Title of Invention

A LOAD DIVERTER SWITCH

Abstract

57) Abstract: A load diverter switch of a tap-changer comprises a force storage device (2), which comprises a tensioning canlage (2.2) continuously movable by a drive shaft, and a drive output member (2.3) which actuates a switch shaft (4). An axially displaceable can-ier (5) which carries cam discs for actuation of vacuum switches and of mechanical switching elements, Is arranged on the switch shaft In dependence on the direction of switching, i.e. the linear movement of the carriage (2.2) of the force storage device (2), the canier (5) is displaced Into an upper or a lower position on the switch shaft In such a manner that different one of the cam discs come into function. With this load diverter switch, asymmetric switchings can be realized, wherein the same sequence of svntching means to be moved or to be actuated is present independently ofthe direction of switching, PRICE: THIRTY RUPEES.

Full Text

The present invention relates to a load diverter switch for a tap-changer. Load diverter switches are described in, for example, German laid-open soecification 42 31 353. In that case, two vacuum switching tubes, termed 'VAC in the following, are orovided for each ohase. The control of these VAC's and mechanical switching contacts is effected by a switch shaft which is rotated rapidly after the release of a force storage device and can rotate in opposite directions. The VAC's are actuated by a cam disc, which is orovided at its end face with a control cam in which a roller is guided. The roller acts on an actuating lever of the associated VAC. Switching over of the mechanical contacts is effected by a switching segment which is similarly rotated by the drive shaft and changes over between fixed contacts arranged at the circumference of the load diverter switch. In this load diverter switch, the cam discs for actuation of the two VAC'S and the switching segment for actuation of the mechanical contacts are moved from one end setting to the other and back again independently of the direction of movement of the tap selector. This means that the contacts which closed last during the forward movement, i.e. rotation of the switch shaft in the one direction, open first during the return movement, i.e. the rotation of the switch shaft in the other direction, and conversely. Such a known load diverter switch is accordingly not suitable for asymmetric switching, in which always the same contact is switched electrically or moved mechanically independently of the direction of switching. Such an asymmetric switching is described in, for examole, German laid-open specification H 07 945 (not prior published) and, in modified form with double-poled switching-over, in German laid-open specification 44 41 082 (also not prior published). A special spring step drive, which independently of direction of drive always releases in one direction, i.e. has only one drive output direction, and which is especially intended for thyristor switches, is described in the specification of International application WO 89/08924. This represents a possibility of providing a switching which is asymmetric in principle. However, the described spring force storage device is of complicated construction, requires a great deal of space due to the multiplicity of necessary detent and coupling elements, and is not suitable for combined actuation of VAC's as electrical switching elements on the one hand and mechanical contacts on the other hand in a predetermined actuating sequence. It is therefore the object of the invention to provide a load diverter switch which in simple manner may, with a switch shaft drivable in opposite directions of rotation, permit asymmetric switching so that the same actuating sequence of components of switching means, such as VAC'S and mechanical switching elements, may be able to be achieved independently of the direction of rotation. Accordingly, the present invention provides a load diverter switch comprising a force storage device, which comprises a tensioning carriage continuously movable by a drive shaft rotatable in opposite directions and a drive output member which is releasable to rapidly follow the carriage movement, a switch shaft rotatable by the drive output member when released, switching means for each of a plurality of phases, and a cam assembly for actuating the switching means by way of actuating elements, the cam assembly comprising a carrier mounted on the switch shaft to be rotatable therewith but movable axially thereof between an upper setting and a lower setting in direction in dependence on the direction of rotation of the drive shaft and a plurality of cam discs carried by the carrier and each having an upper cam track