SU1543517A1 - Ac-to-dc voltage converter - Google Patents

Abstract

The invention relates to electrical engineering and can be used to convert both single-phase and multi-phase alternating voltages into a constant one characterized by self-compensation of the level of pulsations, up to a pulsed rectification in a wide range of control by key elements. The purpose of the invention is to increase energy performance. The advantage of the invention, which is characterized by the constant harmonic composition of the consumed current, regardless of the angle of unlocking of the keys 5-10 and 16-21, is the possibility of obtaining increased energy performance without using complicated key management laws and a more complex version of the transformer, special filters. The goal is achieved by performing a smoothing reactor 12 with two windings 11 and 23, one of which is connected to the output pins of the bridge on the keys 5-10, and the other - in series with the load 22. 1 sludge.

Description

 And I

C

f

ate

4b

coke

The invention relates to electrical engineering and can be used to convert both single-phase and multi-phase alternating voltages into a constant, characterized by self-compensation of the level of pulsations, up to a pulse-free straightening in a wide range of regulation with klychy elements. Jq

The purpose of the invention is to increase energy performance.

The drawing shows a converter circuit, an example of execution.

AC converter -

permanently contains a three-phase transformer 1 with primary phase windings 2-4 connected

start to phase input pins

A, B, C, and the ends to the input terminals jn of a three-phase bridge on the keys 5-10 with unidirectional conductivity, the output terminals of which are connected by a positive pole to the beginning, and

the negative pole - by the end 25 of the main winding 11 of the smoothing reactor 12. The secondary phase windings 13-15 of transformer 1 are connected to the star and connected to the ends of the three-phase bridge on the keys 16-21 with unidirectional conductivity, the output terminals of which are connected positive the pole to the beginning, and the negative pole through the load 22 - to the end of the additional winding 23 smooth - 35

vayu reactor 12. 1

Consider the principle of operation of the converter.

Suppose that the number of turns of the primary and secondary groups of windings of transformer 1 are equal. Let the number of turns of the windings of the reactor 12 are also equal. Suppose further, for the convenience of considering the principle of operation of the inductively 45 coupled reactor windings, that one of the windings (23 or 11) is shorted. In this case, the self-induced EMF of the remaining energized reactor winding smoothes the 50 rectified current flowing through it, reducing the ripple level at the load.

When both reactor windings are turned on due to the doubling of the number of turns in the reduced current loop 5, its inductance increases fourfold (if the EMF of the mutual inductance of the windings 11 and 23 is not taken into account). In this case, due to the flow through the windings

thirty

n

5 5

0 5 0

0

11 and 23, respectively, of the primary and secondary currents of the converter, the magnetic flux of the reactor doubles and, in order to avoid saturation of its magnetic circuit, the cross section of the latter must also be doubled. If the EMF of the mutual inductance of the windings 11 and 23 is not taken into account, then to get the two reactor windings of the former reactor inductance {corresponding to shorting one of the windings 23 or 11), the number of turns of each winding can be halved. If we take into account the EMF of the mutual inductance of the windings 11 and 23, it will turn out that in order to obtain the specified inductance of the reactor by two windings, the number of turns of each winding can be reduced much more than twice, depending on their coupling coefficient. This is due to the fact that the effect associated with the mutual inductance of the windings is not limited to a simple increase in the total inductance of the smoothing reactor.

With any change in the instantaneous value of the current ripple in the winding 23 (11), besides the EMF of self-induction arising in this winding and preventing the specified current change, the EMF of mutual induction in the winding 11 (23) occurs. The EMF of mutual induction in each winding of the reactor is added in accordance with its EMF of self-induction and turns out to be directed antiphase pulsations of the primary on the winding 11 (or secondary on the winding 23) of the rectified alternating voltage system. As a result, each winding of the reactor becomes for its other winding a source of counter electromotive force of the pulsations and the intercompensation of the antiphase pulsations, including components of non-canonical frequency, occurs.

A simpler explanation of the described phenomenon is that the pulsations of the primary and secondary galvanically developed systems of rectified voltages, each of which is connected to one of the mutually inductively connected windings of the reactor with a consistent direction of current flow in them, induce the EMF of the pulses from one winding reactor to another. In this case, due to the inverse polarity of the voltage applied to the winding, the pulsation voltage is induced

51

A pulsation EMF of a pulsed EMF occurs in the primary and secondary circuits of the current flow of the converter.

