Claims:We claim:

1. An arc chute arrangement for a circuit breaker with at least one pole contact system, the one pole contact system having a fixed electrical contact, a moving electrical contact, an electrical flexible conductor, a flexible conductor fixing block connecting the moving electrical contact to the terminal contact, the arc chute arrangement comprising:
a first wall and a second wall; and
a plurality of arc plates supported in-between the first wall and the second wall, a top arc plate of the plurality of arc plates having length 1.5 times greater than other arc plates of the plurality of arc plates, the top arc plate having,
a flat portion covering half length of the movable electrical contact along the direction of the fixed electrical contactduring OFF condition, and
a limb configured perpendicular to the flat portion, the limb being bent on either side,
wherein the top arc plate performs dual function of pulling the arc away from the contacts and act as slot motor for increasing the velocity of the movable electrical contact.

2. The arc chute arrangement as claimed in claim 1, wherein the top arc plate is made of ferromagnetic material.

, Description:Field of the invention

The present invention relates to electric switchgears, and more particularly, the present invention relates to an arc chute arrangement for circuit breaker.

Background of the invention

Switchgears are used for protection of electric network/circuit and equipment. A switchgear consist of a outer enclosure made of insulating material in which switching (make/break) takes place, a current path which is connected to the main supply line and makes/breaks electric supply, a mechanism which may be a combination of a number of mechanical links and springs or may be any arrangement which stores energy and releases in mechanical form when required. The current path/conductor of circuit breakers is made of highly electric conductive materials to reduce the losses. The current path has a fixed contact and a moving contact which moves to make/break (close/open) the circuit. Due to the breaking of circuit, an arc generates because of voltage gradient between the fixed and the moving contacts. This generated arc erodes the fixed and the moving contacts and the enclosure which causes reduced operational life of the switchgears. Most of the switchgears use repulsion type of construction in which a repulsion force generates between the fixed and the moving contact because of the direction of flow of electric current.

Specifically, European Patent EP 1956624B1 discloses a slot motor housing and circuit interrupter including the same. The patent talks about an arrangement having a ferromagnetic material in the form of strips of U-shape, and another piece of slot motor formed with linear strips which are placed in some two molded material housings. . The final effect is achieved by combining the two pieces of strips together.

Another US patent 6831536 discloses a circuit breaker slot motor having a stepped out portion. This patent talks about an arrangement of slot motor in which a different shape of housing to hold ferromagnetic material strips used. The design has narrow and wide paths. The wide path locks near the fix contact to form loop.

However, the circuit breakers with improved slot motors described in the present invention are for withstand type of circuit breaker and for higher current withstand high contact pressure/torque is required.

Further, if high contact torque or contact pressure is used, the movable contact speed during breaking reduces which leads to high let through energy during fault. Furthermore, if the speed of movable contact increased by any suitable means in the prior art patents, it reduces the magnetic repulsion threshold of the movable contacts and thus withstand capability of the circuit breaker.

Accordingly, there exists a need to provide anarc chute arrangement in the circuit breaker with increased movable contact velocity and arc puller for increasing arc-lengthening and faster arc-quenching.

Objects of the invention

An object of the present invention is to increase movable contact velocity.

Another object of the present invention is to increase arc-lengthening and faster arc-quenching.

Yet another object of the present invention is to provide a robust arc chute assembly which can enhance the breaking capacity of the circuit breaker by opening the movable contact fast without affecting the magnetic repulsion threshold of themovable contact and with reduced no of component and cost.

Summary of the invention

Accordingly, the present invention provides an arc chute arrangement for a circuit breaker with at least one pole contact system. The arc chute arrangement comprises a first wall and a second wall. The arc chute arrangement further comprises a plurality of arc plates supported in-between the first wall and the second wall. Specifically, a top arc plate of the plurality of arc plates has length 1.5 times greater than other arc plates of the plurality of arc plates. The top arc plate includes a flat portion covering half length of the movable electrical contact along the direction of the fixed electrical contact during OFF condition, and limb configured perpendicular to the flat portion. Specifically, the limb is bent on either side. Wherein, the top arc plate performs dual function of pulling the arc away from the contacts and act as a slot motor for increasing the velocity of the movable electrical contact.

