FORM 2
THE PATENTS ACT, 1970 COMPLETE SPECIFICATION
(See Section 10)
MAGNETIC BLOW OUT CORE FOR ELECTRIC ARC IN ELECTRICAL CONTACT SYSTEM FOR SWICHGEARS
Numbered as dated
INVENTORS:
a) KEDAR R. PURANDARE
APPLICANT:
M/s. LARSEN & TOUBRO LIMITED
L&T House, Ballard Estate, P.O. Box No 278,
Mumbai, 400 001, Maharashtra,
INDIA
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THE FOLLOWING SPECIFICATION PARTICULARLY DESCRIBES THE
NATURE OF THE INVENTION

MAGNETIC BLOW OUT CORE FOR ELECTRIC ARC IN ELECTRICAL CONTACT SYSTEM FOR SWICHGEARS
A) TECHNICAL FIELD
[0001] The present invention generally relates to circuit interrupters in switchgears and more particularly to a magnetic blow out core for a butt type contact system having a non-repulsion type breaker contacts in electrical circuit breakers, switchgears etc.
B) BACKGROUND OF THE INVENTION
[0002] Extremely high currents, generated due to the short - circuiting of power supply sources, produce disastrous effect unless the high currents are interrupted by some means. Generally a circuit breaker interrupts such high currents by disconnecting the power supply source before the point of short circuit. The power supply is disconnected by physically separating two or more contacts in an insulating medium.
[0003] The two major types of contact systems used in the switch gear field are "repulsion type breaker contacts" and conventional "non repulsion type breaker contacts".
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[0004] The repulsion type breaker contacts generate a magnetic field along the same direction due to their configuration, during a current interruption process, to push the arc drawn between the two contacts into an arc extinguishing device where the arc is extinguished. When the arc is extinguished in the arc extinguishing device, the contacts become electrically isolated from each other. Thus the electrical current passing through the contacts is interrupted. Since the magnetic field aids in extinguishing the electrical arc in the current limiting contact systems, the arcing time and the energy dissipated are low.
[0005] However, in the non repulsion type breaker contact system, the magnetic fields of both the contacts act in opposite directions and hence the resultant magnetic field doesn't apply a significant force on the arc. So, it is very difficult to drive the arc into the arc extinguishing device located on a predetermined side of the contact. Hence, in a non repulsion type breaker contact system, the contact gap has to be more than that in a repulsion type breaker contact system to allow the arc to get extinguished. In this case, the arcing time as well as the energy dissipated in the non repulsion type breaker contact system is much more than that in a repulsion type breaker contact system. Alternately a blow out coil is used in the non repulsion type breaker contact system to generate an overpowering magnetic field in a desired orientation to suppress the magnetic field of the original contact system, to push an arc towards the extinguishing chamber.
[0006] The US patent No.5770827 and GB patent No. 1272780 disclose a system using a blowout coil to generate a magnetic field with desired flux along a desired direction to move an electrical arc towards an arc extinguishing
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device. However utilization of this phenomenon at very high current levels is not possible as the coil size has to be increased unrealistically.
[0007] The EP patent No.0569650 Bldiscloses a phase and neutral circuit breaker provided with a modular housing having magnetic and thermal tripping circuits to permit the release of interlock and to separate the contacts.
[0008] The US patent No.4654614 discloses a current limiting type solenoid operated circuit breaker provided with a conductor that is arranged around an arcing zone to generate a magnetic field, to drive an arc along the guide rails to an arc quenching chamber.
[0009] The US patent No.7081596 discloses an arc quenching device for circuit breaker having a pre chamber surrounded by a magnetic shield to intensify the magnetic blowing action on an arc formed between the arc guide rails of a pre chamber. A blowing loop is inserted into the arc quenching circuit and extended in parallel to an arc guide rail.
[0010] The US pre-grant application No.20060180576 Al discloses an electrical switching device having iron plates and permanent magnetic plates inserted into the cut outs of a housing wall to provide an AC heavy duty switching device and a DC heavy duty switching device. Several plates are provided in a pre chamber area to form a return flow channel from an arc quenching device, to generate a blow out effect by air current circulation in such a manner to increase gaseous blowout force on the arc.
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[0011] The US patent No. 5569894 discloses an arc extinguishing device for circuit breaker provided with a U-shaped magnetic driving core that is arranged near a stationary contact point and extended upwardly from a base plate to surround the stationary contact point. A moving contact is displaced by a magnetic driving force from a magnetic driving core to an arc quenching core.
