EP0907192A2 - Tap changer - Google Patents

Abstract

The invention relates to a tap changer based on the reactor switching principle for uninterrupted load switching by means of vacuum switching cells. According to the invention, this tap changer has three separate insulating shafts; the first of these isolating shafts is used to actuate the movable selector contacts of all phases, the second of these isolating shafts is used to actuate the movable selector contacts, and the third of these isolating shafts is used to actuate the movable by-pass contacts on the one hand and the vacuum switching cell assigned to the respective phase on the other. A single, laterally arranged gear is used to actuate the insulating shafts, through which the corresponding rotary movements of the individual insulating shafts are generated in accordance with the switching sequence to be implemented.

Description

The invention relates to a tap changer based on the reactor switching principle uninterrupted load switching using vacuum switch cells

A tap changer is used in conjunction with a power transformer uninterrupted switching between different winding taps uses this transformer and thus serves for uninterrupted Voltage regulation.

1. Der langsam umschaltende Reaktorschalter, der bis heute in den USA und in Teilen der früheren Sowjetunion dominierend ist. Dabei sind Umschaltimpedanzen vorgesehen, die während der langsamen Umschaltung von einer Wicklungsanzapfung zur nächsten einen Stufenkurzschluß vermeiden und für die Dauerbelastung bemessen sind.

2. Der schnell umschaltende Widerstandsschalter, nach seinem Erfinder auch oft als "Jansen-Schalter" bezeichnet, der sich im Rest der Welt durchgesetzt hat. Hierbei erfolgt die Umschaltung von einer Wicklungsanzapfung auf die nächste schnell, d.h. sprungartig, und es sind Überschaltwiderstände vorgesehen, die einen Stufenkurzschluß, der bei diesem Prinzip der Umschaltung nur für eine sehr kurze Zeitspanne auftreten kann, verhindern.

There are two different basic switching principles for tap changers worldwide:

1. The slowly switching reactor switch, which is still dominant in the United States and parts of the former Soviet Union. Switching impedances are provided which avoid a step short circuit during the slow switchover from one winding tap to the next and are dimensioned for the continuous load.

2. The fast-switching resistance switch, often referred to as the "Jansen switch" by its inventor, which has established itself in the rest of the world. The switchover from one winding tapping to the next takes place quickly, ie suddenly, and there are switching resistors which prevent a step short circuit which, with this switching principle, can only occur for a very short period of time.

The invention relates to tap changers according to the first-mentioned reactor switching principle.

Such a tap changer is already known from the company publication "Load Tap Changer Type RMV II" from Reinhausen Manufacturing, Humboldt, Tenessee, USA, imprint RM 05/91 - 1094/5000.
In this known tap changer, vacuum switching cells are used for the actual load switching, which have numerous advantages over mechanical load switching contacts, in particular also a long service life. When using such vacuum switching cells, there is no contamination of the surrounding oil, which would occur in mechanical load changeover contacts due to arcing and contact erosion.

7 shows the typical sequence of such a known type of step switch when switching from one step A to an adjacent step B for one phase.
N and n + 1 are adjacent taps of the step winding of the transformer. P1 and P2 are the movable selector contacts to be actuated during the switchover, R1 and R2 are the switchover impedances already explained. A vacuum switching cell V is connected between the two branches, and the corresponding connection to the load conductor L is established by a by-pass contact B.
In the case of a stationary switching position, the two movable selector contacts are both connected to the same tap, ie to the same fixed selector contact. At the next stationary switching position after the load has been switched over, one movable selector contact rests on a first fixed selector contact and the other movable selector contact on the adjacent further fixed selector contact. This sequence is repeated with every further load switch.

