HK1178681B - Stepping switch having a freewheel element - Google Patents

Description

The present invention relates to a step switch for continuous switching between at least two winding sockets of a step transformer, having a rotatable switch shaft, which is associated with several action phases for mechanical switches or vacuum switches.

DE 20 21 575 A is a step switch with a total of four vacuum switches per phase, each of which has one vacuum switch tube as the main contact and another vacuum switch tube as the resistance contact in a series circuit with a switch resistor.

In the case of a continuous load switching from the previous winding connection n to a new, pre-selected winding connection n+1, the main contact of the switching side is first opened, after which the resistance contact of the receiving side is closed, so that a compensating current limited by the overclocking resistors flows between the two stages n and n+1. After the previously closed resistance contact of the switching side has opened, the main contact of the receiving side then closes, so that the entire load current from the new winding connection n+1 leads to the Lastable, thus completing the switching.

The vacuum switch tubes used in this well-known step switch and many similar well-known embodiments instead of conventional mechanical contacts for load switching have a number of advantages. Since the contacts themselves are encapsulated in vacuum, high switching power can be achieved. The encapsulated, hermetically sealed contacts can also not lead to scratching and contamination of the insulating oil surrounding them in the step switch by contact fire or light arcs.

However, in various applications of such known step switches with vacuum switching tubes for controlling power transformers, a high shock resistance is required, preferably up to and including 100 kV. Such undesirable shock voltages, the magnitude of which is largely determined by the design of the step transformer and the winding parts between the individual input stages, are, on the one hand, flash shock voltages resulting from the impact of lightning in the mains. On the other hand, switch shock voltages may also occur, caused by unpredictable shock voltages in the mains.

It is already known from DE 23 57 209 B1 and DE 26 04 344 A1 that measures are in place to combat excessive shock voltage between the load branches, or voltage-dependent resistors or both; however, these measures are inadequate in various cases and cannot, or cannot, completely eliminate harmful shock voltage.

DE 195 10 809 C1 describes a load switch of a step switch for the continuous switching between at least two winding contacts of a step transformer. This has a rotating switch shaft on which concentric curved discs with different contours are arranged. Mechanical switching elements or vacuum switching tubes are actuated by different actuators for several actuation phases through the contours of the curved discs.

The DE 21 61 677 A1 has been used to determine a drive for a load switch in which the individual controls are operated by means of one or more curved discs.

GB 1 126 779 A describes a switch arrangement consisting of several vacuum switches in which the movable contacts interact with the cams provided on a drive shaft so that the contacts pass through a predefined switching sequence when the drive shaft is rotated.

One of the aims of the present invention is to propose a step switch of the type described at the outset with high shock resistance, also known as a0 resistance.

To achieve the objective of the invention, a step switch is proposed for uninterrupted switching between at least two winding connections of a step transformer with the characteristics of the independent claim 1. This step switch provides a load branch with at least two parallel paths. Each of these paths may be a series of at least one vacuum tube and at least one mechanical circuit elemental, which in this context may also be referred to as a variable switching or switching circuit elemental. At least two different components of the vacuum circuit elemental may be arranged in a specific way and may be easily and independently of each other, and at least two of these elements may be connected in a vacuum circuit elemental or switched circuit elemental, and the two or more components may be arranged in a vacuum circuit elemental or switched circuit elemental, and the two or more components may be connected in a vacuum circuit elemental or switched circuit elemental, and the two or more components may be arranged in a vacuum circuit elemental or switched circuit elemental, which may be defined in a specific way and which can be operated in a vacuum circuit in a specified direction and which can be operated in a mechanical circuit or switched circuit, and which can be operated in a mechanical circuit or switched circuit, and which can be operated in a vacuum or switched circuit, respectively, in a specified direction and which can be operated in a mechanical or mechanical mode, and which can be operated in a vacuum or in a mechanical mode, and which can be operated in a vacuum or in a mechanical mode, and which can be operated in a mechanical or a mechanical mode, and which can be operated in a mechanical or a mechanical, respectively, in a vacuum or a time, in a vacuum or a vacuum or a vacuum or a vacuum.

According to a preferred embodiment of the step switch of the invention, the shifted switching time or switch-off time has a defined time interval from the other switching times or switching off times of the other mechanical switching elements and vacuum switching tubes.

