FORM 2
THE PATENTS ACT, 1970
(39 of 1970)
&
THE PATENTS RULES, 2003
COMPLETE SPECIFICATION [See section 10, Rule 13]
CONTACT ARRANGEMENT FOR CURRENT LIMITING CIRCUIT BREAKER;
LARSEN & TOUBRO LIMITED, A COMPANY INCORPORATED UNDER THE COMPANIES ACT, 1956, WHOSE ADDRESS IS L&T HOUSE, BALLARD ESTATE, MUMBAI - 400 001, MAHARASHTRA, INDIA
THE FOLLOWING SPECIFICATION PARTICULARLY DESCRIBES THE INVENTION AND THE MANNER IN WHICH IT IS TO BE PERFORMED
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FIELD OF THE INVENTION
The present invention relates to a current limiting circuit breaker, particularly to a
contact arrangement of current limiting circuit breaker to clear short circuit fault as fast as possible.
BACKGROUND ART
Circuit breakers with arc blow out are well known for faster arc extinguishing. The simplest form of arc driving (blow out) means effective for elongating the arc is to provide one or more magnetic windings in the vicinity of the arcing contacts, which exert a repulsive force on arc, blowing it out. But this requires a separate component called " Slot motor" to be used. Mostly, the slot motor is made up of stacked thin laminations of ferromagnetic material. The slot motor creates a magnetic field which electromagnetically forces the arc out.
But there were limitations in this method like imitation on the size of windings to maintain heat loss, the repulsive force acts only until arc remains within the width of slot motor (common length) and a separate" slot motor" is required to be used. Also it is known in the prior art a contact profile which itself acts as a slot motor and contributes to increased arc blow out. But it has the disadvantage that the overall length of contacts parallel to each other is very less in this case, hence repulsion along the length is much less. Also the overall size of the contact profile is limited thus a strong repulsion force can't be produced.
The presently available contact profile also provides very minimal arc blow out force (Force is less because arc and current directions are at an angle and not parallel) and that also just at the time of arc initiation.
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The present available contact arrangements for circuit breaker either require an external body to produce the magnetic field to provide the required blow out field for the arc to be pushed or the contact profile which itself produces the desired magnetic field to produce the necessary blow out field.
Also the contact profile is such that the arc does not come out to be parallel to the current direction so the arc repulsion is not very much effective and so the overall performance of the circuit breaker is hampered. So, there is a need of a contact arrangement for the current limiting circuit breaker which provides a strong magnetic field by creating a loop of larger size around the contact arrangement such that it produces a strong magnetic field and also provides a strong blow out force on the arc. Also there is a need to make the contact arrangement in such a way that the arc comes exactly parallel to the current direction, occurs maximum repulsion yet improving the overall performance of the current limiting circuit breaker.
SUMMARY
An object of the present invention is to provide a contact arrangement for a current limiting circuit breaker to achieve strong magnetic field (blow out field) for moving arm and arc at the time of short circuit.
According to one of the embodiment of the present invention, a contact arrangement for a current limiting circuit breaker, comprises a moving contact button; a fixed contact button; a moving arm to which is attached the moving button; and a fixed current carrying elongated arm with the fixed contact button attached therein, wherein the fixed current carrying elongated arm surrounds the fixed contact button and the moving contact button.
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According to the second embodiment of the present invention, the contact
arrangement further comprises at least two opening(s) on the fixed current carrying
elongated arm. One opening is provided at the front side and the second opening is
provided at the rear side of the fixed current carrying elongated arm. A gas guider
component passes through the rear side opening of the fixed current carrying
elongated arm and one of the arm of the moving arm passes through the front side
opening of the fixed current carrying elongated arm.
BRIEF DESCRIPTION OF THE DRAWINGS
Fig 1 shows perspective view of the contact system arrangement showing left side
chamber of arc chamber according to the present invention.
Fig 2 shows perspective view of the contact system arrangement showing right side
chamber of arc chamber according to the present invention.
Fig 3 shows perspective view of the contact system arrangement according to the
present invention with the arc chamber and arc chute hidden.
Fig.4 shows perspective view of the contact system arrangement according to the
present invention with the arc chamber and the arc chute hidden.
Fig 5 shows the side view of the left side chamber of arc chamber showing the flow of current according to the present invention with arc chamber and arc chute hidden. Fig 6 shows the side view of the right side chamber of arc chamber showing the flow of current according to the present invention with arc chamber and arc chute hidden. Fig 7 shows perspective view of contact system arrangement with side covers of arc chamber.
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Fig 6 shows perspective view of completely closed arc chamber. DETAILED DESCRIPTION OF THE PRESENT INVENTION
The present invention relates to a contact arrangement for a current limiting circuit breaker. The current limiting circuit breaker clears the fault as fast as possible so as to minimize let through energy passing to the connected down stream devices and also to remain safe from thermal stresses due to the let through energy passed. The current limiting circuit breaker also limits the fault current as low as possible so that connected downstream devices does not come under high magnetic stresses under the influence of high magnitude limited current.