The known tap changer has a three-phase design and consists of an oil-filled housing that has selector contacts, preselector contacts, vacuum switch cells and by-pass contacts. The term “preselector contacts” is intended to mean both the contacts for a possible coarse selector and for a possible turner. These two circuit variants are well known from the prior art.
The drive mechanism for actuating the individual contacts and the vacuum switch cells is located in a housing part which is arranged separately to the side of it.
A terminal board is provided in the housing, on which the selector and reversing contacts are arranged, spatially separated for each of the three phases to be switched. The corresponding vacuum switch cell and the associated by-pass contacts are arranged in each case on further circuit boards for each phase:

On one side of the other board, which faces the terminal board, are the fixed and the movable by-pass contact, on the other side of the board is the vacuum switch cell, each with an energy accumulator for its actuation.

A corresponding energy store is known from DE 41 26 824.

All switching elements of all phases are actuated by a single insulating shaft, which from the drive mechanism located in the side housing part, the entire housing goes through. For this purpose, three Maltese drives are provided, one for each phase are also provided on the terminal board. These Maltese drives generate from the rotary movement of the drive shaft, both the movements for actuation the selector and reversing contacts as well as the movements for actuating the by-pass contacts and the tensioning of the energy accumulator for actuating the corresponding one Vacuum switch cells in the predetermined switching sequence, as shown in Fig. 1.

In summary, it follows that in the known tap changer described above, a single insulating shaft actuates three separate Maltese drives. Each Maltese drive in turn actuates the elements of the respective phase arranged on the terminal board, namely the selector contacts and, by means of a separate bolt on the Maltese, the reversing contacts.
Also separately for each phase, the elements of the respective phase, namely the by-pass contact and the energy accumulator of the corresponding vacuum switching cell, which are arranged on the associated further circuit board, are actuated by means of a double-sided groove in a rotatable disk.

Such a disk provided with a double-sided control contour is known from DE 40 11 019 known.

Such a structure is relatively complicated and mechanically demanding.
Maltese drives, in particular, are complicated structures that are subject to high accuracy requirements and are therefore complex to manufacture.

The same applies to the washer with a contour on both sides for simultaneous actuation of the by-pass contact as well as a vacuum switching cell. The two contours are not identical in their course and can also be produced only with great effort.
Finally, the known energy accumulator is complicated; what has been said also applies to him.

The object of the invention is to simplify the step switch of the generic type and to reduce the number of individual parts required, in particular also the number of necessary Maltese drives.
Furthermore, it is an object of the invention to simplify the actuation of the by-pass contacts on the one hand and the vacuum switching cells on the other hand, and, in connection with this, to provide a simple but nevertheless reliably functioning energy store.

These tasks are solved by a tap changer with the features of the first claim.
The subclaims relate to particularly advantageous developments of the invention.

It is particularly advantageous on the tap changer according to the invention that only a single gear, in particular also only a single Maltese drive, is required.
All the necessary movements for actuating the selector contacts, preselector contacts, by-pass contacts and the vacuum switch cells of all phases to be switched are generated in a single gear and transmitted to the corresponding elements via separate insulating shafts, so that mechanical means can largely be omitted there, which the whole structure simplified considerably.
Another advantage is that all switching elements of a phase are each only arranged on a single circuit board, namely the respective phase plate equipped on both sides, which further simplifies the structure. This is particularly true because all phase plates are constructed and equipped identically.
Another advantage is the particularly simple design of the energy store for actuating the respective vacuum switch cell, which nevertheless ideally fulfills the desired switching characteristics for such cells: The vacuum switch cell is opened quickly by means of the energy store and closed in a curve-controlled manner.
Finally, a further advantage lies in the simple mechanical end position limitation, which is provided only once in the single gearbox and which prevents the selector contacts from advancing beyond the permissible switching range. Corresponding necessary end position limits are no longer required on the respective phase plates.

The invention will now be described in more detail by way of example using drawings are explained.

