RU2683246C1 - Single-phase load by the three-phase network phases uniform distribution device - Google Patents

Abstract

FIELD: electrical engineering.

SUBSTANCE: invention relates to the field of electrical equipment and can be used in devices of three-phase network energy conversion into energy for single-phase load supply. Device for uniform distribution of single-phase load on phases of three-phase network comprises transformer, which is single-phase, has one primary and one secondary windings, device comprises a second single-phase transformer with primary and secondary windings, leads of primary winding of the first transformer are inputs for two of three phases of three-phase network, outputs of primary winding of the second transformer are inputs for the third of three phases of three-phase network and neutral wire, and outputs of serial connection of secondary windings of two transformers are outputs of device.

EFFECT: technical result is simple device, high manufacturability, reduced material consumption and weight and dimensions, as well as high efficiency.

1 cl, 1 dwg

Description

The invention relates to circuits of AC distribution networks, and can be used in devices for converting the energy of a three-phase network into energy for supplying a single-phase load.

Known balancing three-phase single-phase AC transformer containing the windings of phases A1, B1 and C1 connected in a "zigzag", and the load outputs are the junction of the ends of the semi-windings of phases B1 and C1 (see RU No. 2321133 C1, Fig. 2).

However, the known transformer does not provide an even distribution of the currents consumed from the three phases, as it distributes the currents in the proportion: 25% - 50% - 25%, which leads to not optimal or incomplete use of the power supply network, the parameters of which, as a rule, are calculated on flow of equal phase currents in strength.

A large number of windings makes the known solution complex and cumbersome.

In addition, safe and reliable operation often requires the connection of an appropriate output terminal to the neutral wire of the supply network. The well-known transformer, all windings of which are galvanically connected, excludes the possibility of such a connection of its load outputs to the neutral wire of the supply network, which, in turn, excludes the possibility of using loads with the requirement of mandatory connection of the load to the neutral and thereby narrows the scope of this solution.

The closest in technical essence - the prototype - is a device for the symmetric distribution of a single-phase load across the phases of a three-phase network, which is a three-phase isolating single or multi-winding (in the secondary circuit) consumer transformer in which each of the secondary windings has additional turns independent of the main winding, designed to compensate for the voltage drop on the line, and each of the consumers of the multi-winding isolation transformer is powered by its own or from the common ( for a single-winding three-phase transformer) of the secondary winding, in which the line of each consumer is powered from three phase transformer coils connected in series, any two of which are connected in concert, and the third is in opposite direction. (See RU 2506676 C2).

The known device contributes to the equalization of currents among themselves in all three phases when feeding single-phase loads.

A disadvantage of the known solution is the complexity and excessive material consumption due to the use of three transformer windings in the primary circuit and the corresponding number in the secondary circuit.

An excessive number of windings reduces the manufacturability of the known device since it requires the involvement of appropriate production resources, lengthening the manufacturing process.

In addition, the known solution requires the presence of excessive overall power of the transformer used (its power is equal to one and a half times the load power). However, an increase in the overall power of the transformer leads to an increase in losses in the transformer and reduces the efficiency of the device as a whole.

The technical result is to simplify the device, increase manufacturability, reduce material consumption and weight and size parameters, as well as increase efficiency.

The specified technical result is achieved in that in a device for uniform distribution of a single-phase load across the phases of a three-phase network containing a transformer, said transformer is single-phase and has one primary and one secondary windings, the device contains a second single-phase transformer with primary and secondary windings, the terminals of the primary winding of the first transformer are the inputs for two of the three phases of the three-phase network, the terminals of the primary winding of the second transformer are inputs for the third of the three phases of a three-phase network and a neutral wire, and the conclusions of the serial connection of the secondary windings of two transformers are the outputs of the device.

In addition: - transformers are made step-down, with the same transformation ratio equal to two.

A device for the uniform distribution of a single-phase load across the phases of a three-phase network is illustrated using the drawing, which shows the connection diagram of the transformer windings.

The following notation is made in the drawing.

1, 2, 3, 4 - conclusions of the primary windings for connecting the phases of the three-phase supply network and the neutral wire, respectively; 5 and 6 - conclusions of the serial connection of the secondary windings for connecting the load; 7 and 8 - the first and second transformers, respectively; 9 - primary windings of transformers; 10 - secondary windings of transformers.

A device for the uniform distribution of a single-phase load across the phases of a three-phase network contains two transformers with primary and secondary windings each. The conclusions of the primary winding of the first transformer are inputs and are designed to connect any two of the three phases of a three-phase network. The conclusions of the primary winding of the second transformer are inputs and are designed to connect the remaining unconnected to the first transformer third of the three phases of the three-phase network and neutral wire. The secondary windings of the two transformers are connected in series, and the order of connection of the terminals of the secondary windings themselves does not matter, since the secondary windings can be connected in series, either in accordance or in series. The findings of the specified serial connection of the secondary windings are the outputs of the device designed to connect a single-phase load D2, D2.

The terminals of the primary windings of the transformers can be connected to the phase conductors of a three-phase supply network in any combination, excluding duplicated connection or short circuit of the phase conductors, i.e. each of the four inputs of the device must be connected to one of the phase wires or a neutral wire, which in this case must be connected to one of the terminals of the second transformer.

Transformers 7 and 8 are single-phase, step-down and can be performed on magnetic circuits of a toroidal or rod structure. Each of the transformers has a primary 9 winding and a secondary 10 winding wound so that the transformation coefficient of each of the transformers is equal to two.

