PRESELECTOR SWITCH ASSEMBLY FOR A VARIABLE TRANSFORMER

Abstract

The invention relates to a switch assembly (1), in particular a preselector, for a variable transformer (4) having a first winding (2) and a second winding (3) with a first and a second tap (3.3, 3.4), said switch assembly comprising: a first connection terminal (2.1) that can be connected to the first winding (2); a second connection terminal (3.1) that can be connected to the first tap (3.3); a third connection terminal (3.2) that can be connected to the second tap (3.4); a first, second, third and fourth fixed contact (5.1, 5.2, 5.3, 5.4); a vacuum interrupter (6); a first moving contact (7) that can be contacted selectively with the first or second fixed contact (5.1, 5.2); a second moving contact (8) that can be contacted selectively with the third or fourth fixed contact (5.3, 5.4), wherein the second and the fourth fixed contact (5.2, 5.4) are connected to the second connection terminal (3.1), the first and the third fixed contact (5.1, 5.3) are connected to the third connection terminal (32), the first moving contact (7) is connected to the first connection terminal (2.1) via the vacuum interrupter (6), and the second moving contact (8) is connected to the first connection terminal (2.1).

Claims

1. A preselector switch assembly for a control transformer having a first winding with a first tap and a second winding with a second tap, the assembly comprising: a first connection terminal connectable with the first winding; a second connection terminal connectable with the first tap; a third connection terminal connectable with the second tap; first, second, third and fourth fixed contacts; a vacuum interrupter; a first movable contact selectably contactable with the first or second fixed contact; and a second movable contact selectably contactable with the third or fourth fixed contact the second and fourth fixed contacts connected with the second connection terminal. the first and third fixed contacts being connected with the third connection terminal, the first movable contact being connected with the first connection terminal by the vacuum interrupter, the second movable contact being connected with the first connection terminal.

2. The switch assembly according to claim 1, wherein the vacuum interrupter is fixed between an upper mount and a lower mount on at least one contact rod.

3. The switch assembly according to claim 2, further comprising: a rocker lever for opening and closing the vacuum interrupter and mounted in the upper mount.

4. The switch assembly according to claim 3, wherein the movable contacts are mounted on a switching tube in parallel one above the other; the switching tube is rotatable; and the movable contacts pivot on rotation of the switching tube.

5. The switch assembly according to 4, further comprising: a cam disk mounted on the switching tube, pivotal on rotation of the switching tube; and mechanically cooperating with the rocker lever in the upper mount to open or close the vacuum interrupter.

6. The switch assembly according to claim 1, wherein each movable contact comprises a housing with contact fingers that at a first end are mechanically slidably and electrically conductively connected with a diverter ring associated with the respective movable contact and at a second end can be selectably connected with the respective fixed contact.

7. The switch assembly according to claim 1, wherein the first tap and the second tap are each arranged at a respective end of the second winding.

8. The switch assembly according to claim 1, further comprising: a fourth connection terminal connectable with a third tap of the second winding between the first tap and the second tap; and a resistor connected with the fourth connection terminal.

9. The switch assembly according to claim 8, further comprising: an isolator connected with the fourth connection terminal in series with the resistor or the vacuum interrupter connected with the fourth connection terminal in series with the resistor.

10. The switch assembly according to claim 1 and that is constructed as a preselector, reverser or coarse selector.

Description

[0050] In the drawings:

[0051] FIG. 1 shows a control transformer with an on-load tap changer that comprises a load changeover switch and a selector as well as a switch assembly according to the invention;

[0052] FIGS. 2a-g show a circuit diagram of a first embodiment of the switch assembly as well as a switching sequence of the switch assembly;

[0053] FIG. 3 shows a perspective view of a preferred embodiment of the switch assembly of FIGS. 2a-g as a constructional configuration for one phase;

[0054] FIG. 4 shows another perspective view of the switch assembly of FIG. 3;

[0055] FIGS. 5a-d show circuit diagrams of second, third, fourth and fifth forms of embodiment of the switch assembly;

[0056] FIG. 6 shows a circuit diagram of a sixth embodiment of the switch assembly; and

[0057] FIG. 7 shows a circuit diagram of a seventh embodiment of the switch assembly.

