EP0406555B1

EP0406555B1 - Shared shunt reactor type transformer

Info

Publication number: EP0406555B1
Application number: EP90109760A
Authority: EP
Inventors: Kentaro C/O Mitsubishi Denki K.K. Taninouchi; Katsuji C/O Mitsubishi Denki K.K. Sokai; Syoji C/O Mitsubishi Denki K.K. Nakatsuka
Original assignee: Mitsubishi Electric Corp
Current assignee: Mitsubishi Electric Corp
Priority date: 1989-07-06
Filing date: 1990-05-22
Publication date: 1993-08-11
Anticipated expiration: 2010-05-22
Also published as: CN1017846B; DE69002708D1; JPH0682582B2; DE69002708T2; JPH0338807A; CN1048626A; HK1003811A1; EP0406555A1

Description

BACKGROUND OF THE INVENTION

Field of the Invention

This invention relates to a shared shunt reactor type transformer used in a power transmission or distribution system.

Description of the Prior Art

There is known a shared shunt reactor type three-phase transformer, as disclosed in Japanese Patent Application laid open under No. 30112/1985. Its construction is schematically shown in FIGURE 1. It comprises a transformer 1, a shunt reactor 2, and a tank 3 in which the transformer and the shunt reactor are installed. The transformer 1 has a limb core 1a, an upper and a lower yoke 1b and 1c and a coil 1d. The excitation of the transformer 1 causes main magnetic flux to pass as shown at 1e. The shunt reactor 2 has an upper yoke 2b a gap core 2a, and a coil 2d. The excitation of the reactor 2 causes magnetic flux to pass as shown at 2e. The coils 1d and 2d are so wound respectively that the main magnetic flux passing through the limb core 1a of the transformer 1 may be of the same polarity as that passing through the gap core 2a of the shunt reactor 2, as shown in FIGURE 1.
FIGURE 2 shows a case that a transformer 1 and a shunt reactor 2 are separate from each other. The transformer 1 is installed in a tank 4, and the shunt reactor 2 in another tank 5. The reactor 2 includes a lower yoke 2c. The transformer 1 and the reactor 2 are otherwise of the same construction as those which have been described with reference to FIGURE 1. If the reactor 2 is connected to the top of the transformer 1 in a common tank 3 so that the upper yoke 1b of the transformer 1 may serve as the lower yoke 2c of the reactor 2, too, a shared shunt reactor type transformer as shown in FIGURE 1 is obtained.
Referring again to FIGURE 1, the modes in which magnetic flux passes through the upper yoke 1b of the transformer 1 consist of three cases, i.e.:

Case 1 - The main magnetic flux 1e of the transformer passes if only the transformer is excited;
Case 2 - The magnetic flux 2e of the shunt reactor 2 passes if only the shunt reactor is excited; and
Case 3 - The magnetic flux passing through it corresponds to the difference between the magnetic flux 1e and 2e if the transformer and the shunt reactor are both excited.

Therefore, the assembly of FIGURE 1 exhibits the same performance as the separate type shown in FIGURE 2, and yet calls for a smaller space for installation, if the upper yoke 1b of the transformer 1 has so large a cross-sectional area that it may not be magnetically saturated in any of the three cases.
It is, however, usual that the maximum magnetic flux passes through the upper yoke 1b of the transformer 1 in Case 1, as the magnitude of the flux 1e is usually greater than that of the flux 2e. This requires the upper yoke 1b to have the same cross-sectional area as the lower yoke 1c. This requirement has hitherto disabled any desirable reduction in weight of the core of the transformer.

SUMMARY OF THE INVENTION

Under these circumstances, it is an object of this invention to provide an improved shared shunt reactor type transformer in which a transformer and a shunt reactor are constructed as a unitary assembly having a reduced transformer core weight.
This object is essentially attained by the features disclosed in claim 1.
This arrangement enables a reduction in the cross-sectional area of the yoke of the transformer, and yet the shared shunt reactor type transformer according to this invention is satisfactory for use in any case where the transformer or the shunt reactor is operated alone, or where they are operated together.
These and other objects, features and advantages of this invention will become more apparent from the following description and the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGURE 1 is a schematic sectional view of a known shared shunt reactor type transformer;
FIGURE 2 is a schematic sectional view illustrating the operation of the apparatus shown in FIGURE 1;
FIGURE 3 is a schematic sectional view of a shared shunt reactor type transformer embodying this invention;
FIGURES 4 and 5 are views similar to FIGURE 3, but showing the operation of the apparatus shown in FIGURE 3;
FIGURE 6 is a schematic sectional view of another embodiment of this invention; and
FIGURE 7 is a schematic sectional view of still another embodiment of this invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

