while ensuring frictionless disengagement of the plurality of moving contacts (6) from the stationary contact (4) against the force of contact pressure of the compression spring (12), during faulty conditions.
Referring to figures 7 to 9, the spring guiding pin (10) is disposed within each slot (14) such that the first end having the convex profile (15) rests within the concave profile of the slot (14) of each moving contact (6) of the plurality of moving contacts (6), whereas the second end of the spring guiding pin (10) rests on a cavity (13) of the rotor (5). Thus, the convex profile (15) of the spring guiding pin (10) that rests on the concave profile of the slot (14) of the plurality of moving contacts (6) offers least possible frictional force during mating between the spring guiding pin (10) and the plurality of moving contacts (6), resulting into faster disengagement of the plurality of moving contacts (6) from the stationary contact (4) in faulty conditions. Hence, in event of a short circuit, the plurality of moving contacts (6) repels open faster resulting in lesser fault interruption time.
The moving contact cover (11), as shown in figure 10, is provided for each moving contact (6) of the plurality of moving contacts (6). The moving contact cover (11) helps in securing the spring guiding pin (10) at desired position and thereinafter locking translational motion of the spring guiding pin (10). Furthermore, the moving contact cover (11) is adapted for maintaining equal spacing between the plurality of moving contacts (6). Thus, the moving contact cover (11) serves a dual purpose. In an embodiment, the locking of the translational motion of the spring guiding pin (10) also ensures reliability of the circuit breaker (1).
The plurality of electrical flexible conductors (7) is operably connected to the plurality of moving contacts (6) through the second end thereof.
The flexible conductor fixing block (8) is operably connected with the plurality of electrical flexible conductors (7). The flexible conductor fixing block (8) helps in connecting the plurality of moving contacts (6) through the second end thereof with the terminal contact (9). The current conducts through the stationary contact (4) and the plurality of moving contacts (6), the plurality of electrical flexible conductors (7), and through the flexible conductor fixing block (8) connecting the plurality of moving contacts (6) to the terminal contact (9) and vice versa.
The system enables smooth and faster disengagement of the plurality of moving contacts (6) from the stationary contact (4) during faulty conditions.
Advantages of the present invention
1. Fast fault interruption.
2. Performance enhancement.
3. Less cat numbers and less component numbers.
4. Less cost of manufacturing.
5. Minimum assembly time.
6. Multiple functions of a single component.
7. High reliability.

The foregoing objects of the invention are accomplished and the problems and shortcomings associated with prior art techniques and approaches are overcome by the present invention described in the present embodiment. Detailed descriptions of the preferred embodiment are provided herein; however, it is to be understood that the present invention may be embodied in various forms. Therefore, specific details disclosed herein are not to be interpreted as limiting, but rather as a basis for the claims and as a representative basis for teaching one skilled in the art to employ the present invention in virtually any appropriately detailed system (100), structure, or matter. The embodiments of the invention as described above and the methods disclosed herein will suggest further modification and alterations to those skilled in the art. Such further modifications and alterations may be made without departing from the spirit and scope of the invention.