RU2221301C2 - Loading selector - Google Patents

Abstract

FIELD: radio electronics. SUBSTANCE: proposed loading selector specifically designed for instance to change over control winding taps in transformer incorporating provision for stepped voltage regulation functions to set changeover vacuum cells and to control them under all operating conditions. Fixed stepping contacts mounted inside insulating cylinder are arranged over circumference in separate horizontal plane for each phase. This insulating cylinder accommodates closing shaft free to rotate therein. Closing shaft has contact holder for each phase mounted for displacement, and two change-over vacuum cells are installed on this shaft in vertical position . EFFECT: reduced space requirement and enhanced safety and reliability afforded by selector for change-over vacuum cells. 8 cl, 6 dwg

Description

 The invention relates to a load selector for transformers with step voltage regulation according to the restrictive part of the claims.

 Similar load selectors are already known from DE 3833126 C2.

 Load selectors in transformers are used to switch the taps of the regulating windings of transformers under voltage and thereby to purposefully equalize voltage changes. Due to the rejection of the generally accepted separation of the selector and the load switch, load selectors can be manufactured and applied at lower cost. In the process of switching in the load selector at different contacts there are electric arcs. To avoid this, the aforementioned DE 3833126 C2 proposes a load selector, in which in each switched phase on the contact carrier there are two movable contacts rotating simultaneously with each other, and one vacuum switching cell connected also to each of the two movable mechanical switching contacts is also installed contact holder. The fixed step contacts of the load selector switched on by rotary mechanical switching contacts are mounted along a concentric circle in the wall of the insulating cylinder. Vacuum switching cells are installed on the contact holder in a horizontal position and are controlled or driven by a cam track placed on another concentric circle, which is mounted in the axial direction between the circle of the fixed stepped contacts and the additional contact ring.

 This known load selector has several disadvantages. Firstly, due to the horizontal position of the vacuum switching cells on the common contact carrier, an undesirably large diameter of the insulating cylinder and thereby the load selector is created. Vacuum switching cells have, depending on their switching ability, certain minimum overall dimensions, in particular, also a considerable length. In addition, pushers also protrude from the vacuum switching cell in the longitudinal direction. Therefore, it is obvious that the common contact carrier must have radial dimensions depending on the overall dimensions of the vacuum switching cell and actuation means, which generally determine the diameter of the load selector. Apart from these general problems of overall dimensions, a particular drawback in the horizontal design of vacuum switching cells according to the prior art is that when filling the load selector with oil, air remains on the upper bends of the bellows of the vacuum cells, which is not completely replaced by oil. This leads to the fact that when the vacuum switching cell is activated, an uneven load is created on the corresponding bellows of the vacuum cell, as a result of which there is a danger of its destruction. Such a finding of residual air in the section of the bellows of the vacuum cell can be reliably excluded in a horizontal position only by filling the load selector in a vacuum, however, such filling under vacuum according to the performed tests is not feasible on site or is feasible only with unacceptably high costs. In addition, it should be borne in mind that the load selectors as a whole, as a rule, have large axial longitudinal dimensions, that is, a significant overall height. The fixed step contacts of the individual switching phases are mounted on top of each other around the circumference of the means for actuating the rotating switching shaft inside the load selector, on which the contact holders of each phase are located, in the head of the load selector, as well as the means for placing this switching shaft in the lower part of the load selector also require space, so that in general, as explained, the load selector has increased longitudinal dimensions. The consequence of this is that the switching shaft has a rather large length in its inner part. Such switching shafts are usually made of fiberglass or other insulating material, of course, metal switching shafts have also been proposed. Contact carriers in known load selectors are mounted on a switching shaft by means of fixing screws.

 DE 4414941 describes another embodiment of the stationary mounting of the contact holder on the switching shaft using a clamping flange. Due to tolerances, different coefficients of thermal expansion of the oil reservoir and the switch sector, bends, etc. in known load selectors, problems may arise when interacting with structural elements installed on individual contact carriers, in particular vacuum switching cells, with actuating means installed around the circumference, especially because pushers of vacuum switching cells usually have only a relatively small linear path of action.

