DESC:Arc Runner Assembly for Circuit Breaker

Field of the invention

The present invention relates to circuit breakers and switching devices, and more particularly to an improved arc runner assembly for circuit breakers for better arc running.

Background of the invention

Opening of a live contact in an electrical circuit results in the development of an electric arc. The contacts of the circuit breaker experience the same during its opening i.e. an arc is formed between the contacts when they separate while interrupting current. The technology used in switchgears for arc quenching makes use of an arc quenching chamber for lengthening and splitting of arc. The faster the arc is quenched the better is the electrical life of the breaker. An arc chute assembly is designed with specific intention for efficient and quick arc quenching.

In order to further improve the arc quenching performance, the arcing chamber comprises a component called as an arc runner. This component facilitates arc running and hence increases the length of the arc. This results in a greater arc voltage development. The aim is to build up the arc voltage and make it greater than the supply voltage and hence create an artificial current zero. The arc runner facilitates this process. Other advantages of the arc runner are reduced time for which the arc stays on the contacts, better arc root transfer from contact surface to arc runner and hence reduced erosion of contact material. Therefore the electrical life of the breaker can also be enhanced.

In one design of the arc runner available currently, the design makes use of a process of bending of a single sheet for obtaining the optimum arc runner angle. The disadvantage of this technology is that the movement of the arc root from the contact surface to the arc runner is not smooth and efficient due to constructional limitations. In case of bending a single runner component, to achieve the required angle for best arc running, a certain radius is unavoidable. Thus, an air gap is introduced on the path of arc root travel from the contact surface to the arc runner. This leads to a comparatively greater time for which the arc stays on the contacts and hence results in heavy erosion of contact material. This causes a higher arcing time and results in inefficient arc quenching. Also due to this, the electrical life of the circuit breaker reduces.

Due to arc root staying on the contact for a longer time, the arc and associated arc cloud and gases stays in the vicinity of the contact gap for longer time. Thus, maximum ionization of the gases occurs in and around contact gap area. So in case of flat deion plate arc chute, where the arc lets experience upward and downward Lorentz force due to the current path on, along and between the deion plates, the greater chance of sustained arc or standing arc can be possible due to high ionized contact gap area. Also due to higher ionization of the gases in the contact gap area, there is comparatively high chances of restrike as the contact gap area needs longer time to regain its dielectric strength of the medium due to highly ionized gases in the surrounding.

Another arc runner design as depicted in US Patent No. 5969314, the contact itself is used as the arc runner (with an extruded or machined profile). In this case, the contact terminal and the arc runner form a single component. This involves greater cost for production due to the various material and mechanical processes involved to achieve a certain shape and the single component feature. Also, another limitation of this design is that the runner material has to be similar to that of the terminal material. As a result of this, cost and performance in the long run is compromised.

Proper transition of the arc root from the contact surface to the arc runner also depends on the arc runner angle along with many other parameters. So, an optimum runner angle and runner length is required to quench an arc efficiently for certain arc chamber geometry and fault level.

Accordingly, there exists a need to provide an arc runner assembly for switching devices/circuit breakers, which overcomes above mentioned drawbacks of the prior art.

Objects of the invention

An object of the present invention is to provide a low cost arc runner with no air gap.

Another object of the present invention is to provide the arc runner with smooth and fast transition of an arc root from a contact surface to the arc runner.

Yet another object of the present invention is to provide the arc runner with enhanced pull force.

Still another object of the present invention is to provide the arc runner with better arc running, improved lengthening of the arc and greater arc voltage development.

Summary of the invention

Accordingly, the present invention provides an arc runner assembly for a circuit breaker. The arc runner assembly along with an arc chute assembly is positioned inside an arc chamber. The arc chute assembly is positioned above a fixed contact within the circuit breaker. The arc chute assembly includes a plurality of flat deion plates positioned vertically above the fixed contact and a movable contact of the circuit breaker for splitting and extinguishing an electrical arc triggered by breaking of current.

The arc runner assembly comprises a flat plate and a profile plate. The flat plate and the profile plate are made up of a material selected from any one of a mild steel sheet material, a low carbon steel sheet material and a weldable ferromagnetic material. The flat plate and the profile plate are coated with any one of zinc, chromium, aluminum and copper plating and any appropriate material for better arc running and quenching performance.

The flat plate includes a first cut portion, a first chamfered surface and at least two holes configured thereon. The at least two holes are adapted for mounting the flat plate on a top surface of the fixed contact.

