RU2383986C1 - Ac/dc converter with eight-fold ripple frequency - Google Patents

Abstract

FIELD: electrical engineering.

SUBSTANCE: ac/dc converter with 8-fold ripple frequency can be used to supply DC low-voltage, for example for supply of charging and welding units. Proposed converter comprises twelve gates and three-phase transformer with its one rod accommodating first phase secondary with intermediate tap and two other rods accommodating two phase windings each. Note that starts of two phase windings are connected to secondary first phase winding, said two phase windings being arranged on two other rods, one on each rod. Twelve gates make six-phase a gate bridge with six AC inputs and two DC heteropolar outputs whereto load is connected. Additional intermediate tap arranged between first tap and winding end is made on secondary first phase winding with a tap. Note here that the ends of two free phase windings are connected to aforesaid tap, while three free starts and three free ends of phase windings are connected to gate bridge AC inputs. Note here that relative number of phase winding turns is taken to make tg 45°, that of phase winding turns connected to first tap is taken to be tg 30°, and relative number of phase winding turns connected to additional tap is taken to be tg 30°·tg 22,5°. Note also that relative number of a part of phase winding turns with taps makes sin 45°-0.5·(1-tg 30°), said winding part being connected between winding start and first tap, while that of the parts of said phase winding between first tap and additional tap makes sin 45°·(1-tg 30°).

EFFECT: ac/dc converter with higher efficiency, reduced weight and dimensions.

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Description

The invention relates to the field of converter technology and may find application for supplying direct current consumers, mainly with low-voltage power, as well as in specialized power converters, for example, for charging and welding units.

Known AC to DC converter with an 8-fold ripple frequency, containing transformer sources of orthogonal voltage systems and a valve circuit consisting of two four-valve rings (A.S. SU No. 1086524, IPC H02M 7/08, publ. 04/15/1984, Bull .№14).

The disadvantage of this converter is the need to use two transformers with a large typical power, i.e. large overall dimensions.

Known AC to DC converter with an 8-fold pulsation frequency, containing sources of orthogonal EMF, the valve winding system of which is connected according to the "square" and has two phase leads from the solders of the phase windings that make up the sides of the square, and the leads are connected to the 8-phase valve bridge (A.S. SU No. 1035755, IPC H02M 7/08, publ. 08/15/1983. Bull. No. 30).

The disadvantage of this converter is also the large overall dimensions, due to the need to use two transformers with a large number of parts of the secondary windings, a large number of valves required to implement the conversion, and a relatively large typical power of the transformers.

Closest to the invention adopted for the prototype is an AC to DC converter with an 8-fold ripple frequency (A.S. SU No. 1356153, IPC H02M 7/06, publ. 11/30/1987. Bull. No. 44; Fig. 8 9, g), providing eight-pulse rectification and containing a valve part with 16 valves, as well as two phase-shifted by 45 el. hail. relative to each other, the source of two EMF orthogonally phase-shifted, built on the secondary windings of a three-phase transformer, the first of the orthogonal EMF sources being formed by a group of three secondary phase windings, and the phase winding of one of the phases of this source is made with an intermediate tap to which the beginnings are connected two equal in size windings of the other two phases, and the second source is made according to the scheme, providing a phase shift between the emf of the sources at 45 el. hail. (Fig.9, g in the description of the prototype), and has at least two phase windings on the phase rods, unlike the phase winding of the first source, made with an intermediate tap.

The disadvantages of this converter are relatively large overall dimensions, which is associated with an increased typical power of the transformer and a large number of valves, as well as a relatively low efficiency, due to the fact that 3 valves are connected in series in the load current circuit.

The objective of the invention is the creation of an AC to DC converter with an 8-fold ripple frequency having better overall dimensions and higher efficiency.

This task is achieved in that the AC to DC converter with an 8-fold ripple frequency contains twelve valves and a three-phase transformer, on one of the rods of which there is a first phase secondary winding having an intermediate tap, and on the other two rods two phase windings, and to the intermediate tap of the first phase secondary winding are connected the beginnings of two phase windings, one placed on two other rods, a six-phase valve bridge is formed from twelve valves six AC inputs and two bipolar DC outputs to which the load is connected, and on the first phase secondary winding having a tap, an additional intermediate tap is placed between the first tap and the end of the winding, and the ends of two unused phase windings are connected to this tap the three free beginnings and three free ends of the phase windings formed in this case are connected to the AC inputs of the valve bridge, while the relative number of turns of the phase winding and with taps it is taken as tg45 °, the relative number of turns of phase windings connected to the first tap is taken as tg30 °, the relative number of turns of phase windings connected to an additional tap is taken as tg30 ° · tg22.5 °, and the relative number of turns of the part the phase winding with tapes located from its beginning to the first tap is sin45 ° -0.5 · (1-tg30 °), and the parts of this phase winding placed from the first tap to additional tap are sin45 ° · (1-tg30 °).

Figure 1 shows a circuit diagram of the proposed Converter; figure 2 shows a vector diagram of the voltage of the valve coil of the transformer of the proposed device (Figure 1), explaining the principle of formation of the vectors of the resulting voltages; figure 3 - topological diagrams of valve windings, presented in the form of amplitude-phase portraits of the voltages of the phase windings: Figure 3, a is a topological diagram corresponding to the circuit diagram in figure 1; Figure 3, b - Figure 3, g - versions of the valve windings with three-phase power systems; Figure 3, d is an embodiment of a valve winding with two-phase orthogonal power systems; figure 4 - diagram of the windings and valves of the Converter; 5 is a timing diagram of a rectified voltage curve.

