WO2009011000A1

WO2009011000A1 - Detachable connecting device for vacuum tap changers for electrical transformers

Info

Publication number: WO2009011000A1
Application number: PCT/IT2008/000336
Authority: WO
Inventors: Silvio Dal Lago
Original assignee: Comem S.P.A.
Priority date: 2007-07-16
Filing date: 2008-05-20
Publication date: 2009-01-22
Also published as: RU2008150083A; EP2168132A1; UA95639C2; ITVI20070199A1; BRPI0805803A2

Abstract

A detachable connecting device for vacuum tap changers (10) for electrical transformers, of the type suitable to constitute at least a fixed contact (12), which is positioned on a tap changer (10) rod-shaped body (11) associated with drive actuators means (13) acting on supports (15) containing mobile contacts set to a reference voltage and sliding on fixed contacts (12); in particular, the detachable connecting device comprises a pin (23) on which is preassembled an elastic element kept in position by a peg (24) placed orthogonally to the walls of the pin (23). The pin (23), inserted into a shaped bush (29) which is inserted, in turn, in a respective opening of the rod-shaped body (11) of the tap changer (10), is pushed beyond the thickness of the aforesaid rod-shaped body (11) and rotated in any direction, in such a way to bring the peg (24) within a seat (39) provided on a surface of the bush (29).

Description

DETACHABLE CONNECTING DEVICE FOR VACUUM TAP CHANGERS FOR ELECTRICAL TRANSFORMERS

DESCRIPTION

This invention relates in general to a vacuum tap changer for electrical transformers and, in particular, concerns a detachable connecting device which can be used in these vacuum tap changer.

They are currently known vacuum tap changers for electrical transformers whose structure substantially presents a rod-shaped body where a series of pin fixed contacts h as been firmly made, arranged orthogonally in series throughout the entire extended body.

The extended body actually consists of a bakelite slat which has laterally the aforesaid pin-shaped fixed contacts, on which at least one mobile contact support, skid-shaped and that can be operate by the user through specific commands, runs, so that to electrically connect a series of fixed contacts.

In particular, according to an illustrative practical embodiment of medium-voltage tap changer, of the so-called "rack" type, the bakelite slat of the tap changer performs the sliding drive for a slide suitable to constitute the support of the mobile contacts and associated with a rod- shaped body which operates the slide through a longitudinal rack integrated with the slide and coupled with a gear wheel which is, in turn, integral with a composite knob fixed to the transformer box and available to the manual handle of the operator.

Alternatively, in the high-voltage top changers with movement of the type known as "at auger", the support of mobile contacts is operated by a worm, usually made of insulating material, with which a lead nut is associated.

In any case, in all the embodiments, the fixed contacts are usually assembled in the tap changer by the manufacturer and the user (normally the transformers manufacturer) fixes on them the electrical conductors through the use of appropriate lead-in wires.

Such pin-shaped fixed contacts may also be connected to the mobile taps of the coils of the transformer and can be mounted on the support slat of the tap changer, even if the same is already mounted on the transformer.

Indeed, by means of a hole, it is possible to weld the conductor to the pin and, then, mount it, along with the piece of cable, on the tap changer already assembled in the electric transformer. This operation is still carried on by mounting a contrast spring on the pin, then inserting the conductor into the hole of the support slat, then inserting a peg into the pin on the opposite side of the slat and finally releasing the pin so that the contrast spring pushes the peg against the insulating slat. It is clear that such an operation is extremely laborious and difficult, especially if the tap changer, connected to the electric transformer, is installed at the top or in any case in uncomfortable positions for the operator.

Therefore, as part of the abovementioned requirements, the aim of the present invention is to get round the cited drawbacks and, in particular, to provide a detachable connecting device for vacuum tap changers for electrical transformers which shows a greater constructive simplicity and permits to carry out more simply the pins assembly and disassembly operations, compared to the traditional solutions.

Another aim of the present invention is to accomplish a detachable connecting device for vacuum tap changers for electrical transformers which allows however to obtain the maximum functionality, reliability and robustness of the traditional tap changers.

These and other aims are achieved by a detachable connecting device for vacuum tap changers for electrical transformers, according to the attached claim 1.

The other dependent claims contain characteristics of detail of the invention.

In an advantageous way, according to the present invention, each fixed contact is made through a spring preassembled on the pin of the contact and kept in position by a peg which crosses the pin itself in orthogonal direction.

The pin is also inserted into a bush, appropriately shaped, so that the peg can pass through the thickness of the bakelite support slat of the pin. It is thus possible to easily and quickly carry out the operations of assembly and disassembly of the single pin.

