Patent Description:
In general, a circuit breaker operates to engage and disengage a selected electrical circuit from an electrical power supply. The circuit breaker ensures current interruption thereby, providing protection to the electrical circuit from continuous over current conditions and high current transients due to, for example, electrical short circuits. Such circuit breakers operate by separating a pair of internal electrical contacts contained within a housing e.g., molded case of the circuit breaker. Typically, one electrical contact is stationary while the other is movable e.g., typically mounted on a pivotable contact arm.

The contact separation may occur manually, such as when a person throws an operating handle of the circuit breaker. This may engage an operating mechanism, which may be coupled to the contact arm and moveable electrical contact. Alternatively, the electrical contacts may be separated automatically when an over current, short circuit, or fault condition is encountered. Automatic tripping may be accomplished by an operating mechanism actuated via a thermal overload element e.g., a bimetal element or by a magnetic element, or even by an actuator e.g., a solenoid.

Upon separation of the electrical contacts by tripping, an intense electrical arc may be formed in an arc chamber containing the electrical contacts. This separation may occur due to heat and/or high current through the circuit breaker or due to sensing a ground or other arc fault. It is desirable to extinguish the arc as quickly as possible to avoid damaging internal components of the circuit breaker.

In power distribution networks, a circuit breaker of type, called a gas-insulated circuit breaker is commonly used. Such gas-insulated circuit breaker is designed in such a way that in the event of separating of the contacts, or in case of a short circuit, the arc is blasted with gas and consequently quenched as quickly as possible. In such circuit breaker, a pressure chamber, in which the arc is created, is connected in a valve-controlled manner to a compression chamber. The compression chamber is connected to a low-pressure chamber via a valve arrangement. The valve arrangement, on the low-pressure chamber side, is pressed by a spring against a valve holder in the direction of the compression volume. Gas can therefore flow from the compression volume into the low-pressure chamber only when its pressure is higher than the spring force.

In a high voltage circuit breaker, a valve is typically implemented to regulate the flow of gas towards arcing contact, as is described in <CIT> and in <CIT>. Such a valve allows the free flow of gas in one direction while gas flow in other direction is dependent on the pressure built in compression volume. It is required that the valve should allow gas flow towards arcing contacts during gas filling. Further, during opening of the circuit breaker, the valve has to be closed such that pressure in the compression volume increases up to specified limit. Also, it is required that once the pressure in compression volume increases beyond specified limit, valve should open.

<CIT> ('<NUM> application) relates to an electric high-voltage circuit breaker comprising a primary chamber and a compression chamber, wherein said circuit breaker further comprises a valve configured to control a fluid flow between said primary chamber and said compression chamber. The electric high-voltage circuit breaker of the '<NUM> application discloses that said valve comprises a valve body, a first valve plate that is arranged axially movable with respect to said valve body, and a second valve plate that is arranged between and movable, preferably at least axially movable, with respect to said valve body and said first valve plate, wherein said first valve plate comprises at least one opening enabling a fluid flow through said first valve plate, wherein a first surface of said valve body forms a valve seat for said first valve plate, and wherein a first surface of said first valve plate forms a valve seat for said second valve plate.

In the circuit breaker of the '<NUM> application, one or more guide pins may be provided for guiding an axial movement of both said first valve plate and said second valve plate. Further, a first spring force mechanism is provided to press said first valve plate to said valve seat of the valve body, and a second spring force mechanism is provided to press said second valve plate to said valve seat of the first valve plate. Each of the spring force mechanisms may comprise one or more springs (for example, helical springs) arranged at said guide pins.

The type of construction implemented for the valve in the circuit breaker, as disclosed in the '<NUM> application, is relatively complicated and requires a large number of components, and that may result in hindrance to the path of flow of gas which is undesirable. It may be appreciated that pressure opening from compression volume is only possible from one side in such configuration. Further, in such configuration of the valve arrangement, typically, a pneumatic press is required to mount the spring on the valve which is an added expense. Also, the load value needs to be set for each of the springs to get desired pressure release output, which may be time-consuming and cumbersome.

In light of the above, it is an object of the present disclosure to provide a circuit breaker with a valve assembly to regulate the flow of gas towards arcing contact, which is simple in construction, is economical to manufacture and is efficient to operate.