 The objective of the invention is to eliminate these drawbacks and create a load selector of the appropriate type, which allows for compact installation of vacuum switching cells and their safe and reliable control in all operating modes.

 The problem is solved by means of a load selector for transformers with step voltage regulation for continuous switching between the taps of the regulating winding of a transformer with step voltage regulation, and the load selector has an insulating cylinder as a housing, fixed step contacts electrically connected to the taps are placed inside the insulating cylinder by circles in a horizontal plane separate for each phase, in the center of the insulating cylinder there is a rotating switching shaft, which also has a rotating contact holder for the fixed step contacts of each phase, each contact holder has at least two mechanical contacts configured to contact the fixed step contacts of the corresponding horizontal plane, at least one of the contacts on each contact carrier are directly electrically connected to the first vacuum switching cell and at least one of the following stations at each contact carrier is electrically connected via an intermediate resistor with a second vacuum switch cell, wherein the respectively other side of the two vacuum switching cells on each contact carrier is electrically connected respectively to one tap of the load. According to the invention, all contact holders are mounted movably on the switching shaft independently of each other, and accordingly, both vacuum switching cells are mounted vertically on the corresponding contact holder so that their pushers are located mainly in the axial direction.

 In the load selector in accordance with the invention, the vacuum switching cells are mounted on the contact holders in a vertical position. Contact holders have sliding contacts, they pass exactly along the rollers in the outlet ring. The vacuum adjusting windings are controlled by cams in this outlet ring. Knife sliding contacts, which are installed in the contact holder, divert current along the outlet ring.

 Other blade sliding contacts on the contact block provide current. According to a further feature of the invention, contact carriers are each mounted for movement on a switching shaft.

 A particular advantage of the load selector in accordance with the invention is, along with the small overall dimensions, that all the forces for actuating the vacuum switching cells, as well as the contact forces, are axially supported by a stable oil reservoir through a discharge ring and fixed contacts. Due to this, the radial load on the switch rods is prevented, in particular their deflection and the resulting change in the duration of control of the vacuum switching cells and a decrease in contact forces. Due to the contact holder installed with the possibility of rotation or axial movement, which passes in the axial direction through the outlet ring, the switching process is also provided when changing the height due to tolerances and different coefficients of thermal expansion of the oil tanks and the switch rod.

The invention is explained in more detail below as an example using the drawings, which show:
FIG. 1 is a first embodiment of a load selector in accordance with the invention with a partial section, side view.

 FIG. 2 is a sectional view of a contact carrier of a given load selector, top view.

 FIG. 3 is a second embodiment of a load selector in accordance with the invention, in partial section, side view.

 FIG. 4 is a schematic illustration of a circuit underlying a load selector in accordance with the invention.

 5 is the same modified circuit.

 6 is a typical switching frequency of the load selector in accordance with the invention.

 The load selector shown in FIG. 1 shows an embodiment of the invention with the contact holder 3 mounted on the switching shaft 2 and rotatable, and the vacuum switching cells 27, 28 mounted vertically on it.