Fig. 1 einen erfindungsgemäßen Stufenschalter in schematischer Darstellung von vorn

Fig. 2 die Getriebeplatte dieses Stufenschalters allein in seitlicher Darstellung

Fig. 3 eine Phasenplatte dieses Stufenschalters allein in seitlicher Darstellung von rechts betrachtet

Fig. 4 ebendiese Phasenplatte von links betrachtet

Fig. 5 ein Detail aus Fig. 4, nämlich die Vakuumschaltzelle mit der dazugehörigen Betätigungsvorrichtung allein

Fig. 6 ein Detail aus Fig. 2, nämlich die Endstellungsbegrenzung allein seitlich dargestellt

Fig. 7 die bereits erläuterte bekannte Schaltsequenz

Show it:

Fig. 1 shows a tap changer according to the invention in a schematic representation from the front

Fig. 2 shows the gear plate of this tap changer in a side view alone

Fig. 3 is a phase plate of this tap changer viewed only from the right side

4 shows this phase plate viewed from the left

Fig. 5 shows a detail from Fig. 4, namely the vacuum switch cell with the associated actuating device alone

Fig. 6 shows a detail from Fig. 2, namely the end position limit alone shown laterally

7 shows the known switching sequence already explained

The tap changer according to the invention is enclosed by an oil-tight housing 1, the front, removable front 4 of which is open here.
On the back of the housing 1 there are lead-through plates 3 for oil-tight routing of the connecting lines, not shown.
On the left wall there is a gear plate 2, which has the only Maltese drive, to be explained in more detail, for actuating the selector and preselector contacts, and a drive mechanism, which is also explained in more detail, for actuating the by-pass contacts and the vacuum switching cells.
In parallel to this gear plate 2, three phase plates 5 - one for each phase to be switched - are provided.
On the right side of each phase plate 5 are the circularly arranged fixed selector contacts 6, which can be connected by a rotatable, centrally arranged movable contact carrier 7 on which there are two movable selector contacts 7.1, 7.2.

Both movable selector contacts 7.1, 7.2 are arranged isolated from each other on the contact carrier 7 and are moved together by its rotation. Furthermore, on this side there are fixed preselector contacts 8, which can be connected by a movable contact carrier 9 on which there is a movable preselector contact 9.1. Furthermore, on this side there are the fixed by-pass contacts 10, which can be connected by a further contact carrier 11 on which there are two by-pass contacts 11.1, 11.2.
Both movable by-pass contacts 11.1, 11.2 are electrically connected to one another.

On the left side of the phase plate 5 is the vacuum switch cell 12 with the corresponding actuating mechanism, which will be discussed in more detail below becomes.

All three phase plates are constructed identically.

From the gear plate 2, three horizontal insulating shafts 13, 14, 15 lead through the entire housing 1. They penetrate all three phase plates 5, in which holes 16, 17, 18 are provided for this purpose. The first insulating shaft 13 is guided through the bore 16 of the phase plate 5 and is connected to the contact carrier 7 and thus the movable selector contacts 7.1, 7.2 of each phase.
The second insulating shaft 14, which is partially covered in FIG. 1, is guided through the bore 17 of the phase plate 5 and is connected to the contact carrier 9 and thus to the movable preselector contact 9.1 of each phase.
The third insulating shaft 15 is guided through the bore 18 of each phase plate 5 and is connected to the contact carrier 11 and thus to the movable by-pass contacts 11.1, 11.2 and the corresponding vacuum switching cell 12 of each phase. The first insulating shaft 13 thus actuates the movable selector contacts 7.1, 7.2 of each phase, which connect the associated fixed selector contacts 6.
The second insulating shaft 14 actuates the movable preselector contact 9.1 of each phase, which connects the associated fixed preselector contacts 8.
The third insulating shaft 15 finally actuates the movable by-pass contacts 11.1, 11.2 of each phase, which connect the fixed by-pass contacts 10, and the respective vacuum switching cell 12 of each phase.

The insulating shafts 13, 14, 15 in turn are made from the only one arranged on the left in FIG. 1 Maltese drive and the other components arranged on the transmission plate 2 are operated together.