The object of the present disclosure is achieved by a circuit breaker comprising first and second electrical contacts, the electrical contacts configured to generate an electrical arc upon being separated during operation of the circuit breaker. The circuit breaker comprises a first chamber at least partially surrounding the first and second electric contacts, and a second chamber filled with insulating gas. The circuit breaker further comprises a valve assembly interconnecting the first chamber and the second chamber. The valve assembly is configured to allow threshold-based flow of the insulating gas into and out of the first chamber. The valve assembly comprises a valve body. The valve assembly also comprises a first valve plate movably mounted in the valve body, and a second valve plate arranged in the valve body so as to move between a first position, a second position and a third position therein, wherein in the first position, the second valve plate is seated on the first valve plate, in the second position, the second valve plate is lifted from the first valve plate to above the first position thereof, and in the third position, the second valve plate is seated on the first valve plate and moves the first valve plate therewith below the first position thereof. The valve assembly further comprises a plurality of Belleville springs radially arranged in the valve body below the first valve plate, the plurality of Belleville springs configured to constrain the movement of the first valve plate up to the third position of the second valve plate in the valve body.

In an embodiment, the second valve plate assumes the second position during filling of the insulating gas into the second chamber thereby, allowing passage to the insulated gas into the first chamber which is at a lower pressure than the second chamber, and wherein the second valve plate assumes the first position upon completion of the filling of the insulating gas when the pressure in the first chamber is higher than in the second chamber.

In an embodiment, the second valve plate assumes the third position upon generation of the electrical arc, moving the first valve plate therewith, by overcoming the constrain on the movement of the first valve plate by the plurality of Belleville springs due to additional pressure built in the first chamber, allowing passage to the insulated gas into the second chamber.

In an embodiment, the plurality of Belleville springs are tensioned to define the constrain on the movement of the first valve plate in the valve body based on desired threshold pressure of the insulating gas in the first chamber.

In an embodiment, each of the plurality of Belleville springs comprises two or more Belleville spring units arranged in a stacked configuration to provide the tension, to define the constrain on the movement of the first valve plate in the valve body based on the desired threshold pressure of the insulating gas in the first chamber.

In an embodiment, the valve assembly further comprises a plurality of fasteners, corresponding to the plurality of Belleville springs, fixed to the valve body. Each of the plurality of fasteners supports one of the plurality of Belleville springs below the first valve plate.

The valve body comprises a stopper formed therein, such that the stopper limits the lifting of the second valve plate up to the second position thereof in the valve body.

In an embodiment, the valve body has a substantially cylindrical shape.

In an embodiment, the first valve plate has one or more openings formed therein. The second valve plate is seated on the first valve plate in a manner so as to seal the one or more openings thereof.

The object of the present disclosure is also achieved by a valve assembly for a circuit breaker having a first chamber and a second chamber filled with insulating gas, the valve assembly being of the configuration as discussed in preceding paragraph.

The object of the present disclosure is further achieved by an arc pressure control arrangement, which may be implemented, for example, in a circuit breaker. Herein, the arc pressure control arrangement comprises a first chamber containing first and second electrical contacts, the electrical contacts configured to generate an electrical arc upon being separated during operation of the circuit breaker. The arc pressure control arrangement further comprises a second chamber filled with insulating gas. The arc pressure control arrangement further comprises a valve assembly interconnecting the first chamber and the second chamber, the valve assembly being of the configuration as discussed in preceding paragraphs.

The object of the present disclosure is further achieved by a method of operating a circuit breaker. The method comprises providing a valve assembly comprising a valve body interconnecting a first chamber and a second chamber in the circuit breaker, a first valve plate movably mounted in the valve body, and a second valve plate arranged in the valve body so as to move between a first position, a second position and a third position therein, wherein in the first position, the second valve plate is seated on the first valve plate, in the second position, the second valve plate is lifted from the first valve plate to above the first position thereof, and in the third position, the second valve plate is seated on the first valve plate and moves the first valve plate therewith below the first position thereof. The method further comprises providing a plurality of Belleville springs radially arranged in the valve body below the first valve plate to constrain the movement of the first valve plate up to the third position of the second valve plate in the valve body, and wherein the valve body comprises a stopper formed therein, such that the stopper limits the lifting of the second valve plate up to the second position thereof in the valve body. The method further comprises filling the second chamber with insulating gas such that the second valve plate assumes the second position during filling of the insulating gas into the second chamber thereby, allowing passage to the insulated gas into the first chamber which is at a lower pressure than the second chamber, and the second valve plate assumes the first position upon completion of the filling of the insulating gas when the pressure in the first chamber is higher than in the second chamber. The method further comprises separating a first electrical contact from a second electrical contact in a first chamber of the circuit breaker to generate an electrical arc, such that the second valve plate assumes the third position upon generation of the electrical arc, moving the first valve plate therewith, by overcoming the constrain on the movement of the first valve plate by the plurality of Belleville springs due to additional pressure built in the first chamber, allowing passage to the insulated gas into the second chamber.

