EP0655759A2 - Electrical switchgear - Google Patents
Electrical switchgear Download PDFInfo
- Publication number
- EP0655759A2 EP0655759A2 EP94308751A EP94308751A EP0655759A2 EP 0655759 A2 EP0655759 A2 EP 0655759A2 EP 94308751 A EP94308751 A EP 94308751A EP 94308751 A EP94308751 A EP 94308751A EP 0655759 A2 EP0655759 A2 EP 0655759A2
- Authority
- EP
- European Patent Office
- Prior art keywords
- electrode
- contact
- main
- arcing
- moving
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Withdrawn
Links
Images
Classifications
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01H—ELECTRIC SWITCHES; RELAYS; SELECTORS; EMERGENCY PROTECTIVE DEVICES
- H01H33/00—High-tension or heavy-current switches with arc-extinguishing or arc-preventing means
- H01H33/02—Details
- H01H33/04—Means for extinguishing or preventing arc between current-carrying parts
- H01H33/12—Auxiliary contacts on to which the arc is transferred from the main contacts
Definitions
- This invention relates to electrical switchgear, and particularly to circuit breakers.
- Circuit breakers have to stop current flow in a circuit as rapidly as possible in the event of an accident or overload.
- a problem encountered by circuit breakers, particularly when stopping high current flows, is arcing as the circuit breaker opens and the circuit is broken. Such arcing can cause considerable damage and while the arc exists current continues to flow in the circuit, preventing rapid shut off.
- One known method of dealing with this problem is to provide separate main and arcing contacts in electrical parallel and to separate the main contacts before the arcing contacts to open the circuit breaker. This ensures that arcing occurs only between the arcing contacts which can be designed to withstand arcing while the main contacts can be designed purely for good current transmission.
- This invention was intended to produce electrical switchgear at least partially overcoming these problems.
- This invention provides electrical switchgear comprising first and second main electrodes a third arcing electrode and a resilient contact element, the first and third electrodes being electrically connected together and attached to a first member and the resilient element being connected to the second electrode and the second electrode being connected to a second member, the second member being able to move relative to the first member between a first ON position and through a second intermediate position to a third OFF position, where in the ON position the main electrodes are in contact and the resilient element and the arcing electrode are out of contact, in the intermediate position the main electrodes are out of contact and the resilient element is in contact with the arcing electrode and in the OFF position the main electrodes are out of contact and the arcing electrode is out of contact with the resilient element, and also being able to move between the third OFF position to the first ON position without the resilient element and the arcing electrode coming into contact.
- an A.C. circuit breaker unit is shown. This is a single phase unit and one such unit will be required for each phase of the electrical supply being switched, for example a conventional three-phase supply will need three such units.
- the entire circuit breaker unit is enclosed within a sealed conductive earthed casing 1 containing sulphur hexafluoride (SF6) gas.
- the casing 1 is earthed at a point 2. Not all of the casing 1 is shown.
- alternating current passes through the circuit breaker unit between a first conductor 3 which is linked to a current source and a second conductor 4 which is linked to a current using circuit.
- the second conductor 4 passes through the casing 1 inside an insulating bush 5.
- the first conductor 3, a contact block 6, a first, main, electrode 7, a third, arcing, electrode 8 and an arc extinguishing coil 9 are all rigidly connected to form a fixed contact assembly.
- the fixed contact assembly is fixed relative to the casing 1 and is attached to the casing 1 by a first insulating support 11 attaching the conductor 3 to the casing 1, and a second insulating support 12 attaching the first, main electrode 7 to a first insulating block 13 which is in turn attached to the casing 1 and third and fourth insulating supports 14 and 15 attaching the third, arcing, electrode 8 and the arc extinguishing coil 9 to the first insulating block 13 and a second insulating block 14 respectively, the second insulating block 14 is attached to the casing 1 and also provides support to the first conductor 3.
- the first conductor 3 is in electrical contact with the contact block 6 and the first, main, electrode 7 which it supports.
- the third, arcing, electrode 8 is rotationally symmetrical about an axis 17 and is a substantialy cylindrical tube with an end portion 22 of increased radius.
- the arc extinguishing coil 9 is wound around the third, arcing, electrode 8 and the inner turn of the coil 9 is in electrical contact with the third arcing electrode 8.
- the outermost turn of the coil 9 is in electrical contact with the contact block 6.
- the coil 9 is surrounded and supported by a coil retaining ring 36 and a coil support moulding 37.
- the second conductor 4 is electrically linked to a contact support bar 18 by a flexible connector 19.
- the contact support bar 18 supports and is electrically connected to a second, main, electrode 20 and a fourth, earthing, electrode 21.
- the contact support bar 18 and electrodes 20 and 21 form a moving contact assembly.
- the contact support bar 18 is attached to an insulating support 23 which is in turn attached at one end to a carrier 24.
- the carrier 24 has a pair of pins 25 attached to it which pass through a slot 26 in a moulding 27 in the form of a planar sheet.
- the insulating support 23 is attached at its second end to a second carrier 24 with pins 25 passing through a second slot 26 in a second moulding 27.