[0058] In FIG. 1 there is schematically shown an exemplifying embodiment of a control transformer 4 that has an upper voltage side or primary side with a first winding 2 and a second winding 3, a lower voltage side or secondary side 40 and an on-load tap changer 46 with a load changeover switch 45, a selector 47 and a switch assembly 1 according to the invention. The control transformer 4 is enclosed by a transformer housing 42. The different winding taps 13 (see FIG. 2) of the control transformer 4 can be connected with the on-load tap changer 46 arranged in the interior 44 of the transformer housing 42. In order to be able to ensure correct functioning of the control transformer 4 the on-load tap changer 46 has to execute the required switching sequence without disturbances. The on-load tap changer 46 projects into the transformer housing 42 that depending on the type of control transformer 4 can be filled with oil. The on-load tap changer 46 here comprises, by example, a load changeover switch 45 and selector 47, but can also be constructed as a load selector.

[0059] The on-load tap changer 46 is actuated through a linkage by a motor drive 48 fastened to an outer wall 43 of the transformer housing 42. However, the motor drive 48 can also be directly mounted on the cover 41, thus on the head of the on-load tap changer 46.

[0060] The control transformer 4 usually has for each phase at least one first winding 2 and second winding 3, which can be electrically connected together by the switch assembly 1 that can be constructed as a reverser or coarse selector, as will be described in detail in the following with reference to FIG. 2.

[0061] A circuit diagram of a first embodiment of the switch assembly 1 for an on-load tap changer 46 is schematically illustrated in FIG. 2a. The switch assembly 1 comprises three connection terminals 2.1, 3.1, 3.2, wherein the first connection terminal 2.1 is connected with the first winding 2, the second connection terminal 3.1 is connected with a first tap 3.3 of the second winding 3 and the third connection terminal 3.2 is connected with a second tap 3.4 of the second winding 3. The first and second taps 3.3, 3.4 are respectively attached to the ends of the second winding 3.

[0062] In this embodiment the first winding 2 is constructed as main winding and the second winding 3 as regulating winding and the switch assembly 1 fulfils the function of a reverser.

[0063] Moreover, the switch assembly 1 comprises four fixed contacts 5.1, 5.2, 5.3 and 5.4, a stationary vacuum interrupter 6 and two movable contacts 7, 8. The second and fourth fixed contacts 5.2, 5.4 are electrically conductively connected with the second connection terminal 3.1. The first and third fixed contacts 5.1, 5.3 are electrically conductively connected with the third connection terminal 3.2.

[0064] The first movable contact 7 is electrically conductively connected with the first connection terminal 2.1 by the vacuum interrupter 6. The second movable contact 8 is electrically conductively connected directly with the first connection terminal 2.1. The first movable contact 7 can be connected or contacted selectably with the first fixed contact 5.1 or second fixed contact 5.2. The second movable contact 8 can be connected or contacted selectably with the third fixed contact 5.3 or fourth fixed contact 5.4.

[0065] In the setting of the switch assembly 1 illustrated in FIG. 2a the first winding 2 is electrically conductively connected with the third connection terminal 3.2 on the one hand by the vacuum interrupter 6, the first movable contact 7 and the first fixed contact 5.1 and on the other hand and parallel thereto by the second movable contact 8 and the third fixed contact 5.3.

[0066] FIG. 2b shows the first step of a switching-over process of the switch assembly 1 of FIG. 2a. In that case, initially the second movable contact 8 is detached from the third fixed contact 5.3, so that the first winding 2 is connected with the third connection terminal 3.2 of the second winding 3 only still by the vacuum interrupter 6, the first movable contact 7 and the first fixed contact 5.1.

[0067] FIG. 2c shows the second step, in which the vacuum interrupter 6 is opened so that there is no electrically conductive connection between the first and second windings 2, 3.

[0068] FIG. 2d shows the third step, in which the first movable contact 7 is detached from the first fixed contact 5.1.

[0069] FIG. 2e shows the fourth step in which the first movable contact 7 is switched to the second fixed contact 5.3.

[0070] FIG. 2f shows the fifth step in which the vacuum interrupter 6 is closed so that the first winding 2 is electrically conductively connected with the second connection terminal 3.1 by the vacuum interrupter 6, the first movable contact 7 and the second fixed contact 5.2.

