Claims:We claim:

1. A jaw contact (100) for plug-in type circuit breaker, the plug-in type circuit breaker having a withdrawable unit including a moving part (130) and a fixed part (140), the withdrawable unit further having a breaker terminal (120) and a plug (110) configured in the moving part thereof, the plug (110) is operably connected to the breaker terminal (120), the jaw contact (100) comprising:
a plurality of jaw fingers (40) having a top jaw finger (20), a plurality of middle jaw fingers and a bottom jaw finger (30), wherein the plug (110) is operably connected to the plurality of jaw fingers (40), thereby establishing an easily detachable electrical connection of the jaw contact (100);
a fixed contact (80) operably connected with the plurality of jaw fingers (40), the fixed contact (80) having a top end and a bottom end, the fixed contact (80) having a cut profile (60) configured at the bottom end thereof; and
a draw-out terminal (90) operably connected to the fixed contact (80) from one end and fixed to a main busbar from other end;
wherein, a gap (50) is formed between the draw-out terminal (90) and the bottom end of the fixed contact (80) due to the cut profile (60) of the fixed contact (80), so that current flows in an optimal path through the plurality of jaw fingers (40), thereby carrying even current in the top jaw finger (20) and the bottom jaw finger (30) and significantly reducing temperature rise at the breaker terminal (120) and the moving part (130) of the withdrawable unit of the plug-in type circuit breaker.

2. The jaw contact (100) as claimed in claim 1, wherein the plurality of jaw fingers (40) is spring loaded.

3. The jaw contact (100) as claimed in claim 1, wherein the top end of the fixed contact (80) is operably connected with the top jaw finger (20) and the bottom end of the fixed contact (80) is operably connected with the bottom jaw finger (30).

4. The jaw contact (100) as claimed in claim 1, wherein the current density in the top jaw finger (20) and the bottom jaw finger (30) is even. , Description:Field of invention:

The present invention relates to a field of protection devices, particularly withdrawable unit of circuit breakers and more particularly, to a jaw contact for plug-in type circuit breaker.

Background of the invention:

Jaw contacts are used extensively in panel boards and withdrawable circuit breakers to have an easily detachable electrical connection. The jaw contact comprises of spring loaded jaw fingers and a terminal. The jaw fingers connected to the terminal will be fixed to the main bus bar. The plug which is bolted to the breaker terminal will be the moving part, which engages with the jaw fingers thus establishing an easily detachable electrical connection.

When the draw-out module is connected to the breaker, heat generated in the jaw contact adds up to temperature of the breaker and results in higher temperature at the moving contact of the breaker. In high current applications, more number of the jaw fingers is used to carry the current. Ideally, the current should divide among the jaw fingers. As the current takes the least resistance path, the current distribution in jaw contacts is non-uniform, leading to high temperature rise in the breaker terminal.

A prior art patent US6448519B1 discloses contact system arrangement for plug-in circuit breaker and base. The prior art patent describes the construction of contact system arrangement for plug-in circuit breakers. The contact arrangement includes a jaw finger mounted on a contact support, which is mounted on a plugin base. A plug is connected to the circuit breaker with a contact support. However, the prior art patent includes drawbacks as given below:
1. Uneven current distribution among the jaw fingers
2. High temperature at the breaker terminal
3. Adding up of spring force and more material consumption, to reduce the temperature rise

Accordingly, there is a need of an improved jaw contact for plug-in type circuit breaker that overcomes above mentioned drawbacks in the prior art.

Objects of the invention:

An object of the present invention is to optimize distribution of current among jaw fingers of a jaw contact for plug-in type circuit breaker.

Another object of the present invention is to reduce temperature rise at a terminal of the plug-in type circuit breaker.

Yet, another object of the present invention is to solve the issues in thermal performance of the breaker when the breaker is connected to withdrawable module.

Summary of the invention:

Accordingly, the present invention provides a jaw contact for plug-in type circuit breaker. The plug-in type circuit breaker includes a withdrawable unit including a moving part and a fixed part. The withdrawable unit includes a breaker terminal and a plug configured in the moving part thereof. The plug is operably connected to the breaker terminal. The jaw contact is assembled in the fixed part thereof. The jaw contact comprises of a plurality of jaw fingers, a fixed contact and a draw-out terminal. The plurality of jaw fingers includes a top jaw finger, a plurality of middle jaw fingers and a bottom jaw finger. The plurality of jaw fingers is spring loaded. The plug is operably connected to the plurality of jaw fingers, thereby establishing an easily detachable electrical connection of the jaw contact.

The fixed contact is operably connected with the plurality of jaw fingers. The fixed contact has a top end and a bottom end. The top end of the fixed contact is operably connected with the top jaw finger and the bottom end of the fixed contact is operably connected with the bottom jaw finger. The fixed contact includes a cut profile configured at the bottom end thereof. The draw-out terminal is operably connected to the fixed contact from one end and fixed to a main busbar from other end.

