An arc chute unit of a pole assembly of a molded case circuit breaker (MCCB)

Abstract

Described herein is an arc chute unit [134] of a pole assembly [102] of a Molded Case Circuit Breaker (MCCB) [100]. The arc chute unit [134] comprises an arc chute member [138], and an arc chute holder [136]. The arc chute holder [136] is adapted to mount on the arc chute member [138]. The arc chute holder [136] includes a first housing member [140] and a second housing member [142]. The first housing member [140] is made up of a first material with a first ablation rate, and first thermal properties. The second housing member [142] is made up of a second material with a second ablation rate, and second thermal properties, such that the first ablation rate is different from the second ablation rate, and the first thermal properties are different from the second thermal properties.

Description

[0001] AN ARC CHUTE UNIT OF A POLE ASSEMBLY OF A MOLDED CASE CIRCUIT BREAKER (MCCB)

[0002] TECHNICAL FIELD

[0003] The present invention relates to the field of circuit breakers, particularly to a Molded Case Circuit Breaker (MCCB). The present invention specifically relates to an arc chute unit of the MCCB.

[0004] BACKGROUND

[0005] This section is intended to provide information relating to the field of the invention and thus, any approach or functionality described below should not be assumed to be qualified as prior art merely by its inclusion in this section.

[0006] A Circuit Breaker is an electro-mechanical switching device capable of making, carrying and breaking a flow of current in an electrical circuit. The circuit breaker is also known as an overcurrent protective device. Under normal circuit conditions, the circuit breaker closes the electrical circuit to allow the flow of current therethrough and breaks the flow of current or the electrical circuit under specified abnormal circuit conditions. Accordingly, it is said that the circuit breaker is an equipment which can open or close the circuit, under all conditions viz. no load, full load and fault conditions. Low voltage circuit breakers are commonly known to be deployed for low voltage applications, for example 1000 Volt or lower.

[0007] Various examples of low voltage circuit breakers are known, for example, a Miniature Circuit Breaker (MCB), a Molded Case Circuit Breaker (MCCB), a Residual Current Circuit Breaker (RCCB), an Air Circuit Breaker (ACB), and the like. Notably, the MCB is used in applications of current rating under 125 Amperes and short circuit current interruption rating of under 10KA, while MCCB is used in applications of current rating up to 1600 Amperes and interrupting short circuit current in a range of lOkA -150kA. Accordingly, it is submitted that MCCB is used for relatively high current rating applications than the MCB.

[0008] The MCCB is commonly a multipolar circuit breaker, which protects the electrical network / circuit and equipment from overloading and / or short-circuiting. Specifically, the MCCB is capable of operating amongst an ON position, an OFF position, and a TRIP position.

[0009] Conventionally, the MCCB includes at least a base assembly, a mid-cover assembly, a fascia plate assembly, at least one pole assembly, a trip assembly, and an actuator assembly. In one embodiment, the MCCB comprises three (3) pole assemblies. In such embodiments, the base assembly, the mid-cover assembly the fascia plate assembly and a hinge cover assembly incombination with each other, form a housing to house and support the three pole assemblies therein.

[0010] Further, the actuator assembly is mounted on at least one of the three (3) pole assemblies, while the TRIP assembly is mounted on at least one of the three (3) pole assemblies, such that the three (3) pole assemblies are connected together and operated together amongst the ON position, the OFF position, and the TRIP position. Notably, each of the three (3) pole assemblies comprises a pair of electrical contact units i.e., a stationary contact unit and a rotary contact unit, wherein the rotary contact unit rotatably engages and disengages with the stationary contact unit. Particularly, the actuator assembly includes a fork that can be manually adjusted, to adjust the three (3) pole assemblies together between the ON position, the OFF position and the TRIP position. More particularly, the actuator assembly is capable of breaking electrical contact between the stationary contact unit and the rotary contact unit of the three (3) pole assemblies, to interrupt the flow of current therethrough to the conductors connected to the load side, in response to normal / fault conditions.

