EP2139801A1

EP2139801A1 - Vertical-stratification winding machine for electric transformers

Info

Publication number: EP2139801A1
Application number: EP08735362A
Authority: EP
Inventors: Gianfranco Gonella
Original assignee: Siltech Srl
Current assignee: Siltech Srl
Priority date: 2007-04-27
Filing date: 2008-04-23
Publication date: 2010-01-06
Anticipated expiration: 2028-04-23
Also published as: EP2139801B1; WO2008131889A1; DE602008005287D1; ITVI20070124A1; ATE500182T1

Abstract

To create medium-voltage windings for distribution transformers of both the oil-filled and cast-resin types, horizontal stratification techniques are still used, with machines being automated to a greater or lesser degree and with the necessity to isolate the various layers with dielectric film. Vertical-stratification winding machines introduce a radical modification with respect to this winding technique: coils are no longer made to rotate around a horizontal axis but are positioned vertically. With the new technique, the winding spirals are preformed by a variable geometry expander and fall under the force of gravity to form concentric spirals as illustrated in the main drawing below (Fig.1). A further important innovation lies in the fact there is no need to insert any form of insulation between layers, resulting in considerable advantages in terms of costs and the thermal dissipation of the coil.

Description

Title:Vertical-stratification winding machine for electric transformers

1. Description of the various techniques adopted for medium- voltage windings in distribution transformers.

2. Description of the technique for which the present patent application is submitted.

3. Advantages that can be obtained with respect to traditional technology.

4. Description of the machine. With stationary coils With rotating coils

1. CURRENT ART AND TECHNOLOGY

In transformer windings of the medium/high-voltage type set in cast resin or in oil, the following techniques are typically used:

A. Winding with horizontal stratification across the entire height of the coil;

B. Galette winding with horizontal stratification

C. Galette winding with tape conductors

A. Horizontal stratification is performed according to the scheme indicated in the drawing in Fig. 2.

The winding machine, automated to a greater or lesser degree, turns the coils about the horizontal axis (X), depositing the conductor (1) with one spiral next to the other. The wire distributor of the winding machine inverts the movement from Xi to X₂, working backwards and forwards, until the number of layers required by the electrical specification has been reached, and with the layers rising through the Y axis. One or more sheets of insulating material (2) are normally inserted between one layer and the next.

B. The galette-winding technique is similar to the technique described in paragraph A, however the difference is that the winding is divided into n disks in accordance with the electrical design (cf. Fig. 3). The winding machine performs stratification from Xi to X₂ for the single galettes and the layers are deposited through the Y axis. At the end of each individual galette (this process is shown in figure 3), the conductor (1) is manually transferred to the next galette.

C. Galette winding with tape conductor (Fig. 4).

With this technique, the winding is turned about the X axis as in the cases of the windings described in paragraphs A and B.

Unlike galette winding with wire (par. B), the galettes are not created by producing layers from Xi to X₂ but by superimposing them through the Y axis. The last spiral of each galette is manually delivered by the operator at the start of the following galette. An insulation film is inserted between the layers. This technique is mainly used in medium-voltage coils for resin transformers. 2. THE TECHNIQUE FOR WHICH A PATENT APPLICATION IS BEING SUBMITTED In the technique used with the machine for which an industrial invention patent is now being sought, the winding is performed as per the process illustrated in Fig. 1.

The coil which is being wound is placed in the vertical rather than in the horizontal position as would occur in traditional technology. The spirals are preformed by a variable-geometry expander (2), which transforms them into concentric spirals, and by a rotating capstan (1) as shown in the figure.

The expander (2) is located in the upper position and lets the spirals fall and deposit by gravitational force. In this way, the layers are gradually formed and grow in volume through the Y axis.

Each spiral is formed with a progressive variation of the diameter of the expander, moving from Xi to X₂ and vice versa in accordance with the parameters of the electrical calculation.

As mentioned earlier, the preformed spirals fall by the force of gravity, however they are not arranged in an exactly geometrical manner as represented in the drawing in Fig. 1 but in a random fashion with a packing rate very close to the geometrical maximum.

The stacking obtained is in fact close to that of a perfectly geometrical arrangement of spirals. For example, the maximum theoretical stacking factor value obtainable in a winding with Xi - X₂ = 30 mm and a conductor diameter of 2 mm is approximately 78%, while with the machine for which a patent is now being requested, the stacking values obtained are in the order of 71 ÷ 73%. Note: 'stacking' factor here refers to the ratio between the net section of the conductors and the occupied geometrical section.

3. ADVANTAGES OBTAINABLE WITH RESPECT TO TRADITIONAL ART

The first immediate advantage obtainable with the machine for which an application is being submitted is a drastic reduction in winding times with respect to those typical of technology hitherto adopted and which were described above in section 1.

