EP1105896B1 - Step switch with selector - Google Patents

Abstract

The invention relates to a tap selector switch with a preselector for uninterrupted switching-over between different winding taps of a tapped transformer. The entire selector is in that case accommodated as a separate assembly in an own insulating material housing, and the fixed preselector contacts are constructed in circular form and arranged around a switch rod in different planes in the interior of this insulating material cylinder. Connection to them is made by preselector contact bridges, which are fastened to the switch rod, with radially resilient contact members.

Description

The invention relates to a tap changer with a selection for uninterrupted switching between different winding taps of a step transformer.

Tap changers have been installed in transformers for many years in order to be able to adjust the voltage, active and reactive power of electrical networks by changing the gear ratio under load.
Known tap changers are known in two basic designs: in one design they consist of the separate modules tap changer and diverter switch, in the second design these two modules are combined to form a load selector that performs both functions. The term "tap changer" used in the following is intended to encompass both of the aforementioned designs.

The gear ratio is set in stages; the transformer with a Step winding equipped, the taps can be switched by the step switch.

To enlarge the possible setting range, it has long been common to equip the tap changer with a preselector. In principle, this known selection can implement the two known functions shown schematically in FIG.
As shown in FIG. 1a, it can serve as a turner for switching the step winding on and off or, as shown in FIG. 1b, for deflecting the step winding to the beginning or to the end of the coarse step. In any case, the preselection doubles the setting range with the same length of the step winding.
The preselector consists of a total of three fixed preselector contacts, whereby one of the two fixed contacts "+" or "-" is connected to the third fixed contact "0", depending on the switch position.
These known selections are known in numerous designs and with a wide variety of contact types and actuation mechanisms.

A step switch is known from the Bulgarian company publications "On-Load Tap Changer Type RS12'1 and" On-Load Tap Changer Type 16 ", which is located inside an insulating material cylinder and whose selection extends outside this insulating material cylinder in its longitudinal direction.
The fixed selector contacts are arranged in a line with the contact sequence "+" - "0" - "-" or "-" - "0" - "+" and are actuated linearly by a shift rod that can be moved in the longitudinal direction.
This shifting rod, which can be moved in the longitudinal direction, has a preselector contact bridge for each phase, through which either one of the two fixed preselector contacts "+" or "-" with the other fixed preselector contact "0", which is arranged between them and forms the root connection of the preselector, is connectable.

The longitudinal movement of the shift rod is described by a Maltese transmission, which is located on the The top of the tap changer is located and the rotary movement of the selector shaft inside the Insulated cylinder of the tap changer for actuating the selector contacts generated by a tapped special gear train.

However, this known tap changer with an external, linearly operable selection has several disadvantages.
On the one hand, due to the large longitudinal extent of the entire selection arrangement, considerable accuracy requirements must be met. Even the slightest tolerances between the fixed selector contacts on the one hand and between them and the movable preselector contact bridge on the other hand mean that the contact bridge cannot run properly onto the fixed contacts to be electrically connected to one another. This problem is exacerbated in the course of the operating time by contact erosion and mechanical wear of the contacts.
In order to reduce inaccuracies, a special guide for the shift rod is required.
Furthermore, in the known tap changer the capacitive switching capacity of the preselector is limited by the selected contact arrangement.

The object of the invention is to provide a generic tap changer with an external, linearly operated preselector, in which no complex guidance of the selector rod carrying the preselector contact bridge is required and nevertheless, even with tolerances that occur, safe switching with essentially constant contact forces is possible.
In addition, the tap changer according to the invention with preselection should also be suitable for high voltage stresses on the preselection.

This object is achieved by a tap changer with a selection having the features of the first claim.
The subclaims relate to particularly advantageous developments of the invention.