[0012] The US patent No.3626127 discloses an arc breaking and quenching unit for electrical circuit breakers provided with a magnetic circuit arranged in an arc quenching chamber and connected with several secondary electrodes for magnetically inducing the movement of an arc away from the contacts. The magnetic circuit has a magnetic core formed between the secondary electrodes and a coil to magnetize the core. A magnetic plate is provided between a magnetic core and the secondary electrodes to break a displacement arc and to elongate and split the broken arc by increasing the length.
[0013] The US patent No. 4656444 discloses a circuit breaker provided with a force generating shunt having folded back portions to generate a repulsive magnetic force to press the closed contacts together and to expedite the opening of the contacts.
[0014] The US patent No. 4417222 discloses an automatic circuit breaker provided with an additional armature system having a magnetic coil, a magnetic core, a magnetic armature and a striker pin. The striker pin is operated to directly strike a movable contact to lift the movable contact from a stationary contact for a given period of time during a short circuiting period.
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[0015] Thus none of the prior art devices discloses a device to generate a sufficient magnetic force on a desired direction without using a coil to drive an arc to an arc extinguishing chamber.
[0016] Hence there is a need to develop a magnetic blow out core to modify the magnetic field distribution in the arcing zone to develop a magnetic flux of desired strength and orientation to drive an arc into an arc extinguishing chamber, without using a blow out coil.
C) OBJECTS OF THE INVENTION
[0017] The primary object of this invention is to provide a magnetic blow out core to generate and apply a suitable magnetic force with a predetermined orientation or direction on an arc produced between the contacts of a circuit breaker to move the arc away from the contacts and towards an arc extinguishing device without using a blow out coil.
[0018] Another object of this invention is to eliminate the need for a blow out coil used for driving an arc towards an arc extinguishing device and to modify the magnetic field distribution in the arcing zone so that the arc is blown into the arc extinguishing device by the inherent magnetic field generated in the circuit breaker device.
[0019] Yet another object of this invention is to provide a magnetic blow out core to quench the arc generated between the contacts of a circuit breaker device quickly and to reduce the energy dissipated in the quenching process.
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[0020] These and other objects and advantages of the present invention will become readily apparent from the following summary and detailed description of the preferred embodiments taken in conjunction with the accompanying drawings.
D) SUMMARY OF THIS INVENTION
[0021] The above mentioned shortcomings, disadvantages, problems, objectives and advantages are addressed herein, which will be understood by reading and studying the following specification.
[0022] According one embodiment of the present invention, a circuit breaker device is provided with a magnetic blow out core to generate a magnetic force of suitable force and desired orientation or direction. The magnetic blow out core is arranged in inverted U- shape to enclose the lower and the upper contacts in a circuit breaker device, to reverse the force acting on the side of the arc column closer to the lower contact so that the entire force on the column is oriented towards the same predetermined side to push the arc column generated between the lower and the upper contacts into the arc extinguishing device.
[0023] The magnetic blow out core is used to enhance the effect of the upper contact and to reduce the effect of the lower contact on the arc column by diverting the magnetic flux of lower contact away from the arc column zone and simultaneously strengthening and distributing the field of the upper contact
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on the length of the arc column so that the entire arc column is pushed outward with a more or less unidirectional force towards an arc extinguishing device. Even though the force distribution due to the magnetic blow out core is uniform, the force is applied along the same desired direction to quench the arc more effectively. The magnetic core is designed and arranged in such a manner that a required filed due to one contact is strengthened, while the unwanted field due to another contact is bypassed.
[0024] The other objects, features and advantages will occur to those skilled in the art from the following description of the preferred embodiments and the accompanying drawings.
E) BRIEF DESCRIPTION OF THE DRAWINGS
[0025] FIG.l shows a block diagram of a repulsion type breaker contact system in a conventional circuit breaker according to a prior art.
[0026] FIG.2 shows a block diagram of a non repulsion type breaker contact system in a conventional circuit breaker according to a prior art.
[0027] FIG.3 shows a block diagram of a non repulsion type breaker contact system with a magnetic blow out core according to one embodiment of the present invention in a circuit breaker device.
[0028] FIG.4 shows a perspective view of a magnetic blow out core according to one embodiment of the present invention, in a circuit breaker device.
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[0029] Although the specific features of the present invention are shown in some drawings and not in others, this is done for convenience only, as each feature may be combined with any or all of the other features in accordance with the present invention.