Fig 1 and 2 shows the contact arrangement of a left side chamber of an arc chamber (1) of the current limiting circuit breaker according to the present invention. The arc chamber (1) is divided into two chambers, the left side chamber and a right side chamber. A fixed current carrying elongated arm (15,28) is housed both in the left side chamber and the right side chamber of the arc chamber (1) as shown in fig 1 and 2. The fixed current carrying elongated arm (15,28) is provided with two openings in it. Through the first opening is provided in the fixed current carrying elongated arm (15,28) one of the arms of the moving arm (2) passes. A gas guider component (8,23) is provided through the second opening in the fixed current carrying elongated arm (15,28). The gas guider component (8,23) is located behind an arc chute (6,21).
Moving arm (2) is designed in such a way that it bridges a moving contact button (3,18) in the left side chamber and the right side chamber of the arc chamber (1) as shown in fig 1 and 2. A fixed contact button (4,19) is fixed to one end of the fixed
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current carrying elongated arm (15,28) and near to the moving contact button (3,18) such that initially when short circuit condition occurs maximum repulsion is established between the imposing faces of fixed contact button (4,19) and the moving contact button (3,18). An arc runner (11,26) is fixed just next to fixed contact button (4,19) on fixed current carrying elongated arm (15,28).
Fixed current carrying elongated arm (15,28) is designed in such a way that it surrounds by making a loop around the fixed contact button (4,19), the moving contact button (3,18) and arc chute (6,21). The fixed current carrying elongated arm (15,28) partially surrounds the fixed contact button (4,19), the moving contact button (3,18) and the arc chute (6,21). The fixed current carrying elongated arm (15,28) carries the current through it and through the whole loop that is being formed therein to produce a magnetic field at each point of the loop. The fixed current carrying elongated arm (15,28) creates a strong magnetic field (blow out field) at the central plane that bisects the width of the fixed current carrying elongated arm (15,28). The moving arm (2) also opens with high speed because of the strong magnetic field at the central plane thus clearing the fault current quickly. Also the opening off current is low because of the fast opening of moving arm (2) and strong blow out field. The strong magnetic field at the central plane creates a strong force on arc towards deion plates (7,22). However the fixed current carrying elongated arm (15,28) can be constructed in such a way that it surrounds the fixed contact button (4,19), the moving contact button (3,18) and arc chute (6,21) completely to give the desired effect.
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The arc chute (6,21) is housed vertically in left side chamber of arc chamber (1). A
plurality of deion plates (7,22) are assembled in arc chute (6,21) and makes an
angle with horizontal plane. Just behind the arc chute, the gas guider component
(8,23) is adapted to the second opening on the fixed current carrying elongated arm
(15,28). The gas guider component (8,23) is designed in such a way that it guides
the ionized gases outside the arc chamber (1). The gases that are present in the
nearby atmosphere are ionized due to the arc (31,32) (not shown) produced to due
to short-circuiting.
Insulation cover (14,27) is provided to fixed current carrying elongated arm (15,28)
and an additional insulation cover (10,25) is provided to the two openings (of the
fixed current carrying elongated arm (15,28)) through which arm of moving arm (2)
passes.
A slit (16,17) is provided in the front side of the arc chamber (1) through which one
of the arms of the moving arm (2) comes out of the arc chamber (1). Two side
covers (not shown) are riveted to the arc chamber (1) in final assembly and for that
purpose rivet shield(s) (9,24) are provided. The rivet shield(s) protect the rivet(s)
from being exposed to the ionized gases at the time of short circuit.
The moving arm (2) is assembled on a contact holder (12) and the contact holder
(12) is further hinged at hinge point (13) and rotates about hinge point (13). Both the
moving arm (2) in the left side chamber and the right side chamber is connected to a
common contact holder (12) hinged at the hinge point (13).
Fig 3 and 4 shows the perspective view of the contact system arrangement of the
current limiting circuit breaker with the arc chute (6,21) and the arc chamber (1)
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hidden. The fixed current carrying elongated arm (15,28) is provided with the two openings in it. Through the first opening provided in the fixed current carrying elongated arm (15,28) one of the arms of the moving arm (2) passes. A gas guider component (8,23) is provided through the second opening in the fixed current carrying elongated arm (15,28). The fixed current carrying elongated arm (15,28) is designed in such a way that it surrounds by forming a loop around the fixed contact button (4,19), the moving contact button (3,18) and arc chute (6,21). The fixed current carrying elongated arm (15,28) partially surrounds the fixed contact button (4,19), the moving contact button (3,18) and the arc chute (6,21).
Fig 5 shows the left side view of fig 1 with the arc chamber (1) and the arc chute (6) being hidden. Direction of flow of the current with the help of arrows is shown in this figure. The moving arm (2) is shown in motion and a perspective arc (31) is also shown here.
