DESC:TECHNICAL FIELD

The present invention relates generally to a circuit breaker and, particularly, to a contact system of circuit breaker which enables it to make, carry and break current under normal circuit condition and also break during abnormal conditions.

BACKGROUND

Circuit Breaker is a mechanical switching device capable of making, carrying and breaking currents. Under normal circuit conditions it will make the circuit, carry current for a specified time and break the circuit under specified abnormal circuit conditions.

Switching devices like, molded case circuit breaker 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.

Rotor construction enables the design of double break arrangement that helps in the better make & break under normal and abnormal conditions involving very high over-currents. The Switching device should interrupt the over current arising due to abnormal conditions in the network, as rapidly as possible to minimize damage caused by thermal and mechanical stresses to the equipment installed downstream.

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.

The rotor should have provisions for providing 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. Rotor should have the provisions for compensating for the erosion so as to maintain the contact pressure even after the erosion of buttons

Currently, all molded case circuit breaker have a rotor/drive shaft which rotates and switches the electrical circuit. The present technology for rotor construction uses an open rotor construction or partially closed construction. During short circuit, the moving contact in the rotor starts rotating due to the repulsion forces produced by electromagnetic interaction during short circuit. Simultaneously, an arc is produced between the fixed and moving contacts. For rotation of moving contact with respect to the rotor, there has to be an opening in the rotor with slot length depending on degree of rotation of moving contact. For erosion compensation, there is a slot on the moving contact aligned with the centre of the rotor thereby allowing the contact arm freedom of rotation to compensate for button erosion.

The prior-art document US Patent number 5310971 as shown in figure 1 discloses a molded case low voltage circuit breaker comprising a rotary contact bridge, a pair of stationary contacts cooperating with the contact bridge, current input conductors to the stationary contacts arranged to generate electrodynamics forces repelling the contact bridge to a repelled open position when a short-circuit occurs, a rotary bar having a transverse orifice housing with clearance the contact bridge which protrudes out from both sides of the bar, at least one pair of tension springs fitted between the bar and the contact bridge to provide a contact pressure of the contact bridge on the stationary contacts in closed position of the circuit breaker, while allowing rotation of the contact bridge to the repelled open position due to the electrodynamics forces.

The prior-art document US Patent number 6870112 as shown in figure 2 discloses a molded case low voltage circuit breaker. A low-voltage circuit breaker, comprising: a rotating contact supporting shaft, is provided with a seat that accommodates the central body of a moving contact so that the first arm protrudes externally from the seat, at least one first spring and one second spring being furthermore arranged in the contact supporting shaft and being suitable to ensure, when the circuit breaker is closed, an adequate contact pressure between the active surface and the fixed contact; the particularity of the circuit breaker consisting of the fact that a first pivot is fixed to the contact supporting shaft and is coupled to a hole formed in the central body, engagement means and at least one second pivot being furthermore arranged on the shaft on mutually opposite sides with respect to the first pivot, the second pivot being movable with respect to the shaft and to the moving contact, the first and second springs being furthermore anchored to the second pivot and to the engagement means and being arranged along two opposite sides of the arm of the moving contact, the second pivot interacting functionally with the first cam-like surface so as to generate a mechanical moment that matches the direction of rotation of the moving contact during at least one portion of the step for separation of the active surface from the fixed contact in a short-circuit condition.

The prior-art document US Patent number 6262642 as shown in figure 3 discloses a molded case low voltage circuit breaker. A rotary contact arrangement for circuit breakers of the type including a pair of contact springs arranged on each side of a rotary contact arm, as the contact springs interconnect between the rotors and the contact arm via a pair of U-shaped levers. The provision of the U-shaped levers provides uniform contact pressure between both pairs of fixed and moveable contacts to prevent contact erosion.

The prior-art document US Patent number 6965292 as shown in figure 4 discloses a molded case low voltage circuit breaker. An electrically isolated rotor assembly for a cassette assembly of a circuit breaker includes a rotor having a first side and an opposing second side, a first isolation cap disposed on the first side, a second isolation cap disposed on the second side. Each isolation cap preferably includes a centrally located knob with a bushing surrounding each knob, wherein the bushings are sized for securement within apertures within first and second cassette half pieces.

Apart from the above mentioned problems, there are many other drawbacks in the existing prior-art, few of them are mentioned below:

1. During arcing hot gases and arc products are produced which can enter inside the rotor damaging the components like springs and pins inside the rotor.
2. An open construction leads to lesser differential pressure on arc, i.e. the pressure difference between the front and rear of arc will be lesser. Increased differential pressure is required for efficient driving of arc into the extinguishing zone.
3. An open rotor construction increases the chance of standing arc because of lesser insulation between the contacts.
4. Slot on the moving contact causes increase in the current density and leads to unnecessary temperature rise.
5. There is no flipping action of moving contact with respect to shaft so that chances of high let through energy.