and a lower cam track with respectively different profiles, the cam discs and the actuating elements being positioned so that the elements are co-operable with the lower cam tracks in the upper setting of the carrier and with the upper cam tracks in the lower setting of the carrier. Preferably, the carrier is mechanically positively coupled by means of a coupling member with cam means at the carriage so that on movement of the carriage the carrier is axially displaceable upwardly or downwardly directionally dependent on this movement and movable into its upper or lower setting. The switching means preferably comprises at least two vacuum switching tubes and at least two mechanical contact members for each phase. Each actuating element for the actuation of the vacuum switching tubes preferably comprises a roller, which is guided by an associated one of the cam tracks, and an angle lever connected therewith. Each actuating element for actuation of the mechanical contact members preferably comprises a first and a second roller, which each co-operate with an associated one of the cam tracks, and over-centre means in the form of spring-loaded toggle levers, wherein each contact member is switchable back and forth between two stationary positions according to whether drive is applied to the respective first roller or the respective second roller. For preference, all first rollers on the one hand and all second rollers on the other hand co-operate with a respective common cam track. Expediently, the mechanical contact members are constructed as double-pole switch contacts. Additional continuous main contacts can also be provided, such contacts being actuable directly by the switch shaft and in the stationary state taking over continuous current conduction. In one embodiment, the cam tracks for actuation of the mechanical contact members can be combined into a single cam disc which is divided into an upper and a lower part with different track profiles. A load diverter switch embodying the invention may have the advantage that it is possible to use a force storage device which has a tensioning carriage and a drive output member of the kind described in, for example, German Patent Specification 28 06 282. In that case, the movement, which is directed perpendicularly to the direction of tensioning and in particular in axial direction of the switch shaft, of a coupling member for axially displacing the carrier is produced by the tensioning carriage itself during the continuous tensioning operation. Respective cam tracks, which have profiles differing from each other, for the switching components to be actuated, such as VAC's and also mechanical contact members, for each direction of movement of the drive shaft are provided on cam discs carried by the carrier, which is axially displaceable on the switch shaft. The cam discs associated with the respective directions of movement of the drive shaft are also displaced axially by the axial movement of the coupling member and can thereby be brought into and out of co-operation with the corresponding actuating elements for the actuation of the VAC's and the mechanical contact members in dependence on direction of rotation. An embodiment of the present invention will now be more particularly described by way of example with reference to the accompanying drawings, in which: Fig. 1 is a schematic sectional elevation of part of a load diverter switch embodying the invention; Fig. 2 is a cross-section of the load diverter along the line A-A of Fig. 1; Fig. 3 is a perspective view of a force storage device, a coupling element and a switch insert of the load diverter switch; Fig. 4 is a circuit diagram illustrating asymmetric switching realisable by the load diverter switch; Fig. 5 is a circuit diagram illustrating construction of the load diverter switch with switching contact members mounted, as in Fig. 1, to be pivotable about pivot points and to function as change-over switches; Fig. 6 is a diagram showing the switching sequence achievable with the Fig. 5 construction; and Fig. 7 is a diagram showing the switching sequence of switching means of the load diverter switch. Referring now to the drawings there is shown a load diverter switch comprising a housing, in this case an insulating material cylinder 1, in which a central switch shaft 4 is arranged. The switch shaft 4 is actuated, in known manner, by a force storage device 2. The force storage device 2 comprises a tensioning carriage 2.2, which is continuously tensioned by a rotating drive dog 2.1 of a drive shaft (not illustrated) and which, on reaching its end setting, rapidly follows a drive output member 2.3. This in turn drives the switch shaft 4 in a known manner. Additionally, two cam slots 2.4, in