Still other aspects, features, and advantages of the invention are readily apparent from the following detailed description, simply by illustrating a number of particular embodiments and implementations, including the best mode contemplated for carrying out the invention. The invention is also capable of other and different embodiments, and its several details can be modified in various obvious respects, all without departing from the scope of the invention. Accordingly, the drawings and description are to be regarded as illustrative in nature, and not as restrictive.

A more complete appreciation of the present disclosure and many of the attendant aspects thereof will be readily obtained as the same becomes better understood by reference to the following description when considered in connection with the accompanying drawings:.

Various embodiments are described with reference to the drawings, wherein like reference numerals are used to refer the drawings, wherein like reference numerals are used to refer to like elements throughout. In the following description, for the purpose of explanation, numerous specific details are set forth in order to provide thorough understanding of one or more embodiments.

In the following description, for the purposes of explanation, numerous specific details are set forth in order to provide a thorough understanding of the embodiments of the invention. It is apparent, however, to one skilled in the art that the embodiments of the invention may be practiced without these specific details or with an equivalent arrangement. In other instances, well-known structures and devices are shown in block diagram form in order to avoid unnecessarily obscuring the embodiments of the invention.

Example embodiments of an arc pressure control arrangement described herein may be included in a circuit breaker to prevent a re-ignition failure of the circuit breaker. In certain example embodiments, upon contact separation, an arc is formed in a compression volume of the circuit breaker. The arc, extending between the first and second electrical contacts (e.g., stationary and moveable electrical contacts), produces arcing gases and also heats up and pressurizes the insulating gas within the compression volume. This causes a flow of the heated insulating gas and arc gasses, due to the pressure change, into a low-pressure volume disposed adjacent to the compression volume, but only at certain times during the arcing event.

A valve assembly is provided between the compression volume and the low-pressure volume to allow flow into and out of the compression volume only at the certain times during the arcing event. For example, the valve assembly may allow gas flow only when an inlet threshold pressure in the compression volume is exceeded. Further, the valve assembly may allow gas flow only when a pressure in the compression volume falls below an outlet threshold pressure. Thus, gas flows into the low-pressure volume after the gas pressure in the compression volume reaches the inlet threshold pressure, is held in the low-pressure volume for part of the arc cycle, and then flows out of the low-pressure volume and back into the compression volume when the pressure in the compression volume falls below the outlet threshold pressure.

Examples of a circuit breaker, a valve assembly for a circuit breaker, an arc pressure control arrangement, and a method of operating a circuit breaker are disclosed and fully described with reference to <FIG> herein.

<FIG> is a diagrammatic perspective representation of an exemplary circuit breaker <NUM>, in accordance with one or more embodiments of the present disclosure. In the present illustration, the depicted circuit breaker <NUM> is a three-pole pillar mounted circuit breaker; however, for the purposes of the present disclosure, the circuit breaker <NUM> may be any type of high-voltage circuit breaker as known in the art. The circuit breaker <NUM> includes a common breaker base <NUM> onto which the various components are mounted. In the present three-pole circuit breaker <NUM>, there pole columns <NUM>, <NUM> and <NUM> are provided which are mounted on the common breaker base <NUM>. The pole columns <NUM>, <NUM> and <NUM> are connected by tubes to a gas compartment (not shown) and are filled with insulating gas, such as, but not limited to, SF6 (Sulphur Hexafluoride) for arc-quenching and insulating purposes. The gas density is monitored by a density monitor (not shown), and the pressure can be displayed by a pressure gauge or a pressure display on the density monitor.