- This arrangement is identical to that described above and is omitted in Figure 1 for clarity.
- the moving contact assembly is normally constrained to only be able to move linearily parallel to the slots 23.
- the second, main electrode 20 and fourth, earthing, electrode 21 are formed by the two ends of a single elongate conductor passing through the contact support bar 18.
- the second, main, electrode 20 is rotationally symmetrical about the axis of symmetry 17 of the arcing electrode 8, which is parallel to the slots 26 so that as the moving contact assembly moves the second, main, electrode 20 moves along the axis 17.
- the second, main, electrode 20 comprises a main body portion 28 adjacent the contact support bar 18, a head portion 29 having a rounded end 30 and five spring fingers 31 extending from the main body portion 28 and surrounding part of the head portion 29.
- the second, main, electrode 20 and spring fingers 31 are shown in more detail in Figure 4.
- Each spring finger 31 has a first portion 37 having a small radius and secured to the head portion 29 of the second, main, electrode 20 at the end of the spring finger 31 nearest the main body portion 28 of the electrode 20 and a second portion 38 of variable radius at the other end of the spring finger 31 which bulges away from the head portion 29 of the electrode 20, leaving a gap between the spring finger 31 and the head portion 29, and then comes back into contact with the head portion 29 of the electrode 20 at its end 39 nearest the rounded end 30 of the electrode 20.
- the ends 39 of the spring fingers 31 are free to move relative to the second, main, electrode 20 so that the second portions 38 of each spring finger 31 can flex.
- the outer surfaces of the spring fingers 31 are curved around the axis 17 so that all of the spring fingers 31 together form a structure circular in cross section and symmetrical about the axis 17.
- the outermost diameter of the spring fingers 31 is slightly less than the minimum inner diameter of the third, arcing, electrode 8.
- a sixth earthing electrode 32 is fixed to the casing 1 by a bolt 33 and is in electrical contact with the casing 1.
- the second, main, electrode 20 separates from the first, main, electrode 7 and as electrical contact between these two electrodes is broken an arc forms between them between the first, main, electrode 7 and the rounded head portion 30 of the second, main, electrode 20.
- This head portion 30 is formed of an arc resistant (also known as anti-arc) material.
- the detents 35 are positioned so that when the pins 25 are urged into them as the moving electrode assembly moves down the slots 26 the second, main, electrode 20 is moved sideways off the axis 17 into an intermediate position such that one of the spring fingers 31 is forced into contact with a raised ridge 61 of reduced diameter running around the inside of the third, arcing, electrode 8.
- the separatiion of the second, main, electrode 20 and the third, arcing, electrode 8 continues to increase until the moving contact assembly stops in the OFF position shown in Figure 2A.
- the head portion 29 of the second, main, electrode 20 is positioned on the axis 17.
- the arc between the second, main, and third, arcing, electrodes 20 and 8 is extinguished by the atmosphere of sulphur hexafluoride within the casing 1 and by the arc rotating magnetic field produced by the arc current passing through the coil 9. Both of these methods of arc extinction are well known and need not be discussed in detail here.
- the head portion 29 of the second, main, electrode 20 is situated on the axis 17 of the third, arcing, electrode 8 and coil 9, giving a symmetrical arrangement to give good arc rotation to ensure rapid arc extinction.
- the larger radius end portion 22 of the third, arcing, electrode 8 and the rounded end 30 of the head portion 29 of the second, main, electrode 20 minimise the damage done by the arcing between them.
- the moving contact assembly can be moved still further away from the fixed contact assembly into an EARTH position, shown in Figure 2C, where the fourth, earthing, electrode 21 is in contact with the fifth, earthing, electrode 32.
- the pins 25 are at the second ends of the slots 26 and the moving contact assembly is at its farthest possible position from the fixed contact assembly. This provides an earthing current path for the conductor 4 by way of the flexible connector 19, contact support bar 18, the fourth and fifth earthing electrodes 21 and 32 and the casing 1, earthing the external circuit supplied by the conductor 4.
- FIG. 5 a second AC circuit breaker is shown which operates in substantially the same manner as the circuit breaker of Figure 1 and as described with reference to Figures 2a to 2c but employs a different mechanism for moving the second, main, electrode 20.
- the circuit breaker is substantially the same as the circuit breaker shown in Figure 1.
- the contact support bar 18 supports and is in electrical contact with a second, main, electrode 20 and a fourth, earthing, electrode 21 to form a moving contact assembly and is attached to an insulating support 51.
- the contact support bar 18 is attached to the insulating support so as to allow sliding movement of the contact support bar 18 relative to the insulating support 51 in a direction perpendicular to the axis 17. The extent of this sliding movement is controlled by surfaces of the contact support bar 18 and insulating support 51 coming into contact and a spring 52 is provided to bias the contact support bar 18 relative to the insulating support 51 at one end of its available range of movement where the second, main, electrode 20 is on the axis 17.
- the insulating support 51 is attached at one end to a carrier 53.
- the carrier 53 has four rollers 54 attached to it for rotation about four respective parallel axes 55.