This will be explained in more detail below.
In the gear plate, all three insulating shafts 13, 14, 15 are rotatably supported independently of one another and spatially separated.
A drive shaft 19 leads from a drive (not shown in more detail) into the housing 1 from below. At the free end of the drive shaft 19 there is a first gear wheel 20 which corresponds to a second gear wheel 21 which is perpendicular thereto. This second gear wheel 21 is mounted in a bearing 22 in the gear plate 2 and is firmly connected to a Maltese driver 23, which has a roller 24 at its end. At the same time, it corresponds to a third gear wheel 25, which in turn is also mounted in a further bearing 51 in the gear plate 2.
On this third gear wheel 25, a rocker arm 26 is attached, which leads to a rotatably articulated lever 27, the other free end of which is in turn rotatably articulated to a further rocker arm 28, which is attached to the insulating shaft 15. A thrust crank mechanism known per se is thus realized.
On the insulating shaft 13, a Geneva wheel 29 is fastened in such a way that the cutouts of the Geneva wheel 29 interact with the roller 24 of the Geneva driver 23.
On the Geneva wheel 29, a single actuating roller 30 is also provided, which engages in a certain position of the Geneva wheel 29 in a pivotable lever 31 which is connected to the insulating shaft 14.

This drive works as follows:
When the tap changer is actuated, the drive shaft 19 rotates, this rotation is transmitted to the second gear wheel 21 via the first gear wheel 20. As a result, the Maltese driver 23 rotates, its roller 24 engages in the Maltese wheel 29, rotates it by a certain angle, which depends on the dimensioning of this Maltese wheel 29 and the incisions located thereon, and thus also rotates the insulating shaft 13 connected thereto by one Switching step. The dimensioning mentioned is designed so that all the fixed selector contacts 6 are swept when the Geneva wheel 29 is rotated completely. With each switching, the movable selector contacts 7.1, 7.2 of each phase are switched from one fixed selector contact to the other, adjacent selector contact - depending on the direction of rotation.
At the same time, the rotary movement is transmitted to the third gear wheel 25 and thus to the rocker 26. The gear wheels are dimensioned such that the third gear wheel 25 rotates by 180 degrees with each changeover. The rocker arm 26 rotates, the further rocker arm 28 and thus the insulating shaft 15 are rotated through the lever 27 by a certain angle and then back again into the starting position. As a result, the movable by-pass contacts 11.1, 11.2 of each phase are briefly deflected from the end position and opened and then moved back into the end position.
While the isolating shaft 13 rotates through a certain angle in the same direction in each circuit and can therefore make complete rotations, the isolating shaft 15 always rotates alternately to the left or right by an angle and back again and transmits this movement to the oscillating movable by-pass contacts 11.1, 11.2 swiveling out of the middle position into an end position and back again.
Due to the roller 30 arranged on the Geneva wheel 29, which engages in a certain position in a cutout of the lever 31, this is then pivoted through a certain angle and with it the insulating shaft 14, which actuates the movable preselector contact 9.1 of each phase. The selection is only activated after a complete rotation of the Geneva wheel 29 and thus after all fixed selector contacts 6 have been run through. In other words, the Geneva wheel 29 can rotate completely once, running through all the fixed selector contacts 6 without the selection being activated, then this is actuated and all the fixed selector contacts 6 can be run through again in the same direction of rotation with the selection selected. Similarly, the selection is switched back after a complete rotation in another direction.

FIG. 3 shows once again the arrangement of the different fixed and movable contacts explained on the respective phase plate 5 and their actuation by the insulating shafts 13, 14, 15.
The movable selector contacts 7.1, 7.2, which are insulated from one another, are dimensioned such that they can both contact two adjacent fixed selector contacts 6, or can rest completely on only one such contact, as is necessary to implement the switchover sequence shown in FIG. 7.

