EP0805464B1 - Tap changer - Google Patents

Abstract

The stepping switch has a number of stationary contacts extending along a linear switch path for cooperating with a sliding switch mechanism. This has a directly driven carriage provided with a mechanical auxiliary contact (HK) and a drawn element with a mechanical main switch contact (SK). The auxiliary contact cooperates with a contact rail (KS) coupled to the load connection (L) via a resistance (R) and a vacuum switch (VH), with 2 further vacuum switches (VS,VL) connected in series between the main switch contact and the load connection.

Description

The invention relates to a tap changer according to the preamble of the first claim.

Such a tap changer is already known from DE 42 37 165 C1.
In this known tap changer, fixed tap contacts extending along a path are provided, which can be connected by a sliding switching mechanism.
The switching mechanism consists of an elevator carriage and driven part.
The elevator carriage is connected to a mechanical contact that acts as a pre-selection contact, which can be brought into contact with each of the fixed step contacts and with its free end slides on a contact rail, which in turn is connected to the load discharge via at least one contact resistance and a first vacuum switch ,
The output part is connected to a trailing mechanical switch contact, which can also be connected to each of the fixed step contacts and in turn is connected to the load discharge via a second vacuum switch.

It is also already known from the associated additional application DE 43 15 081 A1 become, instead of the second vacuum switch in the stripping section two in series and provide at least approximately simultaneously operable vacuum switches to ensure safety against a possible failure of a vacuum switch in the switching branch.

In these known tap changers, the entire load current flows in the stationary state via the switch contact and the associated vacuum switch in this branch.
This places high electrical demands on the vacuum switches used, particularly with larger load currents, which makes them unnecessarily large and expensive.

The object of the invention is to provide a tap changer of the generic type, the high switching capacities, i.e. the carrying of high load currents, permits and at the same time high Functional security offers.

This object is achieved by a tap changer with the features of first claim solved.

The fact that by a additional mechanical contact in the stationary state of the vacuum switch or Switching branch is relieved or relieved.

The additional arrangement of permanent main contacts is parallel to the switching branches in itself e.g. known from DE 44 07 945 C1, to an improved Continuous current flow in a generic tap changer can this known solution however contribute nothing.

Fig. 1

zeigt eine schematische Darstellung eines ersten erfindungsgemäßen Stufenschalters

Fig. 2

zeigt eine entsprechende Schaltsequenz dieses Stufenschalters bei einer Umschaltung vom festen Stufenkontakt n auf den festen Stufenkontakt n+1

Fig. 3

zeigt eine schematische Darstellung eines zweiten erfindungsgemäßen Stufenschalters

Fig. 4

zeigt wiederum die entsprechende Schaltsequenz dieses Stufenschalters.

The invention will be explained in more detail below using two exemplary embodiments.

Fig. 1

shows a schematic representation of a first tap changer according to the invention

Fig. 2

shows a corresponding switching sequence of this tap changer when switching from the fixed tap contact n to the fixed tap contact n + 1

Fig. 3

shows a schematic representation of a second tap changer according to the invention

Fig. 4

again shows the corresponding switching sequence of this tap changer.

In the tap changer shown in FIG. 1, there is a preselecting mechanical auxiliary contact HK which is fixedly connected to and movable with an elevator carriage (not shown here) which can be driven continuously. The auxiliary contact HK grinds on a contact rail KS, which in turn is electrically connected to a load lead L via a switching resistor R and a first vacuum switch VH.
A second mechanical contact, the switching contact SK, is fixedly connected to and movable with an output part - which is likewise not shown here - which can be tracked to the elevator carriage after it has been triggered. It is connected to the load discharge through a series connection of a second vacuum switch VS and a third vacuum switch VL. Instead of the series connection described, only a single vacuum switch can be present in this branch.
The contact rail KS is also firmly connected to the driven part.
A further mechanical contact S _{o is} provided on the driven part, which consequently can also be moved with it. This fixed contact S _o is arranged in such a way that it is connected by an additional contact point HKS of the auxiliary contact HK in the stationary state, ie when mechanical auxiliary contact HK and mechanical switching contact SK are present at the same fixed step contact n. As a result, a direct connection from the respectively switched fixed step contact, here n, to the fixed contact S _o and from there, possibly via a further resistor R _o for load dissipation, bypassing the vacuum switches VS, VL, is possible in the stationary state. It can be seen that these vacuum switches are relieved of the continuous current in the stationary state.

From the switching sequence shown in Figure 2 it can be seen that at the beginning of each changeover, when the leading mechanical auxiliary contact HK leaves the previous fixed step contact n, the additional contact point HKS moves away from the fixed contact S _o , so that the load current on the in the Drawings on the left of the switching branch commutated with the series connection of the vacuum switches VS, VL. At the end of the load switchover, ie when the trailing switch contact has reached the new fixed step contact n + 1, the contact point HKS again meets the contact S _o , which, as explained, has followed the movement of the driven part and thus the switch contact. The vacuum switches VS, VL are then relieved of the continuous current.

Figure 3 shows a modified embodiment of the invention. In this case, instead of a continuous contact rail KS, the latter is designed so that two individual contact rail parts KS _A and KS _B are present, between which the additional fixed contact S _o is located. Here, too, the two contact rail parts KS _A , KS _B and the additional contact S _{o are} fixed and fixed with respect to their relative position to one another on the driven part and are moved with it. The function of this embodiment is unchanged, as can be seen from the switching sequence shown in FIG. 4.

Ultimately, it is a question of the available space and the dimensioning of the. described components, whether you provide the additional mechanical contact S _o in an additional level or integrated into the level of the contact rail, which is then divided. It is only essential that the fixed contact S _{o is} spatially arranged on the driven part in such a way that it can be contacted by the additional contact point HKS of the mechanical auxiliary contact HK in the stationary state - and only in this state.

Claims (1)

1. Tap switch with linear contact actuation, wherein fixed tap contacts extend along a track in the interior of the switch and can be electrically connected by a displaceable switching mechanism, wherein the switching mechanism consists of a directly drivable pull-up carriage and a driven part which abruptly follows the pull-up carriage after triggering, wherein the pull-up carriage is connected with a preselecting mechanical auxiliary contact which can be brought into contact with each of the fixed tap contacts and is electrically connected with the load shunt by way of at least one switchover resistance and a first vacuum switch, wherein the driven part is connected with a mechanical switch contact which can similarly be brought into contact with each of the fixed tap contacts and which is electrically connected with the load shunt by way of a second vacuum switch or a series circuit of a second and a third vacuum switch and wherein in the stationary state the mechanical auxiliary contact and mechanical switch contact lie at the same fixed tap contact, characterised in that the preselecting mechanical auxiliary contact (HK) comprises a further contact position (HKS), that an additional mechanical fixed contact (S_o), which is electrically connected with the load shunt (L) directly or by way of at least one further switchover resistance (R_o), is provided on the driven part and that in the stationary state the further contact position (HKS) of the preselecting mechanical auxiliary contact (HK) lies at the additional contact (S_o) in such a manner that the respectively connected fixed tap contact (n, n+1) is then electrically connected directly with the load shunt (L) without interposition of vacuum switches (VS, VL).

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