FIELD OF THE INVENTION
The present invention relates to air circuit breakers. More particularly, the invention relates to an electric circuit breaker with fixed arcing contact support to protect electrical contacts from being damaged during high current interruption.
BACKGROUND OF THE INVENTION
Damages of electrical contacts occur due to the arcing during interruption of high currents in low voltage circuit breakers. During the process of breaking an electric arc in the circuit breaker, the circuit breaker time delay result in burning of the contacts, even in severe cases, it causes fires and explosions. To overcome it, high speed mechanism was used to operate the moving contact resulting in less damage in the contacts during interruption of high currents.
US Patent No. 4,132,968 relates to circuit breakers having magnetic drive devices to rapidly separate the contacts under high over current conditions and initiate current limiting measures. A current-limiting circuit interrupter having separable contacts supported within a housing and a slotted magnetic drive device mounted within the housing having a slot with an open end and a closed end. The circuit interrupter also includes an elongated movable contact arm supportmg one of the contacts and supplymg current thereto, the contact arm being transversely disposed in the slot so that current flow through the contact arm is in a direction perpendicular to a line connecting the open and closed slot ends. The contact arm is movable between a first position at the open end of the slot which permits current fiow dirough the contacts and a second position at the closed end of the slot which interrupts current flow through the contacts.

-3-GBl 172190 (A) describes improvements in or relating to a Vacuum-Type Circuit Interrupter . According to this invention, the contacts of a vacuum switch are provided with separate arcing areas for high and low current arcs. Each contact has a raised annular contact making surface ; a spirally slotted outer region , for high current arcs; and a circular central recessed region for low current arcs. Tubular stainless steel inserts between the body of each contact and its supporting electrode together with the annular form of the contact surfaces , cause the normal current flow to follow a curved path L which creates a magnetic field. Below the surfaces of regions are inset plates of high permeability metal such as iron or low carbon steel which, during low current flow, distort the magnetic field of loop L so that the arc is driven inwards on to the surfaces . Under heavy current conditions the plates become saturated and the magnetic field then acts in the usual way to drive the arc outwards on to regions where it is rotated by the field created by the spiral slots. The body and outer portions of the contacts may be of pure zone-refmed copper; the contact surfaces of copper-bismuth alloy (0A5% Bi); and the central regions of a material having a low chopping current such as a copper-tm alloy or bronze. Alternatively the plates may be omitted and regions formed of an alloy of iron, or tungsten vwth copper or tin. The heavy current arc supporting regions must be fi-ee of refractory metals.
Publication No. CN202042442 relates to an arc mitiatmg device of a circuit breaker. The arc initiating device comprises an arc extinguishing chamber and an arc extinguishing gate arranged at the rear end of the arc extinguishing chamber, wherein the arc extinguishing chamber is arranged below a static contact mechanism, a static contact arc guide plate which extends to the upper part of the arc extmguishing gate is fixed on the static contact mechanism, and the top part and the bottom of the arc extinguishing chamber are both provided with a flash barrier. The arc initiating device is characterized in that a U-shaped section which stretches into the arc extinguishing chamber is curved on the static contact arc guide plate, magnet steel is fixed at the inner side of the U-shaped section, and the upper part of the magnet steel and the lower part of the magnet steel are

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connected with the flash barriers at the top part and the bottom of the arc extinguishing chamber.
Publication No. W09411894 (Al) teaches an arc extinguishing device for disposition along a pre-determined path of movement between two electrical contacts in an electrical distribution device. The device includes a generally u-shaped cradle member having a bight portion defined by a bottom wall with two upstanding side walls. The bight portion has sufficient width to allow the movement of the electrical contacts between the two side walls. The cradle member is made of a thermoplastic resin. The invention also provides for using a magnetic material as the conductive modifier in a concentration effective to have the composite exhibit magnetic properties which increase the mobility and further dissipate the arc current. A preferred magnetic material as the conductive additive is stainless steel or nickel-coated steel.
US Patent No. 6.229.413 teaches a circuit breaker having at least one cassette for receiving a conductive path. The conductive path is partially looped upon itself so that a first portion and a second portion of the conductive path are in a facially spaced relationship and the portions partially define an area for receiving a ferromagnetic material. The ferromagnetic material is insulated from the first portion and a support structure provides support for the first portion at two positions and the area is positioned in between these positions.
Thus, in view of the discussion of prior art known to the inventors, it is noted that circuit breakers having magnetic drive devices comprising steel plate, and arc extinguishing devices using magnetic material as the stainless steel or nickel-coated steel, are known in prior art. Circuit breakers using stainless steel having low carbon contact tubes as contact in vacuum-type circuit interrupter are also known in prior art. However, there is sUll a need for improving the design of the arcing contact support to protect the contacts from bemg damaged.