[0011] The pole assembly includes a casing unit, the stationary contact unit, the rotary contact unit, and an arc chute unit. Notably, the casing unit of each of the plurality of pole assemblies comprised in the MCCB is such that the plurality of pole assemblies are arranged with each other, in a modular manner. More particularly, a number of the plurality of pole assemblies, in combination, define a number of electrical connection poles of the MCCB, such that one or more of the plurality of pole assemblies can be removed and / or deployed, in order to vary the number of electrical connection poles of the MCCB.

[0012] The arc chute unit is positioned within an arc chute unit portion of the casing unit. The arc chute unit comprises an arc chute holder and an arc chute member. The arc chute holder, and the arc chute member, are arranged together, to effectively quench an arc generated in the event of a short circuit condition, and vent out gases generated by the arc, through a vent channel. The arc is generated due to engagement / disengagement of the rotary contact unit relative to the stationary contact unit, and the gases generated upon arc generation are effectively vented through the vent channel, thus quenching the arc.

[0013] Conventionally, known arc chute units comprising the arc chute holder are bulky in size, and have an abnormally high ablation rate throughout the arc chute holder, which adversely impacts short-circuit performance of the MCCB. The abnormally high ablation rate throughout the arc chute holder causes problems such as but not limited to deformity of the arc chute holder which causes exponential spike in temperatures of other components of the MCCB and risking structuralintegrity or causing fracture of the casing unit of MCCB. Further, the conventionally known arc chute units do not provide complete insulation to the stationary contact unit of the MCCB, thereby resulting in unintentional arcing paths during short-circuit conditions. Furthermore, the conventional arc chute units are constrained by arc chute holders made-up of single grade of plastic, lacking comprehensive characteristics such as thermal stability and desired ablation rates. This limitation impedes the overall enhancement of breaker performance.

[0014] Accordingly in light of the aforementioned drawbacks and several other limitations inherent in the existing art, there exists a well-felt need to provide an improved arc chute unit for the MCCB, which is capable of achieving desired ablation rates wherever required for better short circuit performance, and also achieving desired thermal stability during overload conditions, thereby enabling better current carrying capacity and better overload performance of the MCCB. Further, the arc chute unit protects the structural integrity of the mid-cover assembly during arc generation during high intensity short-circuits.

[0015] SUMMARY OF THE INVENTION

[0016] This section is intended to introduce certain aspects of the disclosed system in a simplified form and is not intended to identify the key advantages or features of the present disclosure.

[0017] The present disclosure relates to an arc chute unit of a pole assembly of a Molded Case Circuit Breaker (MCCB). The arc chute unit comprises an arc chute member, and an arc chute holder that is adapted to mount on the arc chute member. The arc chute holder includes a first housing member and a second housing member. The first housing member is made up of a first material with a first ablation rate, and first thermal properties. The second housing member is made up of a second material with a second ablation rate, and second thermal properties, such that the first ablation rate is different from the second ablation rate, and the first thermal properties are different from the second thermal properties.

[0018] According to an aspect of the present disclosure, the first ablation rate is lesser than the second ablation rate.

[0019] According to another aspect of the present disclosure, the pole assembly comprises a stationary contact unit, and a rotary contact unit.

[0020] According to another aspect of the present disclosure, the arc chute unit houses a slot motor defining a first portion and a second portion, such that the slot motor is made up of a ferromagnetic material, and the slot motor enables faster arc quenching process in event of short circuits and thus providing better short-circuit performance of the MCCB.According to yet another aspect of the present disclosure, the first housing member forms a base portion of the arc chute holder, such that the first housing member encloses the stationary contact unit to avoid unintentional arcing path during the short-circuit conditions.

[0021] According to yet another aspect of the present disclosure, the first material of the first housing member is selected from a group of thermoset materials.

[0022] According to yet another aspect of the present disclosure, the first housing member comprises a locking provision, and at least one first cavity, such that the locking provision is a T-shaped protrusion configured to press fit and slidably lock the second housing member relative to the first housing member, and the at least one first cavity is adapted to receive and house therein a first portion of the slot motor.

[0023] According to yet another aspect of the present disclosure, the second material of the second housing member is selected from a group of thermoplastics.

