A pole module for a circuit breaker arrangement

Abstract

A pole module for a circuit breaker arrangement is disclosed. The pole module (1A) comprises a housing (2A) having a top end and a bottom end (5A), two or more contact arms (6A, 8A), and an interrupter (10A) comprising a stationary member (11A) and a movable member (13A). The pole module (1A) is characterized by one or more vertical creepage ribs (14A) provided on an inner surface of the housing (2A).

Description

[0001] Beschreibung / Description

[0002] A POLE MODULE FOR A CIRCUIT BREAKER ARRANGEMENT

[0003] The invention pertains to a circuit breaker. More particularly, the invention is associated with the pole module of a circuit breaker arrangement.

[0004] Circuit breakers are switches used to protect circuitry from damage due to overload, by their automatic operation. They come in various sizes and voltage / current capacities and are selected for use, according to specifications. Circuit breakers interrupt the flow of current by extinguishing an arc generated in a vacuum during contact opening. Inside the vacuum chamber a pair of electrical switching contacts are arranged. Modern vacuum circuit-breakers tend to have a longer lifetime than former air, oil circuit-breakers. Circuit breakers mainly include a switching module formed from one or more function- oriented units including a base module unit, a pole module, and a drive module unit. The base module unit is fixedly connected to the drive module unit and the pole module is arranged so as to be moveable relative to the base module unit.

[0005] In case of a vacuum circuit breaker, the pole module includes, at least one of, connecting terminal, vacuum interrupter and bridge elements. Further, the drive module unit includes a disconnecting drive that moves a movable part located in the pole module on guide shafts of the base module unit. The drive module unit further includes a switch or contactor drive that jointly actuates movable contacts of at least one of, circuit breakers, vacuum switches, vacuum contactors and bridging elements. Further, a housing or an insulating structure act as an enclosure for critical components to isolate live electrical components from grounded components in the pole module. The design specifications of the insulating structure become crucial as the rated voltage capabilities of the circuit breaker increases. The insulating structure and related components are expected to dielectrically withstand a Basic Insulation Level (BIL) as per IEC standard 62271-1, 62271-100. Therefore, it is important to have sufficient clearances (e.g. , air to air clearance) and creepage distances in all possible directions of failure inside the circuit breaker to comply with the BIL requirement. Typically, a height of the insulating structure is increased to increase creepage distance. In certain scenarios, however, there may be dimensional constraints wherein height of the pole module cannot be increased beyond a specific value.

[0006] FIG 1 (prior art) illustrates a cross sectional view of a pole module 1 of a circuit breaker arrangement, in accordance with prior art. In the present example, the circuit breaker arrangement corresponds to a vacuum circuit breaker. The pole module 1 is an integral part of a vacuum circuit breaker (not shown) . Typically, the pole module 1 includes a housing 2, an interrupter 10, a drive module unit 12 and a contact arm. In the present embodiment, the pole module 1 has two contact arms 6, 8. The housing 2 has a top end 3 and a bottom end 5. The pole module 1 is supported on a supporting structure using a fastening mechanism provided at the bottom end 5. The interrupter 10 includes a stationary member 11 and a movable member 13 at different voltage potentials.

[0007] FIG 2 (prior art) illustrates a perspective view of the pole module 1 in accordance with an embodiment of the prior art. The pole module 1 includes the housing 2 and the two contact arms 6, 8. The housing 2 includes the top end 3 and the bottom end 5. FIG 3 (prior art) shows a cross-sectional view of the bottom end 5 of the housing 2. As may be seen, the bottom end 5 is a cylindrical wall of specific thickness, that electrically isolates the critical components of the circuit breaker arrangement .

[0008] Indian patent application 201631029895 discloses a pole module comprising creepage distance extenders connected to a capping member that serves the purpose of increasing the creepage distance from a stationary member of a vacuum switch to one or more points at earth potential of the circuit breaker.

[0009] In existing art, creepage distance is also improved by modifying a wall or housing of the pole module, given the fact that dielectric failure occurs easily along the surface of the wall (i.e. , dielectric path) if creepage distance is insufficient. For example, horizontal protrusions are provided on the wall. Such horizontal protrusions may be provided outside or inside the wall. However, such horizontal protrusions make demolding of the inner core from a mold tedious. In particular, the protrusions prevent direct demolding of the pole module from the mold by simple application of ejection force. In such cases, a split inner core mold is required. This adds to the complexity of manufacturing the pole module.

[0010] In light of the above, there exists a need for a pole module that provides desired creepage distance with reduced manufacturing efforts compared to pole modules with horizontal protrusions .

