RU186814U1 - Transformer with reduced magnetizing current when operating under load - Google Patents

Abstract

The utility model relates to the field of electrical engineering. Effect: reduction of the magnetizing current when operating under load in a transformer with increased scattering of the magnetic flux.

The utility model solves the problem of reducing the magnetizing current of a transformer operating under load by redistributing the scattering inductances of individual windings in the direction of the prevailing scattering inductance of the primary winding and increasing the voltage drop across the scattering inductance of the primary winding from the load current, the secondary winding is divided in half into two sections, and between the halves of the winding located undivided primary winding. 2 ill.

Description

The utility model relates to the field of electrical engineering, to electromagnetic transformers and relates to single-phase and three-phase power transformers with increased magnetic flux scattering. The scattering of the magnetic flux determines the magnitude of the short circuit currents and the value of the short circuit voltage. Since the short circuit voltage of power transformers used in transformer substations is high (from 5.5% to 12%), they can also be attributed to transformers with increased magnetic flux scattering. Significant short circuit voltage reduces the short circuit current.

Closest to the claimed device is a transformer with a high magnetic flux scattering inductance, consisting of a magnetic circuit, primary and secondary windings wound on the magnetic circuit separately [1].

The disadvantage of this device is the increased magnetizing current when the transformer is under load.

The magnetizing current is determined by the magnitude of the main magnetic flux of the transformer. When the transformer is operating under load, it decreases by an amount proportional to the voltage drop across the leakage inductance and the active resistance of the primary winding. This is especially true for transformers with increased magnetic flux scattering inductance. The distribution of the voltage drop across the leakage inductances of the primary and secondary windings depends on the size and location of the windings. With this arrangement, since the geometric dimensions of the primary and secondary windings are almost the same, the voltage drops reduced to the same number of turns will be approximately equal. Thus, when the transformer is operating under rated load, the magnetizing current will decrease in comparison with idling in proportion to half the voltage drop across the transformer. This decrease is relatively small, which determines the high magnetizing current when working under load.

The proposed transformer with increased magnetic flux dissipation inductance consists of a magnetic circuit, primary and secondary windings wound separately on the magnetic circuit, moreover, to reduce the magnitude of the magnetizing current of the transformer under load by redistributing the scattering inductances of the individual windings in the direction of primary scattering inductance prevailing and increasing the voltage drop across primary winding dissipation inductance from the load current, the secondary winding is divided in half into two sections, and between the halves of the winding is an undivided primary winding.

The scattering inductance of the magnetic flux of each winding is proportional to the square of the number of turns covered by the scattering magnetic flux. The primary winding is completely covered by magnetic flux. The secondary winding is divided into two sections. The inductance of each section, reduced to one number of turns, is 4 times less, since the sections contain 2 times less turns than a single primary winding. With a series connection of the inductance, the scattering of the individual sections add up. As a result, the total reduced inductance of the secondary winding is 2 times less than the primary leakage inductance. The possibility of redistributing the leakage inductances of individual transformer windings has been studied in the literature [2].

When the transformer is operating under load, a voltage drop occurs at the leakage inductances of the individual windings. The voltage drop across the dissipation inductance of the primary winding is large, which determines the voltage drop applied to the magnetizing branch in the equivalent circuit. As a result, the magnetizing current during operation of the transformer under load is lower than that of the prototype.

The essence of the claimed technical solution lies in the fact that by changing the design of the transformer with increased scattering of the magnetic flux, it was possible to reduce the magnetizing current under load, due to the redistribution of the leakage inductances of the individual windings in the direction of primary inductance prevailing.

The inventive utility model solves the problem of reducing the magnetizing current of a transformer operating under load.

The inventive device meets the requirement of "novelty", as it has a new feature: the secondary winding is divided in half into two sections, and between the halves of the winding is an undivided primary winding.

The technical result of the proposed solution is the reduction of the magnetizing current when operating under load in a transformer with increased scattering of the magnetic flux due to the redistribution of the scattering inductances in the direction of primary inductance prevailing.