[0024] According to yet another aspect of the present disclosure, the second housing member comprises a locking cavity and at least one second cavity, such that the locking cavity is adapted to slidably press fit the second housing member relative to the first housing member, and the at least one second cavity is adapted to receive and house therein a second portion of the slot motor.

[0025] According to yet another aspect of the present disclosure, the locking cavity of the second housing member engages with the locking provision of the first housing member, to form the arc chute holder.

[0026] According to yet another aspect of the present disclosure, upon assembly of the first housing member with the second housing member, the at least one first cavity housing the first portion of the slot motor, and the at least one second cavity housing the second portion of the slot motor, mate with each other to completely enclose the slot motor therein.

[0027] According to yet another aspect of the present disclosure, the arc chute holder and the arc chute member are assembled together to effectively quench an arc generated in a short circuit condition, and vent out gases generated by the arc generated due to engagement / disengagement of the rotary contact unit relative to the stationary contact unit through a vent channel of the pole assembly. BRIEF DESCRIPTION OF DRAWINGS

[0028] In order to explain the technical solution in the embodiments of the present application more clearly, the drawings used in the description of the embodiments will be briefly introduced below. It is obvious that the drawings in the following description are only some embodiments of theapplication. For those skilled in art, without any creative work, other drawings can be obtained based on these drawings.

[0029] Figure 1 illustrates an assembled perspective view of a Molded Case Circuit Breaker (MCCB), in accordance with the concepts of the present disclosure.

[0030] Figure 2 illustrates an exploded perspective view of the MCCB, in accordance with the concepts of the present disclosure.

[0031] Figure 3 illustrates a relative arrangement between three (3) pole assemblies and an actuator assembly of the MCCB, in accordance with the concepts of the present disclosure.

[0032] Figure 4 illustrates an exploded view of the relative arrangement between the three (3) pole assemblies and the actuator assembly of the MCCB, in accordance with the concepts of the present disclosure.

[0033] Figure 5 illustrates an exploded view of one of the pole assembly of the three (3) pole assemblies, in accordance with the concepts of the present disclosure.

[0034] Figure 6 illustrates the exploded view of one of the pole assemblies of the (3) pole assemblies depicting an exploded view of an arc chute unit housed therein, in accordance with the concepts of the present disclosure.

[0035] Figure 7 illustrates an assembled perspective view of an arc chute holder of the arc chute unit of the MCCB, in accordance with the concepts of the present disclosure.

[0036] Figure 8 illustrates an exploded perspective view of the arc chute holder of Figure 7, depicting a first housing member and a second housing member, in accordance with the concepts of the present disclosure.

[0037] Figure 9 illustrates a perspective view of the first housing member of the arc chute holder of Figure 7, in accordance with the concepts of the present disclosure.

[0038] Figure 10 illustrates a perspective view of the second housing member of the arc chute holder of Figure 7, in accordance with the concepts of the present disclosure.

[0039] DETAILED DESCRIPTION OF THE INVENTION

[0040] In the following description, for the purposes of explanation, various specific details are set forth in order to provide a thorough understanding of embodiments of the present invention. It will be apparent, however, that embodiments of the present invention may be practiced without these specific details. Several features described hereafter can each be used independently of one anotheror with any combination of other features. An individual feature may not address any of the problems discussed above or might address only one of the problems discussed above. Some of the problems discussed above might not be fully addressed by any of the features described herein. Exemplified embodiments of the present invention are described below, as illustrated in various drawings in which like reference numerals refer to the same parts throughout the different drawings.

[0041] A circuit breaker is an electro-mechanical switching device capable of making, carrying and / or breaking a flow of current in an electrical circuit. The circuit breaker is also known as an overcurrent protective device. Under normal circuit conditions, the circuit breaker closes the electrical circuit for allowing the flow of current therethrough, and breaks the flow of current or the electrical circuit under specified abnormal circuit conditions. Accordingly, it is said that the circuit breaker is an equipment which can open or close the electrical circuit, under all conditions viz. no load, full load and fault conditions. The circuit breaker of the present invention is a Molded Case Circuit Breaker (MCCB)

[0100] ,

[0042] Figure 1 illustrates a perspective view of the MCCB

[0100] , Figure 2 illustrates an exploded perspective view of the MCCB 100, in accordance with the concepts of the present disclosure. Figure 3 illustrates a relative arrangement between three (3) pole assemblies

[0102] and an actuator assembly

[0112] of the MCCB

[0100] , in accordance with the concepts of the present disclosure. Figures 1, 2 and 3 are to be viewed in conjunction with each other, in order to better understand the concepts of the present disclosure. For ease in reference and understanding of a reader, the structure and arrangement of the MCCB

[0100] is elucidated hereunder, in light of the aforementioned accompanying drawings.

