GB2049288A

GB2049288A - A load selector

Info

Publication number: GB2049288A
Application number: GB8011923A
Authority: GB
Original assignee: Maschinenfabrik Reinhausen Gebrueder Scheubeck GmbH and Co KG
Current assignee: Scheubeck GmbH and Co
Priority date: 1979-04-12
Filing date: 1980-04-10
Publication date: 1980-12-17
Also published as: NL8002102A; GB2049288B; NL185878B; ES8101306A1; FR2454167A1; JPH0147885B2; JPS55140215A; DE2914928C2; NL185878C; SE436082B; FR2454167B1; HU178387B; ES490457A0; DE2914928A1; IN153245B; SE8002659L

Abstract

Switching apparatus of a load selector of a tapped transformer comprises stationary contacts (1, 2, 3, 4) arranged in a circle, movable contacts displaceable along the circle and control cams (11, 12; 21, 22; 31, 32; 41, 42) of insulating material disposed adjacent the stationary contacts (1, 2, 3, 4). The movable contacts comprise contact rollers (6, 7, 8) arranged to roll along the stationary contacts (1, 2, 3, 4) and at least one roller (61, 62, 71, 72, 81, 82) of insulating material arranged adjacent a respective one of the contact rollers (6, 7, 8). The control cams (11, 12; 21, 22; 31, 32; 41, 42) are so arranged that during a switching operation the rollers (61, 62, 71, 72, 81, 82) of insulating material run onto the control cams (11, 12; 21, 22; 31, 32; 41, 42) and cause the contact rollers (6, 7, 8) to lift from the stationary contacts (1, 2, 3, 4) before the contact rollers (6, 7, 8) are able to roll off the stationary contacts (1, 2, 3, 4). <IMAGE>

Description

SPECIFICATION A load selector The present invention relates to a load selector for a tapped transformer.

DE-PS 859 650 discloses a contact apparatus in which contact rollers, during a rolling-off operation from a stationary tap contact, roll over the edges of the stationary tap contact. These edges are thus subject to high and irregularwear particularly due to burning-off, whereby it is difficult to keep instant and location of the contact separation constant over the longest possible time. The irregular burning-off of th edges end the contact roller furthermore leads to difficulties during the running-up of the contact rollers onto the stationary tap contact or during the rolling-off from the stationary tap contact. For example, it can lead to canting of the contact rollers, whereby the tracking of the contact rollers is made more difficult.

According to the present invention there is provided a load selector for a tapped transformer, comprising stationary contacts arranged in a circle, movable contacts displaceable along the circle and control cams of insulating material disposed adjacent the stationary contacts, the movable contacts comprising contact rollers arranged to roll along the stationary contacts and at least one roller of insulating material arranged adjacent a respective one of each of the contact rollers, the control cams being so arranged that during a switching operation the roller of insulating material run onto the control cams and cause the contact rollers to lift from the stationary tap contacts before the contact rollers reach edge portions of the stationary contacts.

An embodiment of the present invention will now be more particularly described by way of example and with reference to the accompanying drawings in which Figure 1 shows a simplified plan view of an embodiment of the present invention, Figure 2 shows a side view from the interior of the circle, and Figure 3 shows a perspective view of the embodiment.

Referring to the accompanying drawings, a contact apparatus comprises several stationary tap contacts 1, 2,3 and 4, arranged in a circle, at the wall of a cylinder 5 and are provided with outer connections 14. Three contact rollers 6,7 and 8 are retained by a contact carrier 9, which in turn sits on a rotatable insulating tube 10 (Figure 3). Each contact roller 6,7 and 8 is journalled on a respective shaft 13, which are guided by the contact carrier 9. The contact rollers 6,7 and 8 are pivotable by means of the insulating tube 10 and the contact carrier 9 sitting thereat stepwise in a circle from one stationary tap contact 1 to the adjacent tap contact 3 and to the next tap contact 4 or conversely from the tap contact 1 to the tap contact 2 and so forth.A respective roller of insulating material 61,62,71,72,81 and 82 is arranged beside each contact rollers 6,7 and 8 on the same shaft 13 to both sides of the contact roller.

These rollers of insulating material during the individual switching steps run along a respective control cam 11,12; 21,22; 31,32; and so forth, which are arranged above and below each tap contact 1,2,3 and 4. These control cams 11, 12; 21,22; 31,32; 41 and 42 are so constructed that the middle contact roller6 in the illustrated operating setting bears approximately at the centre of a tap contact 1 against this tap contact, while both the other contact rollers 7 and 8 by means of their parallel rollers of insulating material 71,72 or 81, 82 respectively and by means of the control cams 11 and 12 have no contact with the tap contact 1. In this arrangement, the middle contact roller 6 acts as a main switching contact, while both other contact rollers 7 and 8 serve as resistance switching contacts.

