JPS586292B2 - transformer - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to a transformer in which the low voltage side is used at different rated voltages, and in particular, the percent impedance %IZ (hereinafter referred to as %IZ) between the windings is the same regardless of the rated voltage. Regarding transformers that can be used.

For example, a standby main transformer that can be used for two types of generators with different rated voltages has a rated voltage specification of 20/20/
25 kv, and the rated voltage on the high voltage side is 500 kv, so it is necessary to provide taps corresponding to two types of generator voltages with different rated voltages on the low voltage side of the transformer.

For transformers with such specifications, it is difficult to provide a tap directly on the low-voltage winding.

This is because, for example, when changing from 25 kV to 20 kV, unused tap winding parts are created and no current flows through them, resulting in a large imbalance in the radial magnetic flux between the high and low voltage windings, resulting in a short circuit mechanical force. This is because, especially in the case of a large-capacity transformer, it would be difficult to provide a protruding lead wire from the middle of the winding because the low-voltage side would have a large current.

Therefore, the tap part has to be wound separately, but even in this case, the low-voltage side winding originally has a small number of turns, and the tap winding that makes up a part of it has an extremely small number of turns, for example, when a large iron core The large-capacity transformer used has only a few turns, making it difficult to manufacture, and the low-voltage side has a large current, so a tap changer that is compatible with it cannot be easily obtained.

Therefore, conventionally in such cases, a so-called equivalent tap switching method has been adopted in which the number of turns of the low voltage side winding is constant and a tap is provided on the high voltage side.

Fig. 1 and Fig. 2a show the embodiment, in which the iron core 1
It consists of a separate winding transformer with a low-voltage winding 2 and a high-voltage winding 3 wound around it, and an equivalent tap winding 4 (hereinafter referred to as equivalent tap winding) corresponding to the tap voltage on the low-voltage side is installed on the high-voltage side. )
It has been established.

When the low voltage side is used at the lower rated voltage, the high voltage side uses U and v1 tap terminals, and when the low voltage side is used at the higher rated voltage, the high voltage side uses the U and v2 tap terminals. It uses terminals.

Such an equivalent tap switching system is constructed by arranging an equivalent tap winding 4 outside the high voltage winding 3, as shown in Figure 2a. The leakage magnetic flux distribution between the two is as shown in FIG. 2b.

In Figure 2b, the solid line shows the leakage magnetic flux distribution when the lower rated voltage is selected for the low voltage side, and the dotted line shows the leakage magnetic flux distribution when the higher rated voltage is selected for the low voltage side. .

As is clear from FIG. 2b, there is a large difference between the solid line and the dotted line, as indicated by the vertical hunting.

By the way, the impedance %IZ between the transformer windings is determined by the following formula.

% I Z: % I Xx f B2dV - (
1) Here, %■Z: Percent impedance between windings %IX: Percent reactance between windings B: Magnetic flux density at each part of the winding and main gap V: Volume of each part of the winding and main gap.

As can be seen from equation (1), the magnitude of %IZ is proportional to the square of B.

Therefore, as shown in Figure 2b, there is a large difference in leakage magnetic flux distribution when a lower rated voltage is selected for the low voltage side and when a higher rated voltage is selected, and in such a transformer, (
From equation 1), there will be a very large difference in %IZ.

Therefore, the %IZ changes greatly due to a change in the rated voltage.

The present invention takes the above-mentioned points into consideration, and eliminates the change in %IZ due to a change in rated voltage, which is a drawback of the equivalent tap switching method, and allows the %IZ between windings to be maintained regardless of the rated voltage.
The purpose is to provide a transformer that can do the same.

An embodiment of the present invention will be described below with reference to FIG.

In the transformer according to the present invention, as shown in FIG. 3a, an equivalent tap winding 4 is arranged inside the low voltage winding 2, and the equivalent tap winding 4, the low voltage winding 2, The windings are arranged so as to form a high voltage winding 3.

When the low voltage side is used at the lower rated voltage, use the U and V1 tap terminals on the high voltage side, and when the low voltage side is used at the higher rated voltage, use the U and V2 terminals on the high voltage side. is the same as before.

With such a winding arrangement, the leakage magnetic flux distribution will be as shown in Figure 3b.
The leakage magnetic flux distribution when the low voltage side is used at the lower rated voltage (shown by the solid line) and the leakage magnetic flux distribution when the low voltage side is used at the lower rated voltage (shown by the dotted line) are as shown in . In between, there is a part where the dotted line is larger (the part shown by the vertical hatching) and a part where the solid line is larger (the part shown by the horizontal hatching).

Therefore, the difference in leakage magnetic flux distribution between when used at a lower rated voltage and when used at a higher rated voltage disappears because the vertical line hatching part and the horizontal line hatching part cancel each other out, and as a result ( 1) As is clear from formula,
The %IZ at each rated voltage becomes almost the same.

In this case, it is also possible to adjust the %IZ at each rated voltage to exactly the same value by slightly adjusting the sizes of the windings and the main gap dimensions.

4 and 5 show other embodiments of the present invention,
A tap winding 5 is provided to be connected to an equivalent tap winding 4 in order to have a desired fluctuation range for the high voltage side rated voltage,
This is arranged outside the high voltage winding 3, and in this case as well, the same effects as the embodiment shown in FIG. 3 can be obtained.

As explained above, according to the present invention, two
To provide a transformer which can maintain the same %Z between windings no matter which low-voltage side rated voltage is used when connected to different types of generators and used by changing the low-voltage side rated voltage. be able to.

[Brief explanation of the drawing]

Figure 1 is a wiring diagram of a conventional transformer, Figure 2 a and b are
The winding arrangement diagram and leakage flux distribution diagram of the transformer shown in Figure 3.
Figures a and b are a winding layout diagram and a leakage flux distribution diagram of a transformer according to the present invention, and Figures 4 and 5 are a wiring diagram and a winding layout diagram showing other embodiments of the present invention. 1...Iron core, 2...Low voltage winding, 3...
...High voltage winding, 4...Equivalent tap winding,
5...Tap winding.

Claims (1)

[Claims] 1. In a separate winding transformer whose low voltage side is used with different rated voltages, equivalent tap windings, low voltage windings, and high voltage windings are concentrically wound around the iron core, which are connected to the high voltage winding in order from the inside. A transformer characterized by being configured with.