The step switch in accordance with the invention has a rotatable switch shaft with actuating elements for each actuation phase for the mechanical switching elements or vacuum switching tubes, each of which is connected to concentric curved discs rotatable by the switch shaft with frontal contours. These frontal contours may be formed in particular by protrusions, knots, etc. suitable for actuating the switching elements and/or vacuum switching tubes. In addition, the rotation of at least one of the mechanical switching element circuit breakers to be actuated with time delay is proportional to the time delay of the other mechanical switching elements, independently of their rotation direction or the direction of rotation of the other rotating elements.

In addition, an additional permanent main contact may be provided and/or coupled to the step switch. In such a step switch, there may be an additional mechanical contact (MC) on the switch-off and/or switch-on side, each providing a DC. The contact of such a permanent main contact switch opens preferably on the switch-off side before all other switching elements (MSV, TTV, MTF, TTF), while the contact on the switch-off side closes after all other switching elements.

The delayed switching or triggering of at least one mechanical switch element in each direction of rotation can be achieved in the step switch by having at least one switch and a freewheeling element for the phase shift of the switching time point in each direction of rotation of the switch shaft. This freewheeling element may in particular comprise a circular segmented guide frame for a participant of the switch shaft concentrically arranged to the switch shaft, and a casing-like separator element anchored to the rotating switch shafts and the casing of the switch shafts, and the rotating shaft and the associated crankshaft are separated from each other. This simple separator element is defined by the fact that the two conducting elements work together in a more effective manner, and that the flow of the switch shaft is not controlled by the viscousness of the parts, but by their greater and less viscous distance from each other, and by the fact that the components of the crankshaft are not in the same direction of rotation and are not in a more effective way connected to each other.

The general idea underlying the invention is that by switching a mechanical switch element on one of several load branches independently of the respective direction of the switch, the desired shock resistance or a0-strength can be achieved by switching it down one at a time.

The invention is explained in detail below by means of examples of operation using the drawings described below.Fig. 1 shows a schematic perspective representation of an embodiment of a step-change according to the invention with a free-run element consisting of a switch wave with actuating elements arranged on it and switching elements coupled to it.Fig. 2 shows in a schematic detail a detail of an actuating mechanism of the step-change according to Fig. 1.Fig. 3 shows a schematic perspective representation of the step-change according to Fig. 1 below.Fig. 4 shows a process diagram for the operation of the switch switch switch with a frequency of operation of a switch with different operating elements arranged on it and switching elements coupled to it.Fig. 1 shows a detailed diagram of the operation of a step-change according to a step-change in different directions.Fig. 3 shows a second component in each of the following two directions, while Fig. 5 shows a series of switching components in different directions.Fig. 7 shows an additional example of a step-change in each of the following two directions.Fig. 5 shows a series of switching components in different directions.

The following example is not intended to be a restrictive example but is intended to explain the function and switching capabilities of a step switch according to the invention.

The diagrams in Figures 1 and 2 show an example of a step switch 10 with a switch 22 with its control elements 24 and switching elements 26 attached to it. The diagram in Figure 3 shows a further view of the step switch 10 as shown in Figure 1 below. As illustrated in Figures 4 to 7 below, a downstream switching or switching time of one of two mechanical switching elements TTF has a defined time distance to the other switching or switching points of a first mechanical switch MTF and two vacuum switching elements TTF and TTV. In addition, the switching or switching time is set at a specified time interval in the direction of the switching or switching element TTF, independent of the mechanical switch MS 22 and the other switching or switching elements.

The embodiment of the step switch 10 of the invention shown in Figures 1 to 3 has a switch axis 22 rotatable in both directions, four parallel discs 24 for each operation phase for the mechanical switches 26 and vacuum switches, each consisting of concentric curved discs 28 with circular contours or protrusions 30 and each of them driven by the switch axis. These protrusions 30 can also be arranged horizontally on the curved axes. These protrusions 30 solve the two switches 26 and the discs 27 by driving them in the vacuum block 27 and passing them in the perimeter of the switch block 27 and in the direction of the curve.whereby they rotate or operate the respective mechanical switch element and/or the respective vacuum switch tube around a defined switch path. As shown in Figures 1, 2 and 3, each of the four existing curve discs 28 may have several protruding or knob 30 at their outer perimeter, each equally spaced, so that a complete switch cycle of the step switch 10 does not require a complete rotation of the switch shaft 22 by 360 degrees, but that, for example, a 120° rotation is sufficient for this purpose.The rotation of the shaft 22 shall be delayed by the rotation of the other curved discs 28 or other control elements 24 respectively.