The movable preselector contact 9.1 switches after one revolution of the Maltese wheels 29 from one position to the other and thus switches part of one Winding up or down or deflecting this depends on whether the selection is in the respective circuit of the step transformer as a known coarse selector or well-known turner works. Result for the tap changer according to the invention there are no differences in the construction.

The movable, electrically interconnected by-pass contacts 11.1, 11.2 bridge both fixed contacts 10 in the stationary state and, when switched, rest on only one of these fixed contacts 10.
The contact derivation from the movable, rotatable contacts 7.1, 7.2; 9.1; 11.1, 11.2 is carried out by concentric slip rings 32, 33, 34. Two slip rings 32, insulated from one another, are provided for the contact derivation of the two movable selector contacts 7.1, 7.2, which lie congruently one above the other in FIG. 3, so that only the upper one of them you can see.

FIG. 4 shows the elements arranged on the other side of the respective phase plate 5 without insulating shafts, and in FIG. 5 the elements for actuating the respective vacuum switching cell 12 are shown again, which will be explained in more detail below.
A console 35 is attached to each phase plate 5 and supports the vacuum switch cell 12. The actuating mechanism consists of a control disk 36 which is connected to the insulating shaft 15 and a two-armed lever 37 which is rotatably mounted on the bracket 35 and has a roller 38 at one free end and the other free end of the vacuum switchgear cell 12, more precisely its actuating plunger 45, works. The roller 38 corresponds to a control cam 39 on the control disk 36.
At the rear there is a release contour 40 which is dimensioned such that it deflects a pawl 41 in certain positions of the control disk 36. This triggering contour 40 can be realized in a particularly advantageous manner by means of two individual triggering cams. The lever 37 is then released by the deflected pawl 41, which is otherwise blocked by the non-deflected pawl 41.

In addition, a total of three springs are provided:
A spring 42 is supported on the bracket 35 and presses the roller 38 of the lever 37 against the cam 39.
Another spring 43 presses the pawl 41 against the lever 37 and blocks it in the normal state.
A third spring 44 on the actuating plunger 45 increases the contact pressure in the stationary state and is not in itself necessary for actuation.

This arrangement works as follows:
In the stationary state, the vacuum switching cell 12 is closed.
It has already been explained that the insulating shaft 15 performs an oscillating movement from the central position by a certain angle of rotation to the right or left - depending on the direction of rotation of the drive shaft 19 - and then back to the central position with each switchover.
In the event of a changeover, the insulating shaft 15 first rotates through a certain angle, with it the control disk 36 rotates. The lever 37 with its roller 38, due to the spring 42, endeavors to follow the control curve 39; however, this is not possible because it is locked by the pawl 41. Only at a defined point of the rotary movement does the release contour 40 deflect the pawl 41 against the force of the spring 43. The lever 37 is suddenly released and also opens the vacuum switching cell 12 suddenly with the spring 42. The insulating shaft 15 then rotates and with it the control disk 36 back again. The roller 38 runs on the cam 39 and closes the vacuum switching cell 12 continuously. At a certain point, the pawl 41 engages again on the lever 37 and blocks it; the end position and the starting position for the next changeover have been reached. When the insulating shaft 15 is initially rotated in the other direction, the entire actuation proceeds analogously, since both the control curve 39 and the trigger contour 40 are formed symmetrically on both sides of the central position.
With this actuation, rapid opening of the vacuum switching cell 12 is achieved by suddenly releasing the lever 37 on the one hand and continuous, curve-dependent closing by the running of the roller 38 on the control cam 39 on the other hand. The control cam 39 also locks the lever 37 positively in the stationary state. This prevents accidental triggering, for example due to vibrations.