The proposed Converter (Figure 1) contains a three-phase transformer 1 with a valve winding composed of a phase winding placed on one of the rods and having two intermediate tap, and four phase windings, two of which are placed on the other two rods of the transformer, the ends two of these windings with different rods and identical in size with are connected to a tap located closer to the beginning of the first phase winding, and the beginning of the remaining two, identical in size, phase windings are connected to an additional tap th first phase winding; the converter also contains a six-phase valve bridge 2, the opposite poles of which form the output terminals of the device to which the load 3 is connected. Six free phase terminals of the valve winding 2 are connected to the AC inputs of the six-phase valve bridge.

The principle of operation of the Converter (Figure 1) is illustrated by vector diagrams of voltages, presented in the form of an amplitude-phase portrait of the voltages of the phase windings that make up the valve winding (Figure 2). The relative number of turns of the phase windings, which provides canonical 8-pulse rectification, are shown in Figure 3, a; this figure also shows the private implementation of the valve winding (Figure 2, b-Figure 2, d).

The formation of an 8-pulse rectified voltage at the load occurs in accordance with the order of formation of the vectors of the resulting rectified voltages, which in Fig. 2 are combined with the amplitude-phase portrait of the voltage of the valve coil. The selected construction of the AFP provides the formation of four vectors of the resulting rectified voltages for the first half of the period of the mains voltage and four vectors, antiphase first, for the second half of the period. Moreover, the modules of all 8 vectors are equal and they are formed alternately with a shift of 45 el. hail. that on AFP corresponds to their consecutive rotational movement clockwise.

So, the first vector of the resulting voltage s1 is the sum of the collinear vectors of the phase voltages of the parts (a, a ', a ”) of the phase winding of the phase“ a ”of the transformer. The vector s2 is a linear voltage vector obtained from the phase voltages of the windings c, c 'of the phase "c" of the transformer and part a' of the phase winding of the phase "a" of the transformer. Similarly, the terms of the remaining vectors of the resulting rectified stresses are determined. During the period, 8 identical resulting stresses are formed, forming a symmetric 8-phase system of rectified stresses.

The operation diagram of the windings and valves (Figure 4), obtained from the analysis of the diagrams in Figure 2, allows us to determine that the part of the phase winding a 'located between the solders operates 270 el. hail., phase windings b ', c' connected to the first tap, work 180 el. hail., and the two remaining phase windings (b, c) and two parts of the first phase winding (a, a ”) work 90 el. hail for the period. Four valves connected to the phases belonging to the phase windings b ', c' with a relative number of turns tg30 ° have a conductivity angle of 90 el. hail., other valves - 45 el. hail. The load current in the inter-switching intervals flows around two valves.

The waveform of the rectified voltage obtained on a computer model is shown in Fig.5.

Based on the geometric construction of the diagrams of formation of the vectors of the resulting voltages (Figure 2), the maximum value of the rectified voltage with ideal switching and, accordingly, its average value are determined. Taking the amplitude of the voltage on the secondary phase windings b ′, c ′ as a relative unit (pu), in accordance with the vector diagrams in FIG. 2, the average value of the rectified voltage U _do = 1,688 p.u.

According to the results of the analysis of the secondary windings (Figure 4), their apparent power was determined, amounting to 1.2076 P _d . The installed power factor of the transformer of the proposed converter is 1.116. The similar performance of the prototype is slightly larger (approximately 0.5%), since the power of the secondary windings of the transformer of the prototype is 1.218 P _d .

The total number of phase terminals of the valve winding of the transformer of the prototype is 8, in accordance with this, the number of valves of the bridge valve circuit of the prototype is 16, and the proposed device has a number of phase terminals of the valve winding of 6 and, in accordance with this, the number of valves is 12 .

In the circuit of the flow of the load current of the prototype 3 valves are connected in series, and the proposed device has 2 valves, which provides less power losses in the valves, which means higher efficiency.

Thus, the proposed AC to DC converter with an 8-fold ripple frequency, compared with the prototype, has better overall dimensions and higher efficiency.

Claims (1)

An AC to DC converter with an 8-fold ripple frequency, containing twelve valves and a three-phase transformer, on one of the rods of which there is a first phase secondary winding having an intermediate tap, and on the other two rods - two phase windings, and to the intermediate tap of the first the phase of the secondary winding connected to the beginning of two phase windings, placed one on two other rods, characterized in that of the twelve valves formed six-phase valve bridge with six input alternating current and two bipolar DC outputs to which the load is connected, and on the first phase secondary winding having a tap, an additional intermediate tap is placed between the first tap and the end of the winding, the ends of two unused phase windings connected to this tap, and the three free beginnings and three free ends of the phase windings formed in this case are connected to the AC inputs of the valve bridge, while the relative number of turns of the phase winding from the tap and taken as tg45 °, the relative number of turns of phase windings connected to the first tap is taken as tg30 °, the relative number of turns of phase windings connected to an additional tap is taken as tg30 ° · tg22.5 °, and the relative number of turns of part of the phase winding with tapes located from its beginning to the first tap, it is sin45 ° -0.5 · (1-tg30 °), and part of this phase winding placed from the first tap before additional tap is sin45 ° · (1-tg30 °) .

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