- the rollers 54 rotate in contact with and two on each side of a track member 56.
- the track member 56 has two parallel planar faces 57 and 58 on which the rollers 54 bear.
- the insulating support 51 is similarly attached at its opposite end to a second carrier 53 bearing four rollers 54 arranged on two sides of a second track member 56. This arrangement is identical to that described above and is omitted from Figure 5 for clarity.
- the moving contact assembly is normally constrained to only be able to move linearly parallel to the track member 56 and the axis 17 and as a result the second, main, electrode 20 is normally constrained to move along the axis 17.
- a racheting cam mechanism 59 is arranged to have a projecting cam portion 60 which contacts the end of the contact support bar 18 remote from the second, main, electrode 20 as the moving contact assembly moves along the track member 56 from the ON position to the OFF position and vice versa
- the racheting cam mechanism 59 allows the contact support bar 18 to travel past the cam 60 without moving the contact support bar 18 out of the rest position it is biased into by the spring 52.
- the second, main, electrode 20 travels only along the axis 17 and the spring fingers 31 do not come into contact with the arcing electrode 8.
- the cam 60 of the racheting cam mechanism 59 urges the contact support bar 18 to slide relative to the insulating support 51 against the bias of the spring 52 as the variable radius portions 38 of the spring fingers 31 are passing through the arcing electrode 8.
- the cam 60 causes the contact support bar 18 and thus the second, main, electrode 20 and attached spring fingers 31 to be moved off the axis 17 sufficiently to bring the variable radius portion 38 of at least one of the spring fingers 31 into contact with the raised ridge 61 of reduced diameter inside the third, arcing, electrode 8.
- the spring fingers 31 could by have flat facets instead of being curved, or have a combination of flat and curved surfaces in the region 38 or could be replaced by some other form of resilient conductive element.
- the second, main, electrode 20 comprises a main body portion 41, a head portion 42 having a rounded end 43 and five spring fingers 44.
- the main body portion 41 does not extend all the way to the contact support bar 18 but is separated from a contact support bar 18 by a substantially cylindrical conductive sleeve 45.
- the conductive sleeve 45 has an inwardly projecting circular flange 46 within it to define a cup shaped volume.
- a bolt 47 passes through a bore 49 in the contact support bar 18 along the axis of the conductive sleeve 45 and into a cylindrical threaded bore 49 within the main body portion 41 so that when the bolt 47 is tightened within the threaded bore 49 the main body portion 41 of the second, main, electrode 20 is pulled towards the flange 46.
- the spring fingers 44 are arranged with their ends remote from the head portion 42 of the second, main, electrode 20 folded inwards so that they lie between the end of the main body portion 41 and the flange 46. As a result tightening of the bolt 47 within the threaded bore 49 holds the spring fingers 44 as well as the main body portion 41 in place.
- the earthing electrode is formed by a conductive strip 50 secured to the contact support bar 18 by the head of the bolt 47 and bent through a right angle to form an earthing electrode parallel to the axis 40.
- connection of the contact support bar 18 to the second conductor 4 has been omitted from Figures 3 and 6 for clarity.
- Any other electronegative gas could be used to replace the sulphur hexafluoride.
Landscapes
- Arc-Extinguishing Devices That Are Switches (AREA)
Abstract
Description
- This invention relates to electrical switchgear, and particularly to circuit breakers.
- Circuit breakers have to stop current flow in a circuit as rapidly as possible in the event of an accident or overload. A problem encountered by circuit breakers, particularly when stopping high current flows, is arcing as the circuit breaker opens and the circuit is broken. Such arcing can cause considerable damage and while the arc exists current continues to flow in the circuit, preventing rapid shut off. One known method of dealing with this problem is to provide separate main and arcing contacts in electrical parallel and to separate the main contacts before the arcing contacts to open the circuit breaker. This ensures that arcing occurs only between the arcing contacts which can be designed to withstand arcing while the main contacts can be designed purely for good current transmission.
- There are two main problems with this arrangement, the first is caused by the fact that it is normal to place an arc extinguishing coil adjacent to and in electrical series with the arcing contacts so that the magnetic field generate by the coil helps extinguish the arc. Although the use of such a coil is necessary to ensure rapid arc extinction and has been used in known circuit breakers of this type for safety, the presence of a large reactive component in a power supply is electrically undesirable. The second problem is simply that known designs of this type use very complex mechanical drive systems to ensure that the two sets of contacts move at the correct times, the use of complex mechanical drives is generally undesirable on grounds of cost, but is particularly undesirable in a circuit breaker which must remain in a current transmitting position for long periods of time, generally months to years, and reliably move to a current blocking position in fractions of a second on demand.
- Athough they are most pronounced in circuit breakers these problems are encountered in electrical switchgear generally, the larger the currents being switched the greater the problems become.
- This invention was intended to produce electrical switchgear at least partially overcoming these problems.
