EP0029467B1 - Electrical apparatus comprising a series of voltage taps and mobile selector equipment - Google Patents

Abstract

Electrical contact apparatus comprises a center holder supporting a principal roller actuated by a telescopic movement and two oscillating auxiliary holders each equipped with an auxiliary roller.

Description

The present invention relates to an electrical appliance comprising a series of sockets and a mobile selector assembly provided with contacts cooperating with the sockets and connected to a circuit comprising at least one transition impedance, as well as a connection to a main conductor. The mobile selector unit is actuated by a control device. The typical example of such an electrical appliance with multiple sockets is a stepped electrical transformer equipped with a tap changer for a charge selector. The invention is not however limited to transformers but can be applied to other electrical devices such as compensation inductors, resistance banks or capacitor banks. These devices can be single-phase or can be designed for several phases. As in the vast majority of cases, the circuits of the selector crew or the sets of switches of the different phases are identical between them and present differences only when special effects are envisaged, the description below is limited to the single-phase case .

Step transformers operating with the aid of mobile selector units for on-load tap-changers are well known and described in numerous patents and other prior documents. In these known transformers, during a tap change cycle, a portion of a winding, seat of an electromotive force which one wants to add or subtract, is short-circuited by one or more transition impedances housed on the moving part and put into service during one or more intermediate positions of this moving part. Generally, the different sockets constituting the fixed contacts are electrically connected to the outputs of the adjustment winding, and are arranged, at a sufficient dielectric distance from each other, on the internal face of an insulating cylinder, at the inside which a movable selector assembly is driven in a rotational movement along the axis of the cylinder.

In a particular version, the mobile selector assembly is made up of three rows of rollers. The central row consists of several main rollers which ensure the flow of current when the moving part is stopped in front of a fixed contact, the end rows consist of a single auxiliary roller used to insert the transition impedances when moving the moving element and allowing switching without interruption of current. According to the different embodiments, these three rows of rollers are each mounted on stirrups driven by a telescopic movement or an oscillating movement with a spring device giving each of these rows of rollers an adequate pressure on the fixed contact.

These currently known embodiments have several drawbacks. In the case of mobile equipment fitted with end stirrers with telescopic movement, the direction in which the impact occurs between the auxiliary roller supported by the end stirrup and the fixed contact to which the mobile equipment set moves, has a strong obliquity with respect to the axis of the slide which ensures the telescopic movement. This results in rapid wear of the device, which can seriously disturb the proper functioning of the entire device.

On the other hand, in these embodiments, the lateral space requirement of the three rows of rollers of the moving element reduces the dielectric distance relative to the fixed contacts, close to that before which the moving element is stationary and limits the number of fixed contacts over a determined length of circumference.

This is the case of the moving element described in patent DE-B2-2 219 220. This moving element consists of a central main contact and an 'even number of auxiliary contacts connected, in pairs, to impedances of different values. When the main contact is stopped on the fixed contact, the crew overflows widely on both sides and greatly reduces the isolation distance. Consequently, in order to restore sufficient isolation distances, it is necessary to increase the distance between the fixed and successive contacts and thus increase the total size of the device.

The present invention relates to a movable assembly for temporary contacts according to the preamble of claim 1. It is characterized in that means are provided to allow a translation of the auxiliary rollers in the direction of the main rollers or in the opposite direction according to forces. generated by the displacements of the auxiliary rollers on the tracks of the fixed contact. In a preferred embodiment, it is characterized in that two end stirrups oscillate on either side of their rest position, by an optionally adjustable angle and it makes it possible to remedy these drawbacks. The inclination of the end brackets reduces the lateral dimensions of the moving element at the level of the rollers, consequently, it increases the number of fixed contacts distributed over the same length of circumference and makes it possible to have an adjustment winding. with more intermediate outputs. In addition, the oscillation of the end stirrups on either side of their rest position allows the auxiliary roller to easily slip away when it is on the fixed contact. This arrangement considerably reduces the effects of the impact, at high speed, of the auxiliary roller on the fixed contact towards which the moving element is moving.

