WO2006069802A1

WO2006069802A1 - Off-circuit tap changer, with actuating mechanism, for electrical transformers

Info

Publication number: WO2006069802A1
Application number: PCT/EP2005/014179
Authority: WO
Inventors: Silvio Dal Lago
Original assignee: Comem SpA
Current assignee: Comem SpA
Priority date: 2004-12-27
Filing date: 2005-12-23
Publication date: 2006-07-06
Anticipated expiration: 2007-06-27
Also published as: ITVI20040307A1; RU2377683C2; EP1831904A1; DE602005011180D1; SI1831904T1; ATE414982T1; BRPI0519158A2; RU2007122791A; UA86275C2; ES2315941T3; PL1831904T3; EP1831904B1

Abstract

An off-circuit tap changer (10, 20), with actuating mechanism, for electrical transformers, of the type comprising a frame which includes at least two elongated bars (11), to which a series of stud-type fixed contacts (12) is integrally connected, arranged orthogonally in series, and a set of movable rubbingblock contacts (14) which slide on the fixed contacts (12) thanks to the actuation of a worm screw (23) ; a nut thread is fitted or made in the end part of an insulating tube (27), coaxial with and outside the worm screw (23), so that the set of movable contacts (14) is fixed, by means of a shaped adaptor (28), in the end part of the insulating tube (27) opposite the nut thread. In this way, the nut thread is in a different position from that of the set of movable contacts (14) with respect to the overall length of the tap changer (10, 20), permitting the use of movable contacts (14) unconstrained by the dimensions of the tube (27) and/or worm screw (23).

Description

OFF-CIRCUIT TAP CHANGER, WITH ACTUATING MECHANISM, FOR ELECTRICAL TRANSFORMERS

The present invention refers, in general, to an off- circuit tap changer, with actuating mechanism, for electrical transformers.

The technical solution adopted lends itself particularly to use in high voltage tap changers, but can equally be used in any off-circuit tap changer with actuating mechanism.

Off-circuit tap changers for electrical transformers are currently known whose structure substantially has an elongated body where a set of fixed stud contacts is integrally made orthogonally in series along the whole length of the elongated body.

The elongated body in fact consists of a frame, which laterally has the above-mentioned fixed stud contacts, inside of which there runs at least one support for a pair of movable rubbing-block type contacts, which the user can operate by means of specific controls so that they are brought into opposing positions, and are adapted to alternatively and successively enter into interference with two of the aforementioned fixed contacts . At present, two principal structures have been adopted of off-circuit high-voltage tap changers: rack-type high voltage tap changers (ATCs) and screw-type high voltage tap changers (ATVs) , actuated by means of a worm screw.

In rack-type high voltage tap changers (ATCs) , the frame constitutes the sliding guide for a slide, adapted to constitute the support for the movable contacts, associated with a bar-shaped body which moves it by means of a longitudinal rack forming part of the slide and coupled with a pinion, which in turn results integral with a composite handle fixed to the transformer body, which the operator can operate by hand.

On the other hand, in screw-type high voltage tap changers (ATVs) , the support of the movable contacts is actuated by a worm screw, usually realised in insulating material, which is associated with a lead nut.

Both these traditional constructive solutions, however, foresee the use of movable contacts, which result constrained by the dimensions of the tube or the worm screw, and they foresee a number of pins, which it would be desirable to reduce so to limit the mechanical problems .

Within the scope of the requirements described above, then, the object of the present invention is to avoid the drawbacks mentioned and, in particular, to create an off-circuit tap changer for electrical transformers, with actuating mechanism, which shows a greater constructive simplicity and which foresees a reduced number of parts with respect to traditional solutions.

Another object of the present invention is to create an off-circuit tap changer for electrical transformers, with actuating mechanism, which would be more functional, reliable and robust than traditional tap changers .

A further object of the present invention is to realise an off-circuit tap changer for electrical transformers, with actuating mechanism, which would enable tap changers to be produced at a lower design and manufacturing cost than with the known techniques.

These and other objects are achieved by the off-circuit tap changer for electrical transformers, with actuating mechanism, made according to claim 1 below.