- This invention provides electrical switchgear comprising first and second main electrodes a third arcing electrode and a resilient contact element, the first and third electrodes being electrically connected together and attached to a first member and the resilient element being connected to the second electrode and the second electrode being connected to a second member, the second member being able to move relative to the first member between a first ON position and through a second intermediate position to a third OFF position, where in the ON position the main electrodes are in contact and the resilient element and the arcing electrode are out of contact, in the intermediate position the main electrodes are out of contact and the resilient element is in contact with the arcing electrode and in the OFF position the main electrodes are out of contact and the arcing electrode is out of contact with the resilient element, and also being able to move between the third OFF position to the first ON position without the resilient element and the arcing electrode coming into contact.
- Apparatus employing the invention will now be described by way of example only with reference to the accompanying diagrammatic figures in which;
- Figure 1 shows a cut away view of a first circuit breaker unit according to the invention;
- Figure 2a shows the main part of the circuit breaker unit of Figure 1 in a first "OFF" position;
- Figure 2b shows the same parts in a second "ON" position;
- Figure 2c shows the same parts in a third "EARTH" position;
- Figure 3 shows a perspective view of the moving electrode assembly of the circuit breaker unit of Figure 1 in perspective;
- Figure 4 shows a cut away of a first design of the second main electrode and spring fingers of the circuit breaker unit of Figure 1 sectioned along the
axis 17; - Figure 5 shows a cut away view of a second circuit breaker unit according to the invention;
- Figure 6 shows a cut away of an alternative design of second main electrode and spring fingers suitable for use in either of the circuit breaker units of Figure 1 or Figure 5, identical parts having the same reference numerals throughout.
- Referring to Figures 1 to 4 an A.C. circuit breaker unit is shown. This is a single phase unit and one such unit will be required for each phase of the electrical supply being switched, for example a conventional three-phase supply will need three such units.
- The entire circuit breaker unit is enclosed within a sealed conductive earthed
casing 1 containing sulphur hexafluoride (SF₆) gas. Thecasing 1 is earthed at apoint 2. Not all of thecasing 1 is shown. - In operation, alternating current passes through the circuit breaker unit between a first conductor 3 which is linked to a current source and a
second conductor 4 which is linked to a current using circuit. Thesecond conductor 4 passes through thecasing 1 inside an insulating bush 5. - The first conductor 3, a contact block 6, a first, main,
electrode 7, a third, arcing,electrode 8 and anarc extinguishing coil 9 are all rigidly connected to form a fixed contact assembly. The fixed contact assembly is fixed relative to thecasing 1 and is attached to thecasing 1 by a first insulating support 11 attaching the conductor 3 to thecasing 1, and a secondinsulating support 12 attaching the first,main electrode 7 to afirst insulating block 13 which is in turn attached to thecasing 1 and third and fourth insulating supports 14 and 15 attaching the third, arcing,electrode 8 and thearc extinguishing coil 9 to thefirst insulating block 13 and asecond insulating block 14 respectively, thesecond insulating block 14 is attached to thecasing 1 and also provides support to the first conductor 3. - The first conductor 3 is in electrical contact with the contact block 6 and the first, main,
electrode 7 which it supports. The third, arcing,electrode 8 is rotationally symmetrical about anaxis 17 and is a substantialy cylindrical tube with an end portion 22 of increased radius. Thearc extinguishing coil 9 is wound around the third, arcing,electrode 8 and the inner turn of thecoil 9 is in electrical contact with thethird arcing electrode 8. The outermost turn of thecoil 9 is in electrical contact with the contact block 6. Thecoil 9 is surrounded and supported by acoil retaining ring 36 and a coil support moulding 37. - The
second conductor 4 is electrically linked to acontact support bar 18 by aflexible connector 19. Thecontact support bar 18 supports and is electrically connected to a second, main,electrode 20 and a fourth, earthing,electrode 21. Thecontact support bar 18 andelectrodes - The
contact support bar 18 is attached to aninsulating support 23 which is in turn attached at one end to acarrier 24. Thecarrier 24 has a pair ofpins 25 attached to it which pass through aslot 26 in a moulding 27 in the form of a planar sheet. - The
insulating support 23 is attached at its second end to asecond carrier 24 withpins 25 passing through asecond slot 26 in asecond moulding 27. This arrangement is identical to that described above and is omitted in Figure 1 for clarity. - Thus the moving contact assembly is normally constrained to only be able to move linearily parallel to the
slots 23. - The second,
main electrode 20 and fourth, earthing,electrode 21 are formed by the two ends of a single elongate conductor passing through thecontact support bar 18. - Although this is a convenient method of providing the second, main,
electrode 20 and fourth,earthing electrode 21, other constructions could of course be used. - The second, main,
electrode 20 is rotationally symmetrical about the axis ofsymmetry 17 of thearcing electrode 8, which is parallel to theslots 26 so that as the moving contact assembly moves the second, main,electrode 20 moves along theaxis 17. - The second, main,
electrode 20 comprises amain body portion 28 adjacent thecontact support bar 18, ahead portion 29 having arounded end 30 and fivespring fingers 31 extending from themain body portion 28 and surrounding part of thehead portion 29. The second, main,electrode 20 andspring fingers 31 are shown in more detail in Figure 4. Eachspring finger 31 has afirst portion 37 having a small radius and secured to thehead portion 29 of the second, main,electrode 20 at the end of thespring finger 31 nearest themain body portion 28 of theelectrode 20 and asecond portion 38 of variable radius at the other end of thespring finger 31 which bulges away from thehead portion 29 of theelectrode 20, leaving a gap between thespring finger 31 and thehead portion 29, and then comes back into contact with thehead portion 29 of theelectrode 20 at itsend 39 nearest therounded end 30 of theelectrode 20. Theends 39 of thespring fingers 31 are free to move relative to the second, main,electrode 20 so that thesecond portions 38 of eachspring finger 31 can flex. The outer surfaces of thespring fingers 31 are curved around theaxis 17 so that all of thespring fingers 31 together form a structure circular in cross section and symmetrical about theaxis 17. The outermost diameter of thespring fingers 31 is slightly less than the minimum inner diameter of the third, arcing,electrode 8. - A
sixth earthing electrode 32 is fixed to thecasing 1 by a bolt 33 and is in electrical contact with thecasing 1. - In Figures 1 and 2A the moving contact assembly is shown in an OFF position.