It should be first noted that this technique is particularly convenient for the production of medium-voltage windings for cast resin and oil-filled transformers. To provide a quantitative point of reference relating to the possible reduction in winding times we may affirm that with respect to a winding of comparable mass and dimensions, wound in accordance with traditional art and the technology described in paragraphs A and B of the section, it is possible to attain a value in the region of 25%. By way of a practical example, if an operator using traditional technology takes 4 hours to produce a winding, with our machinery the same operator would take 1 one hour to perform the same task. This statement is not based on theoretical premises or hypotheses but on real winding times recorded with a real prototype machine. DESCRIPTION OF THE MACHINE

4.1 The stationary-coil technique

The variable-geometry expander, Figl (point 2) is the technical mechanism with which it is possible to produce the type of winding described above. The technique can be developed in two ways: the first way is represented schematically in the figure in Fig. 5.

The conductor (7) arrives at the centre of the expander by means of relay pulleys (4) and then reaches the satellite wheel (capstan) (6). It is then inserted under an elastic belt (5) which, turning around the expander, forms the circular spiral and is then freed when it has completed a rotation of about 240 ÷ 270°. The expander continuously varies in diameter, from Xi to X₂, in accordance with the electrical specification and with a diameter variation at each rotation equal to 2 times the diameter of the conductor used at that moment. The expander does not turn about the Y axis but remains still, like the coil which is being formed.

4.2 The rotating coil technique

The conductor, Fig. 6 (point 7) reaches the expander (3) guided by a system of pulleys (8) and inserts itself under the elastic belt (5), which holds it fast and forces it to assume a circular form. After a rotation of about 240 ÷ 270°, the spiral is released. The expander (3) varies in diameter from X] to X₂ in accordance with the electrical specification and with diameter variation at each rotation equal to 2 times the diameter of the conductor used at that moment. All of this occurs in a manner similar to the process illustrated in figure 5. The substantial difference between the two methods lies in the fact that in this latter method the expander (3) rotates about the Y axis, as does the coil which is being formed, while the satellite wheel (6) remains still. An equivalent final result is obtained with the two methods. The latter technique, illustrated in figure 6, requires a more complicated mechanical system with respect to the former, however it also presents the advantage of being able to use strap conductors and not only wire. The techniques illustrated in figures 5 and 6 resemble those employed in coiling machines (well-known devices that have been used for decades Fig. 7), however with some fundamental variations. The principle variation is that in our own system the expander is of the variable-geometry type, while in coiling machines, there is only a flywheel (1) with a defined diameter. The operating principle of coiling machines is shown in figure 7. The depositing of the spirals (4) occurs by making the container (5) turn through a distance equal to the diameter of the spiral so as to obtain an epicycloidal arrangement of the spirals (4). Apart from mechanical differences between our system and coiling machines, the significant difference occurs at the level of savings in terms of stacking of the wire container, and in our own case of the coils that are being wound. With coiling machines, the maximum stacking factor value obtainable lies in the region of 46 ÷ 48%, while with our own technique, a value of 71 ÷ 73% can be obtained.

Claims

1 ) A winding machine for the production of windings which are to be used in electric transformers with average power and average voltage ratings, i.e., transformers employed in the distribution of electric power over supply lines with an average voltage rating of 10,000 - 20,000 V. The machine produces the windings, utilizing a technique which is innovative with respect to known procedures that have been used so far at world level.

The spirals of the winding are locked by a round variable-geometry expander and by a capstan which turns about the expander. The conductor (wire) descends from above and is channelled by means of pulleys below an elastic belt driven by a satellite wheel referred to as a "capstan". The spirals thus formed are released after a rotation of approximately 240-270° and by the force of gravity drop into a container, which remains still, as illustrated in Fig 1. The diameters of the spirals are variable (X1-X2), with such variation being obtained by means of electronic coordination between the motor that turns the capstan and the motor which expands and retracts the expander. The winding thus produced is of the radial type, and the layers develop vertically through the Y axis.

2) A winding machine for the production of windings of the type described under point 1 of the claims herein.

The spirals of the windings are formed by a round, variable-geometry expander. The conductor (wire or strap type) is conveyed by means of pulleys below the elastic belt which connects the expander and a satellite wheel.

In this case, the expander turns, as does the conductor below, while the satellite wheel remains still as represented in figure 6.

The spirals thus formed are released after a rotation of 240-270° and drop by the force of gravity in a manner similar to that described for the machine illustrated under point 1 of these claims.

3) The machines described under points 1 and 2 feature the use of elastic belts which have the following functions:

One elastic belt follows the expander in its variations of diameter and has the purpose of connecting the sectors forming the expander, and facilitating the circularity of the spirals.

A second elastic belt connects the expander to the satellite wheel and is used to compress the spiral that is being formed in order to make it round.