RU2374715C1 - Balance-to-unbalance traction-feeding transformer - Google Patents

Abstract

FIELD: electricity.

SUBSTANCE: balance-to-unbalance traction-feeding transformer includes three-leg core, three-phase symmetric primary winding and three-phase secondary winding. Secondary winding is connected as per three-rayed zigzag scheme, each ray of which consists of two in-series connected similar windings located on different core legs. Each of the windings of one of the rays has voltage which is 2.5-3.0 times less than that of each of the windings in two other rays. Transformer is converter of three-phase voltage into symmetric two-phase one with phase displacement angle between voltage vectors, which is close to 90°.

EFFECT: simplifying the design and economy of materials.

1 dwg

Description

The invention relates to the field of electrical engineering and can be used in the manufacture of traction transformers for electrification of railways with alternating current.

Known traction transformer containing a three-core magnetic circuit and three-phase symmetrical windings - primary HV and secondary LV (1). The HV winding is connected to the mains supply, and the alternating current electric traction is connected to the LV winding. One of the phases of the LV winding is connected to the rails and grounded (for example, c), and the other two phases (for example, a and c) are separately connected to the contact wires of the left and right paths. The phase angle between the linear voltage vectors of the LV winding is sixty degrees.

Such an electrification scheme, even with the same load on two line voltages, is asymmetrical. Since there is no load between the contact wires. The asymmetry of the load leads to the appearance of a large current of the negative sequence and to undesirable voltage unbalance in the supply network. In addition, the power of the transformer is not fully used.

To address these shortcomings, a balancing traction transformer is proposed. The phase connection diagram of the HV and LV voltage windings remains the same, but the phase angle between two loaded linear voltage of the LV winding increases to ninety degrees, instead of the previous sixty. An increase in the phase angle at the same load on the left and right paths ensures the absence of reverse sequence currents in the supply network.

The proposed transformer contains a three-core magnetic circuit, a three-phase symmetrical primary winding of a HV and a three-phase asymmetric secondary winding of a HV, which is connected according to a three-beam zigzag circuit. Each beam of the LV winding consists of two identical windings connected in series. These windings are located on different rods of the magnetic circuit, and each of the windings of one of the beams has a voltage of 2.5-3.0 times less than each of the windings in the other two beams. This allows you to increase the phase angle between the loaded linear voltage of the LV winding from sixty to about ninety degrees. Such a traction transformer becomes a transformer of a symmetrical three-phase voltage into a symmetric two-phase.

The proposed transformer is shown in the drawing.

It contains a three-core magnetic circuit 1, a three-phase symmetrical primary winding 2, intended to be included in the supply network, and a secondary winding 3. The secondary winding 3 is assembled according to the three-beam zigzag scheme. Each beam consists of two identical windings connected in series located on different rods of the magnetic circuit. Each of the windings in one of the rays has a voltage of 2.5-3.0 times less than each of the windings in the other two rays. The shortened beam is designed to be connected to rails and ground, and the other two beams are designed to connect to contact wires.

The transformer operates as follows. The primary voltage from winding 2 is transformed into winding 3. The angle between the vectors of the loaded linear voltages is close to ninety degrees. With the same load of the left and right paths in the primary winding 2, the current of the negative sequence is absent, and the supply voltage is not distorted. But with an unequal load of paths, it appears, and the supply voltage can be distorted. However, this drawback is inherent in all, without exception, transformers of three-phase voltage to two-phase voltage (2).

A distinctive feature of the proposed transformer is the absence of a zero sequence current in each of the windings under various operating conditions.

The transformer is simple to manufacture and in terms of material consumption it is close to general-purpose transformers of the same power.

Information sources

1. Three-phase three-winding transformer TDTNZH-40000 / 110-81U1. Number 03.03.15-91. Industry Catalog of Electrical Engineering, Informelectro, 1991.

2. A.M.Bamdas et al. Static electromagnetic frequency and phase number converters. SEI, ML, 1961.

Claims (1)

Symmetrical traction transformer containing a three-core magnetic circuit, a three-phase symmetrical primary winding and a three-phase secondary winding, characterized in that the secondary winding is connected according to a three-beam zigzag circuit, each beam of which consists of two identical windings connected in series located on different rods of the magnetic circuit, each of the windings one of the rays has a voltage 2.5-3.0 times less than that of each of the windings in the other two rays.