In the view of above mentioned drawbacks and limitations, there is need to provide an improved and efficient mechanism to enhance the working of the existing circuit breakers and enables it to make, carry and break current under normal circuit condition and also break during abnormal conditions.

SUMMARY

This summary is provided to introduce concepts related to an improved double-break circuit breaker rotor construction for current breaking in circuit breakers. This summary is not intended to identify essential features of the claimed subject matter nor is it intended for use in determining or limiting the scope of the claimed subject matter.

In one implementation, an enclosed single rotor construction and the related components are disclosed. The disclosed constructions are secluded from damage and the contact pressure is ensured in normal and abnormal conditions.

In one implementation, the closed construction disclosed, gives higher differential pressure on arc, i.e. the pressure difference between the front and rear of arc will be higher which gives efficient driving of arc into the extinguishing zone.

In one implementation, the disclosed closed construction gives better insulation between contacts so there are less chances of standing arc.

In one implementation, the proposed invention gives provision for erosion compensation in the rotor cover, current density on the moving contact is reduced and the temperature rise is kept under control.

In one implementation, the flipping action of moving contact is provided so it helps to reduce high let through energy.

Accordingly, in one implementation, an improved contact system for a circuit breaker is disclosed. The improved contact system comprises of a rotor (1) with at least one moving contact (2); at least two rotor covers (3a, 3b); at least one spring assembled in a spring holders (5); wherein when said moving contact (2) moves to a repelled position, an arcing happens and arc products and hot gases are produced; and said at least one moving contact (2) comprises at least one cover (17) that isolates a spring chamber from an arcing zone.

BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS

The detailed description is described with reference to the accompanying figures. In the figures, the left-most digit(s) of a reference number identifies the figure in which the reference number first appears. The same numbers are used throughout the drawings to refer like features and components.

Figure 1 illustrates a prior-art from US Patent No: 5310971.

Figure 2 illustrates a prior-art from US Patent No: 6870112.

Figure 3 illustrates a prior-art from US Patent No: 6262642.

Figure 4 illustrates a prior-art from US Patent No: 6965292.

Figure 5 illustrates a basic view of the circuit breaker pole in ON condition, is shown, in accordance with an embodiment of the present subject matter.

Figure 6 illustrates a basic view of the circuit breaker pole in which moving contact is in repelled condition is shown, in accordance with an embodiment of the present subject matter.

Figure 7 illustrates an isometric view of the pole rotor is shown, in accordance with an embodiment of the present subject matter.

Figure 8 illustrates an isometric view of rotor and rotor cap is shown, in accordance with an embodiment of the present subject matter.

Figure 9 illustrates an isometric view of assembly steps of rotor and caps are shown, in accordance with an embodiment of the present subject matter.

Figure 9 (a) illustrates a 1st step of assembling rotor caps with shaft

Figure 9 (b) illustrates a 2nd step of assembling rotor caps with shaft, is shown, in accordance with an embodiment of the present subject matter.

Figure 9 (c) illustrates a trapping feature of rotor which prevents shaft cap rotation with respect to shaft, is shown, in accordance with an embodiment of the present subject matter.

Figure 9 (d) illustrates a cross section view of rotor assembly which shows ribs and slot alignment, is shown, in accordance with an embodiment of the present subject matter.

Figure 9 (e) illustrates an assembly of moving contact is shown, in accordance with an embodiment of the present subject matter.
DETAILED DESCRIPTION

Preferred embodiments of the present disclosure will be described herein below with reference to the accompanying drawings. In the following description, well-known functions or constructions are not described in detail to avoid obscuring the present disclosure in unnecessary detail.

The terms and words used in the following description 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.

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

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.

In one implementation, the present invention is related to an improved double-break circuit breaker rotor construction for current breaking in circuit breakers

In one implementation, the present invention relates to a circuit breaker. More particularly, the invention is concerned about a contact system of circuit breaker which enables it to make, carry and break current under normal circuit condition and also break during abnormal conditions.

In one implementation, an improved contact system for a circuit breaker is disclosed. The improved contact system comprises of a rotor (1) with at least one moving contact (2); at least two rotor covers (3a, 3b); at least one spring assembled in a spring holders (5); wherein when said moving contact (2) moves to a repelled position, an arcing happens and arc products and hot gases are produced; and said at least one moving contact (2) comprises at least one cover (17) that isolates a spring chamber from an arcing zone.