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Thus the present invention aims to provide a unique fixed arcing contact support to protect the contacts from being damaged by forcmg the arc to the arc chutes while interrupting the high currents. The present invention provides an arc accelerator having magnetic drive device comprising an open ended decarburized high perm treated nickel plated steel piece. The magnetic field is increased around the arc with the fixed arcing contact support to accelerate the arc towards arc chute for rapid cooling.
OBJECTS OF THE INVENTION
It is therefore an object of the present invention to propose an electric circuit breaker with fixed arcing contact support to protect electrical contacts from being damaged during high current interruption.
Another object of the present invention is to propose an electric circuit breaker with fixed arcing contact support to protect electrical contacts from being damaged during high current interruption, which includes an arc accelerator device to allow fast separation of the contacts.
Still another object of the present invention is to propose an electric circuit breaker with fixed arcing contact support to protect electrical contacts from being damaged during high current interruption, which exhibits high interrupting capacity through intensification of the magnetic field around the arcing contact.
Yet another object of the present invention is to propose an electric circuit breaker with fixed arcing contact support to protect electrical contacts firom being damaged during high current interruption, which incorporates high perm technology for reducing the watt loss.
A fiirther object of the present invention is to propose an electiric circuit breaker with fixed arcing contact support to protect electrical contacts from being damaged during high current interruption, which is enabled to generate an

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increased magnetic field around the arc with the fixed arcing contact support to accelerate the arc towards the arc chute for rapid cooling.
A still fiirther object of the present invention is to propose an electric circuit breaker with fixed arcing contact support to protect electrical contacts from being damaged during high current interruption, which provides increased magnetic field around the arcing contact by utilizing the ferromagnetic property of nickel.
SUMMARY OF THE INVENTION
Accordingly, the present invention provides an electric circuit breaker for interrupting low voltage power circuits. The magnetic field produced by the current carrying contact forces the arc towards the arc chute. A high interrupting capacity m the air cncuit breaker is realized by intensifying the magnetic field around the arcing contact. A fixed arcing contact support is so designed that it increases the magnetic field around the arcing contact.
In a preferred embodiment of the present invention, a rapid contact separation is achieved by employing an arc accelerator magnetic drive device comprising an open ended decarburized high perm treated steel piece. The decarburized high perm treated Nickel plated material is placed around the contacts which allows creation of high magnetic intensified zone wherein the contacts separate at a high speed.
In another embodiment of the present invention, a high permeability path is provided to the magnetic flux through the decarburized ferromagnetic plates so that when high current flows through the contacts, the magnetic field is produced which drives the contacts apart.

In yet another embodiment of the present invention, the arc accelerator device is open from the top and is integrally placed around the contacts so as to assist the fast separation of the contacts. Even at high currents, the decarburized plates do not get saturated and help in mcreasing the magnetic force to quickly open the contacts and lengthening of the arc. The moving arm which is driven by mechanical force in normal operation is thrown away by the magnetic force under high currents.
In yet another embodiment of the present invenrion, the steel piece is Nickel plated so as to further increase the magnetic effect utilizing the ferromagnetic property of nickel. Extreme over current condhions through the contacts generate magnetic flux in the magnetic accelerator across the open end of the slot which interacts with current flow through the contact arm to produce a magneto dynamic force drivmg the contact arm from the first position to second position. This accelerator includes a saturable magnetic core which increases the magnetic flux intensity and magnetic force on the arc to move it faster towards arc splitter plates.
BRIEF DESCRIPTION OF THE ACCOMPANYING 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 for limiting of its scope, for the invention may admit to other equally effective embodiments.
Fig. 1 shows an elevation view, partly in section, of a pole of air circuit breaker;

Figure 2 shows a detail view of a pole assembly associated with the arc chute of an air circuit breaker;
Figure 3(A), 3(B), 3(C) show the views of fixed arcing contact and the support, according to the invention.
DESCRIPTTON OF THE PREFERRED EMBODIMENTS
Accordingly the present invention provides an air circuit breaker for interrupting low voltage power circuits and protecting the electrical contacts from being damaged by including an arc accelerator magnetic drive device having an open ended decarburized high perm treated steel piece for intensifying the magnetic field around the arcing contact and forcing the arc towards the arc chute. The magnetic field produced by the current carrying contact, forces the arc towards the arc chute. A high interrupting capacity in the air circuit breaker is realized by intensifying this magnetic field around the arcing contact. The fixed arcing contact support is so designed that it increases the magnetic field around the arcing contact.
The invention includes a current limiting circuit breaker having a high perm treated material surrounding the moving contact, and acting as a magnetic accelerator. The threshold value of the tripping current is reduced by concentrating the magnetic flux lines to drive the contact arm faster so as to produce an enhanced current limiting effect. The technology of decarburizing is known to reduce the percentage of carbon & Watt-Loss in ferromagnetic material. Hi perm technology is an advanced process for the production of component that reduces the watt loss. This process is carried out by heat treatment of stampings to reduce the carbon percentage and develop a uniform grain structure. The process results in the reduction of carbon percentage & core loss, improves grain size structure and desired coating thickness on the stampings as a result of decarburizing.