The other, dependent claims cover detailed characteristics of the invention.

Further objects and advantages of the present invention will become clear from the description which follows, related to a preferred but not limiting example embodiment of the off-circuit tap changer with actuating mechanism covered by the present invention, and from the attached drawings, in which:

■ Figure 1 is a perspective view of a rack-type high voltage off-circuit tap changer realised according to the known art;

^■ Figure 2 is a perspective view of a screw-type high voltage off-circuit tap changer made according to the present invention;

^■ Figure 3 is a perspective view of an adaptor element used in the off-circuit tap changer for electrical transformers, with actuating mechanism, according to the present invention.

In particular, figures 1 and 2 show, respectively, a rack-type high voltage off-circuit tap changer (ATC) , generically indicated with 10, and a screw-type high voltage off-circuit tap changer (ATV) , generically indicated with 20.

It should be pointed out here that the technical solution according to the invention lends itself particularly to high voltage tap changers but can likewise be used, without any kind of problem, in any off-circuit tap changer with actuating mechanism.

With particular reference to Figure 1, the ATC rack- type high voltage off-circuit tap changer for electrical transformers 10 (ATC) comprises an outer frame, formed by two parallel bars 11 of substantially rectangular section, which integrally bear stud-shaped fixed contacts 12, arranged orthogonally in series.

A central bar-shaped component 13, at whose end respective rubbing-block type movable contacts 14 are mounted, placed below a plastic protection 15, is utilised as a guide for the sliding of the movable contacts 14 over the fixed stud contacts 12.

In this way, the movable contacts 14 are adapted to alternatively and successively enter into interference with two fixed contacts 12 of one of the bars 11 or with one fixed contact 12 and a contact strip 16 made on the parallel bar 11 which is at the desired voltage.

The sliding guide consists of a longitudinal rack forming part of the central bar-shaped component 13 and coupled with a pinion (not shown in the Figure) , which in turn is connected to an operating device 17 for the operator to actuate.

On the outer side of the bars 11, each of the fixed stud contacts 12 presents a threaded ring 18 associated with related distributor caps 19 for attaching the cable ends.

If required, moreover, two guard rings 21 can be used, tightly fixed to the external structure of the bars 11 and each connected with the stud of the nearest fixed contact 12 so as to be at the same potential as that contact.

The set of movable contacts 14 may take the form of medium-voltage fixed-point and/or pawl tap changers and is protected inside protective elements 22, realised in plastic material and double shoulder shaped in order to provide considerable stability.

Figure 2, where components which have exactly the same form and function as those in Figure 1 are given the same reference number, schematically shows a screw-type

(ATV) high-voltage tap changer, indicated generically with 20, which differs with respect to the rack-type high-voltage tap changer 10 due to the typology of operation of the set of movable contacts 14.

In particular, the set of movable contacts 14 is made to slide over the fixed contacts 12 by means of a worm screw 23 (the so-called "large screw") which is associated with the set of movable contacts 14 by means of a coupling component 24, which is integral with the nut thread 25 (which in the exemplifying and preferred embodiment consists of a lead nut) .

The worm screw 23 can be operated from the outside by means of a movement device 26 available to the operator.

The off-circuit tap changer for electrical transformers, with actuating mechanism, according to the present invention has the same mechanical and electrical components as the tap changer typologies examined so far, and moreover is foresees an actuating mechanism (shown in detail in Figure 3) comprising a worm screw 23 (analogous to that used in the screw-type high-voltage tap changer) , coaxial and inside an insulating tube 27 preferably realised in phenolic resin, on which the nut thread is fitted or made at one end part .

The coupling 24 is connected to the end portion of the tube 27, and bears the set of movable contacts 14, housed inside a shaped protective structure 22.

The coupling 24 is further connected with the tube 27 by means of the interposition of a shaped adaptor 28, which allows for the coupling between the nut thread and the set of movable contacts 14.

With this type of connection and thanks to the use of the adaptor 28, it is possible to use the same components in screw-type tap changers as those used in rack-type ones, reducing the number of pins to a minimum as well as reducing the overall bulk of the structure in general .