- When the moving contact assembly is in the ON position as shown in Figure 2B the first, main,
electrode 20 and second, main,electrode 7 are in contact while the third, arcing,electrode 8 andspring fingers 31 are not in contact because the outside diameter of thespring fingers 31 is less than the inner diameter of the third, arcing,electrode 8, leaving a small clearance. This small clearance is sufficient because in the ON position thearcing electrode 8 andspring fingers 31 are at the same electrical potential. In the ON position thepins 25 are at first ends of theslots 26 and further movement of the moving contact assembly towards the fixed contact assembly is prevented by stops in the actuating mechanism (not shown) which operates the moving contact assembly. The contact of thepins 25 with the ends of theslots 26 could be used in place of the stops to prevent further movement but this is not preferred. - In the ON position a current path exists from the first conductor 3 through the first, main,
electrode 7, the second, main,electrode 20, thecontact support bar 18, and theflexible connector 19 to thesecond conductor 4. - In order to break the current path the moving contact assembly is moved along the
slots 26 away from the fixed contact assembly (downwards in Figure 1) towards the OFF position shown in Figure 2A. - En-route the second, main,
electrode 20 separates from the first, main,electrode 7 and as electrical contact between these two electrodes is broken an arc forms between them between the first, main,electrode 7 and therounded head portion 30 of the second, main,electrode 20. Thishead portion 30 is formed of an arc resistant (also known as anti-arc) material. As the moving electrode assembly continues to move along theaxis 17 one of thepins 25 in eachslot 26 is urged into a detent 35 in one side of itsrespective slot 26. Thedetents 35 are positioned so that when thepins 25 are urged into them as the moving electrode assembly moves down theslots 26 the second, main,electrode 20 is moved sideways off theaxis 17 into an intermediate position such that one of thespring fingers 31 is forced into contact with a raisedridge 61 of reduced diameter running around the inside of the third, arcing,electrode 8. - At this point in the movement of the moving electrode assembly from the ON to the OFF position a current path exists from the first conductor 3 to the
second conductor 4, this current path passes from the first conductor 3 through the contact block 6, through thecoil 9, and the third, arcing,electrode 8, through thespring fingers 31 and the second, main,electrode 20 to theelectrode mounting block 18 and then through theflexible connector 19 to thesecond conductor 4. The current passes along this path in preference to the arc between the first, main,electrode 7 and the second,main electrode 20 and as a result this arc is extinguished. - As the moving electrode assembly continues its movement the
pins 25 in theslots 26 leave thedetents 35, recentering thespring fingers 31 on theaxis 17 and as a result thespring fingers 31 move out of contact with theridge 36 on the third, arcing,electrode 8. This breaking of contact generates an arc between thespring fingers 31 and the third, arcing,electrode 8 and as the moving contact continues to move towards the OFF position this arc transfers from thespring fingers 31 to therounded head 30 of the second, main,electrode 20. - The separatiion of the second, main,
electrode 20 and the third, arcing,electrode 8 continues to increase until the moving contact assembly stops in the OFF position shown in Figure 2A. In the OFF position thehead portion 29 of the second, main,electrode 20 is positioned on theaxis 17. - The arc between the second, main, and third, arcing,
electrodes casing 1 and by the arc rotating magnetic field produced by the arc current passing through thecoil 9. Both of these methods of arc extinction are well known and need not be discussed in detail here. - When the moving contact assembly reaches the OFF position the
head portion 29 of the second, main,electrode 20 is situated on theaxis 17 of the third, arcing,electrode 8 andcoil 9, giving a symmetrical arrangement to give good arc rotation to ensure rapid arc extinction. - The larger radius end portion 22 of the third, arcing,
electrode 8 and therounded end 30 of thehead portion 29 of the second, main,electrode 20 minimise the damage done by the arcing between them. - In the OFF position there is no current path between the first and
second conductors 3 and 4. - From the OFF position of Figure 2A the moving contact assembly can be moved still further away from the fixed contact assembly into an EARTH position, shown in Figure 2C, where the fourth, earthing,
electrode 21 is in contact with the fifth, earthing,electrode 32. In the earthing position thepins 25 are at the second ends of theslots 26 and the moving contact assembly is at its farthest possible position from the fixed contact assembly. This provides an earthing current path for theconductor 4 by way of theflexible connector 19,contact support bar 18, the fourth and fifth earthingelectrodes casing 1, earthing the external circuit supplied by theconductor 4. - When the moving contact assembly is moved from the OFF position shown in Figure 2A to the ON position shown in Figure 2B the
pins 25 are urged against the opposite sides of theslots 26 which are flat and have no detents so the second, main,electrode 20 remains on theaxis 17 throughout this movement and as a result no contact is made between thespring fingers 31 and the third, arcing,electrode 8 during this movement and the first electrical contact is made between the first and secondmain electrodes - Referring to Figure 5 a second AC circuit breaker is shown which operates in substantially the same manner as the circuit breaker of Figure 1 and as described with reference to Figures 2a to 2c but employs a different mechanism for moving the second, main,
