Claims:WE CLAIM:

1. An electrical connection module (100) for a withdrawable circuit breaker (200), the withdrawable circuit breaker (200) placed inside a cradle assembly (150) for racking-in and racking-out operations thereof, the electrical connection module (100) comprising:
• a jaw cage (20) having a first set of projections (5) and a second set of projections (10) configured thereon, the jaw cage (20) mounted on a cradle terminal (140) of the cradle assembly (150) through the second set of projections (10);
• a plurality of jaw fingers (40) mounted on the jaw cage (20) to have the cradle terminal (140) inserted inside an end thereof, each jaw finger of the plurality of jaw fingers (40) having a third set of projections (35) and a groove (38) configured thereon, the third set of projections (35) being engaged with the first set of projections (5) on the jaw cage (20) preventing disengagement of the plurality of jaw fingers (40) from the jaw cage (20) due to arrested movement in vertical direction while allowing swivel movement thereof; and
• a spring (60) having one end mounted in the first set of projections (5) on the jaw cage (20) and another end attached to the groove (38) in the jaw finger of the plurality of jaw fingers (40),

wherein, during the racking-in operation to achieve a connected position of the withdrawable circuit breaker (200), power contacts connected to breaker terminals (160, 170) of the withdrawable circuit breaker (200) get inserted in another end of the jaw finger of the plurality of jaw fingers (40) causing swiveling movement of the plurality of jaw fingers (40) that in turn cause compression of the spring (60) to produce a contact pressure between the jaw fingers (40) and the cradle terminal (140) as well as between the jaw fingers (40) and the power contacts connected to the breaker terminals (160, 170) thereby establishing an electrical connection between the breaker terminals (160, 170) and the cradle terminal (140), and
wherein, during the racking-out operation to achieve a disconnected position of the withdrawable circuit breaker (200), the power contacts connected to the breaker terminals (160, 170) of the withdrawable circuit breaker (200) isolate from another end of the jaw finger of the plurality of jaw fingers (40) thereby breaking the electrical connection between the breaker terminals (160, 170) and the cradle terminal (140).

2. The electrical connection module (100) as claimed in claim 1, wherein the withdrawable circuit breaker (200) is a withdrawable type air circuit breaker.

3. The electrical connection module (100) as claimed in claim 1 is a jaw assembly.

4. The electrical connection module (100) as claimed in claim 1, wherein the third set of projections (35) is configured on a lower side of each jaw finger of the plurality of jaw fingers (40).

Dated this 29th day of March, 2017

Priya Pandey
(Agent for Applicant)
IN/PA-2018
, Description:ELECTRICAL CONNECTION MODULE FOR WITHDRAWABLE CIRCUIT BREAKER

FIELD OF THE INVENTION

The present invention relates to an electrical connection module for a withdrawable circuit breaker. The electrical connection module provides electrical current path between terminals of a draw-out type switching device and terminals mounted on a breaker housing of the switching device.

BACKGROUND OF THE INVENTION

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. Energy is stored in a suitable mechanism which 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.

Switching devices can be segregated into two main categories based on the functionality to shift the device. They are fixed type switching devices and draw out type switching devices. Fixed type devices will be mounted on a suitable framework to facilitate the working of the device; it will remain connected to the framework throughout its operational life. The draw out type device will be loaded on a cassette type structure, herein after called as cradle.

The cradle is made of a suitable material. Sufficient mechanical arrangements will be provided in the cradle to facilitate the movement of the breaker inside the cradle. Cradle will be fixed to a suitable framework for enabling the functionality of the switching device.

There are 3 main positions for the switching device inside a cradle, they are connected, test and disconnected positions. Racking-in is the operation of moving the device from disconnected position to test position and eventually to connected position. Racking-out is the operation of moving the device from connected to test and eventually to disconnected position. In the disconnected and the test positions, terminals of the device and the cradle will be electrically isolated.

Providing a conductive path with less resistance to the flow electric current between the cradle terminals and the switching device/circuit breaker terminals is critical in a withdrawable type switching device as the mechanical joints formed will play a crucial role in the heat generation of the device and heat flow in the system during normal operation and stability of the device during an abnormal electrical condition like short circuit.

Hence, there exists a need to provide an electrical current path between terminals of a draw-out type switching device and terminals mounted on a breaker housing of the switching device that overcomes the above mentioned problem of the prior art.

OBJECTS OF THE INVENTION

An object of the present invention is to provide a low resistance conductive path between switching device terminals (breaker terminals) and cradle terminals while facilitating the racking-in and racking-out operations of a withdrawable switching device.

Another object of the present invention is to limit heat produced in a jaw assembly and eventual overheating of the jaw assembly.
SUMMARY OF THE INVENTION

Accordingly, the present invention provides an electrical connection module for a withdrawable circuit breaker. The withdrawable circuit breaker for example a withdrawable type air circuit breaker is placed inside a cradle assembly for racking-in and racking-out operations thereof. The electrical connection module is a jaw assembly that comprises a jaw cage, a plurality of jaw fingers and a spring.

