Three-phase balancing device

FIELD: electric engineering.

SUBSTANCE: application: in electric engineering. The three-leg transformer in three-phase balancing device is comprised of three coils with the first, nearest to leg, and the utmost leg being connected in series and in accord between each other and the total number of windings in coils is equal to the number of windings in the second coil to be opposite connected in zigzag pattern. Free terminals of the first coils are connected to input and output clips, while free terminals of the second coils are integrated in one common zero point to connect phase loads. Semi-conducting a.c. switch is energised between zero terminal of power system and three-phase transformer.

EFFECT: improved reliability and reduced resistance of zero-sequence current.

2 cl, 1 dwg

 

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

Known three-phase AC voltage stabilizer, containing balancing transformer (1).

The disadvantage is a large installed power transformer.

Known three-phase symmetrise device containing the input terminals for connection to the mains supply and output terminals to which are connected three-phase transformer, the primary winding connected in a "zigzag" (2).

The disadvantage is the complexity and large installed capacity balancing transformer.

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

The drawback is the large resistance zero sequence currents and low reliability due to the development of high stresses in emergency operation during a power outage of one of the phases.

The purpose of the invention is the decrease in the resistance zero sequence currents and increase the reliability of the device in emergency modes of operation during a power outage the ne phase.

This objective is achieved in that in the known device containing the input terminals A1, B1, C1, N1 for connecting the mains supply and output terminals A2, B2, C2, N2, to connect the load to which are connected three-phase three transformer with two primary windings of which are connected counter-sequentially in a "zigzag" in each phase of the transformer entered the third winding at each terminal of the transformer, with the one closest to the terminal of the first winding and at the third winding connected in accordance and consistent in the amount of the number of turns of these windings is equal to the number of turns of the second winding. First free the conclusions of the first windings are connected with the output or input terminals of the phases a, b, C, available the conclusions of the second windings are connected to one common point and are zero output for connection phase loads.

Thus, the proposed device complies with the criteria of the invention of "novelty."

Comparison of the proposed technical solution is not only the prototype, but also with other technical solutions in this field of technology found in them the features distinguishing the claimed technical solution to the prototype that allows to make a conclusion about the technical solutions according to the criterion of "significant differences".

The drawing shows a diagram of the device.

The device contains an input tag what we are to connect the mains A1, B1, C1, N1 and output terminals for connecting a load A2, B2, C2 and N2, three-phase three balancing transformer 1 having a primary winding 2, 3, 4. Winding 2, near to the terminal and the winding 4 extreme at each terminal included in accordance and consistent counter in zigzag windings 2, located on other rods. First free the conclusions of the first windings are connected with the output or input terminals of the phases a, b, C, and free pins of the second windings are connected at one common point 5 and are zero output for connection phase loads N2. Between zero output for connection phase loads N2 and zero output supply network N1 may be turned on the key on the thyristors 6 and 7, the control electrodes of which two counter included the Zener diode 8 and 9 and the series resistor 10 are connected.

The device operates as follows.

When the supply voltage three-phase symmetrise unit zero output for connection phase loads is zero the output 5 of the counter included in the "zigzag" primary windings 2 in accordance with consistently included at each terminal windings 2 and 4 three-phase three transformer 1. When such inclusion primary windings in three-phase zigzag transformer has a high resistance to direct currents and the reverse reproduction is Telenesti and low impedance to zero-sequence currents, ie provides a stable zero point, the balancing phase voltages and filtering of harmonic zero-sequence currents. It is known that when such inclusion windings zero-sequence resistance is determined by the parameters short circuit its transformer elements. Under the proposed three-winding connection of the windings when the first to the terminal 2 and the extreme 4 are connected according sequentially, while the total number of turns of these windings is equal to the number of turns of the winding 3, the zero-sequence resistance will be minimal. The effect is achieved by equality of the numbers of turns of the windings 2 and 4, however, depending on the design of the winding ratio of the numbers of turns of these windings may vary.

Emergency modes of operation of this device may be a power outage of one of the phases, and in this case, the broken symmetry of the formation of the zero point of the transformer 1 and the voltage on the two remaining phases relative to the zero output 5 is determined by the ratio of resistances phase loads. When different loads in one phase voltage will be too high and the other low. Normalization of stress in such modes is ensured thanks to the inclusion of between zero wire of the power supply network N1 and a zero output N semiconductor key on two anti-parallel connected thyristors 6 and 7, the control electrodes of which two counter-series-connected Zener diode 8 and 9 and the series resistor 10 are connected. With this switched on and when the excess voltage between N1 and N2 set level (determined by the breakdown voltage of the Zener diodes 8, 9 and is 8-30V) is automatically activated key and the zero point N1 and N2 are connected. When this happens, the normalization of stress for a period of time associated with the power outage. When restoring the voltage on all phases automatically turn off thyristor key. The semiconductor switch may not be performed on two counter enabled, thyristors, and on one semitone.

This embodiment of the three-phase balancing device enables operation in the mode of creating a stable zero point and zero artificial wire and only in emergency modes with a compound of the neutral wire with the zero wire of the power supply network.

Technical and economic efficiency in the use of the device is achieved by reducing the resistance of the zero-sequence currents and improve the quality of electrical energy associated with this option, and reliability in emergency modes.

1. "Electrical engineering Handbook", Moscow, Izdatelstvo MEI, 1998, str, RES.

2. AS the USSR №1324086. MCL. NM 5/12, 1985.

3 RF Patent №2314620, 02J 3/26, NN 3/253.

1. Three-phase symmetrise device, mainly for three-wire or four-wire mains containing the input terminals, for connection of mains supply A1, B1, C1, N1 and output terminals A2, B2, C2, N2 for load connection, three-phase three transformer with two primary windings: the first one closest to the rod and the second, characterized in that it introduced a third winding that is at least at each terminal included under in series with the first winding and the counter in the "zigzag" with windings that are located on other terminals, the total number of turns of the first and third windings equal to the number of turns of the second winding; the first free pins of the first windings are connected with the output or input terminals, and the free pins of the second windings are connected at one common point N2 are zero output for connection phase loads.

2. Three-phase symmetrise device according to claim 1, characterized in that between the zero output of the power supply network N1 and a zero output for connection phase loads N2 enabled semiconductor key on two opposite parallel connected thyristors, the control electrodes of which two opposite parallel connected Zener and consistent is resistor interconnected.



 

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