EP0805464A2 - 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 acting 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.

From the associated additional application DE 43 15 081 A1 it has also become known to provide two vacuum switches connected in series and at least approximately simultaneously operable instead of the second vacuum switch in the stripping section in order to increase the security 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 which allows high switching powers, ie the guidance of high load currents, and at the same time offers a high level of functional reliability.

This object is achieved by a tap changer with the features of the first claim; the subclaims contain particularly advantageous developments of the invention.

A particular advantage of the tap changer according to the invention is the fact that the vacuum switch or switches in the switching branch are relieved or relieved by an additional mechanical contact in the stationary state.

The additional arrangement of permanent main contacts parallel to the switching branches is already e.g. Known from DE 44 07 945 C1, however, this known solution cannot contribute to improved continuous current guidance in a step switch of the generic type.

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.

Bei dem in Figur 1 dargestellten Stufenschalter ist ein vorwählender mechanischer Hilfskontakt HK vorhanden, der fest mit einem - hier nicht dargestellten - kontinuierlich antreibbaren Auzugsschlitten verbunden und mit diesem bewegbar ist. Der Hilfskontakt HK schleift auf einer Kontaktschiene KS, die wiederum über einen Überschaltwiderstand R und einem ersten Vakuumschalter VH mit einer Lastableitung L elektrisch in Verbindung steht.
Ein zweiter mechanischer Kontakt, der Schaltkontakt SK, ist fest mit einem - hier ebenfalls nicht dargestellten - Abtriebsteil, das nach Auslösung sprungartig dem Aufzugsschlitten nachführbar ist, verbunden und mit diesem bewegbar. Er ist durch eine Reihenschaltung aus einem zweiten Vakuumschalter VS und einem dritten Vakuumschalter VL mit der Lastableitung verbunden. Statt der beschriebenen Reihenschaltung kann auch nur ein einziger Vakuumschalter in diesem Zweig vorhanden sein.
Die Kontaktschiene KS ist ebenfalls fest mit dem Abtriebsteil verbunden.
Auf dem Abtriebsteil ist ein weiterer mechanischer Kontakt S_o vorgesehen, der demzufolge ebenfalls mit diesem bewegbar ist. Dieser feste Kontakt S_o ist derart angeordnet, daß er im stationären Zustand, d.h. wenn mechanischer Hilfskontakt HK und mechanischer Schaltkontakt SK am gleichen festen Stufenkontakt n anliegen, von einer zusätzlichen Kontaktstelle HKS des Hilfskontaktes HK beschaltet ist. Dadurch ist im stationären Zustand eine direkte Verbindung vom jeweils geschalteten festen Stufenkontakt, hier n, zum festen Kontakt S_o und von dort, ggf. über einen weiteren Widerstand R_o zur Lastableitung unter Umgehung der Vakuumschalter VS, VL möglich. Es ist ersichtlich, daß dadurch im stationären Zustand diese Vakuumschalter von der Dauerstromführung entlastet werden.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 a pull-out carriage which can be driven continuously, not shown here. 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 a driven 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 such that it is in the steady state, ie if mechanical auxiliary contact HK and mechanical switch contact SK are connected to the same fixed step contact n, is connected by an additional contact point HKS of auxiliary contact HK. As a result, in the stationary state, 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 transfer, bypassing the vacuum switches VS, VL, is possible. 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 arranged 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 are 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 components described, whether the additional mechanical contact S _{o is provided} on 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 in the stationary state - and only in this - by the additional contact point HKS of the mechanical auxiliary contact HK.

Claims (1)

Step switches with linear contact actuation, with fixed step contacts extending along a path into the interior of the switch and being switchable by a sliding switching mechanism,
wherein the switching mechanism consists of a directly drivable elevator carriage and an output part which, after being triggered, jumps after the elevator carriage,
the elevator carriage being connected to a preselecting mechanical auxiliary contact,
which can be brought into contact with each of the fixed step contacts and is electrically connected to the load discharge via at least one contact resistor and a first vacuum switch,
wherein the output part is connected to a mechanical switch contact, which can also be brought into contact with each of the fixed step contacts and which is electrically connected to the load lead via a second vacuum switch or a series connection of a second and a third vacuum switch
and in the steady state mechanical auxiliary contact and mechanical switching contact are present on the same fixed step contact,
characterized,
that the preselecting mechanical auxiliary contact (HK) has another contact point (HKS),
that an additional mechanical fixed contact (S _o ) is provided on the output part, which is electrically connected directly or via at least one additional switching resistor (R _o ) to the load lead (L)
and that in the stationary state the further contact point (HKS) of the preselecting mechanical auxiliary contact (HK) is connected to the additional contact (S _o ), such that the fixed step contact (n, n + 1) connected in each case then without the interposition of vacuum switches (VS, VL) is directly connected to the load conductor (L).

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