The profile plate includes a second cut portion, an angled portion, a second chamfered surface and a vertical portion. The second cut portion is adapted for aligning with the first cut portion. The angled portion is adapted for lengthening of the arc running thereon. The second chamfered surface is adapted for horizontal positioning or parallel alignment with the flat plate. The vertical portion is adapted for guiding the arc into the plurality of deion plates for arc splitting and also for mounting of the arc runner assembly. The profile plate is with mounting hole or without mounting holes. The profile plate includes a sharp edge B for effective transition of an arc root to an arc running surface of the arc runner from a contact surface of the arcing contact of the fixed contact.

The profile plate is adapted for joining to the flat plate thereby forming the arc runner assembly. The profile plate is welded lengthwise opposite to the arc root running surface along the first chamfered surface of the flat plate such that the cut portions align with each other to form a welded no air gap arc runner assembly that when positioned above the fixed contact eliminates a need of bending to achieve a required arc runner angle (a) and thus eliminates an air gap from an arc root travel path from a contact surface to arc runner thereby achieving a smooth and rapid transition/running of the arc root from the contact surface of the arcing contact on the fixed contact to the arc root running surface of the profile plate.
The angle of the chamfering on the flat plate and the profile plate is decided by the arc runner angle. The first chamfered surface of the flat plate has a chamfer angle selected from a range between 45 to 60 degrees and is equal to the arc runner angle. The second chamfered surface of the profile plate has a chamfer angle selected from a range between 45 to 60 degrees and is equal to the arc runner angle. The profile plate has a bending/ construction angle of 90+a to have the angled portion, wherein a is the arc runner angle selected from a range between 45 to 60 degrees.

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 arc runner assembly for a circuit breaker, in accordance with the present invention;

Figure 2 shows various views of a flat plate of the arc runner assembly of figure 1;

Figure 3 shows various views of a profile plate of the arc runner assembly of figure 1;

Figure 4 and 5a show the arc runner assembly mounted on a fixed contact of the circuit breaker, in accordance with an embodiment of the present invention;

Figure 5b shows the arc runner, in accordance with another embodiment of the present invention;

Figure 6 shows different views of an arc chute assembly, in accordance with the present invention; and

Figures 7 – 8b show configuration of the arc runner assembly of figure 1 within the circuit breaker.

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 runner assembly for a circuit breaker. The arc runner assembly helps in better arc running and improved lengthening of the arc; hence the arc voltage developed is much higher. This helps in creation of artificial current zero and helps in efficient and quicker arc quenching performance. The arc runner assembly reduces time for which the arc stays on the contacts and results in better arc root transfer from a contact surface to the arc runner. Hence, the erosion of contact material is reduced drastically, thereby improving the electrical life of the switchgear device. Further, due to very smooth and fast movement of the arc root from the contact surface to the arc runner in case of no air gap welded arc runner, the gases and surrounding medium in the vicinity of the contact gap area gets less ionization time, hence gets less ionized, so the possibility of sustained arc or standing arc or restrike is less in this case.

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 1-8b, an arc runner assembly (60) for a circuit breaker/switching device (not numbered), in accordance with the present invention is shown. The arc runner assembly (60) along with an arc chute assembly (not numbered) is positioned inside an arc chamber (100) within the circuit breaker as shown in figures 6-8b. The arc chute assembly is positioned above a fixed contact (110) of the circuit breaker. The arc chute assembly includes a plurality of flat deion plates (30) positioned vertically above the fixed contact (110) and a movable contact (120) of the circuit breaker and above the arc runner assembly (60). The plurality of flat deion plates (30) is adapted for splitting and extinguishing an electrical arc triggered by breaking of current. The breaking of current is achieved through separation of a pair of arcing contacts (10) after the separation of a pair of main contacts (20). The arc runner assembly (60) is made up of materials different than those used for the contacts.

In case of fault clearing or breaking of current, when the pair of arcing contacts (10) gets separated, an arc forms in between the pair of arcing contacts (10). Due to magnetic force in the upward direction, the arc enters into a running phase from an immobility phase and one arc root moves from the arcing contact (10) of the fixed contact (110) to the arc runner assembly (60) and enters into the arc chute assembly after the running phase. Then due to lengthening of arc and splitting of arc, arc voltage gets developed and also due to cooling of arc, arc gets extinguished finally in the arc chute assembly.

The arc runner assembly (60) comprises a flat plate (40) and a profile plate (50). The flat plate (40) and the profile plate (50) of the arc runner assembly (60) are made up of a material selected from any one of a mild steel sheet material, a low carbon steel sheet material and a weldable ferromagnetic material so as to achieve a better magnetic pull on the arc root, that helps to reduce the time for which arc root stays on the contacts thus reducing contact erosion than copper or any other non ferromagnetic arc runner of the prior art. Further, the flat plate (40) and the profile plate (50) are coated with any one of zinc, chromium, aluminum and copper plating and any appropriate material for better arc running and quenching performance.