6 finally shows a detail of the Maltese drive, namely a mechanical end position limiter.
It has already been explained that and why the Geneva wheel 29 may rotate a maximum of two revolutions in each direction thereafter an end position blocking must take place which prevents further rotation in this direction. The term "revolution" is defined as a full revolution by 360 degrees minus the angle of rotation, which corresponds to two switching steps.
This is achieved by a blocking disk 46, which is mounted on the insulating shaft 13, but can rotate freely independently of it and is spatially arranged between the gear plate 2 and the Geneva wheel 29. The blocking disk 46 has a driver 47, 48 on each side. The first driver 47 corresponds to a fixed stop 49 on the transmission plate 2, the second driver 48 corresponds to at least one further driver 50 on the Geneva wheel 29.
It is particularly advantageous to implement the two carriers 47 and 48 by means of a single cylindrical pin which penetrates the blocking disk 46.

The mode of action is as follows:
The Geneva wheel 29 can initially rotate in each direction by one turn until the driver 50 meets the driver 48, with the further rotation in the same direction the blocking disk 46 is also rotated. If this has rotated by one turn, the driver 47 hits the stop 49 and blocks both the blocking disk 46 and the Geneva wheel 29, which then has undergone two turns - the end position has been reached. When rotating in the opposite direction, the process is repeated analogously - the floating blocking disk 46 allows two revolutions of the Geneva wheel 29 in both directions, during which all fixed selector contacts 6 are swept twice - once with and once without an activated selection.

By appropriately arranging two drivers 50 on the same pitch circle on the Geneva wheel 29, the end position for any restricted Switching range can already be preset.

If there is only one driver 50, this can be of any shape or size be dimensioned. This makes it possible to easily End position limitation to the permissible revolutions defined above, which are not quite correspond to a full rotation of 360 degrees, but in each case of the two Switching steps corresponding angles are missing to adjust.

List of reference symbols

1

casing

2nd

Gear plate

3rd

Feed-through plate

4th

Front

5

Phase plate

6

fixed selector contacts

7

Contact carrier

7.1

movable selector contact

7.2

movable selector contact

8th

fixed selection contacts

9

Contact carrier

9.1

moving selector contact

10th

fixed by-pass contacts

11

Contact carrier

11.1

flexible by-pass contact

11.2

flexible by-pass contact

12th

Vacuum switch cell

13

Isolation shaft for selector.

14

Isolation shaft for VW / Wenderk.

15

Insulating shaft for by-pass contacts

16

Bore f. 13

17th

Bore f. 14

18th

Bore f. 15

19th

drive shaft

20th

first gear wheel

21

second gear wheel

22

camp

23

Maltese driver

24th

role

25th

third gear

26

Swingarm

27

lever

28

Swingarm

29

Maltese wheel

30th

Actuating role

31

lever

32

first concentric slip ring

33

second concentric slip ring

34

third concentric slip ring

35

console

36

Control disc

37

lever

38

role

39

Control curve

40

Release contour

41

Pawl

42

feather

43

feather

44

feather

45

Actuating plunger

46

Blocking disc

47

Carrier

48

Carrier

49

attack

50

Carrier

51

camp

Claims (10)

