RU2612649C1 - Three-phase balun - Google Patents

Abstract

FIELD: electricity.

SUBSTANCE: three-phase balun is proposed, wherein the three-phase three-legged transformer comprises two or three primary windings included counter in the zigzag . The free leads of the first windings are connected to the input and output terminals through the three-phase automatic switch, and the free leads of the second windings are connected into a common zero point to couple the phase loads. The throttle filter of the residual currents is included between the zero output of the power line and the zero output of the three-phase transformer.

EFFECT: higher reliability.

2 dwg

Description

The invention relates to electrical engineering and can be used in power circuits of various equipment.

Known three-phase AC voltage stabilizer containing a balancing transformer (1). The disadvantage is the large installed capacity of the transformer,

Known three-phase balancing device containing input terminals for connecting the mains and output terminals to which a three-phase transformer is connected, the primary windings are connected in a zigzag (2).

The disadvantage is the complexity and large installed power of the balancing transformer.

Closest to the proposed device is a three-phase balancing device, between the input and output terminals in which a three-phase circuit breaker is connected, and a three-phase transformer is connected to the output or input terminals, the primary windings of which are turned on and connected in a zigzag (3).

The disadvantage is low reliability due to the loss of zero when the input circuit breaker trips, the appearance of high voltages in emergency conditions when one of the phases disappears.

The purpose of the invention is to increase the reliability of the device in emergency conditions by automatically restoring the neutral of the supply transformer or an autonomous AC source.

This goal is achieved by the fact that in the known device containing the input terminals A1, B1, C1, Ν1, for connecting the load to which a three-phase three-rod transformer is connected, a three-phase circuit breaker connected in series with the primary windings, two or three primary windings of which are connected opposite sequentially in a zigzag. The first free terminals of the first windings are connected to the output and input terminals of phases A1, B1, C1, the free terminals of the second windings are connected to one common point to connect the phase loads N2, and a zero-sequence current choke filter is included in series between N2 and N1.

Thus, the claimed device meets the criteria of the invention of "novelty."

Comparison of the claimed technical solution not only with the prototype, but also with other technical solutions in this technical field revealed signs that distinguish the claimed technical solution from the prototype, which allows us to conclude that the technical solution meets the criterion of "significant differences".

The first drawing (Fig. 1) shows a diagram of a device with two primary windings. The device contains input terminals for connecting the supply network A1, B1, C1, N1 and output terminals for connecting the load A1, B1, C1 and N2, a three-phase three-core balancing transformer 1 having primary windings 2, 3. Windings 2 are included in the zigzag with windings 3 located on other rods. The first free terminals of the first windings are connected to the output and input terminals of phases Α1, B1, C1 through a three-phase circuit breaker 4, and the free terminals of the second windings are connected to one common point 5 and are the zero terminal for connecting phase loads N2. Between the zero terminal for connecting the phase loads N2 and the zero terminal of the supply network N1, a throttle filter of zero sequence 6 is connected. The device operates as follows. When voltage is applied to the three-phase balancing device with a zero output, phase output is connected to the zero output of the 5 primary windings 2 and 3 of the three-phase three-core transformer 1, which are included in the “zigzag” one. With this connection of the primary windings to the zigzag, the three-phase transformer has a large resistance for forward and reverse currents sequences and low resistance for zero sequence currents, i.e. provides a stable zero point, phase voltage balancing and filtering of harmonics of zero sequence currents. It is known that with such a turn on of the windings, the resistance of the zero sequence is determined by the short circuit parameters of its transformer elements. The effect is achieved when the number of turns of the windings 2 and 3 is equal.

Emergency modes of operation in such a device may be the loss of zero in the four-pass power supply circuit needed to supply single-phase loads, as well as the voltage failure of one of the phases, in which case the symmetry of the zero point formation by transformer 1 and the voltage on the two remaining phases relative to the zero output are violated 5 determined by the ratio of the resistance of the phase loads. With different loads in one phase, the voltage will be very high, and in the other - underestimated. Voltage normalization in such modes is ensured by the inclusion of a zero sequence current choke filter between the neutral wire of the supply network N1 and the neutral terminal N2. With this inclusion and when the voltage between N1 and N2 exceeds the set level (determined by the rated voltage of the choke filter, which is actually a filter of zero sequence currents, the value of which is (7-15V)), the voltage is automatically limited due to the very small resistance of the zero sequence current choke filter and the zero points N1 and N2 are interconnected. In this case, stress normalization occurs for a period of time associated with a voltage failure. When voltage is restored at all phases, as well as when a three-phase circuit breaker is turned off, terminal N2 is automatically disconnected from terminal N1 due to the high resistance of the zero-sequence current filter choke at low voltages between terminals N1 and N2.

This embodiment of a three-phase balancing device ensures the operation of the device in the mode of creating a stable zero point and ensuring the redistribution of currents in three phases and automatic restoration of neutral only in emergency operation modes by connecting the zero output of the balancing device to the neutral of the supply network. In fig. 2 shows a diagram of a transformer 1, on which three windings are included in a zigzag with a winding ratio of 2: 1: 1 between windings 2; 3 and 4, respectively. Efficiency when using the device is achieved by ensuring the redistribution of currents in three phases with unbalanced loads, reducing the resistance to currents of zero sequence, improving the quality of electric energy and reliability in emergency operation.

Information sources

1. Electrical reference book. M .: publishing house MPEI, 1998, p. 135, fig. 24.19.

2. A.S. USSR No. 1324086, M.C. H02M 5/12, 1985.

3. RF patent No. 2314620, H02J 3/26, H02H 3/253.

Claims (1)

A three-phase balancing device for operation from a four-wire power supply network, containing input terminals for connecting the power supply network A1, B1, C1, N1 and a three-phase circuit breaker connected in series with the primary windings of a three-rod transformer, two or three primary windings of which are connected in a zigzag, common the zero point of these windings is the zero terminal N2 for connecting single-phase loads, characterized in that a throttle filter is introduced between the zero terminal N1 of the supply network and the zero terminal N2 then zero sequence, while the input terminals A1, B1, C1 are also output terminals for connecting the load.

Images