GB2049287A

GB2049287A - Three phase load selector for a tapped transformer

Info

Publication number: GB2049287A
Application number: GB8011446A
Authority: GB
Original assignee: Maschinenfabrik Reinhausen Gebrueder Scheubeck GmbH and Co KG
Current assignee: Maschinenfabrik Reinhausen Gebrueder Scheubeck GmbH and Co KG
Priority date: 1979-04-03
Filing date: 1980-04-03
Publication date: 1980-12-17
Also published as: DE2913271C2; SE8002450L; DE2913271A1; GB2049287B; NL8001887A; JPS55134920A; SE436081B; ES8101305A1; FR2453481A1; NL185877C; FR2453481B1; ES490229A0; JPH0142121B2

Abstract

A three phase load selector for a tapped transformer has stationary tap contacts (4) arranged at the inside wall of a cylindrical oil vessel (1) in which an insulating tube (5) is journalled centrally and carries movable tap contacts (6) rotatable in steps by means of a Geneva wheel (7) and has three movable reversing contact bridges (14) around the tube (5) between the tap contacts (4,6) and the Geneva wheel (7) and respectively cooperating with stationary reversing contacts (15,17,19). The contact bridges (14) are actuable by means of a drive ring (12), at the upper end of the insulating tube (5) and having limited rotation relative to the tube. Each contact bridge (14) is arranged at the lower end of a dishlike insulating support (13), which extends in the longitudinal direction of the insulating tube (5) and is mounted the drive ring (12). Each of the contact bridges (14) is constructed to be U-shaped with its contact arms 16, 18 spaced in the longitudinal direction of the insulating tube (5). <IMAGE>

Description

SPECIFICATION Three-phase load selector for a tapped transformer The present invention relates to a three-phase load selector for a tapped transformer.

In such a load selector, the entire load selector, including for example, the reversing contacts, is subjected to an inspection at prescribed intervals.

The arrangement of the reversing contacts in the cylindrical oil vessel of the load selector has, however, apart from the advantage of accessibility on inspection, also certain difficulties as consequence, in particular in respect of the voltage loading at the reversing contacts. It is not, of course, desired to enlarge the circumference of the oil vessel beyond the dimension predetermined by the tap contacts because of the arrangement of the reversing contacts in the cylindrical oil vessel. On the other hand, it must of course be taken into consideration that the reversing contacts are not arranged in the clean oil of the transformer, but that they are present in th load selector oil which is gradually subjected to pollution.There is accordingly scope for improvement of such a load selector in order to attain a high voltage strength at the reversing contacts with optimum utilization of the limited space available, also taking into consideration the fact that the oil in the interior of the load selector is gradually subject to a pollution and sooting.

In accordance with the present invention there is provided a three-phase load selector for a tapped transformer, the load selector comprising an upright cylindrical oil vessel, a plurality of stationary tap contacts arranged at the interior wall of the vessel, a carrier shaft which is of electrically insulating material and which is mounted in the vessel to be rotatable about the axis thereof, a plurality of movable tap contacts arranged on the carrier shaft to be co-operable with the stationary tap contacts, first drive means arranged at one end of the vessel and operable to rotate the carrier shaft in steps, a plurality of sets of stationary reversing contacts arranged at the interior wall of the vessel, three contact bridging means mounted to be angularly displaceable around the carrier shaft and disposed between the first drive means and the tap contacts, each of the contact bridging means comprising a support, which is of electrically insulating material and which extends in the longitudinal direction of the carrier shaft, and a substantially U-shaped bridging contact, which is arranged at the end portion of the support remote from said one end to be co-operable with a respective set of the stationary reversing contacts and the arms of which are disposed spaced apart in the longitudinal direction of the carrier shaft, and second drive means arranged at the end of the carrier shaft nearest said one end and operable to angularly displace the contact bridging means.

With a load selector embodying the invention, not only is there good utilization of the available space but also the voltage strength at the movable part of the reversing switch may be increased. When the entire circumference of the oil vessel is available for the arrangement of the stationary reversing contacts, then the circumference is appreciably smaller at the location of the movable bridging contacts, since these after all are in the interior. Through the use of three supports for the bridging contacts, for example in a place of an insulating tube, and through the longitudinal arrangement of the supports and also the bridging contacts, the spacing between the bridging contacts for the phases of the reversing switch is increased and the possible formation of soot deposits on the supports is made appreciably more difficult.

An embodiment of the present invention will now be more particularly described by way of example with reference to the accompanying drawing, which is a schematic longitudinal section of a load selector according to the said embodiment.