[0071] FIG. 2g shows the sixth step in which the second movable contact 8 is switched to the fourth fixed contact 5.4, so that the first winding 2 is electrically conductively connected with the second connection terminal 3.1 on the one hand by the vacuum interrupter 6, the first movable contact 7 and the second fixed contact 5.2 and on the other hand and parallel thereto by the second movable contact 8 and the fourth fixed contact 5.4.

[0072] Switching-over in opposite direction takes place analogously in reverse sequence.

[0073] A preferred embodiment of the switch assembly 1 of FIGS. 2a-g is schematically illustrated in FIGS. 3 and 4 as a constructional format for one phase.

[0074] In this embodiment the switch assembly 1 comprises a plurality of vertical contact rods 20 that are disposed in a circle and arranged around a vertical switching tube 21. In that case, the vacuum interrupter 6 is mounted in fixed location or to be stationary and parallel to the contact rods 20, thus vertically, between an upper mount 22 and a lower mount 23. The two mounts 22, 23 are fastened to at least one contact rod 20.

[0075] A first diverter ring 24 and a second diverter ring 25 are mounted on the switching tube 21. The two diverter rings 24 and 25 are mounted so that a relative movement between these and the switching tube 21 is possible. In that case, the diverter rings 24 and 25 are fixedly installed and the switching tube 21 can be rotated about its own axis between two positions.

[0076] The second diverter ring 25 is electrically conductively connected with the vacuum interrupter 6 by a line 26. The line 26 fixes the second diverter ring 25. The first movable contact 7 is secured to the switching tube 21 and through rotation of the switching tube 21 produces an electrically conductive connection between the second diverter ring 25 and selectably the first fixed contact 5.1 or the second fixed contact 5.2.

[0077] The first diverter ring 24 is electrically conductively connected directly with the first connection terminal 2.1 by a line 27. The line 27 fixes the first diverter ring 24. The second movable contact 8 is also fastened to the switching tube 21 and through rotation of the switching tube 21 produces an electrically conductive connection between the first diverter ring 24 and selectably the third fixed contact 5.3 or the fourth fixed contact 5.4.

[0078] During rotation of the switching tube 21 the two diverter rings 24 and 25 remain in a fixed position and do not rotate in company with the switching tube 21.

[0079] The first and second movable contacts 7 and 7 are mounted preferably parallel to one another horizontally on the switching tube 21. When switching is carried out, the movable contacts 7 and 8 execute a pivot movement and thus connect the four fixed contacts 5.1-5.4. In that case, the second and fourth fixed contacts 5.2, 5.4 are mounted one above the other on a contact rod 20 and electrically conductively connected by a line 29. The first and third fixed contacts 5.1, 5.3 are fastened to an adjacent contact rod 20 and similarly electrically conductively connected by a line 28. The third and fourth fixed contacts 5.3, 5.4 are each constructed in such a way that on rotation of the switching tube 21 the second movable contact 8 firstly detaches from the respective fixed contact 5.3, 5.4, whilst the first movable contact 7 moves in parallel therewith, but remains switched for a longer period of time onto the first or second fixed contact 5.1, 5.2.

[0080] Each movable contact 7, 8 comprises a housing 50 and contact fingers 51 that are resiliently mounted therein and that extend from a first end 52 to a second end 53 through the interior of the housing 50. A sliding connection always guaranteed during rotation of the switching tube 21, is present between the first end 52 of the contact fingers 51 and the respective diverter ring 24, 25. The second end 53 of the contact fingers 51 similarly slides on the respective fixed contacts 5.1-5.4 onto or off these.

[0081] In addition, a cam disk 30 is mounted on the switching tube 21 and similarly executes a pivot movement when rotation of the switching tube 21 takes place. When the pivot movement takes place, the cam disk 30 co-operates with a rocker lever arrangement 31, by which the vacuum interrupter 6 is opened or closed.

[0082] The switch assembly 1 is constructed in such a way that through the arrangement of the movable contacts 7, 8, the fixed contacts 5.1-5.4 and the cam disk 30 on the switching tube 21 a switching-over process according to FIGS. 2a-2g can be carried out.

[0083] A second embodiment of the switch assembly 1 is schematically illustrated in FIG. 5a. This embodiment is similar to the first embodiment, so that primarily the differences are explained in more detail in the following.