[0043] The MCCB

[0100] is a low-voltage and high-current circuit breaker, employed to protect electrical networks / circuits from overload or short-circuit conditions. The MCCB

[0100] is positioned between at least one load phase on a load side and at least one line phase on a line side, for providing protection during overload or short-circuit conditions. The MCCB

[0100] operates amongst each of an ON position, an OFF position, and a TRIP position, wherein the MCCB

[0100] is manually adjusted between the ON position and the OFF position, whereas the MCCB

[0100] is automatically adjusted to the TRIP position due to overloading or short-circuiting at the line side or the load side of the MCCB

[0100] , In the ‘ON’ position, the MCCB

[0100] allows a flow of current therethrough, whereas, in each of the ‘OFF’ position and the ‘TRIP’ position, the MCCB

[0100] restricts the flow of current therethrough.Commonly, the MCCB

[0100] is a multipolar circuit breaker. Although, in the present disclosure the MCCB

[0100] is described as a three-pole circuit breaker, it may be obvious to a person skilled in the art that the MCCB

[0100] may also be a single-pole circuit breaker, a four-pole circuit breaker, or a circuit breaker with any number of poles. The MCCB

[0100] includes the three (3) pole assemblies

[0102] , a base assembly

[0104] , a mid-cover assembly

[0106] , a fascia plate assembly

[0108] , a hinge cover assembly

[0110] , the actuator assembly

[0112] and a trip assembly (not shown). Referring to figures 4 and 5, each of the three (3) pole assemblies

[0102] are independent units capable of protecting the electrical networks / circuits from overload or short-circuit conditions. In particular, each of the three (3) pole assemblies

[0102] transmits electric current from one of the line phases to one of the load phases, while providing protection from overcurrent or short-circuit. Each of the three (3) pole assemblies

[0102] operate in each of the ‘ON’ position, the ‘OFF’ position and the ‘TRIP’ position. Notably, the three (3) pole assemblies

[0102] are connected with one or more components of the actuator assembly

[0112] , to adjust each of the three pole assemblies

[0102] together between the ‘ON’ position, the ‘OFF’ position and the ‘TRIP’ position. The structure and arrangement of the base assembly

[0104] will be elucidated hereinafter.

[0044] The base assembly

[0104] is a lower structure that provides a mounting base and support structure for holding and supporting each of the three (3) pole assemblies

[0102] therein. In particular, the base assembly

[0104] defines pole holding cavities to mount and support each of the three (3) pole assemblies

[0102] therein. Notably, the three (3) pole assemblies

[0102] are fixedly attached within the pole holding cavities defined by the base assembly

[0104] , An attachment means for attaching the three (3) pole assemblies

[0102] within the pole holding cavities defined by the base assembly

[0104] includes, such as but not limited to, a bolt attachment means, a screw attachment means, a rivet attachment means, an adhesive attachment means, a fit attachment means, a weld attachment means, and the like. The structure and arrangement of the mid-cover assembly

[0106] will be described hereinafter.

[0045] The mid-cover assembly

[0106] is an upper structure that is engaged with the base assembly

[0104] , to at least partially cover the three pole assemblies

[0102] and protect the same from external environment and mounting of accessories. The mid-cover assembly

[0106] is usually fittingly engaged with the base assembly

[0104] , to at least partially cover the three (3) pole assemblies

[0102] and protect the same from external environment. Although, the mid-cover assembly

[0106] is described to be attached to the base assembly

[0104] by way of a fit attachment means, it may be obvious to a person skilled in the art that any other known attachment means may also be envisioned.The fascia plate assembly

[0108] is fittingly mounted on the mid-cover assembly

[0106] , to cover the mid-cover assembly

[0106] , The fascia plate assembly

[0108] defines portions to define electrical parameters related to MCCB

[0100] , The fascia plate assembly

[0108] also comprises a fascia-plate cavity [108a] and at least two pairs of grooves [108b], The fascia-plate cavity [108a] is a through hole, preferably a rectangular through hole that allows a portion of a fork of the actuator assembly to pass therethrough. The structure and arrangement of the hinge cover assembly

[0110] will be described hereinafter in detail.