The circuit breaker <NUM> also includes an operating mechanism unit <NUM> fastened to the breaker base <NUM>. A mounting plate (not shown) is integrated in the operating mechanism unit <NUM>, which contains all equipment for control and monitoring of the circuit breaker <NUM> and also terminal blocks required for electrical connections. The circuit breaker <NUM> further includes a spring drive mechanism (not shown) located in the operating mechanism unit <NUM>. Typically, the spring drive mechanism includes closing and opening springs, and the energy required for switching is stored in one closing spring common to all three poles and one opening spring. In the circuit breaker <NUM>, the pole column <NUM> is actuated by the spring drive mechanism via a corner gear <NUM> (as shown in <FIG>) and is connected with corner gears of the pole columns <NUM> and <NUM> by means of coupling rods. The circuit breaker <NUM> further includes a switching position indicator <NUM> which indicates the position and status of all switch equipment thereof.

<FIG> is a diagrammatic cross-sectional representation of the pole column <NUM> of the circuit breaker <NUM>. It may be appreciated that all of the three pole columns <NUM>, <NUM> and <NUM> are similar in design and the present illustration can be construed to be representative of any of the three pole columns <NUM>, <NUM> and <NUM> for the purposes of the present disclosure. As illustrated, the pole column <NUM> includes a post insulator <NUM> which provides insulation against earth. Further, the pole column <NUM> includes an insulated drive rod <NUM>. The pole column <NUM> includes an interrupter unit <NUM> mounted on the post insulator <NUM>.

<FIG> is a diagrammatic cross-sectional representation of the interrupter unit <NUM>. Referring to <FIG> and <FIG> in combination, the interrupter unit <NUM> contains the filter material <NUM>, generally in the form of filter bag. The filter material <NUM> is used for the absorption of decomposition products of the insulating gas (like SF6) and for keeping the gas dry. The interrupter unit <NUM> further includes a gas-tight jacket <NUM> which accommodates the breaker contacts. In the pole column <NUM>, the switching motion is transferred from the spring drive mechanism (at earth potential) via a coupling rod <NUM>, a shaft <NUM>, and thereby from the insulated drive rod <NUM> to the interrupter unit <NUM> (at high voltage potential).

As illustrated, the main circuit for the interrupter unit <NUM> includes an upper high-voltage terminal <NUM>, a lower high-voltage terminal <NUM>, a diffuser socket <NUM>, ring-placed contact laminations <NUM> arranged with the diffuser socket <NUM>, a heat cylinder <NUM> and an operating socket <NUM>. Herein, the contact laminations <NUM> are self-sprung and centrically pressed inwards, which ensures the necessary contact pressure on the heat cylinder <NUM> and the diffuser socket <NUM>. Also, the upper high-voltage terminal <NUM> and the lower high-voltage terminal <NUM> are mounted using O-rings <NUM>. Further, an arcing circuit is arranged parallel to the main circuit, which is made up of a pin <NUM> (also referred to as first electrical contact <NUM>) situated in the diffuser socket <NUM> and a moving tube contact <NUM> (also referred to as second electrical contact <NUM>) placed in the heat cylinder <NUM>. Herein, the pin <NUM> and the tube contact <NUM> are made of materials, which produce only minimal contact erosion. Further, as illustrated, a piston <NUM> and a pull rod <NUM> are arranged in the interrupter unit <NUM>. Herein, the tube contacts <NUM>, the piston <NUM> and the heat cylinder <NUM> are mechanically interconnected and coupled with the pull rod <NUM>, and form the moving parts of the interrupter unit <NUM>. In the circuit breaker <NUM>, a valve assembly <NUM> is arranged in cylindrical casting <NUM>, which together with an arc quenching nozzle <NUM> makes up the compression unit for arc quenching purposes.