A particular advantage of the invention is that the longitudinally displaceable shift rod of the preselector does not require any special guidance and the drive system as a whole does not have to meet any special accuracy requirements. Rather, the design of the self-centering preselector contact bridge creates a practically self-adjusting contact system with constant contact forces.
The ring-shaped design of the fixed selector contacts according to the invention also allows high stresses; The selection according to the invention enables high capacitive switching capacities to be managed, so that it will only be necessary in a few special cases to provide additional polarization resistances.
All in all, the chosen structure of the preselector on a separate insulating tube gives a compact, stable and simple structure; the complete selection can be easily prefabricated as a complete assembly and attached just as easily to the side of the isolating cylinder of the tap changer.

Fig. 1

die bereits erläuterten Vorwähler-Grundschaltungen nach dem Stand der Technik

Fig. 2

eine erste Ausführungsform eines erfindungsgemäßen Vorwählers in schematischer seitlicher Schnittdarstellung

Fig. 3

diese Ausführungsform in Schnittdarstellung von oben

Fig. 4

eine alternative Bauform einer Vorwählerkontaktbrücke

Fig.5

eine zweite Ausführungsform eines erfindungsgemäßen Vorwählers wiederum in schematischer seitlicher Schnittdarstellung

Fig.6

die - per se bekannte - Schaltung der in Fig. 5 dargestellten zweiten Ausführungsform

Fig.7

einen kompletten erfindungsgemäßen Stufenschalter, hier bestehend aus einem Lastwähler, der die Funktionen des Stufenwählers als auch des Lastumschalters vereint, und dem seitlich angeordneten Vorwähler, dargestellt in schematischer seitlicher Schnittdarstellung

Fig. 8

den in Figur 7 dargestellten Stufenschalter mit Vorwähler schematisch von oben.

The invention will be explained in more detail below by way of example using drawings.
The figures show:

Fig. 1

the previously described basic selection circuits according to the prior art

Fig. 2

a first embodiment of a preselector according to the invention in a schematic sectional side view

Fig. 3

this embodiment in a sectional view from above

Fig. 4

an alternative design of a preselector contact bridge

Figure 5

a second embodiment of a preselector according to the invention again in a schematic side sectional view

Figure 6

the - known per se - circuit of the second embodiment shown in FIG. 5

Figure 7

a complete tap changer according to the invention, here consisting of a load selector, which combines the functions of the tap selector and the load switch, and the selector arranged on the side, shown in a schematic side sectional view

Fig. 8

the tap changer shown in Figure 7 with preselection schematically from above.

The first embodiment shown in FIGS. 2 and 3 shows a selection which has a tubular insulating material housing 1 as the supporting component. On the inside of the wall of this insulating material housing 1, with its contact leads penetrating it, the fixed preselector contacts 2, 3, 4 - shown here for only one phase - are arranged. Each of the fixed selector contacts is circular, concentric with the insulating housing 1.
Contact 2 has the function of contact "+" from FIG. 1, accordingly contact 3 takes over the function of contact "0" and contact 4 takes over the function of contact "-" from FIG. 1.
In the interior of the insulating housing 1, a longitudinally displaceable switching rod 5 is arranged, which carries the preselector contact bridge 6.
The preselector contact bridge 6 consists in detail of an annular contact carrier 7 enclosing the switching rod 5 and fastened thereon, on which radially movable, spring-mounted contact pieces 8, 9, 10, 11 are arranged. These contact pieces 8, 9, 10, 11 are pressed radially outwards by pairs of springs 12, 13, 14, 15 in such a way that a defined contact pressure is generated when they run onto the respective fixed contacts 2, 3, 4.
The radial path of the contact pieces 8, 9, 10, 11 is limited by respective stops 16 at the top and bottom of the contact carrier 7.
Figure 2 shows the selection according to the invention in the same switching position as in Figure 1, in which the contacts "+" and "0" are connected.
If the preselector is actuated, the selector rod 5 is moved downwards, this is indicated by an arrow in FIG. 2, the contact carrier 7 leaves the preselector contact 2 and runs down through the preselector contact 3 and remains in contact with it. It finally runs onto the preselector contact 4 and thus establishes the new connection of this preselector contact 4 with the function "-" with the preselector contact 3; the switchover is complete.