 The load selector consists of an insulating cylinder 1, and in the center and passing along through the insulating cylinder 1, a switching shaft 2 is installed, preferably of insulating material. The turning shaft 2 is made in a known manner with the possibility of rotation; Maltese drives that are not shown are usually used for this. The support of the switching shaft 2 in the lower part of the insulating cylinder 1 is also not fully depicted. On the switching shaft 2 there is fixed in each plane actuated fixed step contacts 16, which will be explained in more detail below, the contact holder 3 mounted for rotation in the bearing bracket 4 on the switching shaft 2. The bearing bracket 4 is fixed with screws 4.1, 4.2 on the switching shaft 2. The contact holder 3 consists of a support 5, a support housing 6 and a contact housing 7. The individual components of the contact carrier 3 are interconnected by screws 8, 9. For its part, the contact housing 7 consists in the shown embodiment of the upper part 10 of the contact housing and the lower part 11 of the contact housing; both parts are also interconnected by screws 12. The contact housing 7 can also be made integral. The support 5 has a support portion 13 into which a bolt 14 is inserted, which provides a connection to the bearing bracket 4 and thereby rotational movement. The bolt 14 is fixed by the transverse pin 15. In general, due to this, the entire contact carrier 3 as an assembly can rotate around the bolt 14 and thereby relative to the fixed switching shaft 2. Fixed contacts are installed in the wall of the insulating cylinder 1 for each of the switched phases in a separate plane 16, which are in electrical connection with the taps of the regulating winding of the transformer with step regulation of the voltage to be switched. The fixed stepped contacts 16 are connected via the respective contacts 17, 18. The contacts 17, 18 are mounted on the contact holder in a horizontal direction next to each other so that when the switching shaft 2 and thereby the contact holder 3 are rotated, respectively, one of the contacts 17, 18 reaches the neighboring a new fixed step contact 16 before the other of these contacts moves away from the previous fixed step contact. Contact 17 acts in this case as a switching contact, the other contact 18 as an auxiliary contact.

 Figure 2 shows the placement of both contacts 17, 18 on top of each other on the contact carrier 3 and the interaction with the corresponding stationary step contact 16. In the embodiment shown in figure 2, the contact 17, acting as a switching contact, for the greatest current carrying capacity made double, that is, consisting of two electrically interconnected parts 17A, 17b. Each of the contacts 17, 18 consists of the upper part 17.1, 18.1, as well as the lower part 17.2, 18.2 of the contact. In the particular embodiment shown in FIG. 2, contact 17 therefore consists of a total of 4 parts, namely the two upper contact parts 17.la and 17.1b and the two lower contact parts 17.2a and 17.2b. The dual execution of the contact 17, acting as a switching contact, is suitable for various embodiments, but is not required for the invention. Both the upper parts 17.1, 18.1, and the lower parts 17.2, 18.2 of each of both contacts 17.18 are each mounted rotatably around separate centers of rotation 19, 20, 21, 22 on the contact housing 7. The springs 23, 24, 25, 26 they are pressed against each other in the direction to the stationary step contact 16 located between them in the on state.

 Each upper contact part 17.1, 18.1 and each other corresponding contact part 17.2, 18.2 press with a certain force on both sides the corresponding included fixed step contact 16. Due to the described arrangement around separate centers of rotation 19, 20, 21, 22, it is possible to run onto fixed step contacts 16. In FIGS. 1 and 2, only contact parts, centers of rotation and springs located in the front and top view are visible. Then, on each contact holder 3, respectively, the upper and lower mounting clamps 29, 30, 31, 32 are fixed with two vacuum switching cells 27, 28 so that the bellows 33, 34 and the pushers 35, 36 of the vacuum switching cells 27, 28 reach the upper part. Also, from the parts described in FIG. 1, only front parts are visible. To actuate the pushers 35, 36 of the vacuum switching cells 27, 28, two levers 37, 38 are used, each having a roller axis 41, 42 with a control roller 39, 40 at their free end. At their other free ends, they act on the pushers 35 described above. 36. Both levers 37, 38 are rotatably mounted about centers of rotation 43, 44; a common center of rotation may also be provided. For their part, the control rollers 39, 40 of both levers 37, 38 interact with the control ring 45 having an upper control circuit 46 and a lower control circuit 47. The control ring 45 extends radially along the inner wall of the insulating cylinder 1. In FIG. 1, it can be seen that the first the control roller 39 interacts with the lower control circuit 47, that is, rolls along it and in the same way, the second control roller 40 rolls along the upper control cam 46. Both control cams 46, 47 thereby serve to drive the vacuum switching contacts 27, 28, while when the corresponding control roller 39, 40 runs onto the cam, the corresponding lever 37, 38 rotates around the center of rotation 43, 44 and thereby actuates the corresponding lever 35, 36 of the vacuum switching cell 27, 28.

