JPS5885510A - Transformer - Google Patents

Abstract

PURPOSE:To provide a transformer in which increase of current density at ends of windings is prevented and the temperature rise is suppressed without reducing the space factor of foil windings. CONSTITUTION:If load current flows in a low tension winding 4 and a high tension winding 5, eddy current to eliminate the horizontal component of the winding leakage flux scarcely flows at upper and lower ends of a thin metal sheet but it flows in concentration to respective upper and lower ends of an auxiliary winding 11 inside the low tension winding 4 and an auxiliary winding 11 outside the high tension winding 5. Since the upper and lower ends of the windings 4, 5, i.e. upper and lower ends of the metal sheet 7 becomes substantially flowing state of normal load current in the same manner as in the sheet intermediate portion without upper and lower ends, excessive rise of the current density at upper and lower ends of the windings 4, 5 is alleviated significantly. In this constitution, ends of the windings 4, 5 are not subjected to the abnormal temperature rise caused by increase of the current density and the winding leakage flux does not leak out of the shield installed outside the high tension winding 5, thereby overheating of a wall of the tank 1 is prevented and the tank shield becomes unnecessary.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a transformer equipped with a low-voltage winding and a high-voltage winding comprising an auxiliary winding in which a metal sheet and an insulating sheet are wound in layers.

Technical Background of the Invention A transformer equipped with this type of foil-wound winding has a good fertilization rate, so it has the advantage of being able to be made smaller and lighter. Small-capacity transformers with relatively low voltages of several kV or several hundred kVA have already been put into practical use and are on the Kanashi market.

Recently, in view of its excellent advantages, research has been conducted to expand its application to higher voltage, larger capacity transformers such as 275kV and 300MVA.However, the biggest drawback of foil-wound transformers is that large The key to putting large capacity foil-wound transformers into practical use is how to overcome the problem of excessive temperature rise at the ends of the windings due to eddy currents.

A conventional foil-wound transformer has the configuration shown in FIG. An iron core 2 is provided inside a tank 1 filled with an insulating gas such as insulating oil or id'sF gas as an insulating medium, and a low voltage winding 4 is connected to the outer circumference of the legs of the iron core 2 via an insulating cylinder 3.
is wound around the outer circumference of this low voltage winding 4, and an insulating barrier 6 is placed around the outer circumference of this low voltage winding 4.
A high voltage winding 5 is wound through the coil. Each of these windings 4
．． 5 is constituted by a foil-wound wire formed by overlapping and winding a metal sheet 7 made of aluminum or the like and an insulating sheet 8 made of resin film or the like. Clamps 9, 9 for tightening the iron core 2 and each winding 4.5 are arranged above and below the upper and lower ends of each winding 4.5. Due to leakage magnetic flux from windings 4 and 5, υtank 1 is inside the wall of tank 1.
A tank shield 10 is installed which prevents the walls from overheating.

Problems with the Background Art Conventional transformers use low-voltage and high-voltage windings made of rectangular copper wire, so when a load current flows through the windings, the windings as shown by the broken line in Figure 1 Leakage flux occurs, but in a transformer with low-voltage and high-voltage windings 4.5 made of foil-wound windings, when load current flows through windings 4 and 5, the horizontal component of leakage flux is canceled out. A large loop of eddy current flows through the upper and lower ends of the windings 4 and 5. As a result, as shown by the two-dot chain line in Figure 1, the winding leakage flux of the foil-wound transformer passes vertically inside the windings 4 and 5, and straightens at a nearly right angle immediately after exiting the windings 4 and 5. Walk in a curving manner. At this time, since a large eddy current flows superimposed on the load current at the upper and lower ends of each winding 4.5, the current density at the upper and lower ends of the windings 4 and 5 is lower than that of the winding 4 excluding the upper and lower ends. , 5 is extremely high compared to the current density in the middle part. The characteristics of the current density distribution at the ends of the windings 4 and 5 are shown in FIG. According to this diagram, winding 4
At the end of the winding 5, the current density increases from the outer circumference to the inner circumference, D (line A), and at the end of the winding 5, the current density increases from the inner circumference to the outer circumference (line B). ) It can be seen that there is a tendency. As a result of the excessive current density at the ends of the winding 4.5, only the upper and lower ends of the winding 4.5 have an abnormally high temperature.