Brief description of the drawings

Figure 1 shows an isometric view of one pole contact system of a circuit breaker in ‘ON’ condition;

Figure2 shows an isometric view of one pole contact system of a circuit breaker in ‘OFF’ condition;
Figure 3 shows an isometric view of an arc chute arrangement in accordance with the present invention; and

Figure 4 shows an isometric view of a top arc plate of the plurality of arc pates of the arc chute arrangement of figure 3.

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 arc-chute arrangement for circuit breaker which uses a ferromagnetic arc-plate performing dual function of slot motor for increasing movable contact velocity and arc puller for increasing the arc-lengthening and faster arc-quenching. This arrangement provides better performance with comparatively less cost addition.

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

Referring to figure 1, there is shown an isometric view of one pole contact system (100) of a circuit breaker in ON condition. The contact system (100) includes a fixed electrical contact (10), a moving electrical contact (12), an electrical flexible conductor (14), a flexible conductor fixing block (16) connecting the moving electrical contact (12) to a terminal contact (18) and vice versa.Figure2 shows an isometric view of one pole contact system (100) of a circuit breaker in ‘OFF’ condition.

Referring now to figure 3, there is shown an arc chute arrangement (50) of one pole contact system (100) of a circuit breaker for interruption of circuit during high current faults, in accordance with the present invention. Though the arc chute arrangement (50) is described for one pole contact system, it is evident to those skilled in the art that the arc chute arrangement (50) can be used for multipole contact system.

The arc chute arrangement (50) comprises a first wall (22) and a second wall (24). The arc chute arrangement (50) further comprises plurality of arc plates (26) supported and fixed in-between the first wall (22) and the second wall (24). In an embodiment, the first wall (22) and the second wall (24) are made of insulating material.

In preferred embodiment, a top arc plate (26a) of the plurality of arc plates (26) has a length 1.5 times greater than other arc plates of the plurality of arc plates (26).

Specifically, the top arc plate (26a) comprises a flat portion (26b) covering half length of the movable electrical contact (12) along the direction of the fixed electrical contact (10) during OFF condition. The top arc plate (26a) further includes a limb (26c) configured perpendicular to the flat portion (26b). The limb (26c) is bent on either side. In an embodiment, the flat portion (26b) and the limb (26c) are constructed as a single unit. Specifically, both sides of the limb (26c) are bent towards one direction i.e. towards the movable electrical contact (12).

The top arc plate (26a) performs dual function of pulling the arc away from the contacts (10, 12) and act as slot motor for increasing the velocity of the movable electrical contact (12).The top arc plate(26a) augments magnetic field and flux linking the movable electrical contact (12). The top arc plate (26a) increases the velocity of movable contact (12), leading to faster quenching of faults thus reduces the stresses on the overall system. In an embodiment, the top arc plate (26) is made of ferromagnetic material.

The arrangement of the top arc plate (26a) enables the moving electrical contact (12) opens up rapidly as fault current crosses the threshold value and forces the arc quickly in the intended direction away from the contacts (10, 12) into the plurality of arc plates (26). This reduceserosion of the fixed electrical contact (10) and the moving electrical contacts (12), reduces the stresses on primary chamber (outer housing) of the circuit breaker and thus improves safety of downstream equipment’s and increased life of switchgear devices.

Specifically, the arc chute assembly (100) of the present invention increases the velocity of movable contact (12) drastically after a certain angle of opening. The effect of that arrangement on the movable contact (12) in ‘on’ condition of circuit breaker is negligible so it does not affect the repulsion threshold. At the same time the arc chute assembly (100) forms a confined chamber for arcing thus improving arc quenching.

Advantages of the invention

1. The arc chute arrangement (100) of the present invention can be used for switchgears having any number of poles/phases.
2. The arc chute arrangement (100) can be used for switchgears having n- number of current break system or multiple moving contact system.
3. The arc chute arrangement (100) is hardware free and adhesive free fixing of arrangement.
4. The arc chute arrangement (100) doesn’t require any secondary process to make it with any switchgear thus reduced cost and assembly time.
5. The ferromagnetic material of any shape, size and form like strips, solid etc. can be used in this arrangement for reduced losses and improved performance.
6. The arc chute arrangement (100) does not sacrifices repulsion threshold of the contact system.
7. The arc chute arrangement (100) help fast opening of the movable contact.
8. The arc chute arrangement (100) requires less number of components and assembly is robust.

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.