This process results in reduced watt losses, which ultimately benefits in teims of increased efficiency of the products and increased magnetic effect wherever required.
The stampings manufactured at the end confirms to a core loss of 5.5 to 6 watts per K. gauss at 1.5 Tesla at 50 cycles/sec. The process of Hi-Perm constitutes heat treatment or annealing of the stampings up to 700 degree to reduce Watt-Loss. The watt loss of CRCA material is high whereas after the Hi-Perm Process is utilized for manufacturing of the stampings, the result shows only 5.5 To 6 watt loss. Electrostatic flux is impeded or blocked by metallic objects. Magnetic flux passes through most metals with little or no effect, widi certain exceptions, notably iron and nickel. These two metals, and alloys and mixtures containing them, are known as ferromagnetic materials because they concentrate magnetic lines of flux. The concentrated flux increases the magnetic field intensity which results in enhanced magnetic force on the moving arm. The high perm treated material leads in increased permeability leading to higher concentration of the flux, which creates higher magnetic force. The steel piece is Nickel plated so as to further increase the magnetic effect utilizing the ferromagnetic property of nickel. Extreme over current conditions through the contacts generate magnetic flux in the magnetic accelerator across the open end of the slot which interacts with the current flow through the contact arm to produce a magneto dynamic force driving the contact arm from the first position to second position. This accelerator includes a saturable magnetic core which increases the magnetic flux intensity and magnetic force on the arc to move it faster towards the arc splitter plates. The method of producing a rapid contact separation employs an Arc accelemtor magnetic drive device comprising an open ended decarburized high perm treated steel piece. The Decarburized Hi perm treated Nickel plated material when placed around the contacts, leads to creation of a high magnetic intensified zone wherein the contacts separate at high speed. When a high current flows through the contacts, a magnetic field is produced which drives the contacts

apart. The magnetic field intensity increases with the presence of high permeability material which in turn increases the force on the moving contact arm resulting in a faster opening of the contacts. It produces strong magneto dynamic force driving the moving contact rapidly. The force is directly proportional to the magnetic field which depends on the permeability of the material surrounding the current flowing through the contact arms. It provides a high permeability path to the magnetic flux through the decarburized ferromagnetic plates.
The arc accelerator device is open from the top and is mtegrally placed around the contacts so as to allow a fast separation of the contacts. Even at high currents the decarburized plates doesn't get saturated and helps in increasing the magnetic force to quickly open the contacts and lengdiening of the arc. The moving arm which is driven by the mechanism force in normal operation is thrown away by the magnetic force under high currents. In high current interruptmg capacity ah circuit breakers, main and arcmg contacts are used for normally carrymg the load cunent and for transferring the same to the arcing structure upon opening of the breaker. The mam contacts are designed to carry the normal load current without overheating but are not subjected to arcing. The arcing contacts are arranged to transfer the power current from the main contacts upon initial opening of the breaker to the arcing contacts. The arc is initially guided inside the arc chute plates by means of the arc runners. Subsequently the arc moves deeper into the arc chute due to the forces produced by the current carrying contact and the pressure of heated gases. In this invention, the intensification of magnetic field around the arcing contact is made possible with a specially designed arcing contact support. The increased magnetic field forces the arc towards the arc chute plates which helps in achieving the high current interrupting capacity.
Referring to the drawings. Fig. 1 is an elevational view, partly in section, of a pole of air circuit breaker embodying the present invention; Fig.2 is a detail view of pole assembly associated with arc chute of air circuit breiaker; Figs. 3(A), 3(B), 3(C) give the view of Fixed arcing contact and a device support according to the invention. The pole assembly includes an operating rod (1), a contact holder (2), a moving arcing contact (3), a moving arcing horn (4), a fixed arcing contact (5), a