A source (not shown) is giving current input in the fixed current carrying elongated arm (15). The arrows in the fixed current carrying elongated arm (15) shows the direction of the current flowing through the fixed current carrying elongated arm (15). A strong magnetic field B (into the page) is generated by current in the fixed current carrying elongated arm (15), the arc (31) and the moving arm (2). A part of this strong magnetic field B interacts with the moving arm (2) and creates a force on the moving arm (2) in upward direction thus opening of the moving arm (2) becomes very fast. At the same time a part of B also interacts with the arc (31) and creates a strong blowout force on the arc (31). Because of the energy dissipated by the arc (31), highly pressurized gas gets generated and tries to escape from the arc
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chamber (1). Arrows directed toward the gas guider (8) shows the highly pressurized gas escaping from the arc chamber (1). The gas guider (8) gives a guided path to highly pressurized gas to the outside of the arc chamber (1). Pressure inside the chamber becomes very high at the time of short circuit that supports the fault clearing phenomena of the circuit breaker. The arc (31) moves from the fixed contact button (4) to the arc runner (11) and the fixed contact button (4) and the arc runner (11) rests on a part (5) of the fixed current carrying elongated arm (15).
Fig 6 shows the right side view of fig 1 with the arc chamber (1) and the arc chute (6) being hidden. Direction of flow of the current with the help of arrows is shown in this figure. The current is coming from the left side chamber of the arc chamber (1) and flowing into the right side chamber of the arc chamber (1). Moving arm (2) bridges the moving contact button (3) (not shown) and moving contact button (18). A strong magnetic field B' is created by the fixed current carrying elongated arm (28), the arc (32) and the moving arm (2).
A part of magnetic field B' interacts with arm of moving arm (2) thereby opening of the moving arm (2) becomes very fast. A part of magnetic field B' also interacts with the arc (32) and creates blowout force on the same. Highly pressurized gas gets generated because of the heat dissipated by arc (32) and tries to escape from arc chamber (1). Gas guider (23) guides the pressurized gas to the outside arc chamber (1). Arrows heading toward gas guider (23) shows the pressurized gas escaping from arc chamber (1) and arrows going away from the gas guider 23) are shows the escaped gases from arc chamber (1). Pressure inside the chamber becomes very high at the time of short circuit that supports the fault clearing phenomena of the
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circuit breaker. Arc (32) moves from fixed contact button (19) to arc runner (26) and the fixed contact button (19) and the arc runner (26) rest on part (20) of the fixed current carrying elongated arm (28).
Fig 7 shows the perspective view of the arc chamber (1) with side covers (33,34). Cover (34) covers arc chamber (1) from left side and cover (33) covers arc chamber (1) from right side and make final assembly totally closed. Gas guider components (8) and (23) are shown here and these gas guider components (8) and (23) guide highly pressurized gas to the outside arc chamber (1). Rivet points (35) are provided on side covers (33) and (34). A part of shielding for these rivets (35) is provided in arc chamber (1) (shielding (9) and shielding (24)) and remaining part of shielding for these rivets is provided as (36) on the side covers (33) and (34).
Fig 8 shows the perspective view of completely closed arc chamber (1). Final assembly of arc chamber (1) is shown in this figure. Side cover (34) covers the left side chamber of the arc chamber (1) and side cover (33) covers the right side chamber of the arc chamber (1) and also covering from the sides thereby making a completely closed arc chamber.
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.
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WE CLAIM
1. A contact arrangement for a current limiting circuit breaker, comprising:
a moving contact button;
a fixed contact button;
a moving arm having the moving contact button at one end; and
a fixed current carrying elongated arm with the fixed contact button attached
therein, wherein the fixed current carrying elongated arm surrounds the fixed
contact button and the moving arm button.
2. The contact arrangement as claimed in claim 1, further comprising at least two
openings on the fixed current carrying elongated arm.
3.The contact arrangement as claimed in claim 1 and 2, wherein a first opening is
provided on front side of the fixed current carrying elongated arm and second
opening is provided on rear side of the fixed current carrying elongated arm. 4.The contact arrangement as claimed in claim 1,2 and 3, wherein a gas guider
component passes through the second opening.
5 .The contact arrangement as claimed in claim 1, 2 and 3, wherein one of arm of the
moving arm passes through the first opening.
6. The contact arrangement as claimed in claim 1, wherein the fixed current carrying.
elongated arm partially surrounds the fixed contact button, the moving arm button
and part of the moving arm.
7. The contact arrangement as claimed in claim 1, wherein the fixed current carrying
elongated arm creates a magnetic field at the central plane bisecting width of the
fixed current carrying elongated arm.
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8.The contact arrangement as claimed in claim land 7, wherein the magnetic field at
the central plane creates a force on the moving arm thereby enabling the moving
arm to open quickly.
9. The contact arrangement as claimed in claim 1, wherein the force created by the
magnetic field exerts a pushing force on an arc towards the gas guider
component.
10. The contact arrangement as claimed in claim 1, wherein the contact arrangement
for the current limiting circuit breaker could be employed in single pole, multi-pole
circuit break
11. The contact arrangement for a current limiting circuit breaker as herein described
and shown in Fig 1, 2, 3, 4, 5, 6, 7 and 8.
Dated this : 5th day of October, 2006

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ABSTRACT
A contact arrangement for a current limiting circuit breaker, comprising a moving arm button, a fixed contact button, a moving arm to which is attached the moving contact button, and a fixed current carrying elongated arm with the fixed contact button attached therein, wherein the fixed current carrying elongated arm surrounds the fixed contact button and the moving arm button.
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