Referring now to the drawing, there is shown a load selector consisting essentially of a cylindrical oil vessel 1, which is closed by a bottom flange 2 and by a lid 3 and which carries stationary tap contacts 4; an insulating tube 5, which is rotatably mounted centrally in the interior of the oil vessel, carries movable tap contacts 6 and is rotatable in steps by means of a Geneva wheel 7 through a drive mechanism 8 (not illustrated in detail); and a reversing switch 9, which is also arranged in the interior of the oil vessel 1 between the drive means and the tap contacts 4 and 6. The insulating tube 5 carrying the movable tap contacts 6 is on the one hand journalled on a bearing block 10 of the bottom flange-2 and on the other hand firmly connected with the Geneva wheel 7, which in turn is journalled at the lid 3.

Arranged at the upper end of the insulating tube 5 and around an intermediate member 11 is a drive ring 12 for the reversing switch 9, the ring being limitedly rotatable relative to the oil vessel 1 and to the tu be 5. The drive ring 12 carries three dishlike insulating material supports 13, which extend in the longitudinal direction of the oil vessel 1 and the tube 5, respectively, and which at their lower end each carry a respective contact bridge 14, constructed to be U-shaped, of the reversing switch 9. The drive ring 12 is rotatable through the required reversing switch step, in dependence on the setting of the Geneva wheel 7, in usual manner by means of an intermittent gear (not illustrated in detail).On this reversing switch step, the contact bridge 14, which has one end 16 wiping a stationary reversing contact 17 constructed in the shape of a sector, is moved so that its other end 18 is transferred from a first associated stationary reversing contact 19 to a second stationary reversing contact 15 arranged in the same plane as the contact 19. The stationary reversing contacts 15, 17 and 19 are fastened to the wall of the cylindrical oil vessel 1 exactly as the stationary tap contacts 4 and the entire circumference of the oil vessel 1 is thus available for the spacing between the individual stationary reversing contacts lying in one plane.

In order to achieve a high voltage strength between the movable contact bridges 14 of the revers ing switch, the three supports 13 are arranged so that free oil paths are present between the individual phases of the movable part of the reversing switch 9, whereby an electrical bridge formation between the phases is prevented in spite of the smaller circumference relative tote oil vessel 1. These supports 13 narrow towards their lower ends carrying the contact bridges 14 so that a relatively large oil path between the supports is provided in this region. An increased spacing between the movable contact bridges 14 is also achieved due to the fact that they extend in the longitudinal direction of the insulating tube 5. In order to make the formation of deleterious soot deposits on the supports 13 more difficult, these are provided with encircling ribs 20. As a restul, the voltage strength between the contact bridges 14 of the reversing switch 9 and the earth potential present at the drive part is improved.

Claims

1. A three-phase load selector for a tapped transformer, the load selector comprising an upright cylindrical oil vessel, a plurality of stationary tap contacts arranged at the interior wall of the vessel, a carrier shaft which is of electrically insulating material and which is mounted in the vessel to be rotatable about the axis thereof, a plurality of movable tap contacts arranged on the carrier shaft to be co-operable with the stationary tap contacts, first drive means arranged at one end of the vessel and operable to rotate the carrier shaft in steps, a plurality of sets of stationary reversing contacts arranged at the interior wall of the vessel, three contact bridging means mounted to be angularly displaceable around the carrier shaft and disposed between the first drive means and the tap contacts, each of the contact bridging means comprising a support, which is of electrically insulating material and which extends in the longitudinal direction of the carrier shaft, and a substantially U-shaped bridging contact, which is arranged at the end portion of the support remote from said one end to be co-operable with a respective set of the stationary reversing contacts and the arms of which are disposed spaced apart in the longitudinal direction of the carrier shaft, and second drive means arranged at the end of the carrier shaft nearest said one end and operable to angularly displace the contact bridging means.

2. A load selector as claimed in claim 1, the first drive means comprising a Geneva wheel.

3. A load selector as claimed in either claim 1 or claim 2, the second drive means comprising an annular drive member and the support being mounted on the drive member.

4. A load selector as claimed in any one of the preceding claims, wherein each of the supports is of curved cross-section in a direction transverse to said longitudinal direction.

5. A load selector as claimed in any one of the preceding claims, wherein each of the support reduces in breadth in a direction away from said one end.

6. A load selector as claimed in any one of the preceding claims, wherein each of the supports is provided with a plurality of ribs extending in a direction transverse to said longitudinal direction and disposed between the second drive means and the respective bridging contact.

7. Athree-phase load selector for a tapped transformer, the load selector being substantially as hereinbefore described with reference to the accompanying drawing.