A preferred embodiment of this invention will now be described with reference to the drawings which are merely illustrative of this invention and are not intended for limiting the scope thereof.
Reference is first made to FIGURE 3 showing a shared shunt reactor type transformer of a single-phase shell-type. The transformer 1 has a limb core 1a, a yoke 1c, and a coil 1d. The yoke 1c has a diminished yoke X and a bypass yoke Y. The apparatus also includes a shunt reactor 2. The reactor 2 has a gap core 2a, and a coil 2d which is surrounded by the diminished yoke X of the transformer 1 and the bypass yoke Y. The diminished yoke X and the bypass yoke Y form a yoke for the reactor 2, too.
The excitation of the transformer 1 causes a main magnetic flux to pass as shown at 1e, while the excitation of the shunt reactor 2 causes magnetic flux to pass as shown at 2e. The coils 1d and 2d are wound in such a way that the magnetic flux 1e and 2e passing through the diminished yoke X may cancel each other.
Attention is drawn to FIGURE 4 showing a case that a shell type transformer 1 and a shell type shunt reactor 2 are so positioned that the respective yokes 1c and 2b thereof may stay apart from each other, but in a mutually closely adjacent relation. The main magnetic flux 1e and the magnetic flux 2e are designed for passing in opposite directions through the yoke 1c of the transformer 1 and the yoke 2b of the reactor 2, respectively.
The apparatus shown in FIGURE 3 is obtained if the transformer 1 and the shunt reactor 2 which are shown in FIGURE 4 are so combined that the yoke 1c of the transformer 1 may serve as the yoke 2b of the reactor 2, too. Insofar as the magnetic fluxes 1e and 2e pass in the opposite directions, they cancel each other when passing through the diminished yoke X in the apparatus shown in FIGURE 3. It is, therefore, sufficient for the diminished yoke X to have a cross-sectional area which allows for the passage of the amount of magnetic flux equal to the difference between 1e and 2e, and which is smaller than the original cross-sectional area of the yoke 1c.
Attention is also drawn to FIGURE 5 showing the magnetic flux distribution which occurs when only the transformer 1 is excited. As is obvious from the figure, the main magnetic flux of the transformer 1 is distributed through the diminished yoke X and the bypass yoke Y. Therefore, it is sufficient for the diminished yoke X and the bypass yoke Y to have a sum of cross-sectional areas of yokes X and Y which is equal to the original cross-sectional area of the yoke 1c.
Therefore, the apparatus shown in FIGURE 3 enables a reduction in the cross-sectional area of the yoke of the transformer 1 by an amount equal to the difference between that of 1c as shown in FIGURE 4 or 5 and that of X, and thereby a smaller space for installation.
Although the invention has been described as a single-phase apparatus, similar results can be obtained from a three-phase apparatus as shown by way of example in FIGURE 6. Although the invention has been described as a shell type apparatus, similar results can be attained from a core type apparatus as shown by way of example in FIGURE 7.

Claims

A shared shunt reactor type transformer comprising:
a bypass yoke (Y) of a transformer (1) for serving as a yoke of a shunt reactor as well as a part of a yoke of the transformer (1), characterised in that said yoke of the transformer (1) is partially divided into two parts of a diminished yoke (X) and said bypass yoke (Y);
a gap core (2a) of the shunt reactor (2) provided to an open space formed between said diminished and bypass yokes (X,Y) of the transformer (1); and
a coil (2d) of the shunt reactor (2) wound around said gap core (2a) of the shunt reactor (2), for producing magnetic flux (2e) in a direction reducing magnetic flux of the transformer produced in said diminished yoke (X) of the transformer (1).
A shared shunt reactor type transformer as set forth in claim 1, wherein said transformer (1) and said shunt reactor (2) are respectively of a shell type.
A shared shunt reactor type transformer as set forth in claim 1, wherein said transformer (1) and said shunt reactor (2) are respectively of a core type.
A shared shunt reactor type transformer as set forth in claim 1, 2 or 3, wherein said transformer (1) and said shunt reactor (2) are respectively of a single-phase type.
A shared shunt reactor type transformer as set forth in claim 1, 2 or 3, wherein said transformer (1) and said shunt reactor (2) are respectively of a three-phase type.