A gap is formed between the draw-out terminal and the bottom end of the fixed contact due to the cut profile of the fixed contact, so that current flows in an optimal path through the plurality of jaw fingers. Hence, even current carries in the top jaw finger and the bottom jaw finger that means the current density in the top jaw finger and the bottom jaw finger is even. Thus, significant reduction in temperature rise occurs at the breaker terminal and the moving part of the withdrawable unit of the plug-in type circuit breaker.

Brief description of the drawings:

Figure 1 shows a front view of a jaw contact for plug-in type circuit breaker, in accordance with the present invention;

Figure 2 shows a sectional front view of the jaw contact for the plug-in type circuit breaker, in accordance with the present invention;

Figure 3 shows a fixed contact of the jaw contact for the plug-in type circuit breaker, in accordance with the present invention;

Figure 4 shows current distribution in a jaw contact for a plug-in type circuit breaker, in accordance with a prior art;

Figure 5 shows current distribution in the jaw contact for the plug-in type circuit breaker, in accordance with the present invention; and

Figure 6 shows a perspective of the jaw contact for the plug-in type circuit breaker, in accordance with the present invention.

Detailed description of the embodiments 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 embodiments.

The present invention provides a jaw contact for plug-in type circuit breaker. The present invention involves an improved cut profile configured on a fixed contact of the jaw contact that provides a gap in the fixed contact. The gap facilitates optimization of the current path through the jaw fingers of the jaw contact. Hence, even distribution of current reduces the temperature rise at a breaker terminal.

The 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 3 and 5 to 6, a jaw contact (100) for plug-in type circuit breaker, in accordance with the present invention is shown. The jaw contact (100) is extensively used in panel boards and withdrawable circuit breakers to have an easily detachable electrical connection. The plug-in type circuit breaker includes a withdrawable unit including a moving part (130) and a fixed part (140). The withdrawable unit includes a breaker terminal (120) and a plug (110) configured in the moving part (130) thereof. The plug (110) is operably connected to the breaker terminal (120). The jaw contact (100) is assembled in the fixed part (140) thereof. The jaw contact (100) comprises of a plurality of jaw fingers (40), a fixed contact (80) and a draw-out terminal (90).

The plurality of jaw fingers (40) includes a top jaw finger (20), a plurality of middle jaw fingers (not numbered) and a bottom jaw finger (30). The plug (110) is operably connected to the plurality of jaw fingers (40), thereby establishing an easily detachable electrical connection of the jaw contact (100). In an embodiment, the plurality of jaw fingers (40) is spring loaded.

The fixed contact (80) (refer figure 2) is operably connected with the plurality of jaw fingers (40). The fixed contact (80) has a top end and a bottom end. In the embodiment, the top end of the fixed contact (80) is operably connected with the top jaw finger (20) and the bottom end of the fixed contact (80) is operably connected with the bottom jaw finger (30). The fixed contact (80) includes a cut profile (60) (refer figure 3) configured at the bottom end thereof. The draw-out terminal (90) is operably connected to the fixed contact (80) from one end and fixed to a main busbar from other end. A gap (50) (refer figures 2 and 3) is formed between the draw-out terminal (90) and the bottom end of the fixed contact (80) due to the cut profile (60) of the fixed contact (80).

Referring to figure 4, current distribution in a jaw contact (10) for a plug-in type circuit breaker, in accordance with the prior art is shown. When the jaw contacts were used in the conventional way, there was uneven distribution of current among the jaw fingers. As the current took least resistance path, there was difference in current carried by top jaw finger (20) and the bottom jaw finger (30). The concentration of current was more in the jaw fingers near the top jaw finger (20), which leads to uneven current distribution and higher current density at selective spots, leading to high temperature rise.
Referring to figure 5, the current distribution in the jaw contact (100) for the plug-in type circuit breaker, in accordance with the present invention is shown. Due to the gap (50), the distribution of current among the plurality of the jaw fingers (40) is optimized by forcing the current to flow in an optimal path through the plurality of jaw fingers (40). Hence, even current flows in the top jaw finger (20) and the bottom jaw finger (30) that means the current density in the top jaw finger (20) and the bottom jaw finger (30) is even. Thus, there is significant reduction in temperature rise at the breaker terminal (120) and the moving part (130) of the withdrawable unit of the plug-in type circuit breaker.

The present invention involves a novel embodiment to the plug-in the circuit breaker in to the cradle by means of a mechanism operated manually for purposes of maintenance, replacement and checks whenever needed or manually.

Advantages of the invention:

1. Due to gap (50) in the fixed contact (80), the current is forced to take the optimal path.
2. The top jaw finger (20) and the bottom jaw finger (30) carry even current.
3. Even distribution of the current in the jaw contact (100) reduces the temperature hotspots.
4. Watt loss is reduced without addition of copper.
5. By this construction, the jaw contact (100) can be used for high current applications without compromising on the thermal performance.
6. Optimal material consumption.

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.