For each end bracket, the contact pressure of the auxiliary rollers on the fixed contact and the return to the rest position are obtained by a device equipped with one or more springs. This particular provision communicates to the auxiliary roller, responsible for cutting the circulation current established from the moment when the two end stirrups are simultaneously in contact with the successive fixed contacts, a high breaking speed by adding to the speed of the moving equipment that which is communicated by the end bracket return device. This additional characteristic reduces the electrical wear of the auxiliary rollers responsible for cutting off the circulation current which in certain cases can be as high as the line current.

• La figure 1 est une'vue en plan de l'équipage mobile représenté en position repos. Cet équipage mobile est composé d'un étrier central (1) et de deux étriers d'extrémité (2).
• La figure 2 est une coupe partielle de l'étrier central (1).
• La figure 3 est une vue en élévation de l'étrier central (1).
• La figure 4 est une vue de profil d'un étrier d'extrémité (2).
• La figure 5 reproduit schématiquement les diverses positions occupées par l'équipage mobile pour passer d'un contact fixe à un autre contact fixe.

The invention is described. below with reference to an exemplary embodiment presented in the following figures.

• Figure 1 is a plan view of the moving assembly shown in the rest position. This mobile assembly is composed of a central stirrup (1) and two end stirrups (2).
• Figure 2 is a partial section of the central bracket (1).
• Figure 3 is an elevational view of the central bracket (1).
• Figure 4 is a side view of an end bracket (2).
• FIG. 5 schematically reproduces the various positions occupied by the moving assembly for switching from one fixed contact to another fixed contact.

In FIG. 1, representing the mobile assembly at rest, the central stirrup (1) made of a material which is good conductor of electricity is located in the center of the fixed contact (5) and the end stirrups (2), also made of good conductors of electricity are both in their rest position. The whole of this mobile assembly pivots about an axis (6) of a cylinder (7) on which the fixed contact (5) is positioned.

In FIG. 2, representing the central stirrup (1) of the mobile assembly at rest, an axis (8), held at each end in a slide (9) made of insulating material, supports two main copper rollers (10) and a cutter roller made of copper-tungsten alloy (11) and slides in a buttonhole (12). A piston (13), made of insulating material, pushed by a spring not shown, applies the main rollers (10) to the fixed contact (5) with an adequate pressure. A coaxial spring (14) of the axis (8) ensures the continuity of the electrical circuit by applying the sides of the main copper rollers (10) against the stirrup (1).

Figure 3 is an elevational view of the central bracket (1) stopped on the fixed contact (5). This fixed contact (5) consists of two tracks (30) made of a material that is good conductor of electricity and located on either side of a central track (31) made of material resistant to electric arc. The central track (31) is arranged in a plane recessed with respect to the plane of the tracks (30). In addition, the central section (31) is longer than the tracks (30) and ends at each end with an inclined plane (32) which facilitates access to and departure from the cutting roller (11). Likewise, each track (30) made of a material which is a good conductor of electricity ends at each end by an inclined plane (33) which facilitates access to and departure from the main rollers (10).

When the moving part leaves the fixed contact (5) the main rollers (10) roll on the tracks (30) then on the inclined planes (33). When the main rollers (10) have left the inclined plane (33), the cutting roller (11) can in turn roll on the track (31) then on the inclined plane (32). In this way, the breaking of the current carried by the fixed contact (5) is carried out at the inclined plane (32) and the cutting roller (11) both made of material resistant to electric arc.