[0046] The hinge cover assembly

[0110] comprises a first hinge cover plate [110a] and a second hinge cover plate [110b] adapted to be mounted on a top edge and a bottom edge of the fascia plate assembly

[0108] , respectively. In particular, the first hinge cover plate [110a] defines a first pair of snap attachment sections adapted to engage with one of the at least two pairs of grooves [108b] defined proximal to the top edge of the fascia plate assembly

[0108] , While the second hinge cover plate [110b] defines a second pair of snap attachment sections adapted to engage with the other of the at least two pair of grooves [108b] defined proximal to the bottom edge of the fascia plate assembly

[0108] , Further, each of the first and second hinge cover plates [110a] defines a male attachment portion which is adapted to engage with the mid-cover assembly

[0106] , to lock thereto by means of a snap-fit attachment.

[0047] The actuator assembly

[0112] is a multi -part component mounted on one of the pole assemblies

[0102] , The actuator assembly

[0112] connects the three (3) pole assemblies

[0102] together, such that the three (3) pole assemblies

[0102] are manually adjusted together amongst the ON position, the OFF position, and the TRIP position, by means of the actuator assembly

[0112] , The actuator assembly

[0112] includes a fork that may be manually adjusted to adjust the three pole assemblies

[0102] together amongst the ON position, the OFF position, and the TRIP position. In particular, the fork of the actuator assembly

[0112] may be manually manipulated, to adjust the three pole assemblies

[0102] together from the ON position to the OFF position and vice versa. Moreover, one or more of the three (3) pole assemblies

[0102] may be adjusted to the TRIP position, during overload or short-circuit conditions. Additionally, the TRIP assembly is mounted on one of the three (3) pole assemblies

[0102] or on all pole assemblies

[0102] , such that the TRIP assembly triggers the actuator assembly

[0112] to adjust the three (3) pole assemblies

[0102] together to the TRIP position. Further, the manually adjustable fork of the actuator assembly

[0112] may be manipulated to reset the three (3) pole assemblies

[0102] together from the TRIP position to the OFF position.

[0048] The TRIP assembly is mounted and supported on atleast one of the three pole assemblies and is structured and arranged to connect the three (3) pole assemblies

[0102] together, such that the three(3) pole assemblies

[0102] are adjusted together from the ON position to the TRIP position. In particular, in the overload and / or short-circuit conditions of one of load phase or line phase of one of the three (3) pole assemblies

[0102] , one or more of the three (3) pole assemblies

[0102] are adjusted to the TRIP position. Notably, one or more of the three (3) pole assemblies

[0102] can be removed from and / or attached to the MCCB

[0100] , in order to operate the MCCB

[0100] , A structure and arrangement of one of the three (3) pole assemblies

[0102] will be described in detail hereinafter. Similar structure and arrangement of the remaining pole assemblies

[0102] may be envisioned.

[0049] The pole assembly

[0102] includes a casing unit

[0144] , a stationary contact unit

[0128] , a rotary contact unit

[0132] , and an arc chute unit

[0134] , Notably, the casing unit

[0144] of each of a plurality of pole assemblies

[0102] comprised in the MCCB

[0100] is such that the plurality of pole assemblies

[0102] is arranged with each other, in a modular manner. More particularly, a number of the plurality of pole assemblies

[0102] , in combination, define a number of electrical connection poles of the MCCB

[0100] , such that one or more of the plurality of pole assemblies

[0102] can be removed and / or deployed, in order to vary the number of electrical connection poles of the MCCB

[0100] , The stationary contact unit

[0128] is an electric contact plate structure that may be positioned within a defined portion in the casing unit