[0084] In this embodiment the switch assembly 1 comprises a fourth connection terminal 3.6 connectable with a third tap 3.5 of the second winding 3 between the first tap 3.3 and the second tap 3.4, preferably in the center. A resistor 10 electrically conductively connected with ground potential 9 is attached to the fourth connection terminal 3.6. This resistor serves as polarity resistance during a switching-over process of the switch assembly 1.

[0085] A third embodiment of the switch assembly 1 is schematically illustrated in FIG. 5b. This embodiment is similar to the second embodiment, so that primarily the differences are explained in more detail in the following.

[0086] In this embodiment, connected between ground potential 9 and the resistor 10 is an isolator 11 with the help of which the resistor 10 can be electrically isolated from ground potential 9. The isolator 11 is closed prior to actuation of the two movable contacts 7, 8 and is opened after switching-over of the movable contacts 7, 8 has taken place.

[0087] A fourth embodiment of the switch assembly 1 is schematically illustrated in FIG. 5c. This embodiment is similar to the third embodiment so that primarily the differences are explained in more detail in the following.

[0088] In this embodiment, connected between ground potential 9 and the isolator 11 is a vacuum interrupter 12 with the help of which the resistor 10 can be electrically separated from ground potential 9 before the isolator 11 is actuated. The arrangement or sequence of resistor 10, isolator 11 and vacuum interrupter 12 between the fourth connection terminal 3.6 and ground potential 9 can be designed as desired. The vacuum interrupter 12 is closed after closing of the isolator 11, thus before actuation of the movable contacts 7, 8. The vacuum interrupter 12 is opened before opening of the isolator 11, thus after actuation of the movable contacts 7, 8.

[0089] A fifth embodiment of the switch assembly 1 is schematically illustrated in FIG. 5d. This embodiment is similar to the fourth embodiment so that primarily the differences are explained in more detail in the following.

[0090] In this embodiment the isolator 11 is eliminated, so that only the vacuum interrupter 12 is arranged between ground potential 9 and the resistor 10.

[0091] A sixth embodiment of the switch assembly 1 is schematically illustrated in FIG. 6. This embodiment is similar to the first embodiment so that primarily the differences are explained in more detail in the following.

[0092] In this embodiment the first winding 2 is constructed as a regulating winding and the second winding 3 as a main winding and the second tap 3.4 is arranged, by example, at a position in the lower third of the second winding 3, wherein the part between the taps 3.3 and 3.4 is termed coarse step winding or coarse step 54. The switch assembly 1 fulfils the function of a coarse selector. However, the second tap 3.4 can also be arranged at any other desired place of the second winding 3.

[0093] A seventh embodiment of the switch assembly 1 is schematically illustrated in FIG. 7. This embodiment is similar to the sixth embodiment so that primarily the differences are explained in more detail in the following.

[0094] In this embodiment the switch assembly 1 comprises a fourth connection terminal 3.6 connectable with a third tap 3.5 of the second winding 3 between the first tap 3.3 and the second tap 3.4, preferably in the center. A series circuit electrically conductively connected with ground potential 9 and consisting of resistor 10, isolator 11 and vacuum interrupter 12 is attached to the fourth connection terminal 3.6 similarly to the fifth embodiment. The resistor 10 serves as polarity resistance for the switching-over process of the switch assembly 1. The isolator 11 and/or vacuum interrupter 12 can also be excluded depending on requirements.

TABLE-US-00001 REFERENCE NUMERALS 1 switch assembly 2 first winding 2.1 first connection terminal of 1 3 second winding 3.1/3.2 second/third connection terminal of 1 3.3/3.4 first/second tap of 3 3.5 fourth tap of 3 3.6 fourth connection terminal of 1 4 control transformer 5.1/5.2/5.3/5.4 first/second/third/fourth fixed contact of 1 6 vacuum interrupter 7 first movable contact of 1 8 second movable contact of 1 9 ground potential 10 resistor 11 isolator 12 vacuum interrupter 13 taps 20 contact rod 21 switching tube 22 upper mount 23 lower mount 24 first diverter ring 25 second diverter ring 26 line 27 line 28 line 29 line 30 cam disk 31 rocker lever 40 secondary side 41 cover 42 transformer housing 43 outer wall 44 interior 45 load changeover switch 46 on-load tap changer 47 selector 48 motor drive 50 housing 51 contact finger 52 first end 53 second end 54 coarse step