In addition, a special slot on the pin indicates the appropriate setup thereof, as well as a hole made on the pin makes easy the assembly and disassembly on the bakelite slat thereof. Further aims and advantages of the present invention will be clear from the following description, related to a preferred but not limiting implementation example, of the detachable connecting device for vacuum tap changers for electrical transformers, which is the object of the present invention, and from the attached drawings, where:

- figure 1 is a front view of a vacuum tap changer for electrical transformers, built according to the present invention;

- figure 2 is a top view of the vacuum tap changer for electrical transformers of figure 1 , according to the present invention;

- figure 3 is a side view of the vacuum tap changer electrical transformer of figures 1 and 2, according to the present invention; - figure 4 is a top view of an enlarged particular of the vacuum tap changer for electrical transformers of figures 1-3, according to the present invention;

- figures 5A and 5B are two perspective views of a plastic bush used in the detachable connecting device for vacuum tap changers for electrical transformers, according to the invention;

- figure 6 is a plant view from the bottom of the bush of figures 5A and 5B, according to the present invention;

- figure 7 is a top view of the bush of figures 5A and 5B, according to the present invention; - figure 8 is a sectional view along the line VIM-VIM of figure 6;

- figure 9 is a sectional view along the line IX-IX of figure 6;

- figure 10 is a top view of a shaped washer used in the detachable connecting device for vacuum tap changers for electrical transformers, according to the invention; - figure 11 is an enlarged top perspective view of the bush of figures 5A and 5B, complete with screws, washers, pin and peg, according to the present invention;

- figure 12 is a perspective view of the pin used in the bush of figures 5A and 5B, according to the present invention;

- figure 13 is a side view of the of figure 12, according to the present invention;

- figure 14 is a side partly sectioned view of the pin of figure 12, according to the present invention;

- figure 15 is an enlarged view of the particular A of figure 14, according to the invention. First of all, it should be noted that the technical solution according to the invention can be used similarly, without any whatsoever problems, in all the vacuum tap changers at high, low or medium tension.

With particular reference to figures 1-4, a vacuum tap changer for electrical transformers with a structure according to the invention is generically described with 10.

The tap changer 10 comprises a rod-shaped body 11 , made usually in bakelite, with substantially rectangular cross-section, which integrally leads a series of fixed contacts 12, pin-shaped and arranged orthogonally in series along the aforesaid body 11. The rod-shaped body 11 represents the sliding drive for a slide

14 kept in position by the support 21 and which is, in turn, associated with drive actuators means, as a whole indicated with 13, acting on the supports 15 containing the mobile contacts set at a reference voltage; the mobile contacts slide on the fixed contacts 12 on opposed positions and are suitable to interfere, alternately and in succession, with them.

The drive actuators means 13 may include, in illustrative and preferred, but not limitative, embodiments of the invention, a longitudinal rack 16, integrated into the slide 14 and coupled with a gear wheel 17 integrally fixed to a knob 18, which can be handled by the operator and connected, in turn, through a transmission element 22, to the electrical transformer, of which only part of the casing 19 is visible in figure 1.

The drive means 13 furthermore, include, always in this embodiment, a shaft 20 whose end, facing the inside of the transformer, is fixed to the gear wheel 17, while the other end is attached to the manual operation knob 18. According to the invention, a spring is preassembled on each pin 23 of each fixed contact 12 and is kept in position by a peg 24, inserted into the cavity 27 of the body 28 of the pin 23 and which crosses the pin 23 in a direction orthogonal to the latter, as seen in figures 4 and 11-15. The pin 23, substantially cylindrical in shape and including a first cylindrical body 28 combined with a second cylindrical body 26 which has a diameter greater than the body 28, is inserted into the hole (first opening) 36 of a bush 29, made preferably in plastic, which is mounted in correspondence of appropriate openings of the rod-shaped body 11 of the tap changer 10, so that the top head 30 of the body 28 of the pin 23 projects from the central opening (second opening) 37 of the upper shaped surface 31 of the bush 29 and so that the bottom 32, equipped with an axial blind hole 33, of the body 26 of the pin 23 projects below from the hole 36 of the cylindrical portion 34 of the bush 29. The cylindrical portion 34 of the bush 29 is, in turn, linked to a base 35 which leads the shaped surface 31 and leans to the rod-shaped body 11 of the tap changer 10 (in this respect, see figures 5A and 5B and 6-9).

In particular, the outlines of the surface 31 are made in such a way as the peg 24, preassembled on the pin 23, passes inside the hole 36 and the opening 37 of the bush 29 and, consequently, through the thickness of the rod-shaped body 11 of the tap changer 10.

Moreover, the surface 31 presents a series of shaped relieves 38, placed around the opening 37, which define a series of seats 39 made in such a way as to house the peg 24 of the pin 23. In particular, once the pin 23 has been pushed over the thickness of the body 11 made of bakelite of the tap changer 10, it is sufficient to impart to the pin 23 itself a slight rotation towards the right or the left, in order to lead the peg 24 in one of the seats 39 provided among the shaped relieves 38 arranged on the upper surface 31 of the plastic bush 29.

In this way, the contrast spring preassembled on the pin 23 tends to push the pin 23 towards the outside of the rod-shaped body 11 of the tap changer 10, but the pin 23 remains fixed in position thanks to the block action of the peg 24 housed in its seat 39. In addition, the plastic bush 29 is fixed to the rod-shaped body

11 made of bakelite by means of metallic screws 40, inserted into respective holes 41 positioned to the sides of the base 35.

