Pole module for circuit breaker

Abstract

A pole module (100) for a circuit breaker is disclosed. The pole module (100) includes a housing (106) having a top end (106A) and a bottom end (106B) and at least two contact arms (102A,102B). The pole module (100) also includes an interrupter comprising a stationary member (110A) and a movable member (110B) and characterized by heat vent (s) positioned at the top end (106A) of the pole module (100) to allow hot air to escape out of the pole module (100), and the bottom end (106B) of the pole module (100) is open to facilitate a flow of cool air into the pole module (100).

Description

[0001] Beschreibung / Description

[0002] POLE MODULE FOR CIRCUIT BREAKER

[0003] The invention pertains to a circuit breaker . More particularly, the invention is associated with - a vacuum interrupter for the circuit breaker which includes a ventilated enclosure .

[0004] Circuit breaker is an electrical protector for protecting load devices and power lines due to overload . They come in various sizes and voltage / current capacities and are selected for use , according to speci fications . The circuit breaker may be classified into an oi l circuit breaker using oil as an extinguishing medium, a gas circuit breaker using sul fur hexafluoride ( SF6 ) gas or the like , an air circuit breaker using air as an extinguishing medium, and a vacuum circuit bl 06reaker using vacuum insulation strength according to the type of extinguishing medium . 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 li fetime 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] Medium voltage Vacuum Circuit breakers are expected to carry high currents along with voltages in range of I kV- 50kV . These current values can range up to 4000A. Vacuum Interrupter is heart of the Medium- voltage switchgear and generally it determines the maximum voltage , current and short time current withstand capacity of the circuit breaker . As the voltages goes on increasing air clearance between adjacent phases also increases. In order to isolate two adjacent phases sometimes it may take huge clearing distances making the circuit breakers bulkier in size. Hence, to overcome this challenge for higher voltages the main circuit of the circuit breaker is encapsulated in a non-conducting epoxy or other insulating poles. The encapsulated poles act as a barrier between phase and help in improving dielectric strength between phases making it compact .

[0006] 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 increase.

[0007] 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) in all possible directions of failure inside the circuit breaker to comply with the BIL requirement.

[0008] Therefore, being encapsulated in epoxy pole the thermal characteristics of the circuit breaker becomes challenging. As the current value goes on increasing due to I2R ( I (A) - Current in Amperes , R (Q) - Resistance of circuit in Ohms ) , amount of heat generated also goes on increasing . The dissipation of this heat is necessary, i f not that can cause very high temperatures of the main circuit making it undesirable and dangerous .

[0009] FIG 1A (prior art ) illustrates a perspective view o f a vacuum interrupter of a circuit breaker, in accordance with prior art . Consider a circuit breaker (not shown) includes a pole module 100 which is an integral part of the circuit breaker . The interruption of current in vacuum is recogni zed as the ideal switching technology in the medium voltage range and is also applied in high and low voltage applications . Typically, the pole module 100 includes a housing 106 and a vacuum interrupter 110 . The housing 106 includes multiple contact arms 102A, 102B . The housing 106 includes a top end 106A and a bottom end 106B . As may be seen, the bottom end 106B of the housing 106 is a cylindrical wall of speci fic thickness , that electrically isolates the vacuum interrupter 110 from an operations mechanism which may be connected at the bottom end 106b of the housing 106 . Since the bottom end 106B of the housing 106 is sealed, there is no air entering the pole module 100 from outside .

[0010] FIG IB illustrates a cross sectional view of the vacuum interrupter, in accordance with prior art . The vacuum interrupter 110 includes two contacts fixed a contact and a movable contact . Generally, a stem of the fixed contact is at an upper side of the pole module 100 and the stem of the movable contact is at a lower side of the pole module 100 . There is a flexible 104 which is provided at a central portion 108 of the pole module 100 . During the operation of the vacuum interrupter 110 there is a large anount of heat that is generated within the pole module 100 . On both the upper side 106A and the lower side 106B of the housing, the heat generated can be controlled either by reducing a generation of the heat itsel f or by increasing a dissipation of the heat that is generated in the pole module 100 .