In one implementation, a location of said at least one moving contact (2) is secured through insertion of a central anchor pin (7) through a hole (6) on said at least one moving contact (2) aligned with the centre of the rotor thereby allowing said at least one moving contact (2) freedom of rotation within a predetermined locus about said central anchor pin (7).

In one implementation, said rotor comprises of a separation wall (4) to isolate at least one spring from a slot (8) where at least one moving contact (2) rotates and is visible to arcing, hot gases and arc products; at least one hole (9) is provided to give a provision of coupling with at least one adjacent poles using said central anchor pin (7); at least one rib (13) is provided into said at least two rotor covers (3a, 3b) to couple with said rotor (1) by inserting said at least one rib (13) into at least one slots 12 provided in said moving contact (2); and at least one stopper (15) is provided to define a final position of said at least two rotor covers (3a, 3b) with respect to said rotor (1).

In one implementation, said at least two rotor covers (3a, 3b) are assembled into said rotor (1) by inserting said at least one rib (13) into said at least one slots (12) thereby rotating in a given direction so that at least one rib (13) aligns with said at least one slots (12), wherein during rotation, a feature (14) gets trapped in a slot (11) and prevents the circular motion of said at least two rotor covers (3a, 3b) with respect to said rotor (1).

In one implementation, said at least one moving contact (2) consists of at least two buttons (16) which makes contact with a respective fixed contact buttons.

In one implementation, said at least two rotor covers (3a, 3b) consists of at least one hole (20) that enables a passage of through pins for coupling of said rotor (8).

In one implementation, a projection (21) to accommodate an oblong slot (24) that enables a movement of said central anchor pin (7) and thereby a movement of said at least one moving contact (2) for compensating for erosion.

In one implementation, a feature (22) to measure an over travel of said rotor (1) with respect to a cassette.

In one implementation, the figure 5 shows diagram of a new MCCB contact system in ON condition. The current conduction happens through the fixed contact onto the moving contact and again to the second fixed contact. In this condition contact pressure is provided by the springs assembled into the shaft.

As shown in the figure 6 the 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.

Referring now to figure 7, a rotor or shaft (1), which carries a minimum of one contact arm (2), alternately called a moving member or moving contact, which forms the rotary actuating structure, is shown. The rotor covers (3a) and (3b) gives the rotor a closed assembly. The springs that provide the contact pressure are assembled in the spring holders (5). While the moving contact (2) moves to the repelled position, arcing happens as a result of which arc products and hot gases are produced. The moving contact covers (17) shown in figure 9 (e) provides insulation for moving contact (2) from it. The rotor covers (17) shown in figure 9 (e) isolates the spring chamber from the arcing zone. 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 a hole (6) on the moving contact aligned with the centre of the rotor there by allowing the contact arm (2) freedom of rotation within a predetermined locus about the said central anchor pin (7).

Referring to figure 8, the rotor (1) construction includes a separation wall (4) to isolate the springs from the slot (8) where moving contact (2) rotates and is visible to arcing, hot gases and arc products. Holes (9) are provided to give the provision of coupling with the adjacent poles using a through pin. The ribs (13) are provided into the shaft caps (3a) and (3b) to arrest shaft caps with rotor by inserting ribs (13) into slots (12) provided in shaft (2). The stoppers (15) shown are provided to define the final position of the rotor covers with respect to the rotor.

As shown in figure 9 (a) the rotor covers (3a) and (3b) are assembled into the rotor by inserting the ribs (13) (shown in figure 8) into the slots (12) (shown in figure 8). The rotor covers are then rotated as shown in figure 9 (b) in given direction so that the ribs (13) align with the slots (10) (shown in figure 4). The alignment of ribs (13) and slots (10) is shown in figure 9 (d).

While rotating the rotor covers, the feature 14 (shown in figure 8) gets trapped in the slot 11 (shown in figure 8) as shown in figure 9 (c) and prevents the circular motion of cover with respect to the rotor. The features 15 (as shown in figure 8) to the rotor also helps to achieve poka-yoke so that rotor covers (3a) and (3b) does not get interchanged.

As shown in figure 9 (c) the moving contact (2) consists of two buttons (16) which makes contact with the respective fixed contact buttons. The holes (19) accommodate the pins to support the spring holders (5). An opening is necessary in the rotor to enable the connection of moving contact with the springs. The moving contact covers (17) ensure the insulation of spring chamber by closing the opening in the rotor.

Referring to figure 10, the rotor cover design consists of holes (20) to enable the passage of through pins for coupling of rotors. The projection (21) is given to accommodate the oblong slot (24) that enables the movement of center pin and thereby the movement of moving contact for compensating for erosion. It also provides the centering of rotor assembly with respect to the cassette. Diameter of feature (21) is varied in rotor cover (3a) and (3b) which ensures proper assembly of rotor assembly in the pole. The feature (22) is given to measure over travel of rotor with respect to cassette.