[0144] , The stationary contact unit

[0128] is provided to connect to electrical wires from the line side. In particular, in complete assembly of the MCCB

[0100] , the electrical wires from the line side are usually connected to the stationary contact unit

[0128] , The rotary contact unit

[0132] is a moving structure that engages / di sengages with the stationary contact unit

[0128] , to allow / restrict the flow of electric current therethrough. The rotary contact unit

[0132] is rotatably positioned within a defined portion in the casing unit

[0144] and is provided to connect to electrical wires from the load side. In particular, in complete assembly of the MCCB

[0100] , the electrical wires from the line side are usually connected to the stationary contact unit

[0128] , Further, the rotary contact unit

[0132] is rotatably adjusted while being positioned within the casing unit

[0144] , to make and release a contact relative to the stationary contact unit

[0128] , in order to allow and restrict the flow of electric current therebetween, respectively. Notably, the rotary contact unit

[0132] ‘makes’ the contact relative to the stationary contact unit

[0128] to allow the flow of electric current (the ‘ON’ position), the rotary contact unit

[0132] ‘releases’ the contact relative to the stationary contact unit

[0128] , to restrict the flow of electric current (the ‘OFF’ position). Additionally, the rotary contact unit

[0132] is adjusted without complete rotation, to release the contact relative to the stationary contact unit

[0128] to restrict the flow of electric current (the ‘TRIP’ position). The rotary contact unit

[0132] is made up of a rotary housing member, an elongated rotary arm, and a toggling mechanism, suitably arranged with each other to adjust theelongated rotary arm amongst the ON position, the OFF position, and a BLOW open position. Furthermore, the rotary housing member of the rotary contact unit

[0132] defines an extended portion extending horizontally outwards from the rotary housing member, such that the rotary housing member of the rotary contact unit

[0132] is positioned within a rotary contact unit holding portion of the casing unit

[0144] , while the extended portion of the rotary contact unit

[0132] extends within the rear coupling joint of the rotary contact unit

[0132] holding portion.

[0050] The arc chute unit

[0134] is positioned within an arc chute unit portion of the casing unit

[0144] , The arc chute unit

[0134] comprises an arc chute holder

[0136] , an arc chute member

[0138] and the arc chute unit

[0134] houses a slot motor

[0143] , The arc chute holder

[0136] and the arc chute member

[0138] are assembled together forming the arc chute unit

[0134] to effectively quench an arc generated in a short circuit condition, and vent out gases generated by the arc generated due to engagement / disengagement of the rotary contact unit

[0132] relative to the stationary contact unit

[0128] through a vent channel of the pole assembly

[0102] ,

[0051] Referring to figures 6 to 10, the arc chute holder

[0136] is adapted to facilitate mounting and attachment thereon the arc chute member

[0138] of the arc chute unit

[0134] , The arc chute holder

[0136] includes a first housing member

[0140] and a second housing member

[0142] , The slot motor

[0143] is a flat plate-like structure made up of a ferromagnetic material enables faster arc quenching process in event of short circuits by facilitating rapid contacts opening and thus aiding in providing better short-circuit performance of the MCCB. The slot motor

[0143] defines a first portion [143 a] and a second portion [143b] that is adapted to be encased within the first housing member

[0140] and the second housing member

[0142] respectively.

[0052] The first housing member

[0140] forms a base portion of the arc chute holder

[0136] , such that the first housing member

[0140] encloses the stationary contact unit

[0128] , which aids in avoiding an unintentional arcing path during short-circuit conditions. The first housing member

[0140] is made up of a first material, such that the first housing member

[0140] has a first ablation rate and first thermal properties. The first material is a thermoset material such as vulcanized rubber, bakelite, polyester, polyurethane, epoxy resin, and vinyl ester resin but not limited to thereof, such that exorbitantly high temperature during high value overload conditions or during the arc generation are absorbed by the first housing member

[0140] , thus maintaining structural integrity of the midcover assembly

[0106] and the fascia plate assembly

[0108] , Further, the first housing member

[0140] comprises a locking provision [140a], and at least one first cavity [140b], such that the locking provision [140a] is a T-shaped protrusion, but not limited to thereof, enabling slidable, press fit locking of the second housing member