In Figure 4, showing an exemplary embodiment of an end bracket (2) at rest, the rotation of the bracket (2) is provided by an axis (15). A torsion spring (16) co-axial with the axis (15) ends, at each end by a strand (17 and 18) shaped to bear on a spacer (19) integral with the movable assembly. One end of the stirrup (2) supports an axis (20) around which an auxiliary roller (21) made of copper-tungsten alloy pivots, the other end of the stirrup ends with a bar (22) which, in position rest, is aligned with the axis (15) and the spacer (19). When, following the movement of the moving element, the roller (21) comes into contact with a fixed contact (5) the stirrup (2) pivots about the axis (15), a strand (17) of the spring torsion (16) is supported on the spacer (19) while the other strand (18) pushed by the bar (22) of the stirrup (2) deviates from its normal position and the elastic deformation of the spring torsion (16) ensures the pressure 'of the contact between the roller (21) and the fixed contact (5).

For a displacement of the moving element in the opposite direction, the strands (17) and (18) work respectively in the opposite direction in the manner described above. The use of a torsion spring (16) as a calliper return device (2) makes the contact pressure between the auxiliary roller (21) and the fixed contact (5) proportional to the angle, the stirrup (2) deviates from its rest position.

For small deviations of the caliper (2) from its normal rest position, the contact pressures which are too low can be compensated for by the joint use of other traction, compression or torsion springs.

To ensure the continuity of the electrical circuit, a corrugated washer (23) made of a material that is a good conductor of electricity is introduced between the auxiliary roller (21) and each arm of the caliper (2). Current can thus be conveyed from the auxiliary roller (21) to an outlet (24).

When the auxiliary roller (21) leaves the fixed contact (5) the spring (16) returns the caliper (2) to its rest position.

For each end bracket (2), the angular movement is adjustable by an eccentric device modifying the position of the center of rotation of the bracket considered. This angular movement, for each end bracket (2), is also adjustable by a device modifying the position of at least one end stop of the end bracket (2).

In Figure 5, showing the different positions occupied by a mobile assembly to pass from a fixed contact (5) to another fixed contact (25), diagram 5 A shows the mobile assembly at rest on the fixed contact (5). The bracket (1), supporting the main rollers (10) is in the middle of the fixed contact (5) and carries the line current IL at the tap voltage (29), from the fixed contact (5) to a main conductor (28). The end stirrups (2) supporting the auxiliary rollers (21) are respectively designated by (2G) and (21 G) for the stirrup and the auxiliary roller located to the left of the central stirrup and by (2D) and ( 21 D) for the caliper and the auxiliary roller located to the right of the central caliper. Via the main rollers (10) and the central bracket (1), the end brackets (2G and 2D) and the auxiliary rollers (21G and 21 D) are at the potential of the socket (29).

When the drive device moves the moving assembly to the right, diagram 5B, to pass from the fixed contact (5) to the next fixed contact (25) the auxiliary roller (21 G) abuts against the fixed contact (5) and the stirrup (2G) pivots around its axis (15). The electrical circuit connecting the fixed contact (5) to the main conductor (28) is formed by two parallel branches of unequal resistances. The branch of the end clamp (2G) into which the impedance (26) is inserted does not conduct the current; it is the branch of the central stirrup (1) of practically zero resistance which continues to convey the line current IL from the fixed contact (5) to the main conductor (28).

Diagram 5C represents the moving assembly at the moment when the central stirrup (1) has just left the fixed contact (5) by cutting the line current IL, the passage of which is ensured, thereafter, by the branch of the end clamp (2G) through the impedance (26).

Diagram 5D shows the moving assembly when the auxiliary roller (21 D) of the end bracket (2D) approaches the fixed contact (25) while the roller. auxiliary (21G) of the end bracket (2G) has not yet left the fixed contact '(5). The IL line current. reaching the main conductor (28) is practically driven in half by the branch comprising the auxiliary roller (21G), the end clamp (2G) and the impedance (26), the other half of line current flows to through the branch comprising the auxiliary roller (21 D), the end bracket (2D) and the impedance (27). If we assume that the potential of the socket (34) connecting the fixed contact (25) is greater than the potential of the socket (29) connecting the fixed contact (5), a circulation current I _c of the fixed contact is established. (25) to the fixed contact (5) which passes successively through the auxiliary roller (21 D), the calliper (2D), the impedances (27) and (26), the calliper (2G) and the auxiliary roller ( 21 G).