<FIG> are partial schematic representations of an arc pressure control arrangement <NUM>, implemented in the circuit breaker <NUM>, or specifically the interrupter unit <NUM> of the circuit breaker <NUM>, depicting stages of arc quenching operation therein. As illustrated, the arc pressure control arrangement <NUM> includes the first electrical contact <NUM> and the second electrical contact <NUM>. Herein, the first electrical contact <NUM> and the second electrical contact <NUM> are configured to generate an electrical arc upon being separated during operation of the circuit breaker <NUM>. As illustrated, the arc pressure control arrangement <NUM> includes a first chamber (generally represented by numeral <NUM>) at least partially surrounding the first electric contact <NUM> and the second electric contact <NUM>. Further, the arc pressure control arrangement <NUM> includes a second chamber (generally represented by numeral <NUM>) disposed adjacent to the first chamber <NUM>. Herein, the second chamber <NUM> is filled with insulating gas, such as, for example, SF6. It may be understood that the first chamber <NUM> is a compression volume and the second chamber <NUM> is a low-pressure volume in the circuit breaker <NUM>, and the said terms have been interchangeably used in the description without any limitations. In the arc pressure control arrangement <NUM>, as illustrated, the valve assembly <NUM> interconnects the first chamber <NUM> and the second chamber <NUM>. The valve assembly <NUM> regulates the flow of the insulating gas from the second chamber <NUM> into the first chamber <NUM>, and vice-versa. In particular, the valve assembly <NUM> allows the flow of the insulating gas based on desired threshold pressure of the insulating gas in the first chamber <NUM>. Thereby, the valve assembly <NUM> is configured to allow threshold-based flow of the insulating gas into and out of the first chamber <NUM>.

In one or more embodiments, the first chamber <NUM> includes an internal storage volume that is greater than about <NUM><NUM>. For example, an internal storage volume of the first chamber 156may be greater than about <NUM>,<NUM><NUM> for a 600V/250A circuit breaker, or even greater than about <NUM>,<NUM><NUM> for a 600V/250A circuit breaker. In some embodiments, the internal storage volume of the second chamber <NUM> may be about <NUM>,<NUM><NUM> or more. In some example embodiments, the second chamber <NUM> may be a rectangular shape and may include an internal height of about <NUM>, an internal width of about <NUM>, and an internal thickness of <NUM>. Other sizes, shapes, and storage volumes for the second chamber <NUM> may be used.

In an opening operation, the main contact that exists between the contact laminations <NUM> and the heat cylinder <NUM> is opened (as shown in <FIG>). The arcing contact, consisting of the first electrical contact <NUM> and the second electrical contact <NUM> remains closed, with the result that the current commutates onto the arcing contact. During the continued course of the opening operation, the arcing contact opens creating an arc. At the same time, the heat cylinder <NUM> moves downward and compresses the quenching gas between the heat cylinder <NUM> and plate supporting the valve assembly <NUM>. This causes the quenching gas to be forced in the direction opposite to the movement of the moving contact components, into the heat cylinder <NUM> and through the gap between the second electrical contact <NUM> and the arc-quenching nozzle, thus quenching the arc. With large short-circuit currents, the quenching gas surrounding the first electrical contact <NUM> in the arcing chamber is heated by the arc's energy and driven into the heat cylinder <NUM> at high pressure. When the current passes through zero, the gas flows back from the heat cylinder <NUM> into the nozzle and quenches the arc.

<FIG> are different diagrammatic representations of the valve assembly <NUM>. As illustrated, the valve assembly <NUM> includes a valve body <NUM>. Herein, the valve body <NUM> has a substantially cylindrical or annular shape. As shown, the valve body <NUM> has a radially inner, central opening <NUM>. The valve body <NUM> is guided through the wall of the first chamber <NUM>, with a gas passage which connects the first chamber <NUM> and the second chamber <NUM>. Generally, a radially outer surface of the valve body <NUM> may contact a surrounding surface (not shown) of the circuit breaker <NUM> in a sealing (substantially gas-tight) manner. Similarly, a radially inner surface of the valve body <NUM> may contact a radially outer surface of the drive rod <NUM> (as may be seen from <FIG>) or an extension of the drive rod <NUM> protruding through the central opening <NUM> of the valve body <NUM> in a sealing manner. As an example, at both radially outer surface and radially inner surface, suitable sealing may be provided such as sealing rings and the like.