electrode 20. - As can be seen the circuit breaker is substantially the same as the circuit breaker shown in Figure 1. In this case the
contact support bar 18 supports and is in electrical contact with a second, main,electrode 20 and a fourth, earthing,electrode 21 to form a moving contact assembly and is attached to an insulatingsupport 51. Thecontact support bar 18 is attached to the insulating support so as to allow sliding movement of thecontact support bar 18 relative to the insulatingsupport 51 in a direction perpendicular to theaxis 17. The extent of this sliding movement is controlled by surfaces of thecontact support bar 18 and insulatingsupport 51 coming into contact and aspring 52 is provided to bias thecontact support bar 18 relative to the insulatingsupport 51 at one end of its available range of movement where the second, main,electrode 20 is on theaxis 17. - The insulating
support 51 is attached at one end to acarrier 53. Thecarrier 53 has fourrollers 54 attached to it for rotation about four respective parallel axes 55. Therollers 54 rotate in contact with and two on each side of a track member 56. - The track member 56 has two parallel planar faces 57 and 58 on which the
rollers 54 bear. - The insulating
support 51 is similarly attached at its opposite end to asecond carrier 53 bearing fourrollers 54 arranged on two sides of a second track member 56. This arrangement is identical to that described above and is omitted from Figure 5 for clarity. - Thus the moving contact assembly is normally constrained to only be able to move linearly parallel to the track member 56 and the
axis 17 and as a result the second, main,electrode 20 is normally constrained to move along theaxis 17. - A
racheting cam mechanism 59 is arranged to have a projectingcam portion 60 which contacts the end of thecontact support bar 18 remote from the second, main,electrode 20 as the moving contact assembly moves along the track member 56 from the ON position to the OFF position and vice versa - When the moving contact assembly is moved from the OFF position to the ON position the
racheting cam mechanism 59 allows thecontact support bar 18 to travel past thecam 60 without moving thecontact support bar 18 out of the rest position it is biased into by thespring 52. As a result when the moving contact assembly moves from the OFF position to the ON position the second, main,electrode 20 travels only along theaxis 17 and thespring fingers 31 do not come into contact with the arcingelectrode 8. - When the moving contact assembly is moving from the ON position to the OFF position the
cam 60 of theracheting cam mechanism 59 urges thecontact support bar 18 to slide relative to the insulatingsupport 51 against the bias of thespring 52 as thevariable radius portions 38 of thespring fingers 31 are passing through the arcingelectrode 8. Thecam 60 causes thecontact support bar 18 and thus the second, main,electrode 20 and attachedspring fingers 31 to be moved off theaxis 17 sufficiently to bring thevariable radius portion 38 of at least one of thespring fingers 31 into contact with the raisedridge 61 of reduced diameter inside the third, arcing,electrode 8. - As a result the making and breaking of contact and arc formation and extinction are substantially the same in operation as in the circuit breaker described with reference to Figures 1 to 4.
- In either example, the
spring fingers 31 could by have flat facets instead of being curved, or have a combination of flat and curved surfaces in theregion 38 or could be replaced by some other form of resilient conductive element. - Referring to Figure 6 an alternative construction of the second, main,
electrode 20 is shown in cross section along its axis ofsymmetry 40. In this case the second, main,electrode 20 comprises a main body portion 41, a head portion 42 having arounded end 43 and fivespring fingers 44. - In this design the main body portion 41 does not extend all the way to the
contact support bar 18 but is separated from acontact support bar 18 by a substantially cylindricalconductive sleeve 45. Theconductive sleeve 45 has an inwardly projectingcircular flange 46 within it to define a cup shaped volume. Abolt 47 passes through abore 49 in thecontact support bar 18 along the axis of theconductive sleeve 45 and into a cylindrical threaded bore 49 within the main body portion 41 so that when thebolt 47 is tightened within the threaded bore 49 the main body portion 41 of the second, main,electrode 20 is pulled towards theflange 46. - In this case the
spring fingers 44 are arranged with their ends remote from the head portion 42 of the second, main,electrode 20 folded inwards so that they lie between the end of the main body portion 41 and theflange 46. As a result tightening of thebolt 47 within the threaded bore 49 holds thespring fingers 44 as well as the main body portion 41 in place. - In this design, it is not possible to form the earthing electrode from the main body portion of the second, main,
electrode 20 as in the previous example because the main body portion 41 in this design does not pass through thecontact support bar 18. In the example shown the earthing electrode is formed by a conductive strip 50 secured to thecontact support bar 18 by the head of thebolt 47 and bent through a right angle to form an earthing electrode parallel to theaxis 40. - It will be realised of course that there are many other ways of finding an earthing electrode in arrangements of this type.