The flat plate (40) is positioned on the fixed contact (110). The flat plate (40) includes a first cut portion (32), a first chamfered surface (34) and at least two holes (36) configured thereon. The at least two holes (36) are adapted for mounting the flat plate (40) on the fixed contact (110). The first chamfered surface (34) is adapted for supporting and fixing the positioning of the profile plate (50) to achieve a no air gap feature (A) of the arc runner assembly (60).

The profile plate (50) is adapted for guiding the arc while in the running phase. The profile plate (50) includes a second cut portion (42), an angled portion (44), a second chamfered surface (48) and a vertical portion (46). The second cut portion (42) is adapted for aligning with the first cut portion (32). The angled portion (44) is adapted for lengthening of the arc running thereon. The second chamfered surface (48) is adapted for horizontal positioning or parallel alignment with the flat plate (40). The vertical portion (46) is adapted for guiding the arc into the plurality of deion plates (30) for arc splitting and also for mounting of the arc runner assembly (60). The profile plate (50) is with mounting hole (not numbered) or without mounting holes. The profile plate (50) includes a sharp edge (B) for effective transition of an arc root to an arc running surface (52) thereof from a contact surface (not shown) of the arcing contact (10) of the fixed contact (110).

The profile plate (50) is adapted for joining to the flat plate (40) thereby forming the arc runner assembly (60). In an embodiment, the flat plate (40) and the profile plate (50) are joined together to form the complete arc runner assembly (60) by means of a cost effective welding process. Specifically, an inside surface (54) of the profile plate (50) is welded lengthwise to be opposite to the arc travel path and the arc root running surface (52) along the first chamfered surface (34) of the flat plate (40) such that the cut portions (32, 42) align with each other to form a welded no air gap arc runner assembly (60). The welded arc runner assembly (60) when positioned above the fixed contact (110) eliminates a need of bending to achieve a required arc runner angle (a) and thus eliminates an air gap from an arc root travel path (refer figure 4) thereby achieving a smooth and rapid transition/running of the arc root from the contact surface of the arcing contact (10) on the fixed contact (110) to the arc root running surface (52) of the profile plate (50). This leads to reduced time for which arc stays on the contacts and thus low contact erosion which in turn increases the breaker’s electrical life.

Based on the arc runner angle (a), the angle of chamfering on the flat plate (40) and the profile plate (50) is decided. The first chamfered surface (34) of the flat plate (40) has a chamfer angle (a) selected from a range between 45 to 60 degrees and is equal to the arc runner angle (a). The second chamfered surface (48) of the profile plate (50) has a chamfer angle (a) selected from a range between 45 to 60 degrees and is equal to the arc runner angle (a). The profile plate (50) has a bending/ construction angle of 90+a to have the angled portion (44), wherein a is the arc runner angle selected from a range between 45 to 60 degrees.

As per study and test results, optimum runner angle range varies between 45 and 60 degrees. The lengthening time is found to be very high when the runner angle is outside the range mentioned above. Narrow angles (close to 45 degrees) increase the lengthening zone, whereas wider angles (close to 75 degrees) increase the frequency of both back-strikes and immobile arcs. By virtue of the design concept, optimum runner angle (60>a>45 degrees) and a greater length of running path on the arc runner suits best for achieving better arc running and lengthening. Better the lengthening of the arc, greater is the arc voltage developed and more efficient is the arc quenching process. So this invention facilitates the use of optimum runner angle and runner length in order for a certain arc chamber (100) geometry and fault level for effective arc running, development of required arc voltage and quenching. In an embodiment, the optimum runner angle of the arc runner assembly (60) is in between 45 to 60 degrees.
Advantages of the invention