If the numbers of turns of the primary and secondary groups of the windings of transformer 1 are equal (unequal) and the number of turns of the windings of the reactor 12, respectively, are not equal (equal), then at the load 22 the balance between the ripple voltage and the induced pulsation EMF is disturbed. As a result, the shape of the rectified voltage acquires a waviness. Therefore, in order to avoid the latter, in case of inequality between the numbers of turns of the primary and secondary groups of transformer 1 windings at low-voltage or high-voltage rectification, it is necessary to observe the corresponding inequality of the number of turns of the winding of the reactor 12. For example, if V.Tr is less (larger) W., then W , j choose proportionally less (more) W3.

Keys with unidirectional conductivity can be performed both unmanageable and controllable. For example, control can be carried out on the primary or secondary side of transformer 1. At the same time, the dimensions of reactor 12 with increasing depth of regulation increase according to the well-known law due to an increase in the amplitude of the variable component of the magnetic flux of the reactor. However, the shape of the straightened direction is The described effect does not change, retaining its impulse. As a result, the shape of the current in the transformer windings, when the angle of unlocking the keys (for example, thyristors) changes, also does not change and only lags (ahead) in phase from the voltage of the corresponding winding, decreasing in amplitude.

Possible examples of the implementation of the technical solution are not limited to the scheme shown in the drawing. All of them can be built on the basis of known technical solutions - ana-

logs of transformer type. i

For example, on the secondary side of a transformer, with the same as in the drawing, the scheme of connecting its primary side can be made a full-wave circuit with windings connected in two stars with output pins,

0

Q

5 5

0

7

formed by the neutrals of these stars or connected to a six-phase star, as well as a full-wave circuit with triangle-connected windings. In this case, the control can generally be carried out on the primary or secondary side of the transformer, and the load can be included in any rectified current circuit, i.e. both on the secondary and primary side of the converter.

The technical solution can be implemented not only with a three-phase, but also a single-phase, two-phase or multi-phase primary system of alternating voltages. In the latter case, as with the use of circuits designed for phase-phase voltage control from the primary side, compared with, for example, single-phase circuits, the reactor dimensions are reduced due to a decrease in the relative value of the amplitude of the variable component of the reactor magnetic flux.

A prerequisite for the most effective implementation of the technical solution is the antiphase of the mutually compensating pulsations in the primary and secondary current paths, i.e. for example, the equiphase of the primary and secondary system of rectifiable variables of NEP-1 solutions. However, this excludes the possibility of increasing the energy indices in converters with non-uniformity between the primary and secondary systems of rectifiable alternating voltages and / or with an LC filter on the load side. In converters in which the absence of a neutral wire on the primary side can lead to an imbalance in the magnetic system of the transformer, it is necessary to provide for the possibility of connecting one of the free input terminals of the valve bridge to the zero input terminal.

The proposed technical solution, compared to the known one, provides the possibility of obtaining higher energy indicators without using complicated laws to control key elements and / or a more complex in terms of design transformer and other additional means, including special filters, by obtaining a pulse-free spread in wide the control range of the key elements, i.e. straightening, which is characterized regardless of the angle of unlocking the keys by the constant harmonic spectrum of the current consumed.

Claims (1)

Invention Formula AC to DC converter containing a transformer and a bridge on keys with unidirectional conductivity, to one of the output terminals of which is connected Compiled by E.Melnikova Editor A.Ogar Tehred M.Hodanich M.Samborska Proofreader Order 406 Circulation 493 VNIIPI State Committee for Inventions and Discoveries at the State Committee on Science and Technology of the USSR 113035, Moscow, Zh-35, Raushsk nab. 4/5 ........ - -. .-- - -,. - ...-. “-. - - - .--.- - “- - --- - - -. Production and publishing plant Patent, Uzhgorod, st. Gagarin, 101 five the main winding of the smoothing reactor, and the output terminals are connected at least to the terminals of the primary windings of the transformer, the secondary windings of which are connected to keys with unidirectional conductivity, forming a rectifier, characterized in that, in order to improve energy performance, to one of the output terminals of the said rectifier The stirrer is connected in parallel with the additionally introduced winding of the smoothing reactor, made bifilically with the main one. Subscription