[0011] For reducing the heat that is generated within the pole module 100 , resistance plays a maj or role . As a value of resistance (R) reduces a value o f I2R also reduces due to proportionality . As a result , the heat generation within the housing 106 is reduced . Further, the resistance (R) o f the pole module 100 can be reduced by increasing a cross sectional area of a main circuit , reducing a number of main contact circuit j oints and by providing parallel current paths .

[0012] Generally, for higher heat dissipation heat sinks are provided within the pole module 100 . As a surface area of the heat sink is increased, the heat dissipation proportionately increases . A rate of heat dissipation is also dependent on air around the vacuum interrupter 110 . I f air flow is appropriately provided with the cold air swi ftly entering into the pole module 100 , the rate of dissipation of the heat will be higher compared to the exit of the stagnant hot air out of the pole module 100 . The enclosed pole has very less space which can dis sipate the heat from the pole module 100 . The hot air from within the housing 106 needs to pass through terminal or other metallic bodies by conduction or by epoxy pole body through convection . As the heat in the lower end of the housing 106 get trapped, a large amount o f heat gets accumulated in a central portion 108 of the pole module 100 causing accumulation of higher temperatures as shown in the FIG . IB .

[0013] In light of the above , there exists a need for a pole module that manages the heat within the pole module 100 ef fectively at the same time also maintains the dielectric requirements of the circuit breaker .

[0014] Accordingly, it is an obj ect of the invention to overcome the drawbacks of the state of the art . The obj ect of the invention is achieved by independent claim 1 and all the corresponding dependent claims thereof .

[0015] The above-mentioned drawbacks are overcome by providing vertical heat vents at the top portion of the pole . Also , the bottom sealed arrangement is replaced by the open pole to facilate the air flow inside the pole . Also , the heat vent can be a single vent provided throughout the circumference of the top end of the pole module . The vents introduced helps heat and moisture to come out of the pole . Also , as the hot air is less dense than cool air, it rises up and escapes out of the pole . As the air keeps circulating and is not stagnent in the central area, more amount of cool air passes and it has a better tendency to carry heat out of the pole . Further, the proposed invention also includes ample number of heat sinks in proportion to a current rating of the circuit breaker to push the hot air out of the pole module . There are al so fan arrangements provided at a bottom portion of the housing which may be partially included within the housing, which again push the cold air into the housing which eventually increases a velocity of the cold air into the housing .

[0016] In an aspect , a pole module for a circuit breaker i s disclosed . The pole module includes a housing having a top end and a bottom end . The pole module includes contact arms and an interrupter comprising a stationary member and a movable member . The pole module is characteri zed by multiple heat vents at a top end of the housing to allow hot air to escape out of the housing, and the bottom end of the housing kept open to facilitate a flow of cool air into the housing .

[0017] In one or more embodiments , the pole module further includes a fan arrangement at the bottom end of the housing to accelerate the flow of the cool air into the housing and push the hot air out of the housing .

[0018] In one or more embodiments , the pole module further includes heat sinks to increase a rate of flow of the hot air out of the housing .

[0019] In one or more embodiments , a dielectric path passes from a lower conducting area of the housing through the heat vents leading to a backside plate connected to the pole module .

[0020] In one or more embodiments , the housing provides the dielectric path and air clearance to achieve dielectric requirements of a circuit breaker .

[0021] Advantageously, such ventilated housing ensures that there is no accumulation of heat within the vacuum interrupter at any point in time . Since there is also a fan arrangement which is provided at the bottom portion of the hous ing, the cool air entering the housing is accelerated which in turn pushes the hot air outside the housing . As a result , a constant flow of the hot air is ensured, and an average temperature is maintained within the housing .

[0022] The above mentioned and other features of the invention will now be addressed with reference to the accompanying drawings of the present invention . The illustrated embodiments are intended to illustrate , but not limit the invention . The present invention is further described hereinafter with reference to illustrated embodiments shown in the accompanying drawings , in which :

[0023] FIG 1A illustrates a perspective view o f a vacuum interrupter of a circuit breaker, in accordance with prior art ;

[0024] FIG IB illustrates a cross sectional view of the vacuum interrupter, in accordance with prior art ;

[0025] FIG 2A illustrates a perspective view of the vacuum interrupter of the circuit breaker, in accordance with an embodiment of the present invention;

[0026] FIG 2B illustrates a cross-sectional view of the vacuum interrupter of the circuit breaker, in accordance with an embodiment of the present invention; and

[0027] FIG 3 illustrates a dielectric path in the cross-sectional view of the vacuum interrupter of the circuit breaker, in accordance with an embodiment of the present invention .