The jaw cage includes a first set of projections and a second set of projections configured thereon. The jaw cage is mounted on a cradle terminal of the cradle assembly through the second set of projections.

The plurality of jaw fingers is mounted on the jaw cage to have the cradle terminal inserted inside an end thereof. Each jaw finger of the plurality of jaw fingers includes a third set of projections and a groove configured thereon. The third set of projections is configured on a lower side of each jaw finger of the plurality of jaw fingers and engaged with the first set of projections on the jaw cage preventing disengagement of the plurality of jaw fingers from the jaw cage due to arrested movement in vertical direction while allowing swivel movement thereof.

The spring includes one end mounted in the first set of projections on the jaw cage and another end attached to the groove in the jaw finger of the plurality of jaw fingers.

During the racking-in operation to achieve a connected position of the withdrawable circuit breaker, power contacts connected to breaker terminals of the withdrawable circuit breaker get inserted in another end of the jaw finger of the plurality of jaw fingers causing swiveling movement of the plurality of jaw fingers that in turn cause compression of the spring to produce a contact pressure between the jaw fingers and the cradle terminal as well as between the jaw fingers and the power contacts connected to the breaker terminals thereby establishing an electrical connection between the breaker terminals and the cradle terminal.

During the racking-out operation to achieve a disconnected position of the withdrawable circuit breaker, the power contacts connected to the breaker terminals of the withdrawable circuit breaker isolate from another end of the jaw finger of the plurality of jaw fingers thereby breaking the electrical connection between the breaker terminals and the cradle terminal.

BRIEF DESCRIPTION OF THE DRAWINGS

Other features as well as the advantages of the invention will be clear from the following description.

In the appended drawings:
Figure 1 shows an electrical connection module for a withdrawable circuit breaker, in accordance with the present invention;

Figure 2 shows a jaw cage of the electrical connection module, in accordance with the present invention;

Figure 3 shows a contact finger of the electrical connection module, in accordance with the present invention;

Figure 4 is a sectional view of the electrical connection module mounted on a cradle assembly, in accordance with the present invention; and

Figure 5 shows the withdrawable type of circuit breaker with the cradle assembly, in accordance with the present invention.

DETAILED DESCRIPTION OF THE INVENTION
The foregoing objects of the present 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 an electrical connection module for a withdrawable circuit breaker. The electrical connection module provides a low resistance conductive path between switching device terminals (breaker terminals) and cradle terminals while facilitating the racking-in and racking-out operations of the withdrawable circuit breaker.

The present invention is illustrated with reference to the accompanying drawings, throughout which reference numbers indicate corresponding parts in the various figures.

Referring to figures 1-5, an electrical connection module (100) for a withdrawable circuit breaker (200) is described in accordance with the present invention. The withdrawable circuit breaker (200) is placed inside a cradle assembly (150) (refer figure 5) for racking-in and racking-out operations thereof. The movement of the withdrawable circuit breaker (200) is facilitated in the cradle assembly (150) from a disconnected position to a connected position and vice versa.

Specifically, the electrical connection module (100) is a spring loaded electrical connection module that fixes and unfixes switching devices such as the withdrawable circuit breaker (200) for example a withdrawable type air circuit breaker to the cradle assembly (150) during the racking-in operation and the racking-out operation of the withdrawable circuit breaker (200) (herein after ‘the circuit breaker (200)’).

More specifically, the electrical connection module (100) is a jaw assembly for fixing and unfixing breaker terminals (160, 170) of the circuit breaker (200) on cradle terminals (140) of the cradle assembly (150). The cradle terminals (140) in the cradle assembly (150) are fixed with use of terminal supports (130). The electrical connection module (100) (herein after ‘the jaw assembly (100)’) comprises a jaw cage (20), a plurality of jaw fingers (40) and a spring (60) as shown in figure 4.

The jaw cage (20), a structural component of the jaw assembly (100) is made up of a suitable material for example a single sheet of metal to provide adequate support to the jaw fingers (40) and the spring (60). The jaw cage (20) includes a first set of projections (5) and a second set of projections (10) configured thereon as shown in figure 2.

The first set of projections (5) alternatively referred to as pips act as guiding for the contact spring (60) and extension to prevent disengagement motion of the jaw fingers (40). In other words, the first set of projections (5) arrest the movement of the plurality of jaw fingers (40) in vertical direction to prevent disengagement thereof and also help in mounting and trapping of the spring (60) in the jaw cage (20). The second set of projections (10) mount the jaw cage (20) of the jaw assembly (100) on the cradle terminals (140) of the cradle assembly (150) (as shown in figure 4) while restricting vertical movement of the plurality of jaw fingers (40) of the jaw assembly (100) with respect to the cradle terminals (140) but allowing necessary swivel movement of the jaw assembly (100) to ensure proper alignment between the breaker terminals (160, 170) and the cradle terminals (140).