which respective rollers 3.3 of a coupling member 3 engage, are provided one on each side of the carriage 2.2. The coupling member 3 also comprises two levers 3.1, which are mounted at about the height of the force storage device 2 and laterally thereof, and two coupling rods 3.2, which are pivotably connected therewith and extend perpendicularly downwards in the housing 1 parallelly to the switch shaft 4 and which are connected at their lower ends with a carrier or switch insert 5, which is axially displaceable on the switch shaft 4. It is, of course, possible to provide a cam slot 2.4 at only one side of the carriage 2.2 and correspondingly to provide only one lever 3.1 and coupling rod 3.2. The described pairwise arrangement, however, offers advantages of stability. The cam slot 2.4 is structured so that the switch insert 5 is axially moved upwardly or downwardly by a certain amount on the switch shaft 4, according to the direction of movement of the carriage 2.2 of the force storage device 2, by means of the coupling member 3 during tensioning of the force storage device 2, i.e. before the actual load-diverting switching. The switch insert 5, which is axially displaceable on the switch shaft 4, is rotatable together with this by the released force storage device 2. This is achieved, for example, by a splined or repeated tooth formation on the switch shaft 4, which permits rotational entrainment of the switch insert 5 without impairing its axial displaceability. To make certain of this effect, a bearing (not illustrated), for example a ball bearing, is provided for example between the lower part of the coupling member 3 and the switch insert 5. Two cam discs 6 and 7 with switching cams at their periphery are arranged one above the other on the insert 5 and serve for actuation of two VAC'S 11 and 12. Each cam consists of an upper part 6.1 or 7.1 and a lower part 6.2 or 7.2, the two parts being disposed one directly above the other. In addition, two further cam discs 8 and 9 for the actuation of two movable mechanical contact members 13 and 14 are arranged on the insert 5. Respective actuating rollers 11.1 and 12.1 are arranged laterally beside the cam discs 5 and 7 in such a manner that the two upper parts 6.1 and 7.1 or the two lower parts 6.2 and 7.2 correspond with the actuating rollers 11.1 and 12,1, respectively, according to the setting of the switch insert 5. The rollers 11.1 and 12.1 act by way of angle levers 11.2 and 12.2 on the VAC's 11 and 12, respectively, to actuate these. In the stationary state of the load diverter switch, there is a gap between the rollers 11.1 and 12.1 and the cam disc parts 6.1 and 7.1 or 6.2 and 7.2 associated therewith since the VAC's 11 and 12 in the stationary state are closed without external force. The VAC's are mechanically positively actuated by the cam disc parts by way of the rollers and the actuating levers and opened for a short time only during the load-diverting switching. The mentioned gap in the stationary state makes it possible to displace the switch insert 5 and thereby the cam discs 5 and 7 without collision between these and the rollers 11.1 and 12.1. In similar manner, the two further cam discs 8 and 9 on the insert 5 serve for actuation of two pivotally movable mechanical contact members 13 and 14. Each cam disc 8 or 9 is similarly divided into cam disc parts 8,1 and 8.2 or 9.1 and 9.2 arranged one above the other. In dependence on the direction of rotation of the switch shaft, either the two upper parts 8.1 and 9.1 or the two lower parts 8.2 and 9.2 correspond with laterally arranged first rollers 13.1 and 14.1 or second rollers 13.2 and 14.2. In Fig. 1 the engagement of the lower parts 8.2 and 9.2 is illustrated. The rollers 13.1 and 14.1 or 13.2 and 14.2 are respectively connected with spring-loaded toggle levers 13.3 and 14.3, which act on the pivotable contact members 13 and 14 in such a manner that these can be brought over a dead centre into either one of two stable switch settings. The first contact member 13 acts as a switching contact SKM and, according to the setting it assumes, connects either the two fixed contacts SKM„ or the two fixed contacts SKMj, with one another. The second contact member 14 acts as a mechanical auxiliary contact HKM and, according to the position it assumes, connects either the two fixed auxiliary contact HKM, or the two fixed auxiliary contacats HKMp with one another. The contact members 13 and 14 are arranged in the same horizontal plane. The actuation of the rollers 13.1 and 14.1 or 13.2 and 14.2 and thereby of the toggle levers 13.3 and 14.3 by the corresponding cam disc parts 8.1 and 9.2 or 8.2 and 9.2 again is effected in mechanically positive manner, i.e. the cam discs 8 and 