GB2045534A

GB2045534A - Improvements in or relating to a tap switch for a tapped transformer

Info

Publication number: GB2045534A
Application number: GB8008610A
Authority: GB
Original assignee: Maschinenfabrik Reinhausen Gebrueder Scheubeck GmbH and Co KG
Current assignee: Scheubeck GmbH and Co
Priority date: 1979-03-15
Filing date: 1980-03-13
Publication date: 1980-10-29
Also published as: ES489546A1; DE2910161A1; NL186607B; SE435558B; FR2451659A1; SE8001550L; FR2451659B1; JPH0142123B2; NL8001524A; DE2910161C2; JPS55127010A; NL186607C; GB2045534B

Abstract

A tap switch of a tapped transformer comprises a contact bridge, which is rollable along two circular arcs and which includes two contact rollers (8, 9) axially connected with each other and rotatably mounted in a contact bridge carrier. The contact arrangement also comprises stationary contacts, which are arranged on the circular arcs and which are constructed as individual contacts (2, 3) on one arc and as a contact track (6) on the other arc. A connection between two contacts of the two arcs is effected by means of the rollable contact bridge. The axial connection of the contact rollers (8, 9) is by way of a flexible conductor (12). Each roller (8, 9) is rotatably mounted on a respective arm (10, 11) of the contact bridge carrier and the arms (10, 11) are movable relative to each other. <IMAGE>

Description

SPECIFICATION Improvements in or relating to a tap switch for a tapped transformer The present invention relates to a tap switch for a tapped transformer and has particular reference to a contact arrangement in such a switch.

Contact arrangements are often used in load selectors for tapped tramsformers. The individual stationary tap contacts are arranged on a circular arc at the inside wall of a cylindrical oil vessel and the load output line is constructed as a continuous contact track and is arranged above or below the individual contacts. A contact bridge, which has a respective contact roller rolling on each of the track of the individual tap contacts and the continuous contact track, connects, according to its position, an individual tap contact with the load output line. The contact bridge is actuated by means of a contact bridge carrier of insulating material, in which it is journalled and which is entrained by an insulating tube, which is arranged in the centre of the cylinder and is rotatable in steps.Springs producing contact pressure are disposed between the contact bridge carrier; which contains the bearing points for the contact bridge, and a counterbearing.

A difficulty with contact arrangements of that kind is that the two tracks are never exactly parallel at the cylinder wall and the rolling peripheries of the tracks never agree exactly, particularly as one track contains a plurality of individual contacts while the other track is constructed as a continuous contact track. The arrangement of individual contacts inevitably leads to unevenness in that track.

The contact bridge must, during each switching step, adapt itself to these unevennesses in the track of the individual contacts. This in turn leads to friction at the rolling surfaces, especially those of the individual contacts and the contact rollers, and also to friction in the bearing points of the contact bridge. This friction leads to wear and causes material abrasion which contributes to the pollution of the oil filling the load selector.

In accordance with the present invention there is provided a tap switch for a tapped transformer, the switch comprising a plurality of discrete contacts arranged on a first circularly arcuate path, a contact track extending along a second circularly arcuate path co-axial with the first path, and contact bridging means movable to electrically connect selectable ones of the discrete contacts with the contact track and comprising two arms mounted to be displaceable relative to each other, a respective contact roller rotatably arranged on each of the arms to be rollable along a respective one of the paths on movement of the contact bridging means, and an electrically conductive flexible connection axially interconnecting the rollers.

With a tap switch embodying the invention, unnecessary material abrasion at the rolling surfaces and also in the bearing points of the contact bridging means may be avoided, which facilitates operation of the contact bridging means.

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 perspective view of part of a cylindrical oil vessel of a load selector embodying the invention.

Referring now to the drawing, there is shown a load selector comprising on oil vessel with a cylindrical wall 1 having an upper contact track composed of a plurality of stationary tap contacts 2 and 3, which are each provided with an external flat connection 4 for the connection of a conductor and with an internal contact surface 5. Arranged underneath the tap contacts 2 and 3 is a continuous track 6, which serves as load output line or as star point of the load selector. Each tap contact 2 or 3 can be connected with the load output line, thus with the contact track 6, by means of a contact bridge 7.The contact bridge 7 possesses an upper contact roller 8 and an lower contact roller 9, which are rotatably mounted on arms 10 and 11, respectively, of a contact bridge carrier (not shown in detail) of insulating material and which are electrically connected with each other by a flexible conductor 1 2. The two arms 10 and 11 of the contact bridge carrier are movable relative to each other. In addition, contact pressure springs (not shown) act in usual manner of the arms 11 and 1 2. The contact bridge carrier is moved stepwise in known manner by means of a driving tube rotatably mounted in the interior of the oil vessel, so that an individual stationary tap contact 2 or 3 can be selectably connected to the contact track 6. To facilitate the rolling of the contact roller 8 onto and off from the contact surfaces 5 of the stationary tap contacts 2 and 3, these surfaces are provided with ramps 1 3.

