Current phase-to-phase distributor

FIELD: electrical engineering.

SUBSTANCE: invention relates to electrical engineering, and can be used for phase-to-phase distribution of current in magnetically unstable three-phase signals, for example for neutralisation of zero-sequence harmful effects on current feed circuit in three-phase AC-to-DC and DC-to-AC voltage transformers. Proposed device comprises the transformer with its two phase windings connected, each by one output terminal, to zero input terminal, while their other output terminal is connected to appropriate phase input terminal. The transformer comprises two magnetic cores with phase windings connected in series and furnished with central tap. The said windings have their central and extreme free terminals connected to zero and common phase input terminals, respectively. Note here that central output terminal divides the number of turns in each phase windings into unequal parts, smaller ones being connected to opposing phase input terminals.

EFFECT: possibility to use two single-phase transformers with various-shape magnetic cores instead of three-phase transformer.

1 dwg

 

The invention relates to electrical engineering and can be used for phase-to-phase current distribution in magnetic unbalanced three-phase devices, for example, to neutralize the harmful effects on the mains voltage zero-sequence in converters three-phase AC voltage to DC and/or AC.

Widely known for converters three-phase AC voltage to DC (see Oak. A new theory of controlled rectifiers. M., 1970, p.50, 51, RES, 36), is performed on magnetic unbalanced (in the case of connection of the primary winding in star without neutral) three-phase transformer with radiation scheme of the coupling of the secondary windings and valves. Also known converters three-phase AC voltage to DC (see Ali, Agusan-zade. Analysis mnogopolyusnogo straightening - "Electricity", 1977, No. 8), performed on the magnetic unbalanced (in the case of connection of the primary winding in star without neutral) three-phase transformer connection of taps of the secondary winding through the gates on the zigzag for wave (Fig.2), a full-wave 3 - ||) scheme or serial connected in a bridge circuit (Fig.3 - |), which referred to its case, in particular, conversion of the Finance AC voltage to DC.

A feature of these converters is magnetically unbalanced mode of operation of three-phase transformer when connecting the primary windings in a star without the initial zero and no additional short-circuited winding, connected in a triangle. The primary winding of this transformer, in the absence of said additional windings may be connected only in a triangle or a star with the derived zero. The connection of the primary winding of the transformer in star without the initial zero causes its magnetic pulsating with triple frequency magnetic flux disrupting the work of the Converter (see Ilegenes. Electron and ion converters, M. - L., p.3. 1956, p.99). The connection of the primary winding of the transformer in the triangle, due, for example, with increased requirements to its isolation, is not always acceptable. The connection of the primary winding of the transformer in star with the derived zero leads to contamination of the mains current, zero sequence containing higher harmonics whose frequency is a multiple of three.

The problem increases in converters that are managed with the primary side of the transformer, in which the presence of zero wire is a necessary condition of their health.

Known, for example, the Converter crehpa the nogo AC voltage to DC, containing a three-phase transformer, the primary winding which, together with the series-connected with them pairs of anti-parallel connected controllable valves form the star associated with the phase of the input pins and the secondary windings are connected in star and is connected to the rectifier bridge, however additionally introduced a set of secondary windings, a rectifier bridge and managed valves, and the primary winding through additional counter-parallel connected valves connected to the zero input-output, and an additional set of secondary windings and an additional rectifier bridge with main secondary windings and the main rectifier bridge are connected according to the scheme dvenadcatiletnego rectifier (ed. St. No. 752681, CL NM 7/06, from 04.02.76 year).

The disadvantage of this Converter is that flowing through the zero wire current contaminates the supply network of higher harmonics whose frequency is a multiple of three.

The set of obstacles to obtaining the required technical result is that the open circuit this current makes the inverter inoperable.

Additional auth. St. No. 860238, CL NM 7.12, from 02.08.79, to the basic auth. St. No. 752681, CL NM 7/06, from 04.02.76, known only close to the proposed technical solution device is ustwo, containing added a three-phase transformer, the primary windings of which are connected in a star, a common point which is connected to the zero input-output, and the additional windings are connected in a triangle.

A disadvantage of this device is the difficulty lies in the fact that, to achieve complete neutralization of harmful effects on the net current zero sequence near-zero angles of firing of the thyristors, you must have additional transformer winding connected in a triangle. In addition, the inability to use, in accordance with a known schema of separate magnetic circuits limits the operational capabilities of the device.