9 and the rollers 13.1 and 14.1 or 13.2 and 14.2 are not in engagement in the stationary state so that, as was described above in connection with the actuation of the VAC's, an axial displacement of the switch insert 5 is readily possible before the beginning of the load-diverting switching, in particular without collision with the actuating elements (rollers). However, an essential difference exists between the actuation of the VAC'S 11 and 12 and of the mechanical contact members 13 and 14. The VAC'S 11 and 12 are, due to their mode of construction, always closed in the stationary state, thus automatically set into a stable state without additional force influence, due to the vacuum in the interior and an additional spring. It follows from this that a single cam disc is sufficient for actuation, i.e. for the temporary switching over into the other switching state. As soon as the effect of this cam disc disappears, the VAC automatically returns into the stable closed switching state. This is different for the described mechanical contact members 13 and 14. Each member 13 and 14, which is pivotable about a pivot point, can due to the respective spring-loaded toggle lever be moved over a dead centre and assume either one of two stable states. Each member is accordingly associated with a respective upper first roller 13.1 or 14.1 and a lower second roller 13.2 or 14.2, which rollers permit alternate switching over between the two stable states. In order to simplify the construction of the load diverter switch, it is possible to combine the cam discs 8 and 9, which are separate in the illustrated embodiment, into a single cam disc with only one upper part and one lower part, so that the actuation of SKM and of HKM takes place by only a single cam disc part in each switching direction. The previous explanations relate to only one phase of a load diverter switch according to the invention. In the case of a three-phase load diverter switch, the meachnical and electrical actuating elements and the switching elements of all three phases are, to particular advantage, arranged in a single horizontal plane. The Fig. 2 shows such an arrangement schematically from above. It can be seen that the switch shaft 4 with the axially displaceable switch insert 5, which is disposed thereon and rotatable together therewith and which carries the cam discs 6, 7, 8 and 9 one above the other, is arranged within the cylinder 1. Also recognisable are the two VAC'S, of which one acts as an electrical switch contact SKV and the other as an electrical auxiliary contact HKV according to the circuit illustrated in Fig. 4, and the mechanical contact members for the double-pole interruption, of which one acts as a mechanical switching contact SKM and the other as a mechanical auxiliary contact HKM. The VAC's SKV and HKV and contacts SKM and KHM for each phase are arranged centrally around the cam discs. The regions, in which the switching and actuating means of one phase are situated, are identified by arcuate arrows in Fig. 2. An additional arrangement of permanent main contacts for permanent current conduction, i.e. for relief of the switching contacts in stationary operation, is also possible. Such circuits, enlarged by permanent main contacts, are known. Since the permanent main contacts are opened first and closed last independently of the switching direction during the load-diverting switching, their actuation can take place in known manner by a cam slot or cam disc fixedly connected with the switch shaft 4. An axial displacement dependent on switching direction is not required. In the above-described embodiment, such permanent main contacts have, however, been intentionally omitted. The load diverter switch permits a simple realisation of asymmetric switching, i.e. a simple translation of like actuating sequences of electrical and mechanical switching elements which is independent of switching direction and which alternates due to the force storage device being tensionable and releasable in two directions. The required movement for the displacement in dependence on switching direction is produced in simple manner during the continuous movement of the tensioning carriage of the force storage device, thus before the beinning of the actual switching-over operation. Only the described cam slot is required at the carriage; except for this, a known force storage device can be used in unchanged form, which offers further advantages. It is self-evident that the number and form of the cam discs and of the actuating and switching elements, thus the electrical and the mechanical switching elements, can be adapted to switching requirements, and there is no restriction to the illustrated embodiment with two VAC's per phase