Figure 4 shows another embodiment of a preselector contact bridge. In this case, there are pairs of opposing contact pieces directly on the switching rod 5; Of these four contact pieces, the two contact pieces 17, 18 are shown in the sectional view.
The contact pieces 17, 18 are in turn pressed outwards by spring pairs 19 and 20; the path is limited by cross bolts 21 with an outer stop, which are guided in bores of the respective contact pieces 17, 18. Similarly, the two further contact pieces, not shown in the sectional view, are delimited by further transverse bolts 22 in a plane offset by 90 degrees.

Figure 5 shows a second embodiment of a preselector according to the invention in a side sectional view. Here again, a tubular insulating material housing 23 is provided as the supporting component. The fixed preselector contacts 24, 25, 26 are in turn arranged on the inside of the wall of this insulating material housing 23, which in turn are circular and concentric with the insulating material housing 23. In this embodiment too, a longitudinally displaceable switching rod 27 is arranged inside the insulating material housing 23, which in turn carries a preselector contact bridge 28.
As already explained in the first exemplary embodiment, this preselector contact bridge 28 consists of an annular contact carrier 29 on which radially movable, spring-mounted contact pieces are arranged, of which only two contact pieces 30, 31 lying opposite one another are shown in the sectional view. Each of these contact pieces is pressed radially outwards by spring pairs, here the spring pairs 32, 33 are shown. The radial path of the individual contact pieces is in turn limited by upper and lower stops 34. In contrast to the first exemplary embodiment shown in FIGS. 2 and 3, the individual contact pieces, here the contact pieces 30, 31, are tapered in their central region 35, 36. ie drawn in.

Instead of the preselector contact bridge shown in FIG. 5, an embodiment as in FIG. 4 with travel limitation by means of cross bolts provided with a stop is also possible.
The taper described in the respective central area is particularly important for the function of the second embodiment shown in FIG.
This tapering results in a double-pole interruption and changeover function of the preselector. If the preselector is actuated, ie the switching rod 27 is moved downwards, the contact pieces 30, 31 leave both the contact 24 and the contact 25, and with further movement they run simultaneously onto both the contact 26 and the contact 25. Figure 6 shows the basic circuit of such a double-pole switching preselector, acting here as a turner.

In both embodiments of the selection, the concentric design of the fixed Selector contacts on the one hand and the resilient arrangement of the contact pieces on the switching rod on the other hand, automatic centering is guaranteed when these contact pieces emerge. Also at inevitable tolerances of the selector rod, the fixed selector contacts or the Contact pieces is therefore always a uniform and on all involved individual contact pieces split contact ensured.