[0028] 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 speci fic 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 speci fic details . The pole module in accordance with the present invention includes a ventilated housing for passing of hot air out of the vacuum interrupter, as explained below with reference to FIGS 2A to 3 .

[0029] FIG 2A illustrates a perspective view of the vacuum interrupter of the circuit breaker, in accordance with an embodiment of the present invention . Referring to the FIG . 2A, in conj unction to the FIG . 1A, the perspective view of the vacuum interrupter of the circuit breaker is provided . In principle , the pole module 100 is an insulating structure serves to electrically isolate critical components of the circuit breaker, as explained earlier with reference to prior art . The pole module 100 includes a housing 106 which includes a top end 106A and a bottom end 106B . Two or more contact arms 102A, 102B are disposed in at least one orientation on the housing 106 , as shown . In an embodiment , the pole module 100 is made of epoxy . Non-limiting examples of other materials suitable for manufacturing the pole module 100 include ceramics , porcelain, and hard rubber . The pole module 100 is fabricated to include multiple heat vents at the top end of the pole module 100 .

[0030] FIG 2B illustrates a cross-sectional view of the vacuum interrupter of the circuit breaker, in accordance with an embodiment of the present invention . The heat vents 112 are provided such that a first heat vent is at a back portion of the pole module 100 and two heat vents on either sides of the pole module 100 with opening in the central area of the pole module 100 . It may be noted that the number of heat vents 112 can vary and is not fixed . The greater the number of heat vents the larger is the area for exit of the hot air and moisture . The purpose of providing the heat vents 112 is to enable exit of the hot air and the moisture from within the pole module 100 . In another embodiment , the heat vents 112 can be provided throughout the circumference of the top end 106A of the pole module 100 . In another embodiment , the heat vent 112 can be a single vent provided throughout the circumference of the top end 106A of the pole module 100 .

[0031] Also , the bottom sealed arrangement provided in the conventional pole module 100 is replaced by a bottom opening 106B to facilitate the air flow inside the housing 106 . The multiple heat vents 112 introduced in the housing 106 helps the heat to escape out of the pole module 100 . Also , as the hot air is less dense than the cool air, the hot air rises up and escapes out of the pole module 100 . As the air keeps circulating and is not stagnent in the central area of the pole module 100 , more amount of cool air passes and it has a better tendency to carry heat out of the pole module 100 .

[0032] The flow of air can also be accelerated by the use of a fan arrangement 114 at the bottom end 106B of the pole module 100 , which will make the air flow turbulant and carry more amount of heat out of the pole module 100 . The fan arrangement 114 can be provided partially within the pole module 100 or in proximity to the pole module 100 . The fan arrangement 114 can be of two types i . e . , Belt-Drive and Direct-Drive . There are multiple belt drive and direct-drive options too .

[0033] Further, multiple heat sinks can be provided in proper areas within the pole module 100 to facilitate the rate of heat dissipation from the pole module 100 . The heat sinks are provided in the direction of flow of the hot air and closer to the heat vents 112 . Further, the number of heat sinks may be proportional to the current rating of the circuit breaker . The heat sink is a passive heat exchanger, and it is designed to have large surface area in contact with the surrounding ( cooling) medium like vacuum . The components of the pole module 100 which are insuf ficient to moderate their temperature , require heat sinks for cooling . Heat generated by the components of the pole module 100 must be dissipated for improving its reliability and preventing the premature failure of the pole module 100 . The heat sinks not only provide heat dissipation but can also be used for thermal energy management done by dissipating heat when heat is more .

