Claims:We claim:

1. A draw-out circuit breaker (100) with improved plug-in contact assembly, the draw-out circuit breakers (100) comprising:
a cradle (10) having a draw out module (20) loaded therein;
a plurality of plug-in contacts (30) mounted on the draw out module (20);
a jaw contact assembly (40) connected to the main bus in a panel, the jaw contacts assembly (40) having a plurality of contact leafs (42) with cam profile, the plurality of contact leafs (42) held together by springs(44), wherein the plurality of contact leafs (42) form electrical connection when engaged with the plurality of plug in contacts (30),
characterized in that each plug of the plurality of plug-in contacts (30) has taper (32) on bottom face and entry chamfer (34) on both side thereof, wherein the taper (32) on the plug (30) reduces the insertion force/ plugging force and drastically reduces the operating force directly.

2. The draw-out circuit breaker (100) as claimed in claim 1, wherein the plug (30) comprises a tilt neutralizer (36) configured on top portion to have perfect fixing and reducing the tilt when the plug (30) is fixed or fastened to the circuit breaker.

3. The draw-out circuit breakers (100) as claimed in claim 1, wherein the taper (32) on bottom face and entry chamfer (34) on both sides of the each plug of the plurality of plugs (30) opens each contact leaf (42) of the jaw contacts (40) on either side one after one.

, Description:Field of the invention

The present invention relates to withdrawable circuit breakers, and more particularly, the present invention relates to a plug-in type circuit breaker operated manually for purposes of maintenance, replacement and checks whenever needed or manually.

Background of the invention

Withdrawable unit (Draw-out module) of a circuit breaker is an arrangement which is used to Connect, Test, Disconnect the circuit breaker or MCCB to the main bus without unbolting or disturbing the termination. With the help of mechanism, the MCCB is connected to main and auxiliary supplies. In draw-out module, the plug-in is used as base which is having main contacts. Two types of supplies are in the switchboard. One is main supply or power supply and auxiliary supply or control supply. The main supply is for breaker and auxiliary supply is for auxiliaries like shunt release, UV release, and the like.

Three positions are in the draw-out to show the operator where the MCCB is present. They are ‘DISCONNECTION’ (both Aux. connections and power connections not connected), ‘TEST’ (Aux. connections only connected but not power supply) ‘CONNECTION’ (both Aux. connections and power connections established). In the ‘TEST’ position, the auxiliaries are able to be tested alone. The MCCB should be in tripped position so that safety operation is possible during draw-out operation.

Specifically, the plug-in or cradle uses jaw type contacts which are spring loaded as shown in figure 2. The jaw type contact (140) which consists of number of leafs (142) as shown in figure 3 are stacked and may be fixed in unit horizontally or vertically. The basic circuit breaker converted to draw-out/plug-in circuit breaker by fixing the plug (130) and other necessary elements either at customer site or at factory base. The above said circuit breaker is ready to engage with main contacts. In order to engage the draw-out circuit breaker in to the cradle, the plugs (130) are usually provided with entry chamfers and cam profile on the leaf contact or vice versa where the plug opens the contact gradually. Here, the force is always normal to other plane, such that the plugging force or insertion force is optimized. The above methodology follows a wedge principle as shown figure 1 as it is universally followed.

However, the plug in type circuit breakers of prior art causes opening of all fingers of all contacts at given point of time. Further, there is reduced overlap of electrical contacts due to lower included angle of chamfer at plug or vice versa which lead to lower mechanical advantage. Also, there is inefficient material consumption in plug, leaf and jumping of breaker during rack-out by mechanism. Specifically, in the prior art system plugging force/insertion force is proportion with contact spring force which affects reliability of the system.

Accordingly, there exists a need to provide draw-out circuit breakers with improved plug-in contact assembly, which overcomes abovementioned drawbacks.

Objects of the invention

An object of the present is to provide a smooth ergonomical operation by reducing plugging force during draw-out breaker engagement with main contacts in cradle.

Another object of the present invention is to eliminate jumping of draw-out breaker during rack-out to improve system reliability.

Summary of the invention

Accordingly, the present invention provides draw-out circuit breakers with improved plug-in contact assembly. The draw-out circuit breaker comprises a cradle having a draw out module loaded therein. The draw-out circuit breaker further comprises a plurality of plug in contacts mounted on the draw out module and a jaw contact assembly connected to the main bus in a panel. The jaw contacts assembly comprises plurality of contact leafs with cam profile held together by springs. The plurality of contact leafs form electrical connection when engaged with the plurality of plug in contacts.

The draw-out circuit breaker is characterized in that each plug of the plurality of plug in contacts has taper on bottom face and entry chamfer on both sides thereof. The taper on the plug reduces the insertion force/ plugging force and drastically reduces the operating force directly.

