The invention relates to a selector with a preselector which is used in on-load tap changer. The on-load tap changers are built into the power transformers and regulate their high voltage under load, i.e. without interrupting the power supply to consumers. The selector with a preselector is for a three-phase application for a star connected transformer's windings.

BACKGROUND ART

Some known selectors are compared which have a central insulating tube with arranged in tiers current-carrying rings and related with them conductors, passing inside the central tube upward to the oil container of the on-load tap changer. The preselector is mounted sideways on the selector.

There is known a three-phase selector with a preselector (1) comprising an insulating central tube on which six conductive rings are stacked in tiers, one even and one odd for each phase. Each ring is connected to a conductor and the six conductors are located inside the tube. They pass vertically up to the bottom of the oil container, in which a power switch is built in. Between the upper housing and the lower flange are mounted columns of insulating strips, on which are fixed stationary contact elements. There are two Geneva wheels in the upper housing, located one above the other concentrically to the central tube. The Geneva wheels rotate in tiers of a double transfer element with two pairs of drive rollers, located 180° from each other. The Geneva wheels rotate in two consecutive steps at a certain angle depending on whether 10 positions or 12 positions or more are required. Therefore, the Geneva wheels and double transfer element are different for the specific number of positions. A drive column is fixed to each Geneva wheel, consisting of insulating strips, carrying movable contact bridges that connect the current-carrying rings to the fixed contact elements. The preselector is mounted sideways on the selector. It contains two insulating bars, carrying fixed contact elements and drive strips with movable contact bridges. The insulating columns are fastened together by profiled plastic clapboard. i The disadvantage of this selector with a preselector is that the Geneva wheels are large in size and are complicated for production. The Geneva gear may be blocked due to incorrect dimensions. For a different number of situations, Geneva gears are different, making production difficult. The disadvantage is that the entire supporting structure requires strong and straight insulation strips to ensure stability. Another disadvantage is that the stationary even and odd contact elements are not arranged in succession, thereby the insulating distance requirements increase. The disadvantage is that the design of the preselector is complicated.

Another selector with a pre-selector (2) is also is known which also contains a central tube with contact rings and conductors, passing vertically therein, and a cage of insulating strips, attached between the upper housing and the lower flange. Fixed contact elements are mounted on the strips, which are arranged in succession here. In the case, there is a Geneva gear made of two Geneva wheels with large dimensions and a complicated configuration in order to make the rotation in two different angles. The movable contact bridges are mounted on profile insulating carriers, sliding on contact rings having a special profile. They are moved by vertical columns. The preselector is located laterally to the selector and has a complex construction with large contact nodes.

The disadvantage of this selector is that it has large overall dimensions and a complex construction. The Geneva gears are large and complex and require very precise machining. They are different sets for different variants, which makes production difficult. Another disadvantage is that the preselector is also with a complicated construction and with relatively large dimensions.

A selector (3) is also known wherein the fixed contact elements are mounted as sectors which are cut out from an insulating glass-growing cylinder. On the central insulating tube are arranged even and odd contact rings, and six conductors are passing upwards to the bottom of the oil container. The Geneva gears and preselector are not shown, but it is assumed to be similar to those of (1). The insulation sections are fixed in the upper housing and the lower flange. The contact bridges are driven by vertical columns of insulating bars. A disadvantage of this selector is that the stationary contact elements are not arranged sequentially, which degrades the isolation coordination. Other disadvantages are similar to those of (1).

DISCLOSURE OF INVENTION

The task of the invention is to provide a selector with preselector for an onload tap changer with a compact, simple and stable construction. To have a central tube with a stacked six six-conductor rings, arranged in tiers and connected by six wires passing axially inside the tube. The Geneva gears to be simplified and unified for 10, 12 and 14 positions. The carriers of the movable contact bridges to be stable with a small number of simplified elements, providing work with successively stationary contact elements. The preselector to be located sideways the selector and to have simple and stable construction.

The task is solved with selector with preselector for an on-load tap changer, containing an upper metal flange and a lower metal flange with cage-like segments made of insulating material and fixed between them with attached even and odd contact elements. In the centre of the selector there is an insulating tube with even and odd current-carrying rings arranged in tiers to it, connected to conductors passing vertically upwards in the tube. A body is mounted above the upper shield, with a drive system with Geneva Cross mechanisms located therein, connected to vertical driving columns carrying movable current-carrying collector fingers. Laterally on the selector is located a preselector with movable and fixed contact elements.