The switching or activation of the second mechanical switching element TTF (Figures 5 and 6) in each direction of rotation, designated by the reference number 32 in Figures 1 and 3, is achieved in the case of the step switch 10 shown by assigning to the relevant switch or actuator 24 and to the curved disc 28 a frequency switching element 34 to shift the switching time phase according to the rotation direction of the switch shaft 22; this frequency switching element 34 is arranged as a circular, concentrically oriented guide frame 36 for a circular participant of the corresponding switch shaft 28 and a horizontal load element 38 which is mounted on the rotor of one of the switches 22 and 28 and is mounted on the rotor of the other two switches and is located on the center of the rotor of the two switches.The separator element 38 ensures in a simple and effective manner that the crankcase 28 is not rotated uncontrollably when the switch 22 is turned, e.g. by viscous effects of the oil bath in which the components of the step switch 10 are arranged or immersed, but that the crankcase 22 is rotated exclusively by the interacting support elements and controls 36 These interacting support elements and controls 36 define, by their dimensions and arrangements, the hysteresis of the free-run 34, i.e. the shift delay indicating an exact equal time interval between the start of the switch in each rotation of the switch 22 direction.by switching the mechanical switch element 32 or TTF one of several load branches, independently of the respective switching direction of the switch shaft 22, to the desired shock resistance or a0 resistance, in order to ensure that any shock voltages which may occur do not affect the vacuum switch tubes in the load branch not supplying the load current and are therefore harmless to the vacuum switch tubes.

The diagram in Fig. 4 shows an illustrative and qualitatively understandable flow diagram to illustrate the switching processes of an embodiment of the step switch 10 of the invention (see Figures 1 to 3) during a switching cycle in different switching directions. The top diagram illustrates the switching sequence of a step switch consisting of a total of four individual switching units in a first switching direction, while the bottom diagram shows the switching sequence in opposite switching direction. The schematic representations in Fig. 5 (Figures 5a to 5h) show in a total of nine switching images the individual successive switching states of the various components of the first step switch in a switch direction, which in Fig. 5a is denoted by the n → n switching direction.

The step switch 10 shown in Fig. 5 by a basic switch diagram is used to switch continuously between two winding connections 12 and 14 of a step transformer 16. The step switch 10 forms a load branch with two parallel paths 18 and 20. Each of these paths 18 and 20 comprises a serial arrangement of a vacuum switch tube MSV, TTV and a mechanical switch element MTF, TTF, which can also be referred to in this context as a variable-adjustable or switchable switch. The first step 18 is connected by the first vacuum switch tube MSV and the first mechanical switch element MTF connected in series. The second step PTF 20 is connected by a second vacuum switch element TTF, which can be connected by a mechanical switch element TTF and the second step TTF, and the two mechanical switches MTF 12 and TTF 14 can be connected by a switch and switch.

The two vacuum switching tubes MSV and TTV and the two mechanical switching elements MTF and TTF can be switched together in different switching directions (n → n+1 or n+1 → n) with defined time shifting according to Fig. 4. As can be seen from Fig. 4, the second mechanical switching element TTF has a time-shifting or switching point, which is independent of the switching direction, relative to the first switching element MTF and the two vacuum switching tubes MSV and TTV, which allows certain switching states to be achieved in a simple, reliable and precisely reproducible way with the help of a mechanical medium switcher.

The diagram in Fig. 4 shows the operation of a complete switch operation, starting at zero time, at the top for a drive direction from left to right (n → n+1), i.e. ending at a definable time (see Fig. 5), and at the bottom for a drive direction from right to left (n+1 → n), i.e. starting at a definable time corresponding to the scale below and ending at zero at the far left. The position of the step switch 10 at the start of the switch is illustrated in Fig. 5a. The first vacuum tube MSV is closed here, while the switch contact of the second vacuum tube TTV is open. The first mechanical switch MTF is in the first switch position, which can be switched from the first step of the first step to the first step of the first step of the first step of the first step of the first step of the second step of the first step.