and two double-poled mechanical switch contact members per phase. Fig. 4 shows asymmetric switching with double-poled switching over, in which the same actuating sequence, i.e. sequence of switching means to be moved or actuated, is present independently of the direction of switching. Fig, 5 shows the sequential changes in the contact members and the VAC's in consecutive switching states and Fig. 6 graphically represents the switching states of the VAC's and the contacts controlled by the contact members. WE CLAIM: 1. A load diverter switch comprising a force storage device (2), which comprises a tensioning carriage (2.2) continuously movable by a drive shaft rotatable in opposite directions and a drive output member (2.3) which is releasable to rapidly follow the carriage movement, a switch shaft (4) rotatable by the drive output member (2.3) when released, switching means (11, 12, 13, 14) for each of a plurality of phases, and a cam assembly (5, 6, 7, 8, 9) for actuating the switching means by way of actuating elements (11.1, 11.2; 12.1, 12.2; 13.1, 13.2; 14.1, 14.2, 14.3), the cam assembly comprising a carrier (5) mounted on the switch shaft to be rotatable therewith but movable axially thereof between an upper setting and a lower setting in direction in dependence on the direction of rotation of the drive shaft and a plurality of cam discs (6, 7, 8, 9) carried by the carrier and each having an upper cam track (6.1, 7.1, 8.1, 9.1) and a lower cam track (6.2, 7.2, 8.2, 9.2) with respectively different profiles, the cam discs and the actuating elements being positioned so that the elements are co-operable with the lower cam tracks in the upper setting of the carrier and with the upper cam tracks in the lower setting of the carrier. 2. The load diverter switch as claimed in claim 1, wherein the carrier (5) is coupled to the carriage (2.2) by way of a coupling member (3) and cam means (2.4, 3.3), the coupling member and cam means being co-operable to translate movement of the carriage into said axial movement of the carrier. 3. The load diverter switch as claimed in claim 1 or 2, wherein the switching means comprises at least two vacuum switching tubes (11, 12) and at least two mechanical contact members (13, 14) for each phase. 4. The load diverter switch as claimed in claim 3, wherein each of the actuating elements for actuating a respective one of the vacuum switching tubes (11, 12) comprise a roller (11.1, 12.1) guided by an associated one of the cam tracks (6.1, 6.2; 7.1,7.2) and an angle lever (11.2, 11.3) connected with the roller. 5. The load diverter switch as claimed in claim 3 or 4, wherein each of the actuating elements for actuating a respective one of the contact members (13, 14) comprises a first roller (13.1, 14.1) and a second roller (13.2, 14.2) each guided by a respectively associated one of the cam tracks (8.1, 8.2; 9.1, 9.2) and over-centre means (13.3, 14.3) acting on the member to urge it into either one of two stationary positions, the contact member being movable in direction towards one of the positions by the first roller and in direction towards the other one of the positions by the second roller. 6. The load diverter switch as claimed in claim 5, wherein the first rollers (13.1, 14.1) of all the actuating elements are associated with a common first cam track and the second rollers (13.2, 14.2) of all the actuating elements are associated with a common second cam track. 7. The load diverter switch as claimed in any one of claims 3 to 6, wherein each of the contact members (13, 14) is a double-pole switch contact member. 8. The load diverter switch as claimed in any one of the preceding claims, wherein main contacts which are actuable by the switch shaft and which in a stationary state provide continuous current conduction are provided. 9. The load diverier switch as claimed in any one of claims 3 to 7, wherein the cam tracks co-operable with the actuating elements (13.1, 13.2; 14.1, 14.2) for actuating said at least two contact members (13, 14) are provided on a single cam disc comprising an upper part with the tracks for the elements actuating one member and a lower part with the tracks for the elements actuating the other member. 10. A load diverter switch substantially as herein described with reference to the accompanying drawings.

Documents:

0464-mas-1996 abstract.jpg

0464-mas-1996 abstract.pdf

0464-mas-1996 claims.pdf

0464-mas-1996 correspondence -others.pdf

0464-mas-1996 correspondence -po.pdf

0464-mas-1996 description (complete).pdf

0464-mas-1996 drawings.pdf

0464-mas-1996 form-2.pdf

0464-mas-1996 form-26.pdf

0464-mas-1996 form-4.pdf

0464-mas-1996 form-8.pdf

0464-mas-1996 form-9.pdf

0464-mas-1996 others.pdf

0464-mas-1996 petition.pdf