The technical result is achieved by the fact that to reduce the magnitude of the magnetizing current of the transformer under load by redistributing the scattering inductances of the individual windings in the direction of the predominance of the scattering inductance of the primary winding and increasing the voltage drop across the scattering inductance of the primary winding from the load current, the secondary winding is divided in half into two sections, and between the halves of the winding are the undivided primary winding.

In FIG. 1 shows a transformer with a reduced value of the magnetizing current under load, where: 1 - magnetic circuit; 2 - secondary winding, divided into equal parts; 3 - primary winding.

In FIG. 2 shows a diagram of an experimental setup for testing a utility model.

The proposed transformer with a high magnetic flux scattering inductance consists of a magnetic circuit 1, primary and secondary windings 3 and 2, wound separately on the magnetic circuit.

The proposed transformer with increased magnetic flux scattering inductance consists of a magnetic circuit 1, primary and secondary windings 3 and 2, wound separately on the magnetic circuit, and to reduce the magnitude of the magnetizing current of the transformer under load by redistributing the scattering inductances of the individual windings in the direction of primary scattering inductance 3 and increasing the voltage drop across the scattering inductance of the primary winding from the load current, the secondary winding 2 is divided in half into two sections, and between the halves of the winding is an undivided primary winding 1.

For experimental verification of the effectiveness of the proposed device, experiments were conducted with a transformer from a converted welding transformer TD-300. The circuit for conducting the experiments is presented in FIG. 2.

For experimental verification of the effectiveness of the proposed device, experiments were conducted with a transformer from a converted welding transformer TD-300. The circuit for conducting the experiments is presented in FIG. 2. During the experiments, a comparison was made of the magnetizing current, the transformer under load for a transformer with a conventional arrangement of windings and for a transformer having a divided secondary winding. The magnetizing current of the transformer under load was measured using the method [3]. The essence of the method is that shunts are installed in the primary and secondary windings. The ratio between the rated currents of the shunts is chosen equal to the transformation ratio of the transformer. The shunt terminals are connected so that the voltage drop from the secondary current is subtracted from the voltage drop from the primary current. The oscilloscope in such a circuit will show the magnetizing current.

As a result, the following results were obtained: under equal conditions and the same load, the magnetizing current of a transformer with a divided secondary windings always turned out to be less than that of a conventional transformer. During the experiments, a large amount of data was obtained for various levels of supply voltage, various loads. So for one of the modes under the same conditions, the magnetizing current of a conventional transformer under load was 6 A, and for a transformer with a divided secondary winding, 2.6 A.

The experimental data allow us to conclude that the claimed utility model meets the criterion of "industrial applicability".

The higher the leakage inductance of the transformer, the greater the effect that can be achieved. So, for power transformers of power supply systems, it is advisable to use this design of windings for a voltage level of 110 kV and higher, where the short circuit voltage is 12.5%.

Information sources:

1. RF patent 2103760, IPC H01F 38/08, “Welding transformer”, author: Kalashnikov Yu.D., 01/27/1998;

2. Marquardt E.G. "On the scattering of transformer windings." "Electricity", 1937, No. 11, p. 60-63;

3. RF patent №2328749 IPC G01R 19/00, "Method for measuring the magnetizing current of a transformer operating under load", authors: Gukov DV, Gukov AD, Prutchikov IO, Kamlyuk VV, Soldatov V.N., Prokofiev V.E., Spiridonov A.E., bull. No.19 of July 10, 2008

Claims (1)

A transformer with increased magnetic flux dissipation inductance, consisting of a magnetic circuit, primary and secondary windings wound separately on the magnetic circuit, characterized in that to reduce the magnetizing current of the transformer under load by redistributing the scattering inductances of the individual windings to the predominance of the scattering inductance of the primary winding and increasing the fall voltage across the scattering inductance of the primary winding from the load current, the secondary winding is divided in half by ve section, and between the coil halves is undivided primary winding.

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