- The connection of the
contact support bar 18 to thesecond conductor 4 has been omitted from Figures 3 and 6 for clarity. - Any other electronegative gas could be used to replace the sulphur hexafluoride.
- In the switchgear of Figures 1 to 5 the
flexible connector 19 could be replaced by a sliding or pivoting contact arrangement. - There are of course many alternative mechanical constructions which could be used in the switchgear. In particular the structure used to support and electrically link the fixed contacts could be altered and any mouldings used could be replaced by equivalent structures formed in other ways.
Claims (10)
- Electrical switchgear comprising first and second main electrodes a third arcing electrode and a resilient contact element, the first and third electrodes being electrically connected together and attached to a first member and the resilient element being connected to the second electrode and the second electrode being connected to a second member, the second member being able to move relative to the first member between a first ON position and through a second intermediate position to a third OFF position, where in the ON position the main electrodes are in contact and the resilient element and the arcing electrode are out of contact, in the intermediate position the main electrodes are out of contact and the resilient element is in contact with the arcing electrode and in the OFF position the main electrodes are out of contact and the arcing electrode is out of contact with the resilient element, and also being able to move between the third OFF position to the first ON position without the resilient element and the arcing electrode coming into contact.
- Electrical switchgear as claimed in claim 1 where a plurality of resilient elements are secured to the second electrode.
- Electrical switchgear as claimed in claim 2 where the resilient elements surround the second electrode.
- Electrical switchgear as claimed in any preceding claim where the or each resilient element is a spring finger.
- Electrical switchgear as claimed in any preceding claim in which the second member bears a pair of pins which move along a slot which is fixed relative to the first member, the slot having two walls with different profiles and the pins being constrained to follow one wall when moving from the ON to the OFF position and the other wall when moving from the OFF to the ON position such that the path followed by the second member relative to the first member is different when moving in each direction.
- Electrical switchgear as claimed in claim 5 in which one wall of the slot is straight along its entire length and the other wall of the slot is straight along most of its length but bears a detent into which one of the pins is urged when the pin is moving along the slot in one direction only.
- Electrical switchgear as claimed in any one of claims 1 to 4 in which cam and rachet means are provided, the cam and rachet means being arranged to act on the second member so that the path followed by the second member relative to the first member is different when moving from the ON to the OFF position from the path followed when moving from the OFF to the ON position.
- Electrical switchgear as claimed in claim 7 in which the cam and rachet means comprises a rachet mechanism which causes a cam to act on the second member when moving in one direction only.
- Electrical switchgear as claimed in claim 8 in which the cam acts on the second member only when moving from the ON to the OFF position.
- Electrical switchgear as claimed in any preceding claim where the electrical switchgear is a circuit breaker.
Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
GB9324582 | 1993-11-30 | ||
GB939324582A GB9324582D0 (en) | 1993-11-30 | 1993-11-30 | Electrical switchgear |
Publications (2)
Publication Number | Publication Date |
---|---|
EP0655759A2 true EP0655759A2 (en) | 1995-05-31 |
EP0655759A3 EP0655759A3 (en) | 1997-06-11 |
Family
ID=10745919
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
EP94308751A Withdrawn EP0655759A3 (en) | 1993-11-30 | 1994-11-28 | Electrical switchgear. |
Country Status (6)
Country | Link |
---|---|
EP (1) | EP0655759A3 (en) |
AU (1) | AU673631B2 (en) |
GB (2) | GB9324582D0 (en) |
NO (1) | NO944566L (en) |
NZ (1) | NZ270010A (en) |
ZA (1) | ZA949411B (en) |
Families Citing this family (2)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
JP4841875B2 (en) * | 2005-06-29 | 2011-12-21 | 株式会社日立製作所 | Vacuum insulated switchgear |
US7902480B2 (en) | 2007-06-13 | 2011-03-08 | Hitachi, Ltd. | Vacuum insulated switchgear |
Citations (3)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
BE382647A (en) * | ||||
FR2274130A1 (en) * | 1974-06-07 | 1976-01-02 | Hazemeijer Bv | ARC CONTACT ELECTRIC SWITCH |
