EP2850624B1

EP2850624B1 - Transformer with bushing compartment

Info

Publication number: EP2850624B1
Application number: EP12721819.6A
Authority: EP
Inventors: Antal Olah; Zsolt SUKOSD
Original assignee: Siemens AG
Current assignee: Siemens AG
Priority date: 2012-05-14
Filing date: 2012-05-14
Publication date: 2016-04-13
Anticipated expiration: 2032-05-14
Also published as: PL2850624T3; EP2850624A1; WO2013170873A1

Description

Field of the Invention

The present invention relates to an electrical transformer, especially a distribution transformer, with a Bushing Compartment.

Background of the Invention

Traditionally, the bushing compartment of electrical transformers, especially distribution transformers, is arranged on the cover of the transformer tank. The tank is hermetically sealed by placing a sealing gasket between the cover, usually a flat cover, and a pot-shaped casing portion. The bushing compartment comprises electrically insulated conductors extending through an opening of the tank and having substantial vertical oriented outer terminals. Electrical connection of the terminals is easily possible with the bushing compartment arranged on the top of the tank.
However, in cases where additional high current connections are required the available space on the cover of the tank is limiting factor. In some applications the local requirement for individual bushings and associated sealing is not available on the cover of the tank.
In general it would be possible to arrange the bushing compartment on one of the side portions of the tank. However, electrical connectors, projecting from the side walls of the casing, are susceptible for damage and increase the shipping dimensions of the transformer.
An example of a transformer with a bushing compartment is shown in US 3 621 426 .
Thus, it would be desirable to provide an electrical transformer where available space for a bushing arrangement is increased without significantly increasing the shipping dimensions of the transformer.

Summary of the Invention

In accordance with the present invention there is provided an electrical transformer comprising a tank having sidewall portions, a cover and a bottom portion, whereby the cover is carrying a first bushing assembly and wherein a side portion of the tank has an opening.
The magnetic core and a winding assembly are disposed in a usual way in this tank.
A bushing compartment is attached on the side wall portion of the tank having the opening. The attachment is arranged in a way to seal the opening.
The bushing compartment itself has sidewalls, a cover and a bottom portion, whereby the bottom portion of said bushing compartment having a second opening therein for receiving a second bushing assembly.
The second bushing assembly having electrical conductor means being mounted through the second opening and having first terminals being encased and electrically connected with the winding assembly. The electrical conductor means further have second terminals remaining outside of the bottom portion of the bushing compartment.
In other words, the transformer according to the invention has a bushing assembly arranged on two levels: on a first level first bushings on the cover of the transformer, and on a second level second bushings arranged on a bottom portion of an attached bushing compartment (supplementary casing), whereby electrical terminals of the second bushings facing downwardly.
With the attached supplementary casing lateral dimensions of the casing are slightly increased. However, opposed to that, the bottom portion of the attached bushing compartment brings the advantage of a second carrier for further electrical conductors, which are required in high current applications, like setting of proper connection group by off-load and / or off-circuit operation, selection of proper tapping of high current winding in on-load condition ( DE 102008064485 ) or off-load condition, application for external control and measurement.
It is a further advantage of the invention that it is not necessary to modify the transformer assembly process due to having flexible conductors for the inner connections and the possibility to place a large amount of electrical connections on a limited surface.
In a preferred embodiment the covers of the tank are arranged in first plane and the bottom portion of the bushing compartment is arranged in a second plane, whereby the planes having a vertical distance to each other. Electrical terminals of the bushing assembly are arranged in niche and not exposed to be damaged and easy accessible.
For the assembly process of the transformer it can be an advantage when the cover of the tank and the cover of the attached bushing compartment are arranged in a single top plane. The process step of mounting the sealing gasket between the cover and a pot-shaped casing portion is unchanged.
Connecting the second terminals of the second bushing assembly can be easily accomplished when they are oriented vertically and substantially parallel to each other.
In a preferred embodiment the second bushing assembly comprises a flat insulating part acting as a carrier for the electrical conductor means.

Brief Description of the Drawings

In the accompanying drawing,

Fig. 1: is a front, side and top view of distribution transformer according to the invention;
Fig. 2: is a partial sectional drawing of the front and side view of Fig 1;
Fig. 3: is an enlarged view of detail "X" in Fig. 2.