F) DETAILED DESCRIPTION OF THE INVENTION
[0030] In the following detailed description, a reference is made to the accompanying drawings that form a part hereof and in which the specific embodiments that may be practiced are shown by way of illustration. These embodiments are described in sufficient detail to enable those skilled in the art to practice the embodiments and it is to be understood that logical, mechanical and other changes may be made without departing from the scope of the embodiments. The following detailed description is, therefore, not to be taken in a limiting sense.
[0031] Various embodiments of the present invention provide a magnetic blow out core and a circuit breaker with a magnetic blow out core. However, the embodiments are not limited and may be implemented in connection with other circuit breaker or switch gear devices.
[0032] According to one embodiment of this invention, the circuit breaker having non repulsion type breaker contacts is provided with a magnetic blow out core to produce a magnetic field of desired strength along a desired direction. A magnetic filed of desired flux and orientation is achieved by
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reducing the force acting on an arc column due to one contact and by enhancing the force acting on the arc column due to another contact simultaneously, to push the arc column along a preset direction towards an arc extinguishing device, to quench the arc effectively and quickly.
[0033] The Fig.l shows a block diagram of a repulsion type breaker contact system in a conventional circuit breaker. The circuit breaker has a contact system which is operated based on the principle of current repulsion. According to this principle, when die current is passed through the two conductors 1, 2 in mutually opposite directions, the conductors 1, 2 are repelled from each other with a force which is dependent on the magnitude of current carried in each of the conductors 1, 2. The contact system has a lower contact 2 and an upper contact 1. When the current passed through the contacts 1, 2 exceeds a threshold limit, the contacts ls 2 shown above repel each other and the contacts 1, 2 are separated from each other. The arc column 3 generated between the upper contact 1 and the lower contact 2 forms a current loop path 6. The arc column 3 experiences the forces 4, 5 due to the contacts 1, 2 respectively. These forces 4, 5 always act along the indicated directions so that the arc column 3 is blown out along a predetermined direction towards an arc quenching device in which the arc column 3 is cooled and extinguished. The slot motor 7 is used for accelerating the movement of the contacts 1, 2 away from each other and thereby increasing the contact opening velocity to reduce the intensity of arcing.
[0034] The Fig.2 shows the block diagram of a non- repulsion type contact system in a conventional circuit breaker device. The circuit breaker has a contact system provided with an upper contact 11 and a lower contact 12. The
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contacts 11, 12 are of non repulsion type. The upper and the lower contacts 11,12 are aligned in such a manner that the overlapped current reversal is very low as compared to that in a repulsion type breaker contact system and its effect on the arc column 13,which is formed between the two contacts 11,12, is negligible. The arc column 13 experiences the forces 14, 15 due to the upper contact 11 and lower contact 12 respectively. The direction of forces 14, 15 acting on the arc column 13 are indicated by the arrow marks A current loop path 16 is formed so that the current passed through the upper and the lower contacts 11, 12 are not opposite to each other and also the currents through both the contacts 11, 12 do not over lap each other. Hence the current loop 16 causes the arc column 13, to be driven into an arc extinguishing device (not shown) at the top and away from the arc extinguishing device (not shown) at the bottom. Thus the arc doesn't travel smoothly into an arc extinguishing device.
[0035] The Fig. 3 shows a block diagram of a contact system with a magnetic blow out core 27 according to one embodiment of this invention, in a circuit breaker system. The contact system has non repulsion type breaker contacts 21, 22. It is required in a non repulsion type breaker contact system that the arc column 23, which is formed between the two contacts 21, 22, is pushed in one direction only based on the position of an arc extinguishing device. In Fig3 is shown an arrangement for reversing the force on the side of the arc column 23 which is closer to the lower contact 22 so that the entire force acting on the arc column 23 is oriented towards a predetermined side and enables the arc column 23 to be pushed into an arc extinguishing device arranged along the predetermined direction.
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[0036] With reference to Fig.3, the arrangement has a magnetic blow-out core 27, an upper contact 21 and a lower contact 22. An arc column 23 is formed between the upper contact 21 and the lower contact 22. The magnetic blow out core 27 is provided to enhance the effect of the force acting on the arc column 23 due to the upper contact 21 and to reduce the effect of the force acting on the arc column 23 due to the lower contact 22. The effect of the force acting on the arc column 23 due to the lower contact 22 is reduced by diverting the magnetic flux of the lower contact 22 away from the arc column 23 zone. The effect of the force acting on the arc column 23 due to the upper contact 21 is enhanced by simultaneously strengthening and distributing the magnetic field of the upper contact 21 on the length of the arc column 23 so that the entire arc column 23 is pushed outwardly with a more or less unidirectional force towards an arc extinguishing device in which the arc is cooled and extinguished. Even though the force acting on the arc column 23 is not uniform, the arc column 23 is pushed with a unidirectional force towards an arc quenching device to quench an arc quickly and effectively.