GB2260027A (en) * | 1991-09-30 | 1993-03-31 | Long & Crawford Limited | Electrical switchgear |
Family Cites Families (1)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
FR2650434B1 (en) * | 1989-07-26 | 1995-11-24 | Merlin Gerin | LOW VOLTAGE CIRCUIT BREAKER WITH MULTIPLE CONTACTS AND HIGH CURRENTS |
-
1993
- 1993-11-30 GB GB939324582A patent/GB9324582D0/en active Pending
-
1994
- 1994-11-28 NZ NZ270010A patent/NZ270010A/en unknown
- 1994-11-28 ZA ZA949411A patent/ZA949411B/en unknown
- 1994-11-28 EP EP94308751A patent/EP0655759A3/en not_active Withdrawn
- 1994-11-29 NO NO944566A patent/NO944566L/en unknown
- 1994-11-29 AU AU79113/94A patent/AU673631B2/en not_active Ceased
- 1994-11-29 GB GB9424039A patent/GB2284307B/en not_active Expired - Fee Related
Patent Citations (3)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
BE382647A (en) * | ||||
FR2274130A1 (en) * | 1974-06-07 | 1976-01-02 | Hazemeijer Bv | ARC CONTACT ELECTRIC SWITCH |
GB2260027A (en) * | 1991-09-30 | 1993-03-31 | Long & Crawford Limited | Electrical switchgear |
Also Published As
Publication number | Publication date |
---|---|
EP0655759A3 (en) | 1997-06-11 |
NO944566D0 (en) | 1994-11-29 |
GB9424039D0 (en) | 1995-01-18 |
GB2284307B (en) | 1997-10-22 |
AU673631B2 (en) | 1996-11-14 |
GB9324582D0 (en) | 1994-01-19 |
ZA949411B (en) | 1995-08-14 |
NO944566L (en) | 1995-05-31 |
AU7911394A (en) | 1995-06-08 |
GB2284307A (en) | 1995-05-31 |
NZ270010A (en) | 1996-12-20 |
Similar Documents
Publication | Publication Date | Title |
---|---|---|
US6163002A (en) | Vacuum circuit interrupter with contact structure including support pins | |
US4500762A (en) | Resistor-type disconnecting switch for circuit breaker | |
KR100489492B1 (en) | Electrical switching device | |
EP0021577B1 (en) | Electrical switchgear of the rotating arc, double-break type | |
US11087940B2 (en) | Electrical interruption device | |
US4409446A (en) | Electrical switchgear | |
CN108028146B (en) | Mechanical circuit breaker device for high-voltage or very high-voltage electrical circuits with separation device | |
EP0655759A2 (en) | Electrical switchgear | |
EP0012522B1 (en) | Electrical switchgear | |
SU1477255A3 (en) | Disconnector for multipole cell of high-voltage switchgear | |
US3959616A (en) | Spring contact assembly for an electrical switch | |
JP3967387B2 (en) | Arc switching switch | |
US20090133996A1 (en) | Electric switch having an annular stationary contact | |
US6271493B1 (en) | High voltage disconnector with fixed and locking members secure under Lorentz forces | |
GB2260027A (en) | Electrical switchgear | |
US4256934A (en) | Disconnecting switch arrangement | |
GB2188488A (en) | Arc runner/electrode for switch | |
US20080246342A1 (en) | Electrical Switching Device Arrangement | |
US10734175B1 (en) | High voltage electric power switch with anti-flashover nozzle | |
US11177082B2 (en) | Electrical switch with three fixed contacts, a rotating knife contact and three switch positions | |
JP3400081B2 (en) | Gas circuit breaker | |
GB2052160A (en) | Electrical switchgear | |
WO2001015187A1 (en) | Improvements in or relating to electrical switches | |
WO2019243773A1 (en) | A switch for closing a circuit | |
JP2001006519A (en) | Three-pole interlocking fuse |
Legal Events
Date | Code | Title | Description |
---|---|---|---|
PUAI | Public reference made under article 153(3) epc to a published international application that has entered the european phase |
Free format text: ORIGINAL CODE: 0009012 |
|
AK | Designated contracting states |
Kind code of ref document: A2 Designated state(s): BE CH DE DK FR GB IT LI NL SE |
|
RAP3 | Party data changed (applicant data changed or rights of an application transferred) |
Owner name: LONG & CRAWFORD LTD. |
|
PUAL | Search report despatched |
Free format text: ORIGINAL CODE: 0009013 |
|
AK | Designated contracting states |
Kind code of ref document: A3 Designated state(s): BE CH DE DK FR GB IT LI NL SE |
|
17P | Request for examination filed |
Effective date: 19971205 |
|
GRAG | Despatch of communication of intention to grant |
Free format text: ORIGINAL CODE: EPIDOS AGRA |
|
17Q | First examination report despatched |
Effective date: 19990617 |
|
GRAG | Despatch of communication of intention to grant |
Free format text: ORIGINAL CODE: EPIDOS AGRA |
|
GRAG | Despatch of communication of intention to grant |
Free format text: ORIGINAL CODE: EPIDOS AGRA |
|
GRAH | Despatch of communication of intention to grant a patent |
Free format text: ORIGINAL CODE: EPIDOS IGRA |
|
STAA | Information on the status of an ep patent application or granted ep patent |
Free format text: STATUS: THE APPLICATION HAS BEEN WITHDRAWN |
|
18W | Application withdrawn |
Withdrawal date: 20000413 |