SU836740A1 - Self-sustained series inverter - Google Patents

Description

The invention relates to a transduction technique and is intended for induction heating, as well as for powering ultrasonic processing plants.

There is a known serial inverter circuit with on-parallel valves [1]. Such a circuit is capable of operating in the region of small equivalent load resistances, since the excess reactive energy stored in the switching circuit by means of on-parallel switching valves is recovered. However, in the region of high values of load resistance, there is a sharp decrease in the time available to restore the controllability of direct valves, which reduces the stability of the inverter. In addition, a small reverse voltage is applied to the direct valves in the indicated time interval, which leads to an increase in the time required for ^J to restore the controllability of the direct wets and to reduce the limiting frequency of inversion.

Also known is a serial inverter circuit [2], which contains 2 valve bridges with switching capacitors in the diagonals of alternating current. The excess reactive energy in this circuit is discharged directly from the switching inductor to auxiliary capacitors connected between the output terminals and the solders of the filter reactors associated with the positive input terminal. In some cases, when it is necessary to coordinate the load parameters, an output transformer is used, the primary winding of which is connected to the output terminals of the inverter.

The disadvantage of this scheme is that in order to achieve the greatest effect of voltage limitation on the inverter elements, it is necessary to remove the entire switching inductor from the inverter bridge and cover the recovery circuit, while the direct voltage at the moment of switching on the out-of-phase valves is applied the full voltage of the switching capacitor, which is still high . In addition, for the recovery of excess reactive energy from a switching inductor, it is necessary to install auxiliary capacitors3 that do not participate in the formation of a current pulse by the inverter bridge, which leads to an increase in the cost of installed equipment and an increase in its dimensions, and limiting the voltage across the load at a level equal to the voltage auxiliary capacitors at the final value of their capacitance is not enough, which leads to a sharp decrease in the time presented for the restoration of direct valves.

Closest to the proposed inverter is a self-contained inverter [3], containing two thyristor bridges connected to the input terminals through the filter inductors with two series-connected through commutating inductors connected to the alternating current diagonals of the opposite valve bridges, switching capacitors in the alternating current diagonals, two filter capacitors , the first lining of each of which is connected to the anode group of the corresponding thyristor bridge, and the second to the anode group of the oncoming valve a solid bridge connected by its cathode group to the first lining of the additional filter capacitor, the second lining of which is connected to the cathode group of the same thyristor bridge. . ,

The disadvantage of this inverter is the large capacitance of the capacitors, which increases the dimensions. And cost.

The aim of the invention is to reduce the cost of the inverter.

To achieve this, the inverter [h] is equipped with four chokes and an output transformer with four primary windings, two of. which are connected, each, with one end to the first lining of the additional filter capacitor, and the other end through one of these chokes, to the anode group of the corresponding thyristor bridge, and two other primary windings are connected, each, with one end to the second lining of the filter capacitor, and the other through the other of these chokes - with the cathode group of the corresponding thyristor mob. In addition, to increase stability while expanding the functionality, the inverter is equipped with four additional valves, and the primary windings of the output transformer are equipped with boost windings, the first ends of which are connected to the indicated other ends of the primary windings, two of them are connected through an additional valve, connected in the opposite direction, , each, with a second lining of an additional filter capacitor, forming a closed loop, and the second ends are: two voltage boost windings through another additional valve are connected, each, with the first lining of the corresponding filter capacitor.

Figure 1 shows a diagram of an inverter; figure 2 is the same, single-bridge option.

The inverter- (Fig. 1) contains two thyristor bridges assembled on thyristors 1–8, two counter valve washes on diodes 9–16. The diagonal of the thyristor bridges includes switching capacitors 17-20 and switching chokes 21, 22, and each valve bridge is shunted by two chains consisting of switching chokes 23-26, filter capacitors 27-30, primary windings 31-34, to the secondary winding 35 of the output the load 36 is connected to the transformer. Thyristor bridges are connected to the input terminals through the filter chokes 37, 38, and the output terminals through the filter chokes 39, 40, and each primary winding and filter capacitor are shunted by additional valves 41-44,

The circuit depicted in figure 1, operates as follows.

In the first cycle, thyristors 1,2 open and the current flows along the contours: thyristor 1 - capacitor 17 inductor 21 - capacitor 18 - thyristor 2 - inductor 24 - primary winding 32 - capacitor 28 - thyristor 1; thyristor 1 - capacitor 17 inductor 21 - capacitor 18 - thyristor 2 - capacitor 27 - primary winding 31 - inductor 23 - thyristor

1. Two filter capacitors 27, 28 are involved in the formation of the current pulse through the inverter bridge, the current of which flows through the primary windings of the output transformer and is added up to a load of 36 “Since the current through the switching reactors 23, 24 is summed up in the diagonal switching inductor 21, the inductance value the latter should be half as much as the inductance of the commutating chokes connected in series with. filter capacitors, while the voltages at the indicated inductors will be equal and when the thyristors are turned on, 1.2 counter diodes 9, 10 will be closed, because in the circuit: inductor 21 - diode 9 - capacitor 27 - inductor 24 - primary winding 32 diode 10 - inductor 21 and circuit: inductor 21 - diode 9 .- primary both second con-60 coil 31 - inductor 23, capacitor 28 - diode 10 - inductor 21 voltage on commutating reactors (polarity is shown in Fig. 1) are mutually switched to diodes' 9 and 10 65 reverse voltage is applied, the primary choke on per25

- the inductor 24 diode 12 flows output transzhe direction, the inverter bridge, the harmonic level in the output current.

the capacitor 30 is the thyristor thyristor 6. 30, in the second half of the current under the influence of the chokes 22, 25, diodes 15.16 and excess reactive to the supply to which the filter capacitors 27, 28 are charged. In the second half of the current half-cycle, when the voltage is switching inductors 21, 23 receives the polarity indicated in Fig. 1 (in brackets), and the sum of these voltages exceeds the voltage across the filter capacitors and primary windings of the output transformer, counter diodes 11, 12 open. From this moment, the invert bridge current stops pa, overcharging stops commuting capacitors 17, 1θ at a predetermined level, and excessive discharge current flows reactive energy, sealed, hay switching inductors in the contours: choke 21 - diode 11, the primary winding 31 - choke 23, capacitor 28 - diode 21, inductor 12 July; throttle 21 - diode 11 - condense. sator winding 32 21. The discharge current to the primary windings of the formatter is that current reduces the components.

In the second cycle, the thyristors 5.6 and the current open, flowing along the contours: capacitor 29 - thyristor 5 capacitor 19 - inductor 22 - capacitor 20 - thyristor 6 - inductor

- primary winding 33 - capacitor 29, primary winding 34 - inductor 26 Ristor 5 - capacitor 19 22 - co-capacitor 20. The half-voltage capacitor opens the discharge energy in these inductors flows along the circuits; the inductor 22 cel diode 22 34 diode clock is the formation of