FIGS. 7 and 8 show a complete tap changer with a selection according to the invention, arranged on the side, here with the first embodiment shown in FIGS. 2 and 3 with a single break.
The actual tap changer is designed here as a load selector and is located in an insulating cylinder 37. Inside, a rotating isolating rod 38 runs longitudinally through the tap changer, which has a switching element 39.1, 39.2, 39.3 for each of the three phases with the movable contacts and others Switching means carries. Corresponding to the movable contacts, the fixed tap changer contacts, which can be connected, are arranged in the wall of the insulating material cylinder 37. Since the function of such a load selector is well known, the remaining components are not discussed in detail. The selector according to the invention is located in an insulating cylinder 1 on the side of the tap changer, fastened to it by a traverse 45. Inside this insulating cylinder 1 there is the switching rod 5, and for each of the three phases the three fixed selection contacts already described are arranged, ie the Contacts 2.1, 3.1, 4.1 in a horizontal plane for one phase, contacts 2.2., 3.2., 4.2 in a further horizontal plane for the second phase and contacts 2.3, 3.3, 4.3 finally for the third phase in a third horizontal plane , Corresponding to the respective contacts, a preselector contact bridge 6.1, 6.2, 6.3 is arranged for each phase. When the preselector is actuated by moving the selector rod downwards, the contact pieces of the preselector contact bridges 6.1, 6.2, 6.3 leave the corresponding contacts 2.1, 2.2, 2.3, the "+" contacts, run to the respective "0" in all three phases. -Contacts 3.1, 3.2, 3.3 down and finally contact the respective "-" contacts 4.1, 4.2, 4.3. In each horizontal plane assigned to a specific phase, the areas of the fixed preselector contacts are shielded by upper shields 40.1a, 40.2a, 40.3a and lower shields 40.1b, 40.2b.
At its upper end, the switching rod 5 is provided with a lever 41 which is mounted in a bearing 43 in the region of the tap changer head by means of a cross bolt 42. This cross pin 42 is in turn connected to a crank 44 which pivots at its free end a pivoting movement of the Maltese drive of the tap changer. The pivoting movement of the crank 44, which also marks the bearing point, is transferred to a pivoting movement of the lever 41 in the vertical direction, which is transmitted to the shift rod 5. The actuating mechanism described is articulated on an upper crossmember 46, which at the same time realizes the upper fastening of the preselector on the tap changer.

Claims (6)

1. Tap selector switch with a preselector for uninterrupted switching-over between different winding taps of a tapped transformer,
   wherein fixed preselector contacts (2, 3, 4) are arranged in a line, separated according to phases to be switched and externally of the tap selector switch in the longitudinal direction thereof, and are actuable by a switch rod (5) displaceable in this longitudinal direction
   and wherein the switch rod (5) comprises, for each phase to be switched, an electrically conductive preselector contact bridge (6), which is dimensioned in such a manner that two adjacent fixed preselector contacts (2, 3, 4) can be bridged over at a time,
   characterised in that
   the entire preselector is accommodated as an assembly separate from the tap selector switch and in a separate insulating material housing (1; 23), in the interior of which the switch rod (5; 27) extends,
   that the fixed preselector contacts (2, 3, 4; 24, 25, 26) are constructed in the form of a circle and arranged concentrically around the switch rod (5; 27) in different planes in the interior of the insulating material housing (1; 23)
   and that radially resilient contact members (8, 9, 10, 11; 17, 18; 30, 31) are arranged at each of the preselector contact bridges (6; 28) in such a manner that these can each be urged inwardly against a spring force on running-up onto one of the fixed preselector contacts (2, 3, 4; 24, 25, 26).
2. Tap selector switch according to claim 1,
   characterised in that
   each of the preselector contact bridges (6; 28) comprises a contact carrier (7; 29), which at least partially surrounds the switch rod (5; 27) and at which the contact members (8, 9, 10, 11; 17, 18; 30, 31) are arranged.
3. Tap selector switch according to claim 1 or 2,
   characterised in that
   the spring effect of the contact members (8, 9, 10, 11; 17, 18; 30, 31) is achieved by respective spring pairs (12, 13, 14, 15; 19, 20; 32, 33) which bear against the switch rod (5; 27) or the contact carrier (7; 29).
4. Tap selector switch according to claim 1, 2 or 3,
   characterised in that
   the spring travel of the contact members (8, 9, 10, 11; 17, 18; 30, 31) can be limited by upper and lower abutments (13; 34).
5. Tap selector switch according to claim 1, 2 or 3,
   characterised in that
   the spring travel of the contact members (8, 9, 10, 11; 17, 18; 30, 31) can be limited by transverse pins (21), which are guided in respective bores, with an outer abutment.
6. Tap selector switch according to one of the preceding claims,
   characterised in that
   the individual contact members (30, 31) are narrowed in their middle region (35, 36), i.e. drawn in inwardly, in such a manner that a double interruption, i.e. a simultaneous departure from each of the two adjacent fixed selector contacts with which contact was made previously, takes place on actuation.

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