As a countermeasure against this phenomenon, the thickness of the metal sheet 7, which is a conductor in the winding 4.5, may be increased to reduce the current density at the end of the winding to a level where the temperature rise does not become a problem. However, in order to wind the 184°5 winding so that the thickness is uniform in the winding height direction (winding axial direction), it is necessary to wind at least 90% of the total height of the winding, which is not affected by eddy currents, except for the ends of the winding. It is also necessary to uniformly increase the thickness of the metal sheet 7 in the middle portion of the winding. For this reason, the overall thickness of the metal sheet 7 increases,
It is unfortunate that the most important feature of foil-wound wires, which is their good space factor, has been lost. Further, since the thickness of the metal sheet 7 is uniform, there is a problem in that it is difficult to implement a cooling structure that allows cooling of the ends of the winding to be much better than that of the middle part of the winding.

OBJECTS OF THE INVENTION The present invention provides a transformer that suppresses the increase in current density at the ends of the windings and prevents temperature rises without reducing the space factor of the foil-wound windings.

Summary of the Invention The transformer of the present invention has a main winding consisting of a foil-wound winding, which is a low-voltage winding (inner winding), and a main winding, which is a low-voltage winding (inner winding), and a main winding, which is a high-voltage winding (outer winding). By providing an auxiliary winding made of foil winding on one or both of them, eddy currents are hardly generated at the ends of the main winding and are concentrated at the ends of the auxiliary winding. , thus suppressing the increase in current density at the ends of the main winding.

Embodiment 5 of the invention - Figures 3 to 5 show an embodiment of the transformer of the invention. The transformer of this embodiment has an iron core 2 provided inside a tank 1 filled with an insulating medium, similar to the previously mentioned known example.
A low-voltage winding 4 and a high-voltage winding 5, which are foil-wound wires made by overlapping metal sheets 7 and insulating sheets 8, are wound concentrically on the inside and outside, and clamps f9 and 9 are provided.

In the transformer of this embodiment, an auxiliary winding is provided concentrically around the inner circumference of the low-voltage winding 4, which is the inner winding in the tank 1, that is, between the low-voltage winding 4 and the legs of the iron core 2.
This auxiliary wire 11 is wound around the two legs of the iron core via the insulating cylinder 3. Note that an insulating barrier 12 is provided between this auxiliary winding 11 and the low voltage winding 4. Further, an auxiliary winding 1 is arranged concentrically around the outer circumference of the high voltage winding 5 which is the outer winding, that is, between the high voltage winding 5 and the peripheral wall of the tank 1.
1 is provided, and this auxiliary winding 11 is wound around the high voltage winding 5 via an insulating barrier 13. Therefore, overall, the legs of the iron core 2 are centered, the insulating cylinder 3, the auxiliary winding 1,
6- The insulating barrier 12, the low voltage winding 4, the insulating barrier 6, the high voltage winding 5, the insulating barrier 13 and the auxiliary winding 1 are arranged concentrically in this order. Each of these auxiliary windings 11, 1 is a main winding. ;', 'p 4 + s It is composed of a foil-wound wire in which a metal sheet 7 and an insulating sheet 8 are overlapped and wound. However, this auxiliary winding 11.11 has a low winding voltage and a low winding capacity, so even if this auxiliary winding 11.11 is provided, it will have no effect on the overall winding arrangement of the transformer. is almost negligible. Furthermore, magnetic shields 14 and 14 formed by laminating silicon steel plates, for example, are provided on the side faces of the clamps 9.9 provided at the upper and lower ends of the windings 4 and 5, respectively, facing the ends of the windings. be.

Therefore, in the transformer configured in this way, when a load current is passed through the low voltage winding 4 and the high voltage winding 5, each winding 4
, 5, almost no eddy current flows in the upper and lower ends of the thin metal sheet 7 for canceling the horizontal component of the winding flux, and the auxiliary winding 11 provided inside the low-voltage wire 3 and Eddy currents flow concentrated at the upper and lower ends of the auxiliary winding 11 provided outside the high-voltage winding 4. For this purpose, since the upper and lower ends of each winding 4, 5, that is, the condition of the wire mesh sheet 7, are
The extreme increase in current density at the upper and lower ends of 5 is significantly alleviated.