 Further, on the inner side of the insulating cylinder 1, there is a discharge contact ring 48, which has an outwardly connecting element 49 and serves to discharge the load. In the simplest way, the control ring 45 and the outlet contact ring 48 can be combined into one assembly of conductive material, as shown in FIG. For its part, the diverting contact ring 48 also interacts with a mechanical diverting contact 50 mounted on the contact carrier 3 and, like the contacts 17, 18 described above, consists of an upper part 50.1 and a lower part 50.2 of the diverting contact. Both of these parts 50.1, 50.2 of the outlet contact are likewise separately mounted with the possibility of rotation around the centers of rotation 53, 54 and are pressed by the other springs 51, 52 to each other so that they with some force enclose the outlet of the contact ring 48.

 Finally, the contact carrier 3 has two more rollers 55, 56, which are rolled on both sides along the outlet contact ring 48 and thereby lead to the entire contact holder 3. Due to the described arrangement, any tolerances of any kind and, in particular, the deflection of the inclined shaft of large length can be compensated. The contact carriers 3, which are mounted with the possibility of rotation around the switching shaft 2, in any case are guided definitely through the outlet contact ring 48, therefore, despite the tolerances described, the control rollers 39, 40 are precisely controlled and thus the vacuum switching cells 27, 28 are actuated despite their small management paths.

 Figure 3 shows the following embodiment of the load selector according to the invention. Moreover, in contrast to the example explained above, the contact carrier 103 is mounted not rotatably, but with the possibility of longitudinal movement. Inside the insulating cylinder 101 there is also a centrally mounted switching shaft 102, on which a contact holder 103 moving in the longitudinal direction is mounted. The longitudinal movement is provided by the guide 104. In this case, two vacuum switching cells, of which only the front vacuum switching cell 105 is shown, are installed vertically. In each plane there are also fixed stepped contacts 106 around the circumference in the wall of the insulating cylinder 101, they are also connected from the switching contact and the auxiliary contact, in which figure 3 shows only the upper part 107.1 and the corresponding lower part 107.2 of the contact. Similarly, also inside the insulating cylinder 101 is a discharge contact ring 108, which is surrounded by a discharge contact, also consisting of an upper part 109.1 and a lower part 109.2 of the discharge contact. In this case, the direction of the contact holder is carried out by a roller 110, which moves in the circuit of the outlet contact ring 108. The vacuum switching cells are also controlled by two levers 115, 116, each having control rollers 113, 114 at their free ends, also rolling along the lower control loop 111 or the upper control circuit 112 and thereby actuating the pushers of the vacuum switching cells, of which only the pusher 117 of the front in the direction of view is shown Kuhn switching cell 105.

 In FIG. 4 schematically depicts a circuit implemented by a load selector according to the invention. The electrical connections between the contacts 17, 18 with the vacuum switching cells 27, 28 and from them also with the discharge contact 50 and thereby the discharge contact 48 in figure 1, which corresponds to this image, are not shown.

 In FIG. 5 shows a diagram in which, as shown in FIG. 2, the switching contact 17 consists of two adjacent contact parts 17a, 17b. And in figure 2, corresponding to this image, electrical connections are only indicated. It can be seen that the principle of operation is not different, that is, using both the circuit in Fig. 4 and the circuit in Fig. 5, the same switching process is achieved.

 Such an example of the achieved switching process is shown in FIG. 6.

 This shows the load selector with different switching steps. Such a load selector with different switching steps is already known in principle from EP 0160125. The distance between the centers of the fixed step contact located on the main winding and the two fixed step contacts adjacent to it is greater than the distance between the centers of the remaining fixed step contacts. This allows the use of a load selector on transformers with high rated voltages; due to this, it is possible to achieve a higher ultimate impulse voltage withstand the insulation. In this publication, fixed stepped contacts made in different ways also suitable for such a load selector have already been disclosed.

