A DRIVE ARRANGEMENT FOR A CIRCUIT BREAKER

FIELD OF INVENTION

[0001] The present invention generally relates to circuit breakers and more particularly embodiments of the invention relates to a drive arrangement for a circuit

PRIOR ART

[0002] In a multi-pole circuit breaker, for example one comprising of three cassettes, the rotary contact arrangements are typically arranged on a support shaft between the fixed contact arms of the circuit breaker and function to interrupt the flow of current in the event that a short circuit occurs. Commonly, multiple contacts, each disposed within a cassette, are arranged within a circuit breaker system for protection of individual phases of current. Normally, the operating mechanism positioned over one of the cassettes is connected to all of the cassettes in the system.

[0003] An electrically isolated rotor assembly for a cassette assembly of a circuit breaker, known in the prior art includes a rotor having a first side and an opposing second side, a first isolation link disposed on the first side, a second isolation link disposed on the second side. Each isolation link 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.

[0004] An electrically isolating iso-bearing for a circuit breaker,

known in yet another prior art includes an inner surface, an outer surface, and a body extending there between, said inner surface comprising a pair of bosses and a pair of openings, said outer surface comprising at least one boss, said body comprising a pair of rotor protective flaps. The iso-bearings facilitate shielding mounting springs on the face of the rotor and facilitate a smooth rotation of the rotor during circuit breaker mechanism operations.

[0005] However, the devices that isolate the rotor assembly in a circuit breaker do not facilitate protecting conductive rotor parts positioned along a perimeter of the rotor. This is predominantly due to the relative position of the isolation assembly with respect to the circuit breaker. Further, the isolation assembly found in the prior art do not completely eliminate dielectric failure.

[0006] Hence there is a need for a drive assembly for a circuit breaker that (i) increases the degree of separation (a) between each of the cassettes in a multi-pole circuit breaker, and (b) between each cassette and the operating mechanism, (ii) effectively enhances isolation by eliminating dielectric failure.

SUMMARY OF THE INVENTION

[0007] One aspect of the invention includes a drive assembly for a multi-pole circuit breaker. A drive shaft is mounted on the base of the circuit breaker. A plurality of two rotor assembly is mounted on the drive shaft. An isolator link is mounted between two subsequent rotor assemblies. The isolator link includes a first side and a second side having four circular projections which eliminates the dielectric stress between the rotor assemblies.

[0008] Another aspect of the invention provides a multi-pole circuit breaker which includes a drive shaft. A plurality of cassette assemblies are mounted on the drive shaft. Each cassette assembly includes a rotor assembly with a moving contact. A plurality of isolator link is operably coupled to the cassette assembly and bracket mounted on the base of the circuit breaker. The isolator link increases the dielectric strength between the cassette assemblies.

BRIEF DESCRIPTION OF THE DRAWINGS

[0009] So that the manner in which the above recited features of the present invention can be understood in detail, a more particular description of the invention, briefly summarized above, may be had by reference to various embodiments, some of which are illustrated in the appended drawings. It is to be noted, however, that the appended drawings illustrate only typical embodiments of this invention and are therefore not to be considered limiting of its scope, for the invention may admit to other equally effective embodiments.

[0010] Figure 1 shows a circuit breaker with the drive assembly and the operating mechanism according to an embodiment of the invention.

[0011] Figure 2 shows the exploded view of the cassette assembly comprising of drive assembly and the isolator link mechanism according to an embodiment of the invention.

[0012] Figure 3 shows the exploded view of the rotor assembly along with its isolator link mechanism, according to an embodiment of the invention.

[0013] Figure 4 shows a single shaft with isolator link, according to an embodiment of the invention.

[0014] Figure 5 shows the assembly of rotor assembly and the isolator link mechanism inside a circuit breaker, according to an embodiment of the invention.

DETAILED DESCRIPTION OF INVENTION

[0015] Various embodiments of the invention provide a drive assembly for a circuit breaker. FIG.l shows overall view of a circuit breaker 1 with the drive mechanism according to an embodiment of the invention. The circuit breaker 1 includes a plurality of cassettes 2, mounted on a drive assembly 3. A toggle switch 4 is provided over the cassette assembly that allows the circuit breaker to operate between ON, OFF and TRIP conditions.

[0016] FIG.2 shows the exploded view of the cassette assembly comprising of drive assembly and the isolator link mechanism according to an embodiment of the invention. In one embodiment of the invention, a three-pole circuit breaker includes three cassette assemblies 2a, 2b and 2c. One of the cassette assemblies, 2b is provided with the toggle switch 4. The cassette assemblies are provided with a circular connecting member with grooves 8, mounted on the drive assembly 3. An isolator link 6 is mounted on a bracket 7 in between two cassette assemblies. The bracket 7 is mounted on the casing of the circuit breaker.

