SU1175010A1 - Three-phase a.c.voltage-to-three-phase a.c.voltage converter - Google Patents

Abstract

VARIABLE THREE-PHASE VOLTAGE CONVERTER TO THREE-PHASE VARIABLE, containing a single-phase autotransformer with an intermediate terminal, the extreme outputs of which are connected to different pairs of outputs from the first group of terminals via corresponding bidirectional keys. for phase-wise connection, while the second group of terminals for phase-by-phase connection of the load is connected phase-wise to the terminals for connecting the power supply network, which is also distinguished, in order to simplify and improve the mass and dimensional parameters, and connects i through the additionally introduced three bi-directional keys with all outputs (Lmi from the first group of outputs for phase-wise connection of the load.

Description

SP

The invention relates to electrical engineering, in particular to converter equipment, and can be used, for example, as a continuously adjustable three-phase source of source with a close to sinusoidal form of the load current.

The aim of the invention is to simplify and improve the weight and size parameters.

Fig. 1 is a schematic diagram of the proposed device; FIG. 2 shows time diagrams of voltages and a key closure sequence table;

The device (Fig. 1) contains an autotransformer 1, a key switch 2 and two groups of terminals 3 and 3 and for a three-phase connection of phase load 9, with a group of terminals 3-5 connected to terminals A, B and C for connecting the supply network. The winding of the autotransformer 1 with beginning 10 and end 11 has an intermediate pin 12. Key switch 2 consists of unidirectional controlled keys 13-26, with pairs of unidirectional keys that are counter-parallel connected, form bidirectional keys 13 and 14, 15 and 16, 17 and 18, 19, and 20, 21, and 22, 23, and 24, 25, and 26. All pins 10–12 of the auto winding transfer through these bi-directional control keys are connected to stages 6–8 for phase-wise load connection 9.

In Fig. 2, time diagrams of the supply voltage of the phase A id are indicated, six potential voltages Uj-Uyj and an example of the voltage of phase A formed from segments of six sinusoids U ,. when closing controlled keys according to the table, voltage diagram of the winding of the autotransformer. The stress curves of phase B and phase C are similar to the curve, respectively, of the angle and 2f / 3.

The device works as follows.

In each moment of time, in the on state there are generally three keys (one key in each phase). Accordingly, one of the outputs 6-8 of the group of outputs for the phase-wise connection of the load is connected to the intermediate output 12, and

the two remaining pins of the second group are connected to the beginning 10 and the end 11 of the winding of the autotransformer via bidirectional controllable keys. Since in the idealized case the total magnetizing force of the winding of the autotransformer is zero, this allows us to neglect the magnetizing current when analyzing the operation. Accordingly, the current of the included bidirectional switch connecting the intermediate lead of the autotransformer winding to one of the second group of outputs for phase connection of the three-phase load in the winding of the autotransformer splits into two components that are opposite in direction and absolute inversely proportional to the number of turns of the corresponding winding parts autotransformer. At the same time, the intermediate output current of the autotransformer winding is simultaneously the load current of one phase, and the currents in the winding parts of the autotransformer are, respectively, load currents of the remaining two phases.

The regulation of the values of currents and load voltages is achieved, as in the known phase control schemes, by varying the switching phase of controlled keys relative to the supply voltage. In this case, regulation is possible with both lagging and leading currents.

Consider the work interval when the keys 16,17 and 24 are turned on. In this case, the central output 12 of the winding of the autotransformer is connected via key 17 to phase A, and the beginning 10 and end 11 through keys 16 and 24 are connected respectively to phases B and C

The current of phase A 1d in the winding of the autotransformer splits into two equal and oppositely directed components, which are simultaneously load currents ij and i in phases

B and C (-ig -ic -2 ift 2 R

where R is the load resistance. The required 12-PULSE mode ensures the formation of voltage on the load from sinusoids of a certain amplitude, shifted among themselves by 30 el.grad. excluding from the load current all higher harmonics below 1 1y, can be obtained by a suitable choice of combinations of the circuit pack to linear voltage Y, d. that equal keys (figure 2). For example,. in phases A and. With currents 1d -i "when closing the keys 17 and 22 of the copro UCA

The load in phases A and C of the –2R was moved by 30 el. degrees. by

united in series and connected j compared to the interval.

1175010

The sequence of closure KflH} ei 1J ... 26

2

Claims (1)

THREE-PHASE VOLTAGE CONVERTER TO THREE-PHASE VARIABLE, containing a single-phase autotransformer with an intermediate terminal, the extreme terminals of which are connected through the corresponding bidirectional switches to various pairs of terminals from the first group of terminals for phase-by-phase load connection, while the second group of terminals for phase-by-phase load connection is connected in phase with conclusions for connecting the mains, with the fact that, in order to simplify and improve overall dimensions, an intermediate conclusion a single-phase autotransformer is made in the form of a midpoint of the winding and is connected via three additional bidirectional keys introduced with all the terminals from the first group of terminals for phase-by-phase load connection. 1 1175010