Brief description of the drawings

Figure 1 shows a typical plug in contact engaging with a contact leaf of a jaw contact in accordance with wedge principle;

Figure 2 and 3 shows cross sectional and isometric view of the jaw contact assembly of the prior art;

Figure 4 shows a cradle of the draw out type circuit breaker assembly;

Figure 5 shows a draw out module of the circuit breaker;

Figure 6, 7 and 8 shows a plug-in contact assembly of the draw out module, in accordance with the present invention;

Figure 9 shows a plug-in contact for draw-out circuit breakers of the prior art;

Figure 10 and 11 shows opening of a contact leaf by the plug of the plug in contact assembly, in accordance with the present invention; and

Figure 12 shows a plug of the plug in contact assembly pushed out along with breaker due to contact spring force; and

Figure 13 shows draw-out circuit breaker with cradle having a draw out module loaded therein.

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 draw-out circuit breaker with improved plug-in contact assembly. The draw-out circuit breakers provides a smooth ergonomical operation by reducing plugging force during draw-out breaker engagement with main contacts in cradle. Further, the draw-out circuit breaker eliminates jumping of draw-out breaker during rack-out to improve system reliability.

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

Referring now to figures 6, 7, 8, 10, 11 and 12, , there is shown a draw-out circuit breakers (100) with improved plug-in contact assembly in accordance with the present invention.

The draw-out circuit breakers (100) comprises a cradle (10) having a draw out module (20) loaded therein.

The draw-out circuit breaker (100) further comprises a plurality of plug in contacts (30) mounted on the draw out module (20) and a jaw contact (main contacts) assembly (40) connected to the main bus in a panel. The jaw contacts assembly (40) comprises plurality of contact leafs (42) held together by springs (44). In an embodiment, the each leaf of the plurality of contact leafs (42) have cam profile. The plurality of contact leafs (42) form electrical connection when engaged with the plurality of plug (30) in contacts.

The draw-out module (20) is loaded in to cradle (10) shown in figure 4 to engage with main contacts or jaw contacts (40) which are connected to the main bus in the panel.

The draw-out module (20) is characterized in that each plug of the plurality of plug-in contacts (30) has taper (32) on bottom face and entry chamfer (34) on both sides thereof. The taper (32) on the plug (30) reduces the insertion force/plugging force and drastically reduces the operating force directly. To engage the draw-out module (20) effortlessly, the plug (30) is designed in such a way that the force required to open the jaw contacts (40) which are held together by contact spring (44) delivers necessary pressure on the plug (30) for better electrical performance. Although the primary requirement is the electrical performance, the mechanical performance is equally required to enrich the product

Specifically, the plug (30) of the present invention has variation on heights i.e. taper (32) on bottom face and entry chamfer (34) on both the side. The entry chamfer (34) or cam profile on the plug (30) depends on the cam profile on the contact leaf (42).

The taper (32) on the plug (30) further reduces the insertion force or plugging force very drastically up to 50% which reduces the operating force directly. The above is achieved by opening the each contact leaf (42) on either side one after one as shown in figure 10 and 11 which are held together by contact spring (44). The mechanical advantage gained by extending one contact spring (44) in one jaw contact assembly (40) and such six or eight jaw contact assembly is used in the cradle of three and four pole respectively considering one set of jaw contact assembly (40) on one side of one pole. There may be N jaw contact assembly in one side of a pole depending up on the electrical performance. The taper (32) on the plug (30) can be used for any arrangement of this type of assembly.

The plug (30) has a tilt neutralizer (36) configured on top portion as shown figure 8. The tilt neutralizer (36) is provided to have perfect fixing and reducing or eliminating the tilt when the plug (30) is fixed or fastened to the circuit breaker with one screw where the plug (30) is to be vertically or horizontally fixed. The tilt neutralizer (36) gets support from the breaker terminal to avoid tilt. The tilt neutralizer (36) along with one point screw fixing provides higher contact area which aides in improving electrical performance. Figure 9 shows the plug (130) of the prior art without tilt neutralizer and taper on bottom face.

Figure 10 and 11 shows a mechanism of insertion of plug in contact (30) in the jaw contact assembly (40). The plug (30) comes to contact first to any one of the contact leaf (42) as shown in figure 11, which act as a pivot able axis (A) as shown in figure 10. The inset figure of figure 10 shows how the plug (30) opens the contact leaf (42) one by one when it engages. The plug (30) of the present invention breaks the conventional idea of opening the all contact leafs (42) gradually at a time as shown in figure 11 which involves higher force for operation and limitations like space and force saturation

Further, the plug (30) while racking out or disengaging from the loaded contact leaf (42), the plug (30) gets pushed out by the contact spring (42) suddenly at an instant as the spring force is always against the plug (30) creating a positive joint with required pressure. This phenomenon occurs because the plug (30) is plugged out gradually due to change in the profile of the plug (30) i.e. the chamfer (34) provided on the sides as shown in figure 12. The present invention breaks the above paradigm by having the additional taper on bottom face (32) of the plug (30).

Advantages of the invention

1. The draw-out circuit breaker (100) with improved plug-in contact assembly provides smooth ergonomical operation by reducing plugging force during draw-out module engagement with main contacts in cradle.

2. The draw-out circuit breaker (100) with improved plug-in contact assembly eliminates jumping of draw- out module during rack-out to improve system reliability.

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.