In one implementation, the enclosed single rotor construction, the components are secluded from damage and the contact pressure is ensured in normal and abnormal conditions. The proposed invention helps to achieve differential pressure on arc, i.e. the pressure difference between the front and rear of arc will be higher which gives efficient driving of arc into the extinguishing zone. Further, the closed construction gives better insulation between contacts so there are less chances of standing arc. Furthermore, by giving provision for erosion compensation in the rotor cover, current density on the moving contact is reduced and that helps to keep temperature rise under control. The proposed construction helps to reduce high let through energy by flipping action of moving contact with respect to shaft. The proposed construction provides an easy of assembly.

Exemplary embodiments discussed above may provide certain advantages. Though not required to practice aspects of the disclosure, these advantages may include those provided by the following features:

One feature for the invention is that, the proposed invention discloses the enclosed single rotor construction, so that the components are secluded from damage and the contact pressure is ensured in normal and abnormal conditions.

Another feature of the invention is that, the closed construction proposed in the invention gives higher differential pressure on arc, i.e. the pressure difference between the front and rear of arc will be higher which gives efficient driving of arc into the extinguishing zone. Further, the closed construction gives better insulation between contacts so there are less chances of standing arc.

Another feature of the invention is that, by giving provision for erosion compensation in the rotor cover, in the proposed invention, the current density on the moving contact is reduced and the temperature rise is kept under control.

Yet another feature of the invention is that, the flipping action of moving contact is provided so it helps to reduce high let through energy.

Still another feature of the invention is that, the rotor cap construction provide in the proposed invention, helps for easy assembly of rotor caps with rotor, gives poka-yoke for rotor and pole assembly.

Although an improved double-break circuit breaker rotor construction for current breaking in circuit breakers has been described in language specific to structural features and/or methods, it is to be understood that the embodiments disclosed in the above section are not necessarily limited to the specific features or methods or devices described. Rather, the specific features are disclosed as examples of an improved double-break circuit breaker rotor construction for current breaking in circuit breakers.
,CLAIMS:1. An improved contact system for a circuit breaker, said system comprising:
a rotor (1) with at least one moving contact (2);
at least two rotor covers (3a, 3b);
at least one spring assembled in a spring holders (5); wherein
when said moving contact (2) moves to a repelled position, an arcing happens and arc products and hot gases are produced; and
said at least one moving contact (2) comprises at least one cover (17) that isolates a spring chamber from an arcing zone.

2. The improved contact system as claimed in claim 1, wherein a location of said at least one moving contact (2) is secured through insertion of a central anchor pin (7) through a hole (6) on said at least one moving contact (2) aligned with the centre of the rotor thereby allowing said at least one moving contact (2) freedom of rotation within a predetermined locus about said central anchor pin (7).

3. The improved contact system as claimed in claims 1 and 2, wherein said rotor comprises:
a separation wall (4) to isolate at least one spring from a slot (8) where at least one moving contact (2) rotates and is visible to arcing, hot gases and arc products;
at least one hole (9) is provided to give a provision of coupling with at least one adjacent poles using said central anchor pin (7);
at least one rib (13) is provided into said at least two rotor covers (3a, 3b) to couple with said rotor (1) by inserting said at least one rib (13) into at least one slots 12 provided in said moving contact (2); and
at least one stopper (15) is provided to define a final position of said at least two rotor covers (3a, 3b) with respect to said rotor (1).

4. The improved contact system as claimed in claims 1-3, wherein said at least two rotor covers (3a, 3b) are assembled into said rotor (1) by inserting said at least one rib (13) into said at least one slots (12) thereby rotating in a given direction so that at least one rib (13) aligns with said at least one slots (12), wherein during rotation, a feature (14) gets trapped in a slot (11) and prevents the circular motion of said at least two rotor covers (3a, 3b) with respect to said rotor (1).

5. The improved contact system as claimed in claims 1-4, wherein said at least one moving contact (2) consists of at least two buttons (16) which makes contact with a respective fixed contact buttons.

6. The improved contact system as claimed in claims 1-5, wherein said at least two rotor covers (3a, 3b) consists of at least one hole (20) that enables a passage of through pins for coupling of said rotor (8).

7. The improved contact system as claimed in claims 1-6 comprises a projection (21) to accommodate an oblong slot (24) that enables a movement of said central anchor pin (7) and thereby a movement of said at least one moving contact (2) for compensating for erosion.

8. The improved contact system as claimed in claims 1-7 comprises a feature (22) to measure an over travel of said rotor (1) with respect to a cassette.