[0017] Figure 3 shows the exploded view of the rotor assembly along with its isolator link mechanism, according to an embodiment of the invention. The drive mechanism includes a rotor assembly 5comprising of a moving contact 7. A plurality of rotor assembly 5 is mounted on a main shaft axis a - a'. In one embodiment of the invention, the isolator link 6 is substantially circular and comprises of a first circular half and a second circular opposing half. A plurality of projections 6a is provided on the outer surface of each of the half of the isolator link 6. In an example of the invention, each of the projection is configured to form a substantially circular projection as illustrated in the accompanying drawings. The isolator link according to an example of the invention is made from a material, which is a sheet-molding compound (SMC) of FLOMAT 516/25 grade, which has a dielectric strength of 12KV/mm. Further, the material has a lower friction coefficient. The rotor assembly 5 is substantially circular and comprises of a first half and a second opposing half. One of the halves of the rotor assembly is provided with plurality of groove 8. In an example of the invention, each of the grooves is a substantially circular groove as illustrated in the accompanying drawings. Also, both the halves of the rotor assembly 5 are provided with a toggle switch 4. Further, the grooves 8 are configured to receive the projections 6a of the isolator link to enable complimentary fit.

[0018] FIG. 4 shows a single isolator link 6 and rotor assembly 5. The projections 6a on the isolator link 6 and the groove 8 provided on the rotor assembly 5 are arranged to form a lock mechanism. The lock mechanism prevents early rotation of the cassette assemblies adjacent to the cassette comprising the operating mechanism. The middle insulated drive mechanism comprising the operating mechanism connects the entire cassette assembly with the mechanism. Since the shaft is connected to the mechanism through insulating material the leakage current that may pass through the mechanism can be avoided.
The design and the assembly sequence as explained in the drawings help in providing a proper drive arrangement between the poles as well as to provide the required dielectric strength between poles.

[0019] FIG. 5 shows the assembly of rotor assembly and the isolator link mechanism inside a circuit breaker. The rotor assembly 5 with the groove 8 is mounted at the center of the cassette assembly 2 of the circuit breaker. The cassette also includes a rotary moving contact and a fixed contact 9. A plurality of arc chutes 10 are provided for
quenching of the arc generated during rapid opening of the contact.

[0020] In one embodiment of the invention, the rotor assembly 5, the isolator link 6 and the drive shaft upon which the rotor assembly 5 and the isolator link 6 are mounted, are made out of a plastic material. The rotor assembly 5 is linked to the isolator link 6. The linking mechanism helps in increasing the spacing, that exists between cassettes, from less than 2 mm to 5mm with a reduction in the component that provides the drive for the shaft from the mechanism. Hence, the isolation link increases the dielectric strength through elimination of the dielectric stress between the cassettes. Further, the link also prevents early start of the rotor assembly by establishing a link between the mechanism and the drive shaft.

[0021] The isolator link mounted between two subsequent rotor assemblies helps in transferring the force from the main mechanism to these rotor assemblies with higher efficiency. Further, the isolator link eliminates the need for a separate link to transfer force, as well as an isolating member to provide isolation. Thus making the breaker assembly compact and eliminating the need for an additional component for electrical isolation between poles of the circuit breaker.

[0022] The foregoing description of the invention has been set for merely to illustrate the invention and is not intended to be limiting. Since modifications of the disclosed embodiments incorporating the spirit and substance of the invention may occur to person skilled in the art, the invention should be construed to include everything within the scope of the appended claims and equivalents thereof.

We Claim:

1. A drive assembly for a multi-pole circuit breaker comprising

a drive shaft mounted on the base of the circuit breaker; at least two rotor assembly mounted on the drive shaft; and

at least one isolator link mounted between two subsequent rotor assemblies characterized in that the isolator link comprises of a first side and a second side having at least four substantially circular projection thereby eliminating the dielectric stress between the rotor assemblies.

2. The drive assembly according to claim 1, wherein the rotor assembly has a centrally located substantially circular groove for accessing the drive shaft and at least four substantially circular grooves provided on the circumference of the assembly to rotatably lock the isolator.

3. The drive assembly according to claim 1, wherein the rotatable locking of the projections of the isolator link with the grooves of the rotor assembly prevents early start of the rotor assembly.

4. The drive assembly according to claim 1, wherein the rotor assembly and the isolator link are made from a material having lower coefficient of friction.

5. A multi-pole circuit breaker comprising

a drive shaft;

a plurality of cassette assemblies mounted on the drive shaft wherein each cassette assembly includes a rotor assembly with a moving contact; and

a plurality of isolator link operably coupled to the cassette assembly and bracket mounted on the base of the circuit breaker wherein the isolator link increases the dielectric strength between the cassette assemblies.

6. The multi-pole circuit breaker according to claim 5, wherein the isolator link has a first half and a second half provided with substantially circular projections,

7. The multi-pole circuit breaker according to claim 5, wherein the cassette assemblies are provided with substantially circular grooves to rotatably lock the projections on the isolator link.

8. The multi-pole circuit breaker according to claim 5, wherein the independent mounting of the isolator link prevents early start of the rotor assemblies.