[0011] Accordingly, it is an object of the invention to overcome the drawbacks of the state of the art. The object of the invention is achieved by independent claim 1 and all the corresponding dependent claims thereof. In an aspect , a pole module for a circuit breaker arrangement is disclosed . The pole module includes a housing having a top end and a bottom end, two or more contact arms , and an interrupter compri sing a stationary member and a movable member . The pole module is characterized by one or more vertical creepage ribs provided on an inner surface of the housing . In an embodiment , vertical creepage ribs are arranged concentrically . In an embodiment , if the housing is provided with two or more vertical creepage ribs , the vertical creepage ribs form a step-like formation in order of increasing perimeter , such that the vertical creepage rib with the largest perimeter is positioned farthest from the top end .

[0012] Advantageously, such arrangement of the vertical creepage ribs ease s manufacturing effort s , as it enables demolding of an inner core f rom the housing , by s imple application of an ej ection force . In an embodiment , one or more design parameters of the vertical creepage ribs is adapted based on a voltage rating of the pole module .

[0013] The above mentioned and other features of the invention will now be addres sed with reference to the accompanying drawings of the present invention . The illustrated embodiments are intended to illustrate , but not limit the invention .

[0014] The present invention is further des cribed hereinafter with reference to illustrated embodiments shown in the accompanying drawings , in which :

[0015] FIG 1 illustrates a cros s sectional view of a pole module of a circuit breaker arrangement , in accordance with prior art ; FIG 2 illustrates a perspective view of the pole module, in accordance with prior art;

[0016] FIG 3 illustrates a cross sectional view of a bottom end of the pole module, in accordance with prior art;

[0017] FIG 4 illustrates a cross-sectional view of a housing suitable for a pole module, in accordance with an embodiment of the present invention;

[0018] FIG 5 illustrates a perspective view of the bottom end of the housing, in accordance with an embodiment of the present invention;

[0019] FIG 6 illustrates design parameters of vertical creepage ribs provided at the bottom end, in accordance with an embodiment of the present invention; and

[0020] FIG 7 illustrates a design of a bottom end of a pole module, in accordance with another exemplary embodiment of the present invention;

[0021] FIG 8 illustrates the pole module suited to a vacuum circuit breaker arrangement, in accordance with an embodiment of the present invention.

[0022] Various embodiments are described with reference to the drawings, wherein like reference numerals are used to refer 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 . It may be evident that such embodiments may be practiced without these specific details .

[0023] The pole module in accordance with the present invention includes one or more vertical creepage ribs provided on an inner surface of a housing of a circuit breaker arrangement , as explained below with reference to FIGS 4 to 8 .

[0024] FIG 4 shows a cros s- sectional view of a housing 2A as sociated with a pole module 1A suitable for a circuit breaker arrangement , in accordance with an exemplary embodiment of the present invention . In principle , the housing 2A is an insulating structure serves to electrically isolate critical component s of the circuit breaker arrangement , as explained earlier with reference to prior art . The housing 2A also include s a top end 3A and a bottom end 5A . Two or more contact arms 6A, 8A are disposed in at least one orientation on the housing 2A, as shown . In an embodiment , the hous ing 2A is made of epoxy . Nonlimiting examples of other material s suitable for manufacturing the housing 2 include ceramics , porcelain , and hard rubber . The housing 2A i s fabricated to include a plurality of vertical creepage ribs 14A within , as shown . In the present embodiment , the vertical creepage ribs 14A are provided adj acent to the bottom end 5A . However , it must be understood that the housing 2A is fabricated to include vertical creepage ribs 14A anywhere between the top end and the bottom end 5A, e . g . , near the top end or a middle section def ined between the top end and the bottom end 5A of the housing 2A . In the pre sent embodiment , the vertical creepage ribs 14A are arranged concentrically as may be understood from the perspective view of the bottom end 5A illustrated in FIG 5 . Each of the vertical creepage ribs 14A is oriented perpendicular to the surface of the supporting structure . The housing 2A is provided with three vertical creepage ribs 14A, with the vertical creepage ribs 14A forming a step-like formation in order of increasing perimeter, such that the vertical creepage rib with the largest perimeter is positioned farthest from the top end. In general, if a housing is provided with two or more vertical creepage ribs, the vertical creepage ribs form a step-like formation in order of increasing perimeter, such that the vertical creepage rib with the largest perimeter is positioned farthest from the top end of the pole module 1A. Advantageously, such an arrangement facilitates demoulding of the inner core from the housing by application of a force along a lengthwise axis of the housing 2A, as opposed to state-of-the-art arrangements that require introduction of split inner core to facilitate demoulding. This also makes manufacturing of the pole module 1A easier, by eliminating the need for a mould with a split inner core.