Detailed Description of Preferred Embodiments

Fig. 1 shows a front view, a side view and a top view of a preferred embodiment of a distribution transformer 1 according to the invention. The transformer 1 has casing or tank 2 made of steel, having side wall portions 3, a cover 4 and a bottom portion 5.
A first bushing assembly 6 is attached on the cover 4, having terminals 7 for primary and secondary electrical connection of the transformer 1.
A bushing compartment 11 is welded on the side wall 3 of the tank 2. The cover 13 of the bushing compartment 11 and the cover 4 of the tank 2 are arranged in a horizontal plane 20 and formed integrally in one piece. The bottom portion 14 of the bushing compartment 11 is arranged in a plane 21. There is a vertical distance 22 between the plane 21 and the plane 20 of the cover 4 of the tank 2.
The bottom portion 14 has an opening 15, adapted for receiving a second bushing assembly 16.
With this design, the transformer according to the invention has a bushing assembly arranged in two levels: a first level in plane 20, a second level in plane 21. The two-level construction of a bushing assembly opens the possibility for arrangement of further connection means required in high current applications. Electrical terminals 19 facing downwardly from the bottom portion 14 of the bushing assembly 11 are protected in a niche.
The bushing assembly 16 comprises electrical conductor means 17 having first terminals 18 and second terminals 19. The second terminals 19 extend outward of the bushing compartment 11. The terminals 19 are oriented substantially vertically and parallel to each other.
Fig. 2 shows a partial sectional drawing of the front and side view of Fig 1. In the area where the bushing compartment 11 is attached on the side wall 3 of the tank 2 there is an opening 8 in the side wall 3. This opening 8 is sealed by welded side wall portions 12 and bottom portion 14 of the bushing compartment 11.
Flexible conductors connect the terminals 18 through the opening 8 with the winding assembly 10 located on the magnetic core 9 in the tank 2.
Fig. 3 shows an enlarged view of detail "X" in Fig. 2. The side walls of the bushing compartment 11 and bottom portion 14 are pot-shaped. The bottom portion 14 has the opening 15 for receiving the second bushing assembly 16. A plate-shaped insulating part 23 acts as a carrier for electrical conductors 17. A sealing gasket 24 is located between the insulating part 23 and the bottom portion 14. The insulating part 23 is fixed with screws.
The invention provides sufficient space for electrical connections required in additional high current applications.
The foregoing merely illustrates the principal of the invention. Those skilled in the art will be able to diverse numerous arrangements which, although not explicitly described or shown herein, embody those principles and are within the scope of the invention.

List of used reference signs

1: transformer
2: tank, casing
3: side wall portion
4: cover
5: bottom portion
6: first bushing assembly
7: terminals of first bushing assembly 6
8: opening in the side wall portion 3
9: magnetic core
10: winding assembly
11: bushing compartment
12: side wall portion of the bushing compartment 11
13: cover of the bushing compartment 11
14: bottom portion of the bushing compartment 11
15: second opening
16: second bushing assembly
17: electrical conductor means
18: first terminals
19: second terminals
20: first plane
21: second plane
22: distance
23: insulating part
24: sealing gasket

Claims

Electrical transformer, comprising:
a tank (2) having sidewall portions (3), a cover (4) and a bottom portion (5), whereby the cover (4) is carrying a first bushing assembly (6) and wherein a sidewall portion (3) has an opening (8) ;

a magnetic core (9) and a winding assembly (10) disposed in the tank (2);

a bushing compartment (11) attached on the side wall portion (3) and disposed to seal the opening (8);

said bushing compartment (11) having sidewalls (12), a cover (13) and a bottom portion (14), whereby the bottom portion (14) of said bushing compartment (11) having a second opening (15) therein for receiving an second bushing assembly (16),

said second bushing assembly (16) having electrical conductor means (17) being mounted through the second opening (15) and having first terminals (18) being encased and electrically connected with the winding assembly (10) and second terminals (19) remaining outside of the bottom portion (14) of said bushing compartment (11),

characterized in that, the cover portion (4) of the tank (2) is arranged in a first plane (20) and the bottom portion (14) of the bushing compartment (11) is arranged in a second plane (21), whereby the planes (20, 21) having a vertical distance (22) to each other, wherein the cover (4) of the tank (2) and the cover (13) of the bushing compartment (11) are arranged in the first plane (20), wherein the second terminals (19) are oriented substantially vertically and parallel to each other.
Transformer as claimed in Claim 1, wherein said second bushing assembly (16) comprises a flat insulating part (23) acting as a carrier for the electrical conductor means (17).
Transformer as claimed in Claim 2, wherein in a mounted position of the second bushing assembly (16) a sealing gasket (24) is arranged between the insulating part (23) and the bottom portion (14) of the bushing compartment (11).
Transformer as claimed in Claim 3, wherein the insulating part (23) of the second bushing assembly (16) is fixed on the bottom portion (14) by screws.
Transformer as claimed in one of the preceding Claims, wherein the bushing compartment (11) and the tank (2) is made of steel.
Transformer as claimed in Claim 5, wherein the bushing compartment (11) is welded on the sidewall potion (3) of the tank (2).
Transformer as claimed in Claim 5, wherein the cover (4) of the tank (2) and the cover (13) of the bushing compartment (11) are made in one piece.
A method of manufacturing an electric transformer comprising the steps of:
a. forming a tank (2) having sidewall, top and bottom portions (2,3,14), whereby a cover (13) having a bushing assembly (6) and a side wall portion having an opening (8);

b. mounting a bushing compartment (11) having sidewall, top and bottom portions on the side wall portion of the tank and thereby sealing the opening (8), whereby a bottom portion (14) of the bushing compartment (11) having a second opening (15) adapted for receiving a second bushing assembly (16), wherein the cover portion (4) of the tank (2) is arranged in a first plane (20) and the bottom portion (14) of the bushing compartment (11) is arranged in a second plane (21), whereby the planes (20, 21) having a vertical distance (22) to each other, wherein the cover (4) of the tank (2) and the cover (13) of the bushing compartment (11) are arranged in the first plane (20), wherein the second terminals (19) are oriented substantially vertically and parallel to each other;

c. connecting first terminals (18) of the second bushing assembly (16) to extended leads of winding assembly (10) ;

d. disposing a magnetic core (9) and the winding assembly (10) in the tank (2);

e. sealing second bushing assembly (16) by means of sealing gasket (24) at the second plane (21)

f. sealing cover (4, 13) to the tank (2) at the first plane (20);

g. connecting the second terminals (19) to the terminals of a device of a high current application.