Step switches based on the reactor switching principle for uninterrupted load switching using vacuum switch cells,
where fixed selector contacts are provided in a housing for each phase, which can be connected by movable selector contacts,
In this housing, fixed preselector contacts are provided for each phase, which can be connected by a movable preselector contact.
In this housing, fixed by-pass contacts are provided for each phase, which can be connected by movable by-pass contacts,
wherein a vacuum switch cell is provided in this housing for each phase, which can be actuated by means of a force accumulator,
and a drive mechanism for actuating all movable contacts and all vacuum switching cells in the corresponding switching sequence is provided in a separate side housing part,
characterized, that for each phase all fixed contacts (6, 8, 10) and all movable contacts (7.1, 7.2; 9.1; 11.1, 11.2) and the vacuum switching cell (12) of this phase are arranged together on a phase plate (5), that three insulating shafts (13, 14, 15) extend through the housing (1) and penetrate the three phase plates (5), the first insulating shaft (13) actuating all movable selector contacts (7.1, 7.2), the second insulating shaft (14) all movable preselector contacts (9.1) are actuated and the third insulating shaft (15) all movable by-pass contacts (11.1, 11.2) and all vacuum switch cells (12) are actuated, that the drive mechanism has a single Geneva wheel (29) which can be driven by a Geneva driver (23) connected to a drive shaft (19) and is connected to the first isolating shaft (13), in such a way that the first isolating shaft (13) can be rotated through an angle that corresponds to a switching step, that the drive mechanism has first actuating means which act on the second insulating shaft (14), and that the actuating mechanism has second actuating means which act on the third insulating shaft (15). Step switch according to claim 1,
characterized, that the first actuating means consist of a roller (30) on the Geneva wheel (29) and a corresponding lever (31), such that in a certain position of the Geneva wheel (29) the roller (30) into a cutout of the lever (31) engages and thereby the second insulating shaft (14) can be pivoted by a certain angle of rotation depending on the direction of rotation. Step switch according to claim 1 or 2,
characterized, that the second actuating means consist of a further gear wheel (25) and a lever drive (26, 27, 28) connected to it, which in turn acts on the third insulating shaft (15), in such a way that with each rotation of the Geneva wheel (29) the third isolating shaft (15) performs an oscillating rotation by a certain angle and back into the starting position, depending on the direction of rotation. Step switch according to one of the preceding claims,
characterized, that on each phase plate (5) fixed and movable by-pass contacts (10; 11.1, 11.2) are arranged on one side and the respective vacuum switch cell (12) is arranged on the other side. Step switch according to one of the preceding claims,
characterized, that two movable selector contacts (7.1, 7.2) are provided for each phase, which are arranged electrically isolated from each other on a contact carrier (7) and are moved together by its rotation and that for each phase two movable by-pass contacts (11.1, 11.2) are provided, which are arranged electrically connected to one another on a further contact carrier (11) and are moved together by its rotation. Step switch according to one of the preceding claims,
characterized, that the energy accumulator for actuating the respective vacuum switching cell (12) consists of a control disk (36) with a control cam (39) which is connected to the third insulating shaft (15) and can be rotated with it, that it also consists of a two-armed lever (37) which has a roller (38) at one free end, which runs on the control cam (39), and which is locked in the stationary state by a pawl (41), and which with its other free end acts on an actuating plunger (45) of the vacuum switching cell (12), that the control cam (39) has a trigger contour (40) on its rear side, and that the trigger contour (40) corresponds to the pawl (41), such that the pawl (41) is released at a certain position of the third insulating shaft (15) and thus of the control disk (36) and the vacuum switching cell (12) opens suddenly becomes. Step switch according to one of the preceding claims,
characterized, that vacuum switch cell (12), control disc (36) with control cam (39) and rear trigger contour (40), two-armed lever (37) with roller (38) and springs (42, 43), which have a positive runout of the roller (38) allow the control cam (39) on the one hand and a positive actuation of the pawl (41) by the release contour (40) on the other hand, are on a common bracket (35) for each phase and each bracket (35) is attached to the corresponding phase plate (5) is. Step switch according to claim 6 or 7,
characterized, that the trigger contour (40) is formed by two cams. Step switch according to one of the preceding claims,
characterized, that the only Geneva wheel (29) interacts with a mechanical end position limiter, which consists of a blocking disk (46) which is arranged on the first insulating shaft (13), spatially in the region of the Geneva wheel (29), but freely rotatable independently of it, that the blocking disc (46) has a driver (47, 48) on each side, that one driver (47) corresponds to a fixed stop (49) on the housing (1), and that the other driver (48) corresponds to a further driver (50) on the Geneva wheel (29), such that the Geneva wheel (29) can make two rotations in each direction of rotation. Step switch according to claim 9,
characterized, that the two drivers (47, 48) are formed by a single cylindrical pin which penetrates the blocking disc (46), and that two drivers (50) are arranged on the same reference circle on the Geneva wheel (29), such that the maximum possible angle of rotation of the Geneva wheel (29) is limited.

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