The valve assembly <NUM> further includes a first valve plate <NUM> (as better illustrated in <FIG>) movably mounted in the valve body <NUM>. The valve assembly <NUM> also includes a second valve plate <NUM> (as better illustrated in <FIG>) movably seated on the first valve plate <NUM>. In the present examples, the valve body <NUM>, along with the first valve plate <NUM> and the second valve plate <NUM>, may be formed of any suitable metallic material, such as, but not limited to, stainless steel or the like. Herein, the valve body <NUM> has generally larger diameter than the first valve plate <NUM> and the second valve plate <NUM>, while the first valve plate <NUM> and the second valve plate <NUM> have substantially similar diameter. Generally, the first valve plate <NUM> and the second valve plate <NUM> may be pressed to the valve body <NUM> in a sealing manner.

In the present embodiments, the second valve plate <NUM> is arranged in the valve body <NUM> so as to move between a first position, a second position and a third position therein. Herein, in the first position, the second valve plate <NUM> is seated on the first valve plate <NUM>. In the second position, the second valve plate <NUM> is lifted from the first valve plate <NUM> to above the first position thereof. In the third position, the second valve plate <NUM> is seated on the first valve plate <NUM> and move the first valve plate <NUM> therewith below the first position thereof.

In one or more examples, the first valve plate <NUM> may include seats defined therein onto which the second valve plate <NUM> is seated. As can best be seen from <FIG>, the first valve plate <NUM> has one or more openings <NUM> formed therein, presently five openings <NUM>. The openings <NUM> are radially segregated on planar exposed surface of the first valve plate <NUM>. Further, the second valve plate <NUM> is a substantially solid annular member seated on the first valve plate <NUM> in a manner so as to seal the one or more openings <NUM> thereof. Further, as may be seen, the valve body <NUM> has one or more openings <NUM>, presently five openings <NUM>. Similar to the openings <NUM>, the openings <NUM> are radially segregated on planar exposed surface of the valve body <NUM>. Herein, the openings <NUM> are generally disposed in-line with the openings <NUM> in the first valve plate <NUM>, enabling a fluid flow through the first valve plate <NUM>, for example in a basically axial direction of the circuit breaker <NUM>.

The valve assembly <NUM> further includes a plurality of Belleville springs <NUM>. Belleville spring is a type of spring shaped like a washer. Belleville spring, also known as a coned-disc spring, conical spring washer, disc spring, Belleville washer or cupped spring washer, is a conical shell which can be loaded along its axis either statically or dynamically. Belleville spring has the frustoconical shape that gives the washer its characteristic spring properties. As illustrated, the Belleville springs <NUM> are radially arranged in the valve body <NUM> below the first valve plate <NUM>. In the present configuration, the Belleville springs <NUM> are coupled to the first valve plate <NUM>.

As can best be seen from <FIG>, the valve assembly <NUM> further comprises a plurality of fasteners <NUM>, corresponding to the plurality of Belleville springs <NUM>, fixed to the valve body <NUM>. Each of the plurality of fasteners <NUM> supports one of the plurality of Belleville springs <NUM> below the first valve plate <NUM>. In particular, each of the fasteners <NUM> include a shaft <NUM> onto which the corresponding Belleville spring <NUM> is mounted and a nut <NUM> which supports the corresponding Belleville spring <NUM> on the shaft <NUM>. Such assembly may be contemplated by a person skilled in the art in light of the included drawings and thus has not been explained herein for the brevity of the present disclosure.

Herein, the plurality of Belleville springs <NUM> are configured to constrain the movement of the first valve plate <NUM> up to the third position of the second valve plate <NUM> in the valve body <NUM>. For this purpose, the plurality of Belleville springs <NUM> are tensioned to define the constrain on the movement of the first valve plate <NUM> in the valve body <NUM> based on desired threshold pressure of the insulating gas in the first chamber <NUM>. It may be appreciated by a person skilled in the art that the constrain may be defined based on the voltage rating of the circuit breaker <NUM>, in order to be able to quench the generated arc in required time to avoid any damage, as will be discussed in more detail in the proceeding paragraphs.