In this regard, in order to avoid that these metallic screws 40 may represent a floating voltage dangerous from the dielectric point of view, it is preferably used a particular shaped washer 42, described in detail in figure 10, which electrically connects the screw 40, inserted into the aperture 43 of the washer 42 and supported in correspondence of the annular area 44 at the side walls of the body 28 of the pin 23, through curved arms 45, as can be seen in detail in figure 11 , thus binding the voltage of the screw 40 itself. The shaped washer 42 performs its function for both the adjacent seats 39 of the peg 24 placed among the shaped relieves 38.

It is also possible to make a special circumferential slot 46 on the body 26 of the pin 23, which is placed at the level of the hole 36, below the cylindrical body 34, when the peg 24 is housed in the proper seat 39, so as to obtain for the user an appropriate signalling of the setup of the pin 23.

Finally, it is possible to make a hole 25 on the body 26 of the pin 23 to facilitate the assembly and disassembly of pin 23 itself.

Thanks to the aforementioned arrangement and by virtue of the fact that a spring and a peg 24, preassembled on the pin 23 inserted, in turn, into the shaped bush 29, are used, it is so possible to use fixed contacts 12 of detachable type, simply inserting and disconnecting the pin 23 from inside of the bush 29, through a slight rotation of the same pin 23 (which thus becomes easily removable) in order to engage and release, respectively, the peg 24, integral with the side walls of the pin 23, from a relative seat 39 defined by the shaped relieves 38 of the surface of a base 35 of the bush 29.

In this way, the electrical conductors may simply be preassembled on the fixed contacts on 12 and the latter directly connected to and disconnected from the tap changer 10, thus obtaining clear advantages in terms of ease of use, especially if the tap changer 10, connected to the electric transformer, is installed in inconvenient positions to carry out the manual operations of wiring, by the insertion in a position of push spring and blocking pegs for the connection of lead-in wires.

From the description made the characteristics of the detachable connecting device for vacuum tap changers for electrical transformers, which is the object of the present invention, are clear, as well as clear are the resulting advantages.

It is, finally, clear that many other variations can be made to the connecting device in question, without for this reason going out of the novelty principles inherent of the idea inventive, as it is clear that in the practical implementation of the invention, materials, forms and dimensions of the details described could be any depending on the needs and the same could be replaced with other technically equivalent.

Claims

1. Detachable connection device for vacuum tap changers (10) for electrical transformers, of the type suitable to constitute at least a fixed contact (12), positioned on a rod-shaped body (11) of the tap changer (10), said rod-shaped body (11) being associated with drive actuators means (13) acting on supports (15) containing the mobile contacts set to a reference voltage and suitable to interfere with the fixed contacts (12), characterized in that it includes at least one pin (23) on which is preassembled at least one elastic element kept in position by a peg (24) mounted on at least one side wall of the pin (23).

2. Detachable connection device as claim 1 , characterized in that said pin (23) is inserted into at least one first opening (36) of a shaped bush (29), said shaped bush (29) being inserted into a respective opening of the rod-shaped body (11 ) of the tap changer (10).

3. Detachable connection device as claim 1 , characterized in that the peg (24) is preassembled on said pin (23) and is inserted into at least one cavity (27) of the pin (23) orthogonal to the walls of said pin (23).

4. Detachable connection device as claim 2, characterized in that said shaped bush (29) presents a cylindrical portion (34), coupled with a base (35), which presents a shaped surface (31), for the bearing to the rod-shaped body (11) of the tap changer (10).

5. Detachable connection device as claim 4, characterized in that said surface (31) presents a series of outlines made in such a way as said peg (24), preassembled on the pin (23), passes insi de said first opening (36) of the shaped bush (29) and inside at least one second opening (37) of said surface (31) of the base (35), said second opening (37) being defined by said outlines, said peg (24) being thus able to pass through the thickness of said rod-shaped body (11) of the tap changer (10).

6. Detachable connection device as claim 5, characterized in that said outlines include a series of relieves (38), arranged around said second opening (37), which define a series of seat (39), suitable to house said peg (24) of the pin (23), in blocking position, following a rotation of said pin (23).

7. Detachable connection device as claim 4, characterized in that said shaped bush (29) is fixed to the rod-shaped body (11) of the tap changer (10) through metallic screws (40), inserted inside of respective holes (41) present in said base (35).

8. Detachable connection device as claim 7, characterized in that each one of said screws (40) is electrically connected to said pin (23), in order to bind the voltage of said screws (40), by means of at least one shaped washer (42) which presents at least one aperture (43), within which said screw (40) is inserted, and at least one shaped arm (45), provided between said aperture (43) and said pin (23).

9. Detachable connection device as claim 1 , characterized in that said pin (23) presents a substantially cylindrical shape and includes at least two cylindrical bodies (26, 28) having different diameters.

10. Detachable connection device as claim 1 , characterized in that said pin (23) presents at least one slot (46) on said side wall, suitable to provide for the user an appropriate signalling of the setup of the pin (23) on the tap changer (10).

11. Detachable connection device as claim 1 , characterized in that said pin (23) presents at least one hole (25) on said side wall, in order to facilitate the assembly and disassembly thereof.