The use of the same components as for the rack-type high-voltage tap changer also permits lower expenditure on the production of the moulds and on research into the suitability of the electric contacts.

Next, the use of an nut thread fitted or made in the end portion of the tube 27 and coaxial with the worm screw 23, with the set of movable contacts 14 fixed to the end part of the tube 27 itself opposite the internal thread, makes it possible for the aforementioned nut thread in a diverse position, with respect to that of the set of movable contacts 14, depending on the overall length of the tap changer.

Because of the aforementioned arrangement, and by virtue of the use of a shaped adaptor 28 fitted into the tube 27 at the opposite end from the nut thread, it is thus possible to employ movable contacts 14 which are entirely unconstrained by the size of the tube 27 and/or that of the worm screw 23, with obvious benefits from the point of view of practicality in use, reduction in overall size and total costs, as stated above.

The overall structure of the tap changer, indeed, is decidedly simpler than that of traditional ones, yet functional and robust; moreover, such structure can, as we have seen, be readily adapted to various transformer typologies, including many that have already gone into production.

The characteristics of the off-circuit tap changer for electrical transformers with actuating mechanism covered by the present invention, and its advantages, are clear from the above description.

Lastly, it is obvious that numerous other variants of the off-circuit tap changer in question could be designed while preserving the innovative principles inherent in the inventive idea, as it is clear that the materials, forms, and dimensions of the illustrated details may be of any type depending on the requirements, and that those details could be substituted with other technically equivalent details.

Claims

1. Off-circuit tap changer (10, 20) , with actuating mechanism, for electrical transformers, of the type comprising at least one frame, which includes elongated bars (11) , to which a series of stud-type fixed contacts (12) is integrally connected, arranged orthogonally in series, said tap changer (10, 20) moreover comprising a set of movable rubbing-block type contacts (14) which slide on the fixed contacts (12) thanks to at least one actuating element (23) , characterised in that said at least one actuating element (23) is at least partially fitted inside an insulating tubular element (27) which is coaxial with said actuating element (23) , so that the set of movable contacts (14) is connected with at least one end portion of said tubular element (27) .

2. Off-circuit tap changer (10, 20) , with actuating mechanism, as in claim 1, characterised in that said at least one actuating element (23) consist of a worm screw (23) and at least one nut thread is fitted or made in the end part of said tubular element (27) , coaxial with and outside of said the worm screw (23) .

3. Off-circuit tap changer (10, 20) , with actuating mechanism, as in claim 2, characterised in that the set of movable contacts (14) is connected, through at least one shaped adaptor element (28) which permits the coupling between the nut thread and the set of movable contacts (14) , to an end portion of said tubular element (27) , opposite said nut thread, so that the nut thread is situated in a different position from that occupied by the set of movable contacts (14) , with respect to the overall length of the tap changer (10,

20) , in order to permit the use of movable contacts

(14) unconstrained by the dimensions of said tubular element (27) and/or worm screw (23) .

4. Off-circuit tap changer (10, 20) , with actuating mechanism, as in claim 1, characterised in that said stud-type fixed contacts (12) have respective threaded rings (18) , associated with related distributor caps (19) , for attaching the cable ends.

5. Off-circuit tap changer (10, 20) , with actuating mechanism, as in claim 1, characterised in that said elongated bars (11) are connected to respective guard rings (21) , each connected with a stud of the nearest fixed contact (12) , so as to be at the same potential.

6. Off-circuit tap changer (10, 20) , with actuating mechanism, as in claim 1, characterised in that said set of movable contacts (14) is placed inside shaped protective elements (22) realised in plastic material.

7. Off-circuit tap changer (10, 20) , with actuating mechanism, as in claim 1, characterised in that said tubular element (27) is connected, at one of its end portions, to said set of movable contacts (14) , by- means of at least one coupling element (24) .

8. Off-circuit tap changer (10, 20) , with actuating mechanism, for electrical transformers, as substantially described and illustrated and for the specified objects.