SU1066000A1 - A.c./d.c. converter - Google Patents

Abstract

1. AC INverter to DC, containing a rectifier assembled on the valves in a three-phase bridge circuit, the DC diagonal of which is connected to the output terminals, the first diagonal alternating current is connected to one capacitor plate, the second is diagonal through the choke, and the third is directly connected with input you-. water to connect single-phase 7O AC source, characterized in that, in order to reduce the total installed power, it is equipped with two serially connected windings, located on the magnetic core and connected to the input pins, two connected terminals of the choke and the second capacitor plate, respectively their common junction point is to the third diagonal of the alternating current of the indicated rectifier. 2. The converter according to claim 1, characterized in that the windings g are connected to the input terminals via an AV (L transformer circuit.) 3. The converter is П, 1, characterized in that the windings are connected to the input terminals via the TOR Format circuit.

Description

about a

The invention relates to power converter technology and is intended to be powered by a consumer's AC source, which is characterized by an operating short circuit. Such consumers are electric arc in different environments, periodically charged capacitors, some types of electric actuators, etc.

To limit the short-circuit current in known rectifiers, the inclusion of active, inductive or capacitive impedance, or a combination of them in the form of special schemes U and 2j, is used.

These converters consume the variable inductive or capacitive current components from the network, which is a disadvantage of these devices.

The closest to the present invention is an AC-DC converter containing a rectifier assembled on three-phase bridge valves, the DC diagonal of which is connected to the output pins, the first AC diagonal is connected to a single-phase AC source through a cosensor The second diagonal is through a choke, and a third is directly connected to the input terminals for connecting a single-phase AC source 3j.

The disadvantage of this device is the large installed power of the elements, since the load on them in the short circuit mode is almost three times higher than in the nominal modes. i The purpose of the invention is to reduce the apparent installed power. ; The goal is achieved by the fact that the inverted-to-constant-current converter, containing a rectifier assembled on the valves in a three-phase bridge circuit, the DC diagonal of which is connected to the output terminals, the first diagonal of the alternating current is connected to one capacitor plate, the second diagonal is through the choke, and the third is directly connected to the input terminals for connecting a single-phase AC source / is provided with two positons located on the magnetic core and connected to the input terminals edovatelno connected windings, two extreme vtoda which are respectively connected to the choke and a second plate of the capacitor, and their total point compounds - for the third AC diagonal of said rectifier. In this case, the windings can be connected to the inputs of the HfciM terminals either by autotransformer or by transformer circuits.

FIG. 1 shows a diagram of a converter with an autotransformer; in fig. 2 - vector diagram for the mode of high load currents; FIG. 3 shows the same for the mode of low load currents; in fig. 4 shows a converter circuit with a transformer; in fig. 5 - vector diagram for the mode of high load currents; in fig. b - the same .dl mode of low load currents.

The converter (Fig. 1) consists of a three-phase rectifying bridge 1, including 1: 1 valves 2-7, droplets 8, a capacitor 9 and a phase-shifting transformer 10 including windings 11 and 12. The output of load 1 is connected to the output of the rectifying bridge 1 one of the inputs is a single-phase power supply 14, and to the others, inputs choke 8 and capacitor 9. Transformer 10 is connected in series with one of the reactive elements — choke 8 or capacitor

The converter works as follows.

From the single-phase power source 14, power is supplied to the valves 2 and 5 through the choke 8, to the valves 4 and 7 through the windings 11 and 12 of the transformer 10 and through the capacitor 9, to the valves 6.3 directly. The windings of transformer 10 are phased in such a way that the voltage supplied to capacitor 9 is shifted in phase by 180 ° relative to the voltage that is applied to choke 8. The transformation ratio of transformer 10 is one.

The resistance of the consumer 13 varies during operation from zero (short circuit) to infinity (open circuit). With a change in consumer resilience 13, the operation of the entire rectifier changes significantly. Therefore, the operation of the converter must be considered in three separate modes: I - operation at high load currents and during a short circuit; II - work in nominal mode and around it; III - work at low load currents near idle.