[0142] relative to the first housing member

[0140] , and the atleast one first cavity [140b] is adapted to receive and house therein a first portion [143 a] of the slot motor

[0143] ,

[0053] The second housing member

[0142] is adapted to lock relative to the first housing member

[0140] , The second housing member

[0142] comprises a complimenting locking cavity [142a] and at least one second cavity [142b], such that the locking cavity [142a], such that the complementing locking cavity [142a] is a T-shaped cavity, but not limited thereof, enabling slidable, press fit and snap fit locking of the second housing member

[0142] , relative to the first housing member

[0140] , and the at least one second cavity [142b] is adapted to receive and house therein a second portion [143b] of the slot motor

[0143] , Further, the second housing member

[0142] may also be attached to the first housing member

[0140] by means of gluing. Upon assembly of the first housing member

[0140] with the second housing member

[0142] , the at least one first cavity [140a] housing the first portion [143 a] of the slot motor

[0143] , and the at least one second cavity [142a] housing the second portion [143b] of the slot motor

[0143] , mate with each other to completely enclose the slot motor

[0143] therein. The slot motor

[0143] creates a U-shaped partial loop that aids in enhancing electromagnetic flux density within the arc chute holder

[0136] , which reduces leakage / stray flux by providing a path of least reluctance to electromagnetic field lines generated therein, thereby aiding in rapid opening of the rotary contact unit

[0132] during the short-circuit condition enabling faster arc quenching process and thus providing better short-circuit performance of the MCCB

[0100] , The second housing member

[0142] is made up of a second material, such that the second housing member

[0142] has a second ablation rate, and second thermal properties. The second material is a thermoplastic material, such as polyethylene, polypropylene, polyvinyl chloride, polystyrene, acrylic, nylon, Teflon, but not limited to thereof.

[0054] The first ablation rate is different from the second ablation rate, and the first thermal properties are different from the second thermal properties. Particularly, the first ablation rate is lesser than the second ablation rate. The first ablation rate being lesser than the second ablation rate enables the first housing member

[0140] to maintain its structural integrity under intense arcing during the short-circuit conditions, and the second ablation rate being relatively higher than the first ablation rate of the second housing member

[0142] enables faster quenching of the arc generated during the short-circuit condition. Thus, differential first and second ablation rates and thermal properties of the first housing member

[0140] and the second housing member

[0142] enable better short circuit performance and thermal stability during overload conditions. The locking cavity [142a] of the second housing member

[0142] lockingly engages with the locking provision [140a] of the first housing member

[0140] , thus together forming the arc chute holder

[0136] , The first and second materials of the first housing member

[0140] and the second housing member

[0142] respectivelyensure differential ablation rates enabling better short circuit performance of the MCCB

[0100] , Various advantages of the presently disclosed arc chute holder

[0136] are disclosed. Firstly, the arc chute holder

[0136] defining the first housing member

[0140] and the second housing member

[0142] of the first and second material respectively enables differential ablation rates. The differential ablation rates ensure integrity of arc chute unit

[0134] , thus ensuring structural integrity of the MCCB

[0100] , Further, in case of failure of the arc chute holder

[0136] , either of the first or the second housing member [140, 142] can be replaced resulting in lower repair costs and adding to sustainability. Furthermore, during long duration sustained overload conditions, the present invention provides thermal stability thereby enabling better current carrying capacity and better overload performance of the MCCB

[0100] ,

[0055] However, it may be understood that the above listed advantages are merely illustrative and not exhaustive. Those skilled in the art may contemplate additional advantages not described herein above, in light of the concepts of the present disclosure.

[0056] While the preferred embodiments of the present invention have been described hereinabove, it should be understood that various changes, adaptations, and modifications may be made therein without departing from the spirit of the invention. It will be obvious to a person skilled in the art that the present invention may be embodied in other specific forms without departing from its spirit or essential characteristics. The described embodiments are to be considered in all respects only as illustrative and not restrictive.