After a short time, the second vacuum switch tube TTV is closed (see Figure 5b), after which the first vacuum switch tube MSV is opened (see Figure 5c). This opening shortly after the start of switching is illustrated in Figure 5d. In this switching state of the step switch 10 with the first vacuum switch tube MSV and the second vacuum switch tube TTV open and the second vacuum switch tube TTV closed and in the first switching position of the second mechanical switch element TTF shown in Figures 5a to 5g, the load current flows from the first winding of the step transformer 12 through the second branch 16 or second branch 20, respectively, and can also be referred to as the LAZ or the Rastable load current, as shown in Figures 5d and 5e.

After a further short period of time, the first mechanical switch element MTF is switched (Fig. 5d, Fig. 5e), preparing the closure of the first vacuum switch tube MSV (Fig. 5e, Fig. 5f) and the subsequent opening of the second vacuum switch tube TTV (Fig. 5f, Fig. 5g). The load current IL flows from the second winding socket 14 of the step transformer 16 through the first mechanical switch element MTF and the closed first vacuum tube MSV to the Lastable LA, as shown in Fig. 5g. Finally, during this switching cycle, the second mechanical switch element TTF is switched to the second cycle TTP (Fig. 14g), which is the second cycle TTP (Fig. 5g), which is the second cycle TTP (Fig. 5g).

The representation of the individual switching operations of the switching cycle (n → n+1; Fig. 4 above) in Fig. 5 shows that the second mechanical switching element TTF is switched last in the manner described above. Since the present invention also states that this is the case in the opposite direction of the switch, appropriate arrangements must be made to allow the second mechanical switching element TTF to be switched last in the case of the other components MTF, MSV and TTV switching in reverse order. This delayed switching is ensured by means of a suitable freewheeling device to be configured in accordance with the present invention, as illustrated in Figures 1 to 3.

The diagrams in Fig. 6 show the individual, consecutive switching states of the different components of the stepper switch in a second switching direction in several diagrams. The diagram in Fig. 4 shows the operation of a complete reverse switching operation for a drive direction from right to left (n+1 → n), i.e. starting at a time corresponding to the lower scale and ending at zero at the far left. The switching position of the stepper switch 10 at the start of switching within a first period is illustrated in Fig. 6a. The first upper MSV circuit is closed, while the switch contact of the second vacuum switch TTF is open. The first MTF circuit is located in the corresponding second switcher, which is connected to the second circuit by a mechanical loop.

The invention provides that the second mechanical switching element TTF is not switched at an early stage but remains in the second switching position shown in Figure 6a (as well as in Figures 6b to 6f), which can be achieved only by at least partially decoupling the switching motion of the second mechanical switching element TTF from the switching movements of the other switching elements or vacuum tubes by means of the free-running element shown in Figures 1 to 3.

After a definable time, the second vacuum tube TTV is closed (see Fig. 6a), after which the first vacuum tube MSV is opened (see Fig. 6b). This opening of the first vacuum tube MSV takes place within a definable time after the start of the switch, as shown in Fig. 6b (Opening) and in Fig. 6c (MSV Open). In this switching state of the step switch 10 with the open vacuum tube MSV and the closed second vacuum tube TTV and in the second switching position of the second mechanical element MSV shown in Figures 6a to 6 the flow of the ILTF in the loading loads in the manner shown in Figures 6c and 6c can be described as the first vacuum tube TTF, and the second vacuum tube LTF, respectively, can be described as the second vacuum tube TTF, and the second vacuum tube LTF can be described as the second vacuum tube TTF, in the manner shown in Figures 6c and 16c.

After a further short period, the first mechanical switch element MTF is switched (Fig. 6c, Fig. 6d), preparing for the closure of the first vacuum switch tube MSV (Fig. 6d, Fig. 6e) and the subsequent opening of the second vacuum switch tube TTV (Fig. 6e, Fig. 6f). The load current IL thus flows again from the first winding-up loop 12 of the step transformer 16 through the first mechanical switch element MTF and the closed first vacuum switch tube MSV to the Lastable LATF, as shown in Fig. 6f. Finally, the second cycle of reversal is shown below, where the mechanical switch element TTP is switched back to the first cycle of the first cycle TTF. This is shown in Fig. 6a.