In FIG. 5E, the end bracket (2G) has left the fixed contact (5) and the auxiliary roller (21G) has cut off the aforementioned circulation current. The line current IL., At the voltage of the socket (34) is again conveyed by the central stirrup (1) from the fixed contact (25) to the main conductor (28).

Diagram 5F shows the moving part at rest in front of the fixed contact (25). Via the main rollers (10) and the central bracket (1), the end brackets (2G) and (2D) and the auxiliary rollers (21G and 210) are at the potential of the socket (34) .

Claims (7)

1. Mobile equipment for temporary contacts comprising at least one row formed of one or more main rollers and at least one row formed of one or more auxiliary rollers, these rows of rollers being each given a telescopic movement by means of a spring device for applying the rollers (10, 11, 21) of the mobile equipment with an adequate pressure against the tracks (30, 31) of a fixed contact (5) opposite which the mobile equipment is situated, and these rows of rollers each pivoting about an axis of rotation so as to make the rollers (10, 11, 21) of the mobile equip. ment run on the tracks (30, 31) of the fixed contact (5), characterised in that means are provided for allowing displacement of the auxiliary rollers (21) in the direction of the main rollers (10) or in the opposite direction in accordance with forces produced by the displacements of the auxiliary rollers (21) on the tracks (30, 31) of the fixed contact (5).

2. Mobile equipment for temporary contacts according to claim 1, characterised in that the mobile equipment for temporary contacts is constituted by three rows of rollers each supported by a stirrup, in that a central stirrup (1) supporting the main rollers (10, 11) is given a telescopic movement and in that the two end stirrups (2), supporting an auxiliary roller or auxiliary rollers (21), are given each a limited rotational movement about a pivot (15) arranged parallel to the axis of rotation (20) of the auxiliary roller or rollers (21) in such a manner that the auxiliary roller or rollers (21) approach the main rollers (10, 11) under the action of the forces produced, in the course of the displacement of the mobile equipment from a fixed departure contact (5) towards another fixed arrival contact (25), when the auxiliary roller or rollers (21) of the stirrup (2) engage on a track (31) of the fixed arrival contact (25) and in such a manner that the auxiliary roller or rollers (21) move away from the main rollers (10, 11) under the action of the forces produced when the auxiliary roller or rollers (21) of the end stirrup (2) are on the point of leaving the track (31) of the fixed departure contact (5).

3. Mobile equipment for temporary contacts according to one of claims 1 or 2, characterised in that, for each end stirrup (2), the angular deflection is adjustable by an eccentric device which modifies the position of the centre of rotation of the stirrup in question.

4. Mobile equipment for temporary contacts according to one of claims 1 or 2, characterized in that, for each end stirrup (2), the angular deflection is adjustable by a device modifying the position of at least one end-of-travel stop of the end stirrup (2).

5. Equipment for temporary contacts according to one of claims 1, 2, 3 and 4, characterised in that for each end stirrup (2) the contact pressure of the rollers (21) on the track (31) of the fixed contact (5) and the return of the stirrup (2) to its rest position are effected by one or more torsion springs (16) which are coaxial with the axis of rotation (15) of the end stirrup (2).

6. Mobile equipment for temporary contacts according to one of claims 1, 2, 3, 4 and 5, characterised in that for each end stirrup (2) the contact pressure of the rollers (21) on the track (31) of the fixed contact (5) and the return of the stirrup (2) towards its position of rest are effected by one or more draw springs, at least one fastening point of each said draw spring being slidable.

7. Mobile equipment for temporary contacts according to one of claims 1, 2, 3, 4, 5 and 6, characterised in that for each end stirrup (2) the contact pressure of the rollers (21) on the track (31) of the fixed contact (5) and the return of the stirrup (2) towards its position of rest are effected by one or more compression springs.

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