According to the invention the drive system consists of a double transfer element, fixed to a driving shaft. On the one side of the double transfer element there are two pins with rollers located at a certain angle between them. On the other side of the double transfer element there are also two rollers located oppositely at 180°. An even unit of a Geneva Cross wheel and a gear wheel are mounted on a parallel vertical spindle and a similar odd unit of a Geneva Cross wheel and a gear wheel are mounted thereunder. The gear wheel from the even unit is engage with a larger even gear wheel mounted coaxially on the upper end of the central tube. On the extended cylindrical end this gear wheel is mounted an odd gear wheel with the same number of teeth which is engaged with the gear wheel of the odd block.

To the extended cylindrical end of the even large gear wheel is fixed an even, driving insulating segment with profile-cut lugs, on which are mounted carriers with even collector fingers with contact springs. To an extended segment of the odd large gear wheel is fixed an odd, driving insulating segment with profile-cut lugs, on which are mounted carriers with odd collector fingers.

Each one of the Geneva Cross wheels of the two units has six channels with an angle between them of 60°. The angle between the two pins with rollers of the double transfer element is similar. It meets the requirement, on rotation of the double transfer element through 180°, the Geneva Cross wheel rotates smoothly and continuously in two steps through a total of 120°.

In the case of selectors with 10, 12 and 14 positions, the double transfer element and the Geneva Cross wheels do not change and attainment of the corresponding angles of rotation at one switching of 72°, 60° and 51°26' is achieved by changing the preliminary ratio between the gear wheels. In that the inter-centric distance is the same.

The large even and odd gear wheels are supported coaxial ly on the central tube by rolling-contact bearings.

In a different number of positions, or respectively a different number of fixed contact elements per phase, there may be a different number of insulating segments, but for 12 positions it is recommended for the segments to be four in number each with three contact elements. For 14 positions it is recommended to be four of which two segments each with three contact elements and two segments each with four contact elements. For 10 positions a good option is five segments each with two contact elements. The arrangement of the insulating segments is to be such that there is always oil insulation between the first and the last contact element by number.

The driving of the preselector is characterized by the fact that on the spindle of the two units with a gear wheel and Geneva Cross wheel is mounted Geneva Cross sector. The sector is connected on one side with a pin with a roller, mounted on a disc attached to the large odd gear. The Geneva Cross sector on the other site is connected to a gear ring on an arm, mounted on the driving shaft on the double transfer element. The arm is connected to vertical insulating strips carrying movable collector fingers of the preselector.

An advantage of the selector with preselector for a power step voltage regulator, according to the invention is that it has a simplified, small-sized and lightweight construction. Another advantage is that the Geneva wheels are the same in a different number of positions. Generally, they are made more difficult than the toothed wheels for which there are specialized high performance machines.

It is also advantageous that the large gears are mounted coaxially on the central tube by rolling bearings due to the fact that their outer diameters are relatively small. This guarantees to stable attachment of the driving sectors and their slight rotation. The sectors are so shaped that gripping the movable contact fingers does not require additional elements. A linear arrangement of the fixed contact elements is guaranteed and between the first and the last number of contact elements there is oil insulating distance. As an advantage it can also be considered that the selector driving system is simple and stable.

BRIEF DESCRIPTION OF THE DRAWINGS

On example embodiment of selector with preselector for a power step voltage regulator is shown in the attached figures, of which:

Figure 1 is a longitudinal section through the selector and the preselector.

Figure 2 is a cross-sectional view over the Geneva and toothed gears.

Figure 3 is a cross-sectional view over of the drive mechanisms and the preselector.

Figure 4 is a cross-sectional view over of the contact systems.

