JPS60195913A - On-load tap changing transformer - Google Patents

Abstract

PURPOSE:To form a small size windings of a transformer which assures a high lightning impulse test voltage of low voltage terminal and a broad tapping range by providing an intermediate tap to a capacitor and connecting such tap to the intermediate tap of tap winding. CONSTITUTION:An intermediate tap is provided to a capacitor to be connected to a tap winding, two terminals A, C of capacitor are connected between the maximum taps of tap winding 3 and an intermediate tap B of capacitor is connected to the intermediate tap of tap winding 3. Not only a lightning impulse voltage generated between the maximum taps can be reduced but also potential vibration inside the tap winding can be suppressed by connecting a capacitor also to such intermediate tap, so that a winding which is resistive to lightning impulse voltage can be manufactured without excessive enhancement of insulation property of tap winding 3. A capacitor to be used forms a capacitor having an intermediate tap through combination of three electrodes 6 which are insulated by dielectric material (for example, insulation paper) 7 and are wound in a spiral manner.

Description

DETAILED DESCRIPTION OF THE INVENTION FIELD OF APPLICATION OF THE INVENTION The present invention relates to on-load tap-changing transformers, and more particularly to transformers with null-place tap windings.

[Background of the invention]

As an example of a tap-changing transformer on load, the method of connecting the windings of an autotransformer that switches the voltage on the low voltage side is shown in Figure 1. In Figure 6, 1 is a series winding.

2 is a shunt winding, 3 is a tap winding, and 4 is a polarity switch.

5 is a tap selector, H is a high voltage terminal, L is a low voltage terminal, and C is a capacitor.This connection method is called a fork connection. As in this example, when the tap winding 3 is connected to the line side, unlike when the tap winding 3 is connected to the neutral side, there is no transition from the line side to the low voltage terminal during the lightning impulse test. A large voltage may be generated depending on the voltage. This impulse voltage transition is caused by the capacitance between the shunt winding 2 and the tap winding 3. In order to reduce this transition voltage, it is necessary to widen the distance between the shunt winding @2 and the tap winding 3, and to strengthen the insulation of the tap winding, which makes the winding larger and more expensive. There were drawbacks. In order to compensate for this drawback, an attempt was made to reduce the voltage generated between the maximum taps by inserting a capacitor C between the maximum taps of the tap winding 3 and electrostatically coupling them, as shown in Figure 1. What it does is known.

An example of the structure of a capacitor used for this purpose is shown in FIG. 2, which considerably improves the above-mentioned drawbacks.
If the lightning impulse test voltage of the low voltage terminal is high and the tap range is wide, the potential oscillations generated inside the tap winding 3 will increase due to the inductance and capacitance of the tap winding 3, and A large voltage is also generated. In such a case, simply inserting the capacitor C between the largest taps as shown in FIG. 1 will not be sufficient in terms of insulation, and it will be necessary to strengthen the insulation of the tap windings. In the figure, 6 is an electrode and 7 is an insulator.

[Purpose of the invention]

The object of the invention is also for transformers with high lightning impulse test voltage of low voltage terminals and wide tap range.

The purpose of the present invention is to provide an inexpensive on-load tap change transformer with a smaller winding.

[Summary of the invention]

The gist of the invention is that the capacitor is provided with a middle tap, which is connected to the middle tap of the tap winding.

(Embodiments of the Invention) Hereinafter, one embodiment of the present invention will be explained using FIG. , C are connected between the largest taps of the tap winding 3, and the intermediate tap B of the capacitor is connected to the intermediate tap of the tap winding 3. In this way, by connecting a capacitor to the intermediate tap, it is possible to not only reduce the lightning impulse voltage that occurs between the maximum taps, but also to suppress potential oscillations inside the tap winding. 3. It is possible to manufacture a winding that can withstand lightning impulse voltage without excessively strengthening the insulation, and the transformer can be made smaller and cheaper. 6. An example of a capacitor used in this embodiment This capacitor, shown in Figure 4, is made by combining three electrodes 6 insulated with a dielectric material (for example, insulating paper) 7 and winding them in a spiral to form a capacitor with a center tap. ing.

Further, in the above embodiment, the three terminals of the capacitor are drawn out from the same position, but they may be drawn out from positions separated from each other as shown in FIG. 5. In this case, the insulation between the terminals is is easy and advantageous.

Further, the shape of the capacitor may be formed into a polygonal shape to match the shape of the tank of the transformer, as shown in FIGS. 4 and 5.

〔Effect of the invention〕

According to the present invention, it is possible to suppress potential oscillations when a lightning impulse enters the tap winding and reduce the generated voltage, so that the winding can withstand lightning impulse voltage without excessively strengthening the insulation of the tap winding. can be manufactured, and the transformer can be made smaller and cheaper.

[Brief explanation of the drawing]

FIG. 1 is a wiring diagram of a conventional winding, FIG. 2 is a perspective view of a capacitor with a conventional structure, and FIG. 3 is an explanatory diagram of an embodiment of the present invention.
FIGS. 4 and 5 are explanatory diagrams of capacitors used in the present invention. 1...Series winding, 2...Shunt winding, 3...Tap winding. 4...Polarity switch, 5...Tap selector, 6...
electrode.

Claims (1)

[Claims] 1. An on-load tap changer consisting of an iron or low voltage winding, a high voltage winding, a tap winding, a polarity switch, a tap selector, and a switching switch; When a capacitor is inserted between the taps, three or more insulated conductors are closely attached to each other, formed into a spiral shape, and the conductors at both ends are connected between the largest taps of the tap winding. , an on-load tap-changing transformer characterized in that the intermediate conductor is connected to an intermediate tap of the tap winding; 2. In claim 1, bringing the conductors and bodies into close contact with each other;
1. An on-load tap-changing transformer, characterized in that the conductor is formed into a spiral shape, and the ends of the conductor are drawn out to positions separated from each other and connected to the maximum taps and intermediate taps of the tap winding. 3. In claim 1, the capacitor is formed by forming three or more insulated conductors in close contact with each other and winding them into a polygonal shape to match the shape of a tank of four transformers. An on-load tap-changing transformer, characterized in that the conductor is connected to the largest taps and to an intermediate tap of the tap winding.