The characteristics of the current density distribution at the ends of the windings 4 and 5 in this case are shown in FIG. In this diagram, Ai is the 4th end of the involute
Line B' shows the current density at the end of the winding 5. According to this diagram, it can be seen that the current density is significantly lower than the current density at the end of the winding in the conventional transformer shown in FIG. Therefore, volume &! At the 4°5 end, there is no abnormal rise in temperature due to an increase in current density. Since the winding leakage magnetic flux does not leak outside the auxiliary winding 11 provided on the outside of the high-voltage winding 5, overheating of the wall of the tank 1 due to the leakage magnetic flux can be prevented. The tank shield 10, which had been used for 11 years, is no longer necessary, because the winding leaks inside the auxiliary wire-saving wire 11 installed inside the low-voltage core 4, and the magnetic flux does not leak out, so the leakage magnetic flux from the winding Overheating of the iron core 2 and the metal structural materials around it can be prevented. Furthermore, the clamp 9,
The magnetic shields 14 and 14 attached to the windings 9 have the effect of further increasing the straightness of the winding leakage magnetic flux within the windings 4 and 5, and further reducing the slight eddy current remaining at the upper and lower ends of the windings 4 and 5. be. Since it is necessary to increase the overall thickness of the metal sheet 7 in each of the windings 4 and 5 in order to avoid temperature rise due to eddy currents, a reduction in the space factor of the windings 4 and 5 can be prevented.

Auxiliary winding 'Mzdll, 11 is a tertiary winding with a low rated voltage,
Alternatively, it may be connected to either the neutral tap winding of the step-insulated high-voltage winding, but in either case, the test voltage level is low, and the auxiliary The insulation distance d7 between the winding 1 and the circumferential wall of the tank 1, and the insulation distance d3 between each phase in the case of three phases, may be shorter. Comparing the insulation distance d4 between the high voltage winding 5 and the tank shield 10 shown in Fig. 1 and the insulation distance d1 between the high voltage winding 5 and the auxiliary winding -9 = wire 11 shown in Fig. 2, , the latter insulation path l1IIlda can be made shorter. That is, in the transformer of the present invention, since the auxiliary winding 11 is arranged concentrically with the high voltage winding 5, the insulating barrier 13 has a so-called multi-barrier structure in which the two are partitioned into a narrow gap by an insulating tube.
This is because by providing this, it is possible to significantly shorten the insulation distance d1.

The effect of the invention is that by providing auxiliary windings made of foil windings on both sides, it is possible to prevent an increase in current density at the ends of the windings and prevent a temperature rise without impairing the space factor of the windings.

[Brief explanation of drawings]

Fig. 1 is a longitudinal side view showing the schematic configuration of a conventional transformer, Fig. 2 is a diagram showing the current density distribution at the end of the winding in the conventional transformer, and Fig. 3 is a diagram showing the current density distribution of the winding end of the conventional transformer. FIG. 4 is a plan view of the same, and FIG. 5 is a diagram showing the current density distribution at the end of the winding in the transformer of the embodiment. 1...tank, 2...iron core, 3...insulation tube, 4...
...Low voltage winding, 5...High voltage winding, 6...Insulation barrier, 7...Metal sheet, 8...Insulation sheet, 9...
Clan 1.11... Auxiliary winding, 12, 7.9...
Insulating barrier, 14...magnetic shield. Applicant's agent Patent attorney Takehiko Suzue 11- Aoi 2

Claims (1)

[Claims] A low-voltage winding made of a foil-wound winding made of overlapping metal sheets and insulating sheets is wound around an iron core provided inside the tank, and a high-voltage winding made of the foil-wound winding is placed outside of this low-voltage winding. What is claimed is: 1. A transformer in which an auxiliary winding made of the foil-wound wire is provided on either or both of the inside of the low-voltage winding and the outside of the high-voltage winding.