fixed arcing contact tip (6), a fixed arcing contact tip (7), Legs (8) of the support (18), an upper terminal (9), Main contacts (10), a lower terminal (11), a copper flexible (12), a wire Mesh (13), an arc chute plates (14), an arc chute (15), a fixed arcing horn (16), Rivet holes (17), Hole on the fixed arcing contact support (18), Hole on the fixed arcing contact (19) and Slots of the fixed arcing contact (20).
The pole assembly of the air circuit breaker as shown in the Fig. 1 consists of one each moving and fixed contact structure I and II respectively. The fixed contact structure (II) is connected to the breaker upper terminal (9) and the movable contact structure (I) to the lower terminal (11). The moving contact structure (I) through a contact holder (2) is linked to an operating rod (1) which is connected to an operating mechanism through a crossbar (not shown), A copper flexible (12) wire connects the lower terminal (U) to the moving contact. The circuit breaker shown is in closed cux;uit position. During opening operation of the circuit breaker, the main contacts (10) move apart and transfer the current to the arcing contacts (3,5). The arcing contacts (3,5) are subjected to the arc while closing and opening of the circuit breaker as it is the first to make and last to break contact. The arcing horns both fixed (16) and movable (4) guides the arc towards the arc chute (15). The arc chute (15) is provided with a number of parallel interleaving ridges or barriers (14) shown in Fig, 2, that form between them a tortuous or zigzag arc passage extending through the chute. During opening, the arc generated in the arcing contacts (3,5) is subjected to a magnetic field of the current carrying contact. This magnetic field forces the arc towards the arc chute (15). The arc on extending gets cooled, exhaust gases after deionization, and passes through the wire mesh (13). The arc accelerator rapid the cooling process, and consists of a magnetic device that drives the arc while interrupting high current for rapid cooling of the arc chute (15). The arc accelerator constitutes a fixed arcing contact support (7) made of soft magnetic material, such as iron or cold rolled steel. The legs (8) of the fixed arcing contact support (7) are U-shaped, and fitted in the slots (20) of the fixed arcing contact (5) and riveted at the hole (17) shown m Fig 3(A). The legs (8) on either side of the fixed arcing contact Up

(6), are constructed as U-shaped magnetic yokes. The fixed arcing contact (5) along with the support (7) is screwed to the upper terminal (9) through the holes (18,19). When the arcing contacts (3,5) get separated, the power arc is initially formed. The arc upon forming is allowed to move rapidly into the chute without excessive burning of the contact structure (IJI). To achieve the phenomenon, the chute is provided widi a fixed arcing horn (16) arranged to cooperate with the movable horn (4). The arcing horns at the point of initial arcing between the contacts (3,5), are closely spaced from each other by a short air gap, specially a U-shape gap.
This gap is formed between the movable horn (4) and the adjacent side walls of a U-shaped recess (8) extending along the arcing face of the fixed hom (16). The arc is now entirely on the diverging arcing horns (16,4), so that the arc moves into the chute (15) under the influence of a magnetic field generated due to the flow of current in the fixed arcing contact (5) while the breaker opening progresses. As the U-shaped recess (8) is formed of high magnetically permeable material, the magnetic field induced is greater than that of the induced air. The Lorentz force acting on the arc is greater than the force which would have acted on the arc without U-shaped recess (8). This accelerates the arc towards the arc chute (15) without damaging the contact structures I and IL
Numerous modifications and adaptations of the system of the present invention wilt be apparent to those skilled in the art, and thus it is intended by the appended claims to cover all such modifications and adaptations which fall within the true spirit and scope of this invention.

WE CLAIM:
1. An electric circuit breaker with fixed arcing contact support to protect electrical contacts from being damaged during high current interruption, the air circuit breaker essentially consisting of one each moving contact structure (I) and fixed contact structure (II) that are respectively connected to the lower terminal (11) and upper terminal (9) of the pole assembly of the ckcuit breaker, the main contacts (10) moving apart during opening of the circuit breaker to transfer the current to the arcmg contacts (3,5), one each fixed and movable arcing horns (16,4) guiding the arc towards an arcing chute (16) provided with plurality of barriers (14) under the influence of magnetic field force generated during the opening, the arc upon extending and cooling passmg through an wire-mesh (13), characterized m that an arc accelerator havmg U-shaped legs (8) formed of magnetic yokes including a fixed arcing contact support (7) made of soft magnetic material is provided, m that the legs (8) are fitted into a corresponding number of slots (20) configured on the fixed arcing contacts (5), in that the movable horn (4) creating an air gap with the side walls of said legs (8) extending along the arcing face of the fixed horn (16), and in that the magnetic field induced due to high magnetically permeable materials of the legs (8) causes acceleration of the arc towards the chute (15) without damaging the fixed and moving contact structures (I,II).
2. The air cbxuit breaker as claimed in claim 1, wherein the decarbunzed high perm treated steel piece is Nickel plated.
3. The an- ckcuit breaker as claimed in claim 1, wherein the decarbunzed high perm treated Nickel plated steel piece placed around die contacts leads to creation of high magnetic intensified zone increasing the force on the moving contact arm resulting in faster opening of the contacts.

4. The air circuit breaker as claimed in claim 1, wherein the arc accelerator
device is kept open from the top and is integrally placed around the
contacts so as to assist the fast separation of the contacts.
5, The air circuit breaker as claimed in claim 1, wherein at high currents the
decarburized plates do not get saturated and allows an increase in the
magnetic force to quickly open the contacts and lengthening of die arc.