[0025] In an embodiment, design parameters associated with the vertical creepage ribs 14A is adapted based on a voltage rating of the pole module 1A. In an example, the design parameters include number of vertical creepage ribs 14A. As the number of vertical creepage ribs 14A increases, a creepage distance between a live component (having a first potential) adapted to fit into the pole module 1A and a grounded component (having a second potential) increases. The term 'creepage distance' as used herein refers to the linear distance measured along insulating surfaces between the live component and the grounded component and is directly indicative of a surface insulation resistance associated with the pole module 1A. The surface insulation resistance is responsible for minimizing leakage current flow from the live component to the grounded component, as is understood by a person skilled in the art. Furthermore, the surface dielectric strength of the pole module 1A also increases due to increase in length of the failure path through which the leakage current flows from the live component to the grounded component. Additionally, the one or more vertical creepage ribs 14A also improve a Dielectric Withstanding Voltage ( DWV) of the housing 2A ba sed on the voltage rating of the pole module 1A, compared to a hous ing without ribs . The DWV refers to the voltage that potentially causes an arc between the live component and the grounded component . Therefore , a higher DWV is required to prevent arcing between the live component and the grounded component .

[0026] Other de sign parameters of the rib are adaptable to adj ust the creepage distance for a specific voltage rating of the pole module 1 . Non-limiting examples of rib design parameters include rib height ' h' , rib width 'w' , rib draft angle , and distance between ribs 'd' as illustrated in FIG 6 . For example , if a first design of the housing 2 cons ists of 'n' vertical creepage ribs 14 of rib height 'h' and rib width 'w' , another design of the housing 2 may consist of les ser number of vertical creepage ribs 14 with increased rib height or rib width . The housing 2 of FIG 3 includes three vertical creepage ribs 14 of a predef ined height for meeting DWV requirements for a specific voltage rating of the pole module 1A . The design parameters of vertical creepage ribs 14A may be adapted to suit DWV requirement s for any given voltage rating of the pole module 1 . In particular , the creepage distance must be higher as the Basic Insulation ( BIL ) requirement increa ses with the voltage rating of the circuit breaker . FIG 7 illustrate s a design of a bottom-end 5B suitable for pole module 1A, in accordance with another exemplary embodiment of the present invention . The bottom-end 5B is fabricated to include a s ingle vertical creepage rib 14B .

[0027] FIG 8 illustrates the pole module 1A suited to a vacuum circuit brea ker arrangement , in accordance with an embodiment . Various conf iguration of the pole module 1A as dis closed in conj unction with FIGs 4 to 7 may be used in the vacuum circuit brea ker arrangement. The pole module 1A includes a switching module comprising a base module unit (not shown) , a pole module 1A and a drive module unit 12A. The drive module unit 12A includes a mechanism to operate a movable member 13A. The base module unit is fixedly connected to the drive module unit 12A to actuate the movable member 13A. Further, the pole module 1A includes a housing 2A comprising a top end 3A and a bottom end 5A, and a vacuum interrupter 10A including a stationary member 11A and the movable member 13A. In an example, the stationary member 11A may be at a first potential and the movable member 13A at a second potential. In particular, the stationary member 11 may be at a higher voltage potential than the second potential. The operation of the vacuum interrupter 10A is evident to a person skilled in the art and hence no additional explanation is provided. The pole module 1A is supportable on a supporting structure (not shown) by means of fastening mechanism provided at the bottom end 5A. In some embodiments, the one or more points at the second potential is a pole support 9.

[0028] It must be understood that the aforementioned housing 2A with the vertical creepage ribs 14A may be adapted for other types of circuit breaker arrangements including, but not limited to, gas-insulated circuit breakers, air-insulated circuit breakers and oil-insulated circuit breakers.

[0029] While the present invention has been described in detail with reference to certain embodiments, it should be appreciated that the present invention is not limited to those embodiments. In view of the present disclosure, many modifications and variations would be present themselves, to those skilled in the art without departing from the scope of the various embodiments of the present invention, as described herein. The scope of the present invention is, therefore, indicated by the following claims rather than by the foregoing description. All changes, modifications, and variations coming within the meaning and range of equivalency of the claims are to be considered within their scope.

Claims

Patentanspruche / Patent claims1. A pole module (1A) for a circuit breaker arrangement, the pole module (1A) comprising: a housing (2A) having a top end (3A) and a bottom end (5A) ; two or more contact arms ( 6A, 8A) ; and an interrupter (10A) comprising a stationary member (11A) and a movable member (13A) ; characterized by: one or more vertical creepage ribs (14A) provided on an inner surface of the housing (2A) .

2. The pole module (1A) according to claim 1, wherein the vertical creepage ribs (14A) are arranged concentrically.

3. The pole module (1A) according to claim 1 or 2, wherein if the housing (2A) is provided with two or more vertical creepage ribs (14A) , the vertical creepage ribs (14A) form a step-like formation in order of increasing perimeter, such that the vertical creepage rib with the largest perimeter is positioned farthest from the top end.

4. The pole module (1) according to any of the claims 1 to 3, wherein one or more design parameters of the vertical creepage ribs (14A) is adapted based on a voltage rating of the pole module (1A) .

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