In the event of a short circuit, the voltages on the choke 8 and on the capacitor 9 are maximum and these voltages are. approximately equal to the voltage of the power source.  This mode mainly determines the set power of the reactant elements.  The output current here is equal to the sum of the currents of the drossel 8 and the capacitor 9, and the current consumed from the power source 14 is small (with ideal circuit elements equal to zero).  As the load resistance increases, the current consumed increases, reaches a maximum, and then decreases.  The maximum current consumption is nominal lm mode.  As the load resistance increases, the output voltage increases steadily.  In nominal mode, it reaches a level that is approximately 1.4 times higher than the voltage of power source 14, and at idle it is twice as high as this voltage.  The currents of the droplet 8 and the capacitor 9 in the third mode are equal to the current through the consumer 13, and the current from the power source 14 is twice as large as these currents.  The efficiency of using circuit elements is determined, on the one hand, by the output power of the converter in the nominal mode and, on the other hand, by the power on the reactive elements in the short circuit mode.  The ratio of these powers is the specific installed capacity and determines the weight and size parameters and the cost of the rectifier.  The use of a transformer increases the power at the load in the nominal mode by approximately S 2.5 times.  In this case, the reactive power on the choke 8 and on the capacitor 9 in the short-circuit mode does not change.  This achieves a reduction in the specific installed power. The described properties of the converter are explained by the fact that the rectifying bridge 1 operates KONwyTaTOpOM, which, depending on the magnitude of the load, Forms different current contours from the reactive elements.  The formation of six current loops is possible, part of which is divided into two parts due to passing through the transformer 10.  These circuits follow: 1) power supply 14 - choke 8 - valve 2 - load 13 - valve 3 - power source 14; 2) winding 12 - capacitor 9 - valve 4 - load 13 ventil 3 - winding 12, power source 14 - winding 11 - Power source 14; 3) winding 12 - capacitor 9 - valve 4 - load 13 - valve 5 - choke 8 - power source 14 winding 12, power source 14 - winding 11 - power source 14; 4) droosel 8 - power supply 14 - valve b - load 13 - valve 5 - choke 8; 5) capacitor 9 - winding 12 - valve b load 13 - valve 7 - capacitor 9, power source 14 - winding 11 - power source 14; b) power source 14 - choke 8 - power 2 - load 13 - weityl 7 capacitor 9 - winding 12 - power source 14, power source 14 winding 11 - power source 14.  All circuits pass through power supply 14, rectifier bridge 1, load 13, and they differ mainly in that they contain different reactive elements.  In circuits 1) and 4), the power supply, inductance and load are connected in series; in circuits 2) and 5), the power source, capacity, and load; in circuits 3) and 6) - power source, inductance, capacitance and load.  In these three pairs of contours, one circuit (for example, 1) exists in one popupperiod, and the second (for example, 4) in the second half-period.  The three operating modes shown are distinguished by the composition, sequence, and duration of the illustrated current loops.  When operating in the first mode, circuits 1) and 2) of the current exist in one half period, and circuits 4 and 5 in the second half period.  The contours 3) and 6) are practically not formed. The currents and voltages in the part of the circuit up to the rectifying bridge in the first mode are approximately sinusoidal, due to which one can use the vector diagram (Fig. 2). Nn dex of current vectors j and voltages (J (nafig.  2) correspond to the designations of the elements on.  FIG.  one.  The voltages at the input to the rectifier bridge are denoted as Ud,, and Oz. The voltage drop across the dissipation inductance of the transformer 10 is designated O.  In the event of a short circuit at the output of the bridge in circuits 1) and 4) the choke 8 is connected to the power supply source 14, and in circuits 2) and 5) the capacitor 9 is connected through the transformer 10 to the power supply voltage.  The reactive co-connections between the chokes 8 and the capacitor 9 are chosen under the condition ХцГ Хр - Хд, where XL, is the inductive resistance of the chokes 8; Xj.  -.  capacitance of the capacitor 9; x is the inductance resistance of the transformer 10 transformer.  Then the currents are 3g and 3, (FIG.  2) will be equal in absolute value and shifted by the same angle to different sides with respect to the voltage vector and {, the geometric sum of these currents is the consumed current c, which is in phase with the vector of the supply voltage.  