1. The arc chamber (100) with ‘no air gap’ (A) design of the arc runner assembly (60) provides much higher arc voltage that helps in creation of artificial current zero and helps in efficient and quicker arc quenching.
2. The arc runner assembly (60) is formed by welding, a cost effective process compared to single component (contact terminal and runner) extrusion or machining. By avoiding the single component feature for both contact terminal and arc runner assembly (60), the production cost is much less compared to the extruded and machined ones. The welding process is inexpensive compared to the extrusion or machining to produce the contact terminal with extended arc runner as a single component.
3. The arc runner assembly (60) helps in better arc running and thus better arc quenching performance, reduced time for which arc stays on the contacts, better arc root transfer from the contact surface to the arc runner, reduced erosion of contact material, and improved running of arc, thereby greater arc voltage build up and thus effective quenching of arc.
4. The angled portion (44) of the profile plate (50) helps in the arc lengthening and running phase and the vertical portion (46) of the profile plate (50) helps the arc transition to the plurality of deion plates (30) for arc splitting.
5. The arc chamber (100) with the welded arc runner assembly (60) eliminates the need of bending to attain the required runner angle, thus no air gap is introduced on the arc travel path.
6. The profile plate (50) with sharp edge (B) helps in effective transition of the arc root from the contact surface to the arc runner assembly (60).
7. The welded no air gap arc runner assembly (60) uses a steel sheet or any other appropriate ferromagnetic material as the arc runner material, so better magnetic pull on the arc column helps to reduce the time for which arc stays on the contacts. Thus, the erosion of contact material is reduced drastically, thereby improving the electrical life of the circuit breaker.
8. Further, due to very smooth and fast movement of the arc root from contact to the arc runner assembly (60), the gases and surrounding medium in the vicinity of the contact gap area gets less ionization time, hence gets less ionized, so the possibility of sustained arc or standing arc or restrike is less in this case.

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.
,CLAIMS:We claim:

1. An arc runner assembly (60) for a circuit breaker, the arc runner assembly
(60) positioned along with an arc chute assembly inside an arc chamber (100) positioned above a fixed contact (110) of the circuit breaker, the arc chute assembly having a plurality of flat deion plates (30) positioned vertically above the fixed contact (110) and a movable contact (120) of the circuit breaker for splitting and extinguishing an electrical arc triggered by breaking of current, the breaking of current being achieved through separation of a pair of arcing contacts (10) after the separation of a pair of main contacts (20) to break the current, the arc runner assembly (60) comprising:
• a flat plate (40) having a first cut portion (32), a first chamfered surface (34) and at least two holes (36) configured thereon, the at least two holes (36) adapted for mounting/ positioning the flat plate (40) on a top surface of the fixed contact (110); and
• a profile plate (50) having a second cut portion (42) for aligning with the first cut portion (32), an angled portion (44) for lengthening of the arc running thereon, a second chamfered surface (48) for horizontal positioning or parallel alignment with the flat plate (40) and a vertical portion (46) for guiding the arc into the plurality of deion plates (30) and for mounting of the arc runner assembly (60), the profile plate (50) adapted for joining to the flat plate (40) thereby forming the arc runner assembly (60) that when positioned above the fixed contact (110) eliminates a need of bending to achieve a required arc runner angle thus eliminates an air gap from an arc root travel path thus achieving a smooth and rapid transition/running of the arc root from a contact surface of the arcing contact (10) on the fixed contact (110) to an arc root running surface (52) of the profile plate (50).

2. The arc runner assembly (60) as claimed in claim 1, wherein the profile plate (50) is welded lengthwise opposite to the arc root running surface (52) along the first chamfered surface (34) of the flat plate (40) such that the cut portions (32, 42) align with each other to form a welded no air gap arc runner assembly (60).

3. The arc runner assembly (60) as claimed in claim 1, wherein the profile plate (50) includes a sharp edge (B) for effective transition of the arc root to the arc root running surface (52) thereof from the contact surface of the arcing contact (10) of the fixed contact (110).

4. The arc runner assembly (60) as claimed in claim 1, wherein the flat plate (40) and the profile plate (50) are made up of a material selected from any one of a mild steel sheet material, a low carbon steel sheet material and a weldable ferromagnetic material.

5. The arc runner assembly (60) as claimed in claim 1, wherein the profile plate (50) includes mounting holes configured thereon.

6. The arc runner assembly (60) as claimed in claim 1, wherein the profile plate (50) does not include mounting holes.

7. The arc runner assembly (60) as claimed in claim 1, wherein the flat plate
(40) and the profile plate (50) are coated with any one of zinc, chromium, aluminum and copper plating.

8. The arc runner assembly (60) as claimed in claim 1, wherein the angle of the chamfering on the flat plate (40) and the profile plate (50) is decided by the arc runner angle (a).

9. The arc runner assembly (60) as claimed in claim 1, wherein the first chamfered surface (34) of the flat plate (40) has a chamfer angle (a) selected from a range between 45 to 60 degrees and is equal to the arc runner angle (a).

10. The arc runner assembly (60) as claimed in claim 1, wherein the second chamfered surface (48) of the profile plate (50) has a chamfer angle (a) selected from a range between 45 to 60 degrees and is equal to the arc runner angle (a).

11. The arc runner assembly (60) as claimed in claim 1, wherein the profile plate (50) has a bending/ construction angle of 90+a to have the angled portion (44), wherein a is the arc runner angle selected from a range between 45 to 60 degrees.