The apparatus operates as follows when, for example, it is to be switched over from tap contact 1 to the adjacent tap contact 3: By rotation of the insulating tube 10, the contact carrier 9 is pivoted in the arrow direction through the required switching step. In this case, the contact roller 6 at first runs along the contact surface of the tap contact 1, while the rear contact roller 7 released by the control cams 11 and 12 likewise run up onto the contact surface of the tap contact 1. The front contact roller 8 at first runs by its upper roller of insulating material81 along the upper control cam 11 and then changes by means of the lower insulating material roller 82 from the lower control cam 12 onto the lower control cam 32 of the tap contact 3.Then, both the rollers of insulating material 61 and 62 of the middle contact roller 6 run up onto the control cams 11 and 12 so that the middle roller lifts off from the contact surface of the tap contact 1 and before it reaches the edge of this tap contact. Now, only the rear contact roller7 bears transiently against the tap contact 1, whereby a resistance is-switched in. While the rear contact roller7 rolls along on the contact surface of the tap contact 1, the rollers of insulating material 81 and 82 of the front contact roller8 run downwardly on the control cams 31 and 32 so that this contact roller 8 contacts the contact surface of the tap contact 3.The middle contact roller 6, guided transiently by means of its upper insulating material roller 61 and the upper control cam 11, again moves by means of its lower insulating material roller 62 onto the lower control cam 32 of the tap contact 3. In the further course, both the insulating material rollers 71 and 72 of the rear contact roller 7 then run against the control cams 11 and 12 of the tap contact 1 and thus separate this contact roller 7 from the tap contact 1, avoiding the separation at the edge of the tap contact. Then the rollers of insulating material 61,62 run downwardly on the control cams 31 and 32 of the tap contact 3 and the contact roller 6 contacts the tap contact 3.Finally, the rollers of insulating material 81 and 82 of the front contact roller 8 again run up onto the control cams 31 and 32 of the tap contact 3 so that the contact roller 8 no longer contacts the tap contact and so that the middle contact roller 6 gets into the middle position on the tap contact 3. The rear contact roller7 is prevented by means of its rollers of insulating material 71 and 72 and by means of the control cams 31 and 32 of the tap contact 3 from making contact with this tap contact. The switch-over operation is now completed.

The upper control cams are each time displaced relative to the lower ones. This serves to prolong the creep distances between the stationary tap contacts.

A certain transition of the control cams, for example 31 and 32, of the one tap contact, for example 3, to the control cams, for example 41 and 42, of the adjacent tap contact, for example 4, is required in order that the rollers of insulating material cannot remain hanging between the control cams of the adjacent tap contacts. On the other hand, control cams, which run through from one to the other tap contact, would however substantially shorten the creep distances between the tap contacts. Since the guidance of the rollers of insulating material in the transition phase can take place one above and then below through the displaced arrangement of the control cams 31 and 32 or 41 and 42, continuous control cams are avoided so that creep path prolongation is attained between the individual tap contacts.

An advantage of the above described embodiment is that contact separation does not take place at the edge of the stationary tap contact. The location of the contact separation is on the contact surface of the tap contact itself, whereby a greater burning-off volume can be utilized. Also the contact rollers are securely and reliably guided.

Claims

1. A load selector for a tapped transformer, comprising stationary contacts arranged in a circle, movable contacts displaceable along the circle and control cams of insulating material disposed adjacent the stationary contacts, the movable contacts comprising contact rollers arranged to roll along the stationary contacts and at least one roller of insulating material arranged adjacent a respective one of each of the contact rollers, the control cams being so arranged that during a switching operation the rollers of insulating material run onto the control cams and cause the contact rollers to lift from the stationary tap contacts before the contact rollers reach edge portions of the stationary contacts.

2. A load selector as claimed in claim 1, wherein a respective roller of insulating material is disposed at each axial end of each contact roller and a first plurality of the control cams is associated with the rollers of insulating material at one axial end of the contact rollers and a second plurality of the control cams is associated with the rollers of insulating material at the other axial end of the contact rollers, each control cam of said first plurality having a prolongation extending in a common circumferential direction, each control cam of said second plurality having a prolongation extending in a common respectively opposite circumferential direction, and the prolongation of adjacent ones of the control cams being so arranged as to augment each other in co-operation with a respective pair of said rollers of insulating material at the axial ends of the same contact roller in such a manner as to have the effect substantially of a continuous cam surface.

3. A load selector for a tapped transformer, substantially as hereinbefore described with reference to the accompanying drawings.