Figure 5 is a longitudinal sectional showing front view of the carriers of the movable contact bridges. EMBODIMENTS OF THE INVENTION

Between an upper metal flange 1 and a lower metal flange 2, a number of segments 3 cut-out of the insulating cylinder and arranged as a circular cage. On the segments 3 there are mounted in tiers odd contact fixed elements 4 and even contact fixed elements 5. On a flange 1 is located a body 6 in which are placed the driving mechanisms of the selector. In the center of the selector an insulating tube 7 is attached above to the body 6 and below to the lower flange 2, around which are mounted one under another the odd current-carrying rings 8 and even current-carrying rings 9. The central tube 7 is connected to the body 6 by a ring 10 and to the lower flange 2 by an axle 11 with a flange 12. Inside the central tube 7 are located six conductors 13, three of which are connected to the odd current-carrying rings 8 and three to the even current-carrying t rings 9. The conductors 13 are passing up into the central tube 7 and over the body 6, they have bent edges 14 through for connecting by a known manner to a not shown oil container and a to a power diverter switch.

On the ring 10 is mounted an even drive gear wheel 16 by a roller bearing 15, connected with its cylindrical end 17 to an even driving insulating segment 18. An odd gear wheel 19 is mounted on the end 17, the extended segment 20 of which is connected to an odd driving isolating segment 21. The two segments 18 and 21 have at their lower end arms 22 and 23, by which they are mounted 24 on the axis 11. The two gear wheels 16 and 19 are rotated in shifts at a certain angle with a double transfer element 25 through two blocks 26 and 27, comprised of one Geneva cross wheel 28 and one gear wheel 29. The double transfer element 25 has four pins with rollers 30, two on one side and two on the other. It is attached to a drive shaft 31 which rotates in a known manner by a not shown free-wheeling clutch. The two blocks 26 and 27 are mounted on a spindle 32. The conductors 13 are fortified in their upper part by an insulating plate 33 with fixed channels. It is mounted on top of body 6.

The even insulating segment 18 has profile-cut lugs 34, on which are attached carriers 35 with mounted on them contact fingers 36 with contact springs 37. In a similar way, the odd insulating segment 21 has lugs 38 on which are also mounted such carriers 35 with contact fingers 36 and contact springs 37. In the example under consideration there are 12 pes stationary contact elements arranged sequentially in a clockwise direction. The odd contact elements 1, 3, 5, 7, 9, 11 occupy the upper row of each phase, but the even 2, 4, 6, 8, 10, 12 (K) are arranged under them. There are selectors in which the even contact elements are on the top and the odd ones are under them, but this does not change the essence of the invention.

The pre-selector, executed as a reverser is located sideways to the selector. It has an upper sector 38 and a lower sector 39, between which an insulating segment 40 is attached on which are mounted two stationary contact elements 41 and 42 per phase. To the end-contact elements 5 are held T-shaped current-carrying elements 43. With them and alternatively - with contact elements 41 and 42 contacts contact fingers 44 with contact springs 45. The fingers 44 are attached to carriers 46 mounted on insulating strips 47 which are fixed above to an arm with a gear ring 48 and below - to an arm 49 mounted to the lower sector 39. The arm 48 is mounted on a shaft 31 and its gear ring is engaged with a gear ring of the Geneva cross sector 50, mounted on a spindle 32. A disc 51 with a pin and with a roller 52 is mounted to the segment 20 of the odd gear wheel 19. The disc 51 rubs with his rim on the respective arm of the Geneva cross sector 50 and locks it in a normal working position.

The action of the selector with the preselector is as follows. In the drawings, the even movable contact fingers 36 connects the even contact rings 9 with a stationary contact element 5, which is situated on the twelfth position associated with the preselector. The selector is for twelve positions i.e. it has six odd contact elements 4 and six even contact elements 5 per one phase. The odd moving contact fingers are on the first position. On switching from the eleventh to the first position, the preselector was actuated, and the contact fingers 44 passed from the contact element 42 to the contact element 41. The current already passes through the contact circuit of the first position. On reversing motion, due to the presence of a free-wheeling clutch, shaft 31 rotates to a small angle in the opposite direction clockwise and the selector contact systems remain stationary but switch only the power diverter switch. The current already passes through the contact elements of the twelfth position. On further rotation of the shaft 31 by 180° in the opposite direction clockwise, the double transfer element 25 turns on the Geneva cross wheel 27 of an odd gear in two successive steps and as a result of which, the gear wheel 19 with a disc 51 are !stated in the opposite direction clockwise at 30°. The odd contact fingers go from first position to eleventh. A pin with roller 52 inverts the Geneva cross sector 50 and the contact fingers 44 of the preselector pass from the contact element 41 to the contact element 42.