[0057] LIST OF COMPONENTS

[0058] 100 - Molded case circuit breaker (MCCB)

[0059] 102 - Pole assembly

[0060] 104 - Base assembly

[0061] 106 - Mid-cover assembly

[0062] 108 - Fascia-plate assembly

[0063] 108a - Cavity

[0064] 108b - Two pairs of grooves

[0065] 110 - Hinge cover assembly

[0066] 110a - First hinge cover plate

[0067] 110b - Second hinge cover plate112 - Actuator assembly

[0068] 128 - Stationary contact unit 132 - Rotary contact unit 134 - Arc chute unit

[0069] 136 - Arc chute holder

[0070] 138 - Arc chute member 140 - First housing member 140a - Locking provision 140b - First Cavity

[0071] 142 - Second housing member 142a - Locking cavity

[0072] 142b - Second cavity

[0073] 143 - Slot Motor

[0074] 143a - First portion

[0075] 143b - Second portion

[0076] 144 - Casing unit

Claims

We Claim:

1. An arc chute unit [134] of a pole assembly [102] of a Molded Case Circuit Breaker (MCCB) [100], the arc chute unit [134] comprising:an arc chute member [138];an arc chute holder [136] adapted to mount thereon the arc chute member [138], the arc chute holder [136] including:o a first housing member [140] made up of a first material with a first ablation rate and first thermal properties; ando a second housing member [142] made up of a second material with a second ablation rate and second thermal properties, such that the first ablation rate is different from the second ablation rate, and the first thermal properties are different from the second thermal properties.

2. The arc chute unit [134] as claimed in claim 1, wherein the first ablation rate is lesser than the second ablation rate.

3. The arc chute unit [134] as claimed in claim 1, wherein the pole assembly [102] comprises a stationary contact unit [128], and a rotary contact unit [132],4. The arc chute unit [134] as claimed in claim 1, wherein the arc chute unit [134] houses a slot motor [143] defining a first portion [143a] and a second portion [143b], such that the slot motor [143] is made up of a ferromagnetic material, and the slot motor [143] enables faster arc quenching process in event of short circuits and thus providing better short-circuit performance of the MCCB [100],5. The arc chute unit [134] as claimed in claims 1 and 3, wherein the first housing member [140] forms a base portion of the arc chute holder [136], such that the first housing member [140] encloses the stationary contact unit [128] to avoid unintentional arcing path during the short-circuit conditions.

6. The arc chute unit [134] as claimed in claim 1, wherein the first material of the first housing member [140] is selected from a group of thermoset materials.

7. The arc chute unit [134] as claimed in claims 1 and 4, wherein the first housing member [140] comprises a locking provision [140a], and at least one first cavity [140b], such thatthe locking provision [140a] is a T-shaped protrusion configured to press fit and slidably lock the second housing member [142] relative to the first housing member [140], and the at least one first cavity [140b] is adapted to receive and house therein a first portion [143a] of the slot motor [143],8. The arc chute unit [134] as claimed in claims 1 and 3, wherein the second material of the second housing member [142] is selected from a group of thermoplastics.

9. The arc chute unit [134] as claimed in claims 1 and 7, wherein the second housing member [142] comprises a locking cavity [142a] and at least one second cavity [142b], such that the locking cavity [142a] is adapted to slidably press fit the second housing member [142] relative to the first housing member [140], and the at least one second cavity [142b] is adapted to receive and house therein a second portion [143b] of the slot motor [143],10. The arc chute unit [134] as claimed in claims 1 to 9, wherein the locking cavity [142a] of the second housing member [142] engages with the locking provision [140a] of the first housing member [140], to form the arc chute holder [136],11. The arc chute unit [134] as claimed in claims 1 to 10, wherein upon assembly of the first housing member [140] with the second housing member [142], the at least one first cavity [140a] housing the first portion [143 a] of the slot motor [143], and the at least one second cavity [142a] housing the second portion [143b] of the slot motor [143], mate with each other to completely enclose the slot motor [143] therein.

12. The arc chute unit [134] as claimed in claims 1 to 11, wherein the arc chute holder [136] and the arc chute member [138] are assembled together to effectively quench an arc generated in a short circuit condition, and vent out gases generated by the arc generated due to engagement / disengagement of the rotary contact unit [132] relative to the stationary contact unit [128] through a vent channel of the pole assembly [102],

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