In this way, the reactive component of the consumed tokS is compensated; in the first mode.  In the event of a short circuit, the currents Jg and Zc are almost out of phase, they are compensated and only a small amount is consumed from the power source. k to cover energy loss.  The current back through the capacitor 9 at the same time finds in phase with the current Jg through the choke 8.  Therefore, the sum of the short-circuit currents of the droplets 8 and the capacitor 9 passes through the place of the short for: mycan. During operation in the third mode, there is a current loop 3 in one half-period, and a current loop b in the second half-period.  When working on resistive loads, you can also use a vector diagram here (FIG.  3).  The designation of the vectors in FIG. 3 is the same as in FIG.  2, Vectors 0 and E: are located in FIG.  3, in one direction, while in FIG.  2 between them is an angle of 180.  This is caused by 1Tem. In circuits 3 and 6, the secondary winding 12 of transformer 10 is connected to power supply 14 in series, and in circuits 1-5 there is no such connection.  The serial connection of the 14 yitani source and the secondary winding 12 of the transformer 10 causes a doubling of the voltage that is applied through the heating bridge 1 to the load 13.  Throttle: Sel 8 and condenser 9 will appear in Circuits 3 and 6 connected in series. , and their resistances are selected according to the condition given above.  Therefore, the voltage drops across the reactive elements cancel each other out (Fig.  3).  In addition, if the load is active, the current consumed does not contain a reactive component.  The capacitor 9, the leakage inductance of the transformer 10 and the choke 8 form in the third mode a series oscillatory circuit tuned to the frequency of the power source 14.  The presence of such a circuit, connected in series with a rectifying bridge, is advantageous, since it has a suppressive effect on the higher harmonic current consumption.  In the second mode, each half-period is subdivided into 4 in, erval with different current circuits.  The current contours in the intervals are as follows: in the first interval, contours 1 and 2 (4 and 5) in the second are contours 2 and 3 (5 and b), in the third - contour 3 (b); in the fourth - contours 3 and 4 (6 and 1).  The outlines for the second half period are given in parentheses.  The first interval is obtained when the supply voltage passes through zero.  The current contours of the first interval of the second mode correspond to the contours of the first mode, the contours of the third interval of the second mode - the contours of the third mode.  This means that in the second mode in the same half-period there is sometimes a parallel connection of the throttle 8 and the capacitor 9, as in the first mode, and sequential switching-on, as in the third mode.  In this connection, the currents and voltages on the circuit elements are not sinusoidal.  The harmonic factor of the consumed 1ka depends on the nature of the load and the location of the operating point.  In the nominal mode, it is about 10 when the load is active, and when operating at back-EMF it is about 20%.  At the frequency of higher harmonics, the resistance of capacitor 9 is smaller than drossel 8, therefore the current load on capacitor 9 will be carried--.  more than choke 8.  But the reactive component in the consumed current with active-inductive load is small - the coefficient of reactive power tg × 0.1.  When operating on counter-DPT, when the reverse voltage is 60% or more of the peak value of the rectifier idle voltage, there is an increase in the inductive component in the consumed current to 0.30, 4.  The rated voltage of the rectifier mode is approximately 70% of the no-load voltage, and the rated mode current is 60% of the short-circuit current.  At this time, the reactive cell current in the nominal mode is 85-90% of the short circuit current of these cells.  The use of a transformer changes the flow of switching processes in the rectifier bridge.  Low reactance circuits arise, due to which the reactive power of the capacitor and throttle are used in the nominal operating mode better than the prototype.  This makes it possible to reduce the specific installed power of the reactive elements, which leads to a decrease in the weight, size, and cost of the rectifier.  At the same power and the same current of the reactive elements during a short circuit, the output power in the nominal mode of this device is approximately 2.5 times greater. than the prototype.  Since the converter is designed for operation in the operational short-circuit mode, the installed power of the circuit elements should be selected taking into account the electrical loads of this mode.  