The set of obstacles to obtaining the required technical result is that the device is made on a common magnetic core further introduced a three-phase transformer.

The challenge which seeks the proposed technical solution is the simplification and enhanced operational capabilities.

This task is solved in that in the proposed device for phase-to-phase current distribution that contains the transformer, two phase windings of which are connected each with one output for zero input, the output and the other to the corresponding phase I is demo conclusion, the transformer has two magnetic circuits with series-connected phase windings and the intermediate output of each connected intermediate and free extreme conclusions respectively to zero and the total phase of the input to the output, the intermediate conclusion divides the number of turns of each phase winding on unequal parts, twice the smaller of which is connected with the opposite phase of the input pins.

Technical result achieved in the offer, is the ability to use two single-phase transformers with cores of different configurations, including twisted band ring-shaped, instead of one three-phase and no need for an additional winding connected in a triangle with the same quality neutralize the harmful effects on the network of higher harmonics of the current in the ground wire.

The drawing shows a schematic diagram of a device for phase-to-phase current distribution of the zero sequence inverter three-phase AC voltage, a transformer whose magnetic balanced connection of its primary winding in a star with the derived zero, where the arrows indicate the direction of flow of the shares of current zero-sequence I0in its positive half-cycle triple frequency.

The device soda is separated by two single-phase transformers 1 and 2 with windings respectively 3, 4 and 5, 6. The number of turns of the winding 3 (5) two times less than the number of turns of the winding 4 (6). The end (beginning) of the winding 3 (5) of the transformer 1 (2) is connected to the input output phase And (C). Beginning (end) of the winding 4 (6) connected to the input output phase C. General point opposite conclusions pairs of the windings 3, 4 and 5, 6 are connected to the zero input output 0, which is connected to the wire for the current flow of zero sequence above transformer Converter three-phase AC voltage.

Assume that the input conclusions a, b, C and 0 connected primary winding of the transformer three-phase inverter connected in star with the derived zero, the Converter operates in such a way that zero wire runs AC triple frequency, and in the positive half-cycle of this current flows in the direction from the input / output 0 input findings And, In, With, and in the negative half-cycle in the opposite direction.

In the positive half-cycle of this current, it breaks into two equal parts, the first (second) of which at a common point of the windings 3 and 4 (5 and 6) is divided into two unequal parts, and twice as much of them flows from the beginning (of the end) to the end (beginning) of the winding 3 (5) with half the number of turns and then to the input output phase And (C), and halve of them flows from the end (the beginning) to the Achal (the end) of the winding 4 (6) twice with a large number turns and then input output phase C. the Branching current part, inversely proportional unequal numbers of turns of the winding sections of each transformer having a common intermediate output is connected with the existence of the autotransformer connection between these areas, providing the necessary balance ampere-turns. On the other hand, transformers 1 and 2 are not independent of load and relative to the current zero-sequence function as current dividers, self-sufficient providing the ideal distribution of currents. Thus, the share of current in the considered half triple frequency in each winding with a smaller (larger) number of turns is one third (one-sixth) of the total current. The total current flowing through the input output 0, is divided into three equal parts flowing through each one of the phase of the input pins in the direction of the supply network.

As a characteristic feature of the Converter is alternately oneness in time load current zero sequence only one of the phases of the mains supply, the current in each discrete intervals is distributed between the phases of the network in the ratio of 2/3, 1/3, 1/3 instead of the ratios 1, 0, 0, which is true in the absence of interfacial dispenser current.

In the negative half-cycle of current flow n the left sequence is similar to that described reverse process of summation of the fractions of the current in the common ground wire.

Finally, in each period of the mains voltage in the linear wires are formed currents, in which there are no higher harmonics, multiples of three.

A device for phase-to-phase current distribution that contains the transformer, two phase windings of which are connected each with one output for zero input, the output and the other to the corresponding phase of the input to the output, wherein the transformer has two magnetic circuits with series-connected phase windings and the intermediate output of each connected intermediate and free extreme conclusions respectively to zero and the total phase of the input to the output, the intermediate conclusion divides the number of turns of each phase winding on unequal parts, twice the smaller of which is connected with the opposite phase of the input pins.



 

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