The circuit delays of the second mechanical switching element TTF shown herein are an implementation of the general idea of the invention, which is to achieve the desired shock resistance or a0 resistance by means of a suitable free-flow element in the step switch, by means of a down-loaded switch of the mechanical switching element TTF in one of two load branches, regardless of the direction of the respective switch.

The illustration in Fig. 7 shows a variant of a step switch with two additional switches or MC main contacts, in addition to the mechanical MC contacts on the switch side and on the switch side. These MC main contacts or additional switches each supply a DC current. They are also switched so that the MC2 switch on the switch side opens before all other switch elements (MSV, TTV, MTF, TTF) and the MC2 switch on the switch side closes after all other switch elements.

Claims (7)

1. Tap changer (10) for uninterrupted changeover between at least two winding taps (12, 14) of a tapped transformer (16), which has a rotatable switching shaft (22), with which actuating elements (24) for a plurality of actuation phases for mechanical switching elements (MTF, TTF) or vacuum switching tubes (MSV, TTV) are associated, wherein the actuating elements (24) are respectively associated with concentric cam discs (28), which are rotatable by the switching shaft (22), with end-face or circumferential contours, projections, lobes (30) or the like, characterised in that a freewheel element (34) is provided, which is formed from a gate guide (36), which is of circularly segmental shape and arranged concentrically with respect to the switching shaft (22), for a circularly annular entrainer of the corresponding cam disc (28) as well as from a sleeve-like separating element (38) so that the rotational movement of the switching shaft (22) and the cam disc (28) mounted thereon are decoupled from one another in such a manner that the switching instants figured by at least one cam disc (28) are delayed in terms of time, independently of the rotational direction of the switching shaft (22), relative to the rotational movements of the remaining cam discs (28) or the remaining actuating elements (24).
2. Tap changer according to claim 1, in which a freewheel element (34) for phase displacement of the switching instant in dependence on the respective rotational direction of the switching shaft (22) is associated with at least one of the switching means or actuating elements (24) and the cam disc (28) associated therewith.
3. Tap changer according to claim 1 or 2, in which the sleeve-like separating element (38) of the freewheel element (34) is fixed in position relative to the rotatable switching shaft (22) and the can discs (28).
4. Tap changer according to any one of claims 1 to 3, in which a load branch with at least two parallel paths (18, 20), which each comprise a series arrangement of at least one vacuum switching tube (MSV; PTV) and at least one mechanical switching element (MTF; TTF, 32), is provided, wherein a resistance (R) arranged in series with the respective vacuum switching tube (TTV) and the mechanical switching element (TTF) is associated with at least one path (18, 20), wherein the at least two winding taps (12, 14) can be variably coupled together/or acted on by a load diverter (LA), wherein the total of at least two vacuum switching tubes (MSV; TTF) and at least two mechanical switching elements (MTV, TTF) are switchable in common with a defined offset in time relative to one another in respectively different switching directions, and wherein at least one of the mechanical switching elements (TTF) has a switching or trigger instant displaced to follow in time relative to the remaining switching elements (MTF) or vacuum switching tubes (MSV, TTV) and independently of the switching direction.
5. Tap changer according to claim 4, in which the switching or trigger instant displaced to follow has a defined spacing in time from the remaining switching or trigger instants of the further mechanical switching elements (MTF) and vacuum switching tubes (MSV, TTV).
6. Tap changer according to claim 4 or 5, in which the mechanical switching element (TTF) having a switching or trigger instant displaced to follow in time switches subsequently to all remaining switching elements (MTF) and vacuum switching tubes (MSV, TTV).
7. Tap changer according to any one of claims 1 to 6, in which additionally present on each of the sides switching on and switching off is a respective mechanical contact (MC) conducting a permanent current, of which the contact on the side switching off opens before all remaining switching elements (MSV, TTV, MTF, TTF) and the contact on the side switching on closes after all remaining switching elements.