[0034] FIG 3 illustrates a dielectric path in the cross-sectional view of the vacuum interrupter of the circuit breaker, in accordance with an embodiment of the present invention . Referring to the FIG . 3 , consider a drive box 116 connected to the vacuum interrupter through an operation mechanism . A top cover plate 118 of the drive box 116 i s placed close to the pole module 100 such that an air clearance 120 is available between the top end of the pole module 100 and a cover plate 118 o f the drive box 116 . The bottom end of the pole module 106B is connected through drive connection linkages to a bottom plate 112 of the drive box 116 .

[0035] The drive box 116 may include a plurality of links , springs , motors , and the l ike to provide a necessary driving force such that the movable member H OB ) is brought into contact with and separated from the stationary member 110A of the interrupter 110 . A power trans fer mechanism is provided within the drive box 116 for trans ferring a driving force of the operatin gmech- anism to the movable member 110B .

[0036] Generally, when the circuit breaker achieves the required thermal performance , it is also important that the circuit breaker withstands the dielectric testing . For higher voltage levels generally, sealed poles are provided to help the circuit breaker withstand the dielectrics . In the proposed solution a ventilated pole design is used to facilitate the thermal performance .

[0037] However, it may be noted that the proposed solution also achieves the dielectric requirements by keeping long surface paths . As shown in the FIG . 3 , the dielectric path passes from the lower conducting area through the heat vents 112 and then from top opening of the pole module to the cover plate 118 . This is a long path for dielectric failure as the surface length of tracking is high . Further, i f the breakdown occurs then it has to clear the air clearance from top of the heat vents 112 till the cover plate 118 . In all , the dielectric path is addition of long surface as well as the air clearance , which make a strong dielectric pathway sustaining the dielec- trie testing of the circuit breaker .

[0038] Therefore , advantageously, the proposed solution takes into consideration the fact that the amount of heat in a particular area is dependent on the source of heat generation and the rate at which the heat is getting dissipated . In earlier arrangements the pole module was a sealed pole , so there existed no space for the heat to escape out . In the proposed solution the heat vents 112 are provided from the central area of the pole until the top, this helps the heat to escape out , along with this the long surface path and air clearance i s maintained in order to make the circuit breaker suitable for the dielectric requirements .

[0039] It must be understood that the aforementioned pole module 2A with the ventilated housing may be adapted for other types of circuit breaker including, but not limited to , gas-insulated circuit breakers , air-insulated circuit breakers and oil-insulated circuit breakers . 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 modi fications and var- iations 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 , modi fications , 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 (100) for a circuit breaker comprising: a housing (106) having a top end (106A) and a bottom end(106B) ; at least two contact arms (102A, 102B) ; and an interrupter (110) comprising a stationary member (110A) and a movable member (HOB) ; characterized by: at least one vent (112) positioned at a top end (106A) of the housing (106) to allow hot air to escape out of the pole module (100) , and wherein the bottom end (106B) of the housing (106) is open to facilitate a flow of cool air into the pole module (100) .

2. The pole module (100) according to the claim 1, further comprising: a fan arrangement (114) at least one of: in proximity of the bottom end (106B) of the housing (106) and at least partially accommodated at the bottom end (106B) of the housing (106) , to accelerate the flow of the cool air into the pole module (100) and push the hot air out of the pole module (100) .

3. The pole module (100) according to the claim 1, further comprising: at least one heat sink in proximity to the at least one vent (112) to increase a rate of flow of the hot air out of the pole module (100) .

4. The pole module (100) according to the claim 3, wherein a number of heat sinks is determined based on a current rating of the circuit breaker.

5. The pole module (100) according to the claim 1, wherein a dielectric path is created from the bottom end (106B) of the housing (106) through the at least one heat vent (112) ,leading to a cover plate (118) connected to the pole module (100) .

6. The pole module (100) according to the claim 3, wherein the dielectric path satisfies dielectric requirements of the circuit breaker.

7. The pole module (100) according to the claim 3, wherein air clearance satisfies dielectric requirements of the circuit breaker.

8. The pole module (100) according to the claim 1, wherein the at least one vent (112) is provided at the top end(106A) of the housing (106) to increase a length of the dielectric path of the pole module (100) .

9. A circuit breaker, wherein the circuit breaker comprises a pole module (100) disclosed according to any of the claims 1 to 8.

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