[0037] The magnetic blow out core 27 is designed in such a manner that the required field is strengthened and the unwanted field is bypassed to push an arc column 23 along predetermined direction towards an arc extinguishing device to quench an arc. According to one embodiment of this invention, the magnetic blow out core 27 is arranged in a U- shape. The magnetic blow out core 27 is arranged to enclose the contact system in three sides. The arc extinguishing device used in one embodiment of the invention is an arc chute type arc extinguishing device.
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[0038] The Fig.4 shows a perspective view of a magnetic blow out core according to one embodiment of this invention. The magnetic blow out core is formed in a U-shape and arranged around the upper and the lower contacts in a circuit breaker device to reduce the effect of force acting on the arc column due to lower contact and to enhance the effect of force acting on the upper contact to move an arc column towards an arc extinguishing device.
[0039] Thus various embodiments of the present invention provide a circuit breaker with a magnetic blow out core and a magnetic blow out core for non repulsion type breaker contacts in a circuit breaker, a switch gear etc.
[0040] It will be obvious for a person of skilled in the art to practice the present invention with several modifications. However, all those modifications will be deemed to be covered within the scope of the present invention as covered in the claims mentioned hereunder.
G) ADVANTAGES OF THE INVENTION
[0041] According to one embodiment of the present invention, a magnetic blow out core is provided in a circuit breaker device to produce a magnetic field of desired flux along a desired direction to move an arc column along the desired direction towards an arc extinguishing device to quench an arc easily, effectively and quickly, without using a coil. Thus the magnetic blow out core eliminates the need for a coil to generate a drive magnetic field and modifies the magnetic field distribution in the arcing zone so that the arc is blown into the arc extinguishing chamber by the inherent magnetic flux available in the
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circuit breaker system. The energy distributed in the arc quenching process is reduced. The electromagnetic analysis of the flux due to a magnetic blow out :ore reveals that the distribution of magnetic flux is not uniform but is oriented dong a predetermined direction to quench an arc more effectively.
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CLAIMS
What is claimed is:
1. A circuit breaker device, comprising:
a) a contact system including upper and lower contacts;
b) an arc extinguishing device arranged at either side of the contact system;
c) a magnetic blow out core arranged to enclose the contact system;
d) Wherein the magnetic blow out core enhances the effect of force acting on an arc column which is generated between the contacts, due to one contact and reduces the effect of force acting on arc column due to another contact to move the arc column along a predetermined direction towards the arc extinguishing device.
2. A circuit breaker device according to claim 1 wherein the said magnetic
blow out core is formed in a U-shape.
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3. A circuit breaker device according to claim 1 wherein the said magnetic core is arranged to surround the said contact system so that the contact system is enclosed in three sides and the fourth side is kept open.
4. A circuit breaker device according to claim 1 wherein the said magnetic core enhances the effect of force acting on the arc column due to the upper contact by strengthening and distributing the magnetic field of the upper contact on the length of the arc column simultaneously so that the entire arc column is pushed outwardly with a more or less unidirectional force towards the arc extinguishing device.
5. A circuit breaker device according to claim 1 wherein the said magnetic core reduces the effect of force acting on the lower contact by diverting the magnetic flux due to the lower contact away from the arc column zone.
6. A circuit breaker dev ice according to claim 1 wherein the said arc extinguishing device is an arc chute type arc extinguishing device.
7. A circuit breaker device according to claim 1 wherein the said contact system is a non repulsion type breaker contact system.
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8. A magnetic blowout core for a circuit breaker having non repulsion type breaker contact system.
Dated this the 13™ day of March, 2007

Rakesh Prabhu,
Patent Agent, ALMT Legal,
No.2, Lavelle Road, Bangalore-560 001, INDIA
To,
The Controller of Patents,
The Patent office,
At Mumbai
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ABSTRACT
The present invention provides a magnetic blow out core for a circuit breaker having non repulsion type breaker contacts to generate a magnetic field of desired flux and direction to move an arc column generated between the contacts in a contact system along a preset direction to an arc extinguishing device. The magnetic blow out core is formed around a contact system having upper and lower contacts to reduce the effect of force acting on the arc column due to the lower contact and to enhance the effect of force acting on the arc column due to the upper contact to push the arc column along a predetermined direction towards an arc extinguishing device in which the arc column is cooled and quenched.
8 Claims, 4 Drawing Sheets.
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