In one or more embodiments, each of the plurality of Belleville springs <NUM> comprises two or more Belleville spring units <NUM> (as better illustrated in <FIG>). The two or more Belleville spring units <NUM> in each of the plurality of Belleville springs <NUM> are arranged in a stacked configuration to provide the tension to the corresponding Belleville spring <NUM>, to define the constrain on the movement of the first valve plate <NUM> in the valve body <NUM> based on the desired threshold pressure of the insulating gas in the first chamber <NUM>. As may be contemplated, by stacking multiple Belleville spring units <NUM> in a single Belleville spring <NUM>, desired tension for the corresponding Belleville spring <NUM> can be achieved. In the present configuration, as illustrated in <FIG>, each of the Belleville springs <NUM> comprises six Belleville spring units <NUM>. Alternatively, each of the plurality of Belleville springs <NUM> may include single Belleville spring unit <NUM> which may have suitable stiffness to achieve the required tension for the corresponding Belleville spring <NUM> to define the constrain on the movement of the first valve plate <NUM> in the valve body <NUM> based on the desired threshold pressure of the insulating gas in the first chamber <NUM>. It may be appreciated by a person skilled in the art that with the use of Belleville springs <NUM>, load value can be set for different pressure release value by stacking different number of Belleville spring units <NUM>.

In one or more embodiments, as better illustrated in <FIG>, the valve body <NUM> comprises a stopper <NUM> formed therein. The stopper <NUM> is in the form of a tab protruding out from an inner wall of the valve body <NUM>. The stopper <NUM> limits the lifting of the second valve plate <NUM> up to the second position thereof in the valve body <NUM>. That is, the stopper <NUM> may be integrated into the valve body <NUM> and limits the movement of the first valve plate <NUM> when the circuit breaker <NUM> closes.

<FIG> are representations depicting various positions of the valve assembly <NUM> during arc quenching operation in the circuit breaker <NUM>. As illustrated in <FIG>, during normal state of the valve assembly <NUM>, the second valve plate <NUM> in the first position, i.e. the second valve plate <NUM> is seated on the first valve plate <NUM>. In particular, the first valve plate <NUM> is arranged in the valve body <NUM> with the second valve plate <NUM> seated on the first valve plate <NUM>.

Further, as illustrated in <FIG>, during filling operation, the valve assembly <NUM> is moved to gas upward state. Herein, the second valve plate <NUM> assumes the second position, i.e. the second valve plate <NUM> is lifted from the first valve plate <NUM> to above the first position thereof, during filling of the insulating gas into the second chamber <NUM> thereby, allowing passage to the insulated gas into the first chamber <NUM> which is at a lower pressure than the second chamber <NUM>. In other words, the second valve plate <NUM> gets lifted from the first valve plate <NUM> due to pressure of the insulating gas in the second chamber <NUM> to provide a flow path for the insulating gas to flow from the second chamber <NUM> into the first chamber <NUM>. Subsequently, the second valve plate <NUM> assumes the first position (akin to the normal state of <FIG>) upon completion of the filling of the insulating gas when the pressure in the first chamber <NUM> is higher than in the second chamber <NUM>.

As discussed, upon contact separation, an arc is formed in the first chamber <NUM> of the circuit breaker <NUM>. The arc, extending between the first electrical contact <NUM> and the second electrical contact <NUM> (e.g., stationary and moveable electrical contacts), produces arcing gases and also heats up and pressurizes the insulating gas within the first chamber <NUM>. This causes a flow of the heated insulating gas and arc gasses, due to the pressure change, into the second chamber <NUM> disposed adjacent to the first chamber <NUM>, but only at certain times during the arcing event.

As illustrated in <FIG>, upon generation of the electrical arc, the valve assembly <NUM> is moved to gas downward state. Herein, the second valve plate <NUM> assumes the third position, i.e. the second valve plate <NUM> is seated on the first valve plate <NUM> and have moved the first valve plate <NUM> therewith to below the first position thereof, by overcoming the constrain on the movement of the first valve plate <NUM> by the plurality of Belleville springs <NUM> due to additional pressure built in the first chamber <NUM>, allowing passage to the insulated gas into the second chamber <NUM>. In other words, the first valve plate <NUM> is separated from the second valve plate <NUM> due to further pressure build-up of the insulating gas in the first chamber <NUM> overcoming the constrain of the Belleville springs <NUM> coupled thereto to provide a flow path for the insulating gas to flow out of the first chamber <NUM> to the second chamber <NUM>.