The winding process of each of the windings determines the presence of the beginning and end of the corresponding winding. One example of the device is shown in the drawing, where the beginnings of the primary windings 9 are connected to the phases A and C of the supply network, and the ends of the primary windings, respectively, to phase B and the neutral wire N of the supply network. The secondary 10 windings in the indicated embodiment are connected in series according to, and the ends of their series connection, namely the terminals 5 and 6, are the outputs of the device and are intended to be connected to the load Dl, D2. In this case, any of the outputs of the single-phase load can be connected to the neutral wire of the supply network (not shown in the drawing).

The parameters of the first and second transformers are selected from the conditions of normal operation with the linear and phase voltage of a three-phase network, respectively. These voltages can have standard values of 220/127 V, respectively, or 380/220 V, respectively, or 10 / 5.8 kV, respectively, or other values that differ by √3 times.

A device for uniform distribution of a single-phase load operates as follows.

Single-phase transformers, taking into account their connection diagrams, provide the conversion of the energy of a three-phase network into energy for supplying a single-phase load, evenly taking power from all three phases of the supply network. The magnitude of the currents in the phases and the current of the neutral wire are equal to each other. This provides the most favorable mode of operation of the supply network, since the supply wires are loaded evenly.

When a three-phase voltage of the mains is supplied to the inputs 1, 2, 3 and 4 of the device, in which the phase wires and the neutral can be designated as A, B, C, N, respectively, the output single-phase voltage is generated at the outputs 5 and 6 of the device. When the load Dl, D2 is connected to the outputs, current flows through the load.

Under the condition that the device operates from a standard electric three-phase network with a nominal voltage of 380 V, the voltage on the primary and secondary windings of the first transformer is 380 V and 190 V, respectively, the voltage on the primary and secondary windings of the second transformer is 220 V and 110 V, respectively.

The result of summing the alternating voltages of the secondary windings, taking into account their phase values, gives an alternating voltage of 220 V.

A smaller number of windings in comparison with the prototype simplifies the device and makes it more technologically advanced to manufacture, and also reduces the overall overall power of transformers by 10%, while also reducing the weight and cost of transformer materials.

In cases for which the mass and size parameters of the device are not important, the transformers can be chosen the same, with an estimated operating voltage of at least a line voltage and a transformation ratio of 2. If the three-phase network is of a standard voltage of 380 V, then both transformers in this case must be designed for operating voltage of at least 380 V. The option with two identical transformers ensures the unification of the nodes and the possibility of their interchangeability.

Calculations using vector voltage diagrams show that in order to ensure equal currents of phase conductors and a neutral wire, the transformation coefficients of both transformers should be equal to two, in this case the voltage of the secondary windings will differ by √3 times.

Since the total overall power of the transformers is determined by the product of the arithmetic sum of the voltages of the secondary windings by the load current, a smaller overall power and, therefore, a device with an arithmetic sum of the voltages of the secondary windings is less efficient. In the device for uniform distribution of a single-phase load at a voltage of a three-phase supply network of 380 V, the sum of the voltages is 190 V + 110 V = 300 V, which is lower than in the prototype: 110 V + 110 V + 110 V = 330 V.

Thus, a device for the uniform distribution of a single-phase load requires a lower total overall power of the transformers.

Since energy losses occur in transformers that reduce the overall efficiency of the device, the losses will be the less, the smaller the overall transformer power required to convert the same amount of energy. Therefore, a decrease in the required overall power of the transformers will lead to an increase in the efficiency of the device. At the same time, the overall dimensions of the device will decrease.

In addition, due to the decrease in one and a half times the required number of windings compared to the prototype (4 instead of 6), the design of the device is simplified and the process of its manufacture is simplified.

A device for uniform distribution of a single-phase load provides the ability to connect any of the load outputs to the neutral wire of the supply network. Thus, a load requiring a connection to the neutral can be connected to the neutral wire of the supply network by any one of its conclusions.

To ensure the solvable task of three-phase-single-phase conversion while ensuring a uniform phase load while providing galvanic isolation of the load circuits from the supply network, there is no simpler device scheme than the proposed one.

Despite the simplicity of the device, the prior art does not contain solutions characterized by a combination of formulated features.

The transformers of the device can be manufactured using standard transformer iron and winding wire.

Thus, a device for evenly distributing a single-phase load across the phases of a three-phase network is structurally simpler and more technologically advanced, has lower material consumption, weight and dimensions, and greater efficiency.

In addition, the reduction of the overall dimensions of the device is ensured under the condition of galvanic isolation between the inputs and outputs, which makes it possible to connect one of the load outputs to the neutral wire of the supply network, which expands the scope of the device.

Claims (2)

1. A device for uniform distribution of a single-phase load across the phases of a three-phase network, comprising a transformer, characterized in that said transformer is single-phase, has one primary and one secondary winding, the device contains a second single-phase transformer with primary and secondary windings, the terminals of the primary winding of the first transformer are inputs for two of the three phases of the three-phase network, the terminals of the primary winding of the second transformer are inputs for the third of the three phases of the three-phase network and neutral th wires, and outputs the serial connection of the secondary windings of the two transformers are the outputs of the device. 2. The device according to p. 1, characterized in that the transformers are made step-down, with the same transformation ratio equal to two.

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