JPH0252417B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a large current transformer, and more specifically to a large current transformer used in thyristor equipment and the like.

As the capacity of thyristor devices increases, the influence of harmonics on power supplies has become a problem. For this reason, in transformers used in thyristor equipment, the secondary winding is divided into two, and these windings are combined with star and delta connections to perform multiphase rectification to reduce the effects of harmonics. It is configured as follows. Since this type of transformer is often used for large currents, a sheet coil made of a copper plate is used as the winding.

Embodiments of the present invention will be described below based on the drawings. Figure 1 shows the winding structure on the secondary side of a conventional transformer of this type, and the figure only shows the winding for one phase in the vector diagram shown in Figure 2. . Further, FIG. 5 shows a perspective view of the secondary winding shown in FIG. 1.

Now, as shown in Fig. 1 and Fig. 5, on the secondary side of a conventional transformer, a star-connected secondary winding 2 (hereinafter simply referred to as 〓 winding) and a delta-connected secondary winding 2 are connected. It was manufactured in two stages with winding 3 (hereinafter simply referred to as Δ winding), and the current density in each winding was almost the same.

In addition, since the number of turns of the winding is 1/√3 of the Δ winding, the gap δ between turns of the winding becomes large, resulting in a disadvantage that the space factor is low.

Furthermore, in a self-cooling type transformer as shown in Fig. 3, the oil temperature rise varies greatly depending on the height (H) of the transformer. There is a temperature difference Δt between the temperature and the oil temperature around the winding located at the bottom, and as the oil temperature around the Δ winding increases, the cooler also had to be designed to match the Δ winding. .

An object of the present invention is to provide a large current transformer in which the space factor of the secondary winding is improved.

The features of the present invention are that the number of stages of star-connected sheet coils on the secondary side is smaller than the number of stages of delta-connected sheet coils, and the current density of the star-connected sheet coils is lower than the current density of the delta-connected sheet coils. The main feature is that the cross-sectional area of the copper plates forming these sheet coils is selected so as to increase the height.

That is, the present invention provides that if the loss generated in the lower winding on the secondary side is increased, the pressure difference between the cold oil in the radiator 4 and the hot oil in the loss generating part will be increased, and the heat dissipation effect of the radiator 4 will be improved. Even if the loss generated in the lower winding increases, the surrounding oil temperature of the lower winding is low and the temperature of the winding does not increase.Furthermore, by reducing the loss of the Δ winding wound on the upper part of the iron core 1, the secondary winding Focusing on the fact that the loss of the entire wire does not increase and the temperature of both windings is in equilibrium, the thickness of the copper plate used for the winding is reduced, and as a result, the structure of the secondary winding is The purpose is to improve the space factor of the winding by using one stage rather than the conventional two stages.

Hereinafter, one embodiment of a large current transformer according to the present invention will be described based on FIGS. 3, 4, and 6. FIG. 4 shows the winding structure on the secondary side of the large current transformer according to the present invention, and this embodiment is the first one.
The difference in structure from the conventional example shown in the figure is that the winding is changed from two stages to one stage, and the cross-sectional area of the copper plate used for the winding is changed so that the current density of the winding 12 is higher than the current density of the winding 13. This is because the selection was made so that it would be high. A perspective view of the winding of the secondary winding shown in FIG. 4 is shown in FIG. In this case, the winding 12 has a higher calorific value per unit volume, a higher calorific value per unit surface area, and a higher heat dissipation amount than the Δ winding.

According to this embodiment, (1) the winding is in one stage, and
Since the copper plate used for the winding is made thin so that its cross-sectional area is small, the space factor of the secondary winding can be improved. In addition, (2) since the coil is in one stage, it is easy to manufacture the winding, and the manufacturing time is reduced to approximately 50% compared to the conventional method. Furthermore, (3) since the winding generates a high amount of heat and is disposed below the iron core, the head difference between the winding and the cold oil in the radiator 4 is high, allowing the number of people to install the radiator to be reduced. In addition, (4) Even if the heat dissipation density of the winding is higher than that of the Δ winding, the oil temperature around the winding is lower than that of the Δ winding, as shown in Figure 3B. It is possible to create a transformer with almost equal temperature rise and a well-balanced temperature distribution. Furthermore(5)
By increasing the current density of the windings, the amount of copper used for the windings can be reduced, making it possible to reduce costs by about 5% compared to conventional transformers.

Note that, as shown in FIG. 4, the neutral point terminal x ₂ forming the star connection of the windings is wound inside the windings, making it easy to form the line side terminals. In addition, as a means to increase the space factor of the winding,
It is also effective to insert a cooling duct on only one side of the copper plate, as shown in the figure.

As described above, according to the present invention, it is possible to realize a large current transformer that is easy to manufacture and that improves the space factor of the secondary winding.

[Brief explanation of the drawing]

Figure 1 is an explanatory diagram showing the winding configuration on the secondary side of a conventional large current transformer, Figure 2 is a vector diagram of the transformer, Figure 3A is a configuration diagram of the transformer, and Figure 3B is Characteristic diagram showing the relationship between transformer winding height and oil temperature, No. 4
The figure is an explanatory diagram showing the winding structure on the secondary side of the transformer according to the present invention, FIG. 5 is a perspective view showing the external appearance of the secondary winding shown in FIG. 1, and FIG. 6 is the same as FIG. FIG. 7 is an explanatory diagram showing another embodiment of the winding structure of the secondary winding of the transformer according to the present invention. be. 1, 10, 20... Iron core, 2, 12... Winding, 3, 13... Δ winding, 4... Radiator, 2
3... Cooling duct.

Claims (1)

[Claims] 1 A sheet coil formed by winding a copper plate with two or more star-connected or delta-connected secondary windings, and a delta-connected secondary winding placed above the winding in the axial direction, and a star-connected secondary winding. In a large current transformer in which a secondary winding is disposed at the lower part of the winding in the axial direction, the number of stages of the star-connected sheet coils is smaller than the number of stages of delta-connected sheet coils, and the star-connected sheet coils are star-connected. A large current transformer characterized in that the cross-sectional area of the copper plates forming these sheet coils is selected so that the current density of the sheet coils is higher than the current density of the sheet coils connected in delta.