Thus, the insulating gas flows into the second chamber <NUM> after the gas pressure in the first chamber <NUM> reaches the inlet threshold pressure, is held in the second chamber <NUM> for part of the arc cycle, and then flows out of the second chamber <NUM> and back into the first chamber <NUM> when the pressure in the first chamber <NUM> falls below the outlet threshold pressure. This gas flow may cool down the first chamber <NUM> and may also increase dielectric strength thereof. In one or more embodiments, the gas flow around the arc increases the arc voltage, thereby providing better current limiting performance.

<FIG> is a flowchart <NUM> listing steps involved in a method of operating a circuit breaker, such as the circuit breaker <NUM>. At step <NUM>, the method includes providing a valve assembly <NUM> comprising a valve body <NUM> interconnecting a first chamber <NUM> and a second chamber <NUM> in the circuit breaker <NUM>, a first valve plate <NUM> movably mounted in the valve body <NUM>, and a second valve plate <NUM> arranged in the valve body <NUM> so as to move between a first position, a second position and a third position therein, wherein in the first position, the second valve plate <NUM> is seated on the first valve plate <NUM>, in the second position, the second valve plate <NUM> is lifted from the first valve plate <NUM> to above the first position thereof, and in the third position, the second valve plate <NUM> is seated on the first valve plate <NUM> and moves the first valve plate <NUM> therewith below the first position thereof. At step <NUM>, the method includes providing a plurality of Belleville springs <NUM> radially arranged in the valve body <NUM> below the first valve plate <NUM> to constrain the movement of the first valve plate <NUM> up to the third position of the second valve plate <NUM> in the valve body <NUM>. At step <NUM>, the method includes filling the second chamber <NUM> with insulating gas such that the second valve plate <NUM> assumes the second position during filling of the insulating gas into the second chamber <NUM> thereby, allowing passage to the insulated gas into the first chamber <NUM> which is at a lower pressure than the second chamber <NUM>, and the second valve plate <NUM> assumes the first position upon completion of the filling of the insulating gas when the pressure in the first chamber <NUM> is higher than in the second chamber <NUM>. At step <NUM>, the method includes separating a first electrical contact <NUM> from a second electrical contact <NUM> in a first chamber <NUM> of the circuit breaker <NUM> to generate an electrical arc, such that the second valve plate <NUM> assumes the third position upon generation of the electrical arc, moving the first valve plate <NUM> therewith, by overcoming the constrain on the movement of the first valve plate <NUM> by the plurality of Belleville springs <NUM> due to additional pressure built in the first chamber <NUM>, allowing passage to the insulated gas into the second chamber <NUM>.

Claim 1:
A circuit breaker (<NUM>), comprising:
first and second electrical contacts (<NUM>, <NUM>), the electrical contacts (<NUM>, <NUM>) configured to generate an electrical arc upon being separated during operation of the circuit breaker (<NUM>);
a first chamber (<NUM>) at least partially surrounding the first and second electric contacts (<NUM>, <NUM>);
a second chamber (<NUM>) filled with insulating gas; and
a valve assembly (<NUM>) configured to allow threshold-based flow of the insulating gas into and out of the first chamber (<NUM>), the valve assembly (<NUM>) comprising:
a valve body (<NUM>) interconnecting the first chamber (<NUM>) and the second chamber (<NUM>);
a first valve plate (<NUM>) movably mounted in the valve body (<NUM>); and
a second valve plate (<NUM>) arranged in the valve body (<NUM>) so as to move between a first position, a second position and a third position therein, wherein in the first position, the second valve plate (<NUM>) is seated on the first valve plate (<NUM>), in the second position, the second valve plate (<NUM>) is lifted from the first valve plate (<NUM>) to above the first position thereof, and in the third position, the second valve plate (<NUM>) is seated on the first valve plate (<NUM>) and moves the first valve plate (<NUM>) therewith below the first position thereof,
characterized in that the valve assembly (<NUM>) comprises a plurality of Belleville springs (<NUM>) radially arranged in the valve body (<NUM>) below the first valve plate (<NUM>), the plurality of Belleville springs (<NUM>) configured to constrain the movement of the first valve plate (<NUM>) up to the third position of the second valve plate (<NUM>) in the valve body (<NUM>), and wherein the valve body (<NUM>) comprises a stopper (<NUM>) formed therein, such that the stopper (<NUM>) limits the lifting of the second valve plate (<NUM>) up to the second position thereof in the valve body (<NUM>).