 Regardless of this, it is particularly preferable to make the fixed stepped contacts 16 not curved, as is customary in the prior art, that is, parallel to the curvature of the insulating cylinder 1, but straight, as shown in FIG. While according to the prior art, the upper and lower parts 17.1, 18.1; 17.2, 18.2 of the contacts are constantly rolled along the same path of the stepped contacts 16, by making the contacts straight, it is achieved that other points of the surface of the fixed stepped contacts 16 are always in contact, which reduces their wear.

Claims (8)

1. Load selector for transformers with step voltage regulation for continuous switching between the taps of the regulating winding of the transformer with step voltage control, the load selector having an insulating cylinder as a housing, fixed step contacts electrically connected to the taps are placed inside the insulating cylinder around a circle in a separate for each phase of the horizontal plane, in the center of the insulating cylinder there is a rotating switching a shaft having also for rotating step contacts of each phase a rotating contact carrier, each contact carrier has at least two mechanical contacts configured to contact fixed step contacts of the corresponding horizontal plane, at least one of the contacts on each contact carrier directly electrically connected to the first vacuum switching cell and at least one of the next contacts on each contact holder it is connected through an intermediate resistor to the second vacuum switching cell, while the other side of both vacuum switching cells on each counter-holder is respectively electrically connected to one load tap, characterized in that all contact holders (3) are mounted movably on the switching shaft (2) independently from each other and, accordingly, both vacuum switching cells (27, 28) are mounted vertically on the corresponding contact holder (3) so that their pushers (35), (36) are located married mainly in the axial direction. 2. The load selector according to claim 1, characterized in that each contact carrier (3) is mounted on the switching shaft (2) with the possibility of rotation around the center of rotation. 3. The load selector according to claim 1, characterized in that each contact carrier (103) is mounted on the switching shaft (102) with the possibility of axial longitudinal movement. 4. The load selector according to claim 1 or 2, characterized in that each contact (17, 18) consists of at least one upper part (17.1, 18.1) and one lower part (17.2, 18.2) of the contact and each part (17.1, 18.1; 17.2, 18.2) the contact is pressed against each other under the action of at least one spring (23, 24, 25, 26) so that when the fixed step contact (16) is turned on, it is mechanically surrounded on both sides and electrically closes. 5. The load selector according to one of claims 1, 2 or 4, characterized in that a control ring (45) is installed on the inner wall of the insulating cylinder (1) for each switching phase and thereby for each horizontal plane of the fixed stepped contacts (16) having an upper control circuit (46) and a lower control circuit (47), on each contact holder (3) for both vacuum switching cells (27, 28) there is a lever (37, 38) rotating around the center of rotation (43, 44), and each lever (37, 38) acts with one free end to the plunger (35, 36) of the vacuum switching cell (27, 28), and with its other free end it moves along one of the corresponding control loops (46, 47) so that depending on the spatial shape of the corresponding control loop (46, 47) the corresponding vacuum switching cell is activated (27, 28). 6. The load selector according to one of claims 1, 2, 4 or 5, characterized in that each load tap consists of a concentric outlet contact ring (48) mounted on the inner wall of the insulating cylinder (1), which has an outwardly directed connecting element ( 49) and which is made with the possibility of closing with a discharge contact (50) mounted on the corresponding contact holder (3), electrically connected to the corresponding vacuum switching cells (27, 28) on this contact holder (3). 7. The load selector according to one of claims 1, 2, 4-6, characterized in that each contact carrier (3) has two other rollers (55, 56), which are rolled on both sides along the corresponding outlet contact ring (48) so so that the corresponding contact carrier (3) is forcibly driven. 8. The load selector according to one of claims 1, 2, 4-7, characterized in that the control ring (45) and the outlet contact ring (48) of each phase are combined into one node.

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