The plurality of jaw fingers (40) (herein after ‘the jaw fingers (40)’) are mounted on the jaw cage (20) to have the cradle terminal (140) inserted inside an end thereof. The number of the jaw fingers (40) mounted on the jaw cage (20) depends on current rating of the circuit breaker (200). Higher the rating, more jaw fingers (40) will be used. In an embodiment, for 1600A current, 16 jaw fingers (40) on top side and 16 jaw fingers (40) on bottom side are used as shown in figure 4.
Each jaw finger (40) includes a third set of projections (35) and a groove (38) configured thereon as shown in figure 3. The third set of projections (35) is small projections configured on a lower side of the each jaw finger (40). The third set of projections (35) is trapped / engaged with the first set of projections (5) on the jaw cage (20). The engagement between the first and the third set of projections (5, 35) prevents disengagement of the jaw fingers (40) from the jaw cage (20) due to arrested movement of the jaw fingers (40) in vertical direction while allowing swivel movement thereof. In an embodiment, the jaw fingers (40) are metallic fingers made up of a current conducting material such as Copper components and are generally silver plated on surface.

The spring (60) at one end is mounted in the first set of projections (5) on the jaw cage (20) and another end thereof is attached to the groove (38) in the jaw fingers (40). Thus, two springs (60) get trapped between the first set of projections (5) and the groove (38). The springs (60) ensure necessary joint pressure between the jaw fingers (40) and the cradle terminals (140) and the breaker terminal (160, 170). In an embodiment, the jaw assembly (100) includes one spring for two jaw fingers (40) as shown in figure 1.

During the racking-in operation to achieve the connected position of the withdrawable circuit breaker (200), power contacts connected to the breaker terminals (160, 170) of the withdrawable circuit breaker (200) get inserted in another end of the jaw finger (40) and an electrical contact is established between power contacts connected to the breaker terminals (160, 170) and the jaw fingers (40). The power contacts causes swiveling movement of the jaw fingers (40) pushing the jaw fingers (40) away from each other thereby causing compression of the spring (60) to produce contact pressure between the jaw fingers (40) and the cradle terminals (140) as well as between the jaw fingers (40) and the power contacts connected to the breaker terminals (160, 170). As a result, an electrical contact is established between the breaker terminals (160, 170) and the cradle terminals (140). Thus, the cradle terminals (140) can be connected to conductors (i.e. the jaw assembly (100) and bus bar system so as to connect the breaker to an electrical system. Electrical contact with this assembly, its overlap and contact pressure established between the power contacts connected to the breaker terminals (160, 170) and the jaw fingers (40) greatly affect the performance of the circuit breaker (200).

During the racking-out operation to achieve the disconnected position of the withdrawable circuit breaker (200), power contacts connected to breaker terminals (160, 170) of the withdrawable circuit breaker (200) isolate from another end of the jaw fingers (40) thereby breaking the electrical connection between the breaker terminals (160, 170) and the cradle terminal (140).

ADVANTAGES OF THE INVENTION

1. The spring loaded electrical assembly of the electrical connection module (100) is easy to assemble and requires minimum number of components. Further, the assembly requires no hardware to fix the springs (60) and the jaw fingers (40) on the jaw cage (20). The projections (5) in the jaw cage (20) and the projections (35) and the grooves (38) in the jaw fingers (40) facilitate mounting of the springs (60) and the jaw fingers (40) on the jaw cage (20) without requiring hardware.
2. No hardware is required to mount and fix the jaw fingers (40) of the jaw assembly (100) onto the cradle terminals (140).
3. During operational life of the circuit breaker (200), heat will be generated due to the inherent losses. Design of components reduces temperature rise due to the open type construction of the jaw cage (20) of the jaw assembly (100) that provides consistent contact pressure thereby helping in heat dissipation through high convection rate thus limiting temperature rise in the circuit breaker (200).
4. Single component design for the jaw cage (20) holds the springs (60) to ensure consistent contact pressure on the jaw fingers (40) during the connected position and hence reduces resistance at the joints.
5. Adequate overlap and contact pressure between the circuit breaker (200) (power contacts connected to the breaker terminals (160, 170)) and the cradle terminals (140) with use of compressible springs (60) to limit heat losses.
6. By virtue of its geometry and fixing on the cradle terminals (140), the jaw assembly (100) undergoes swiveling motion that facilitates auto adjustment and self-alignment with power contacts connected to the breakers terminals (160, 170) when they are racked-in to connected position of the circuit breaker (200).

The foregoing descriptions of specific embodiments of the present invention have been presented for purposes of illustration and description. They are not intended to be exhaustive or to limit the present invention to the precise forms disclosed, and obviously many modifications and variations are possible in light of the above teaching. The embodiments were chosen and described in order to best explain the principles of the present invention and its practical application, and to thereby enable others skilled in the art to best utilize the present invention and various embodiments with various modifications as are suited to the particular use contemplated. It is understood that various omissions and substitutions of equivalents are contemplated as circumstances may suggest or render expedient, but such omissions and substitutions are intended to cover the application or implementation without departing from the spirit or scope of the claims of the present invention.