The contact bridge 7 is capable of readily adapting itself to the inevitably present unevenness of the tracks, especially the track composed of the individual tap contacts 2 and 3, since each contact roller 8 and 9 is carried by an individual arm 10 and 11, respectively, of the contact bridge carrier and because the two contact rollers 8 and 9 are movable relative to each other due to the flexible conductor 1 2. Canting of the contact bridge is accordingly of no greater consequence that the inevitable differences in the circumferential speeds of the two contact rollers.

1. A tap switch for a tapped transformer,

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. SPECIFICATION Improvements in or relating to a tap switch for a tapped transformer The present invention relates to a tap switch for a tapped transformer and has particular reference to a contact arrangement in such a switch. Contact arrangements are often used in load selectors for tapped tramsformers. The individual stationary tap contacts are arranged on a circular arc at the inside wall of a cylindrical oil vessel and the load output line is constructed as a continuous contact track and is arranged above or below the individual contacts. A contact bridge, which has a respective contact roller rolling on each of the track of the individual tap contacts and the continuous contact track, connects, according to its position, an individual tap contact with the load output line. The contact bridge is actuated by means of a contact bridge carrier of insulating material, in which it is journalled and which is entrained by an insulating tube, which is arranged in the centre of the cylinder and is rotatable in steps.Springs producing contact pressure are disposed between the contact bridge carrier; which contains the bearing points for the contact bridge, and a counterbearing. A difficulty with contact arrangements of that kind is that the two tracks are never exactly parallel at the cylinder wall and the rolling peripheries of the tracks never agree exactly, particularly as one track contains a plurality of individual contacts while the other track is constructed as a continuous contact track. The arrangement of individual contacts inevitably leads to unevenness in that track. The contact bridge must, during each switching step, adapt itself to these unevennesses in the track of the individual contacts. This in turn leads to friction at the rolling surfaces, especially those of the individual contacts and the contact rollers, and also to friction in the bearing points of the contact bridge. This friction leads to wear and causes material abrasion which contributes to the pollution of the oil filling the load selector. In accordance with the present invention there is provided a tap switch for a tapped transformer, the switch comprising a plurality of discrete contacts arranged on a first circularly arcuate path, a contact track extending along a second circularly arcuate path co-axial with the first path, and contact bridging means movable to electrically connect selectable ones of the discrete contacts with the contact track and comprising two arms mounted to be displaceable relative to each other, a respective contact roller rotatably arranged on each of the arms to be rollable along a respective one of the paths on movement of the contact bridging means, and an electrically conductive flexible connection axially interconnecting the rollers. With a tap switch embodying the invention, unnecessary material abrasion at the rolling surfaces and also in the bearing points of the contact bridging means may be avoided, which facilitates operation of the contact bridging means. 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 perspective view of part of a cylindrical oil vessel of a load selector embodying the invention. Referring now to the drawing, there is shown a load selector comprising on oil vessel with a cylindrical wall 1 having an upper contact track composed of a plurality of stationary tap contacts 2 and 3, which are each provided with an external flat connection 4 for the connection of a conductor and with an internal contact surface 5. Arranged underneath the tap contacts 2 and 3 is a continuous track 6, which serves as load output line or as star point of the load selector. Each tap contact 2 or 3 can be connected with the load output line, thus with the contact track 6, by means of a contact bridge 7.The contact bridge 7 possesses an upper contact roller 8 and an lower contact roller 9, which are rotatably mounted on arms 10 and 11, respectively, of a contact bridge carrier (not shown in detail) of insulating material and which are electrically connected with each other by a flexible conductor 1 2. The two arms 10 and 11 of the contact bridge carrier are movable relative to each other. In addition, contact pressure springs (not shown) act in usual manner of the arms 11 and 1 2. The contact bridge carrier is moved stepwise in known manner by means of a driving tube rotatably mounted in the interior of the oil vessel, so that an individual stationary tap contact 2 or 3 can be selectably connected to the contact track 6.To facilitate the rolling of the contact roller 8 onto and off from the contact surfaces 5 of the stationary tap contacts 2 and 3, these surfaces are provided with ramps 1 3. The contact bridge 7 is capable of readily adapting itself to the inevitably present unevenness of the tracks, especially the track composed of the individual tap contacts 2 and 3, since each contact roller 8 and 9 is carried by an individual arm 10 and 11, respectively, of the contact bridge carrier and because the two contact rollers 8 and 9 are movable relative to each other due to the flexible conductor 1 2. Canting of the contact bridge is accordingly of no greater consequence that the inevitable differences in the circumferential speeds of the two contact rollers. CLAIMS

1. A tap switch for a tapped transformer, the switch comprising a plurality of discrete contacts arranged on a first circularly arcuate path, a contact track extending along a second circularly arcuate path co-axial with the first path, and contact bridging means movable to electrically connect selectable ones of the discrete contacts with the contact track and comprising two arms mounted to be displaceable relative to each other, a respective contact roller rotatably arranged on each of the arms to be rollable along a respective one of the paths on movement of the contact bridging means, and an electrically conductive flexible connection axially interconnecting the rollers.

2. A tap switch for a tapped transformer, the tap switch being substantially as hereinbefore described with reference to the accompanying drawing.