Therefore, the total specific installed power of the circuit elements is 2-2.5 times less than that of the prototype.  Fig. 4 shows a converter using a transformator, i. e.  The windings 11 and 12 are connected to the input terminals of the transformer circuit by introducing the primary winding 15.  The converter operates in the same way, with the possible formation of six circuits: 1, winding 11 — cores 8 — valve 2 — load 13 valve 3 — winding 11; 2  winding 12 - capacitor 9 - valve 4 load 13 - valve 3 - winding 12; 3, Winding 12 - condenser 9 valve 4 - load 13 - valve 5 - throttle 8 - winding 11 - winding 12; 4, the throttle 8 - winding 1 valve 6 - load 13 - valve, throttle 8; 5, capacitor 9 - JAMOTKa 12 - valve 6 - load 13 valve 7 - capacitor 9; 6 winding 11 - throttle 8 - valve 2 -.  load 13 - valve 7 - condenser tor 9 - winding 12 - winding 11.  In circuits 1 and 4, load 13 receives power through inductance and in circuits 2 and 5 through capacitance. The supply voltage in these circuits is equal to half the voltage of the secondary windings 11 and 12.  In circuits 3 and b, the load receives the full voltage of the windings 11 and 12 through the series-connected inductance and capacitance.  In these three pax contours, one circuit (for example, 1) exists in one half-period, and the second (for example, 4) - in the second half-period.  The composition, sequence and duration of the current circuits depends on the mode of operation.  When operating in the first mode, there are 1 and 2 current circuits in one half cycle, ABO, and a second half cycle, 4 and 5 current circuits.  Contours 3 and b are practically not formed.  Currents and.  voltage in the circuit to a rectifying bridge in the first mode is approximately sinusoidal, so. here you can use the vector diagram {FIG.  five).  The indices of the vectors of currents, voltages and EMF (FIG.  5 and b) correspond to the names of the elements in FIG.  four.  Input voltage. A rectifying bridge is indicated by, l and U d. The voltage drop across the resistance of the equivalent inductance of the winding 11 is denoted by Ojg, on the resistance of the equivalent dissipation of the winding 12 to the resistance of the inductance dissipation between windings 15 and 11, 12.  Vector diagram (FIG.  5) built relative to the midpoint of the windings 11 and 12 of the transformer.  In this case, when going from the secondary circuit to the primary current and voltage vectors, the windings 12 change their direction to the opposite, and the current and voltage vectors of the winding 11 do not change their Hp1prod.  The currents of the secondary winding 3 and J;, 2, referred to the primary winding, are denoted by and Tsg. The reactive resistances of throttle 8 and capacitor 9 are selected while observing the condition with L + -, where x is the capacitance of capacitor 9; x - inductive resistance Drossel 8; x is the leakage inductance between the windings 15 and 11, 12 of the transformer 10.  When a short circuit at the output of the bridge in circuits 1 and 4, the choke 8 is connected to the winding 11 of the transformer 10 and in the circuits 2 and 5, the capacitor 9 is connected to the winding 12 of the transformer 10.  The currents and 1-2 are in this case practically in antiphase and equal in absolute value, therefore they are compensated and only a small current is consumed from the power source to cover the energy losses.  The current 3j through the capacitor 9 at this time, at the time, is in phase with the current la through the inductor 8, therefore the sum of the short-circuit currents of the throttle 8 and the capacitor 9 passes through the short circuit.  With a small load resistance at the output of the bridge currents 3J.  2 (FIG.  2) will also be equal in absolute value and shifted by a shifted angle in different directions from the voltage vector, and.  The geometric sum of these currents is the current consumed by 3.5 / which is in phase with the supply voltage vector. In this way, wasp. There is compensation for the reactive component of the current consumed in the first mode.  When operating in the third mode, there is a current loop 3 in one half cycle and a current loop in this half cycle.  When working on resistive loads, you can also use the vector diagram on the 1st (Fig.  3).  The designation of the vectors in FIG.  b is the same as in fig.  five.  Vectors E and E are located in the same direction, while in FIG.  5, an angle of 180 ° between them, since the vector diagram in FIG.  b constructed relative to the connection point of the capacitor 9 with the winding 12.  In circuits 3 and b, windings 11 and 12 are connected consistently to which corresponds the arrangement of vectors B f and in FIG. b  In these circuits, choke 8 and capacitor 9 are connected in series, and their resistances are selected according to the condition given,.  Therefore, the voltage drop across the reactive elements is mutually compensated (Fig.  3), and through the rectifying bridge 7, almost the sum of the voltages of the windings 11 I is applied to the load 13; 12.  In addition, if the load is active, then the current consumed practically does not contain reactive components.  The capacitor 9, the choke 8 and the leakage inductance between the O1 windings 10 and 12 form in the third mode a series oscillatory tuned to the frequency of the power supply 16.  The presence of such a circuit, connected in series with a rectifying bridge, is advantageous, since it will have a suppressive effect on the higher harmonic current consumption.  In the second mode, each half cycle is subdivided into 4 intervals with different current loops.  The contours in the intervals are as follows: in the first interval, contours 1 and 2 (4 and 5); in the second interval, contours 2 and 3 (5 and b); in the third interval, circuit 3 (6); in the fourth interval, the contours of Zi4 (6 and 1).  The outlines for the second half period are given in parentheses.  The first interval is obtained when the supply voltage passes through zero.  The current contours of the second mode interval correspond to the contours of the first mode, and the contours of the third interval and the second mode correspond to the contours of a third of its mode.  This means that in the second mode, in one half-period, there are sometimes a parallel connection of the throttle 8 and the capacitor 9, as in the first mode, and a series connection, as in the third mode.  In connection with this, the currents and voltages in the circuit elements are different from sinus-shaped.  The harmonic coefficient I of the consumed current in the nominal mode when operating at a resistive load is approximately 10%, and working at the back-EMF is 15-20%.  The load on the reactive elements 8 and 9 in the nominal mode is about 95% of the load on these elements in the short-circuit mode, which ensures good utilization of the installed power of these elements.  The relatively low harmonic coefficient and the large load on the reactive elements in the nominal mode are caused by the fact that the main share of power (70-80%) is transferred to the load through circuits 3-6.  In the prototype similar contours are missing.  At the frequency of higher harmonics, the resistance of the capacitor is 9 less, h. I eat Drossel 8.  Therefore, the current load on the capacitor 9 will be slightly more than the choke 8.  But the reactive component in the consumed current with active-inductive load is a small coefficient of reactive power, l.  When operating at counter-emf, when the reverse voltage is 60% or more of the peak no-load voltage of the converter, there is an increase in the inductive component in the consumed current to tg If g 0.3-0.4.  In the nominal mode, the content of higher harmonics in the consumed current of this device and the prototype is approximately the same, at load currents less than the nominal value of this device, lower than that of the prototype, as it forms a series oscillatory circuit from the drossel and capacitor, which reduces the level of higher harmonic currents.  The prototype has separate current circuits across the entire load range through a choke and a capacitor.  When the load currents are greater than the nominal content of this device, the higher harmonic content of the consumed current is greater than that of the prototype, since the prototype, in series with the capacitor, has an additional choke, the inductance of which is greater than that of the transformer of this device.

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Claims (3)

1. AC to DC Converter, containing a rectifier assembled on the valves according to a three-phase bridge circuit whose DC diagonal is connected to the output terminals, the first diagonal of the alternating current is connected to one capacitor plate, the second diagonal is connected via the inductor, and the third is directly connected to the input terminals for connecting a single-phase AC source, characterized in that, in order to reduce the total installed power, it is equipped with located on the magnetic circuit and nennymi with input terminals of two serially connected coils, two extreme withdrawal which are respectively connected to the choke and the second plate of the capacitor, and their common connection point - the third AC diagonal of said rectifier. 2. The converter according to π. 1, characterized in that the windings are connected to the input terminals by an autotransformer circuit. 3. Converter pop, 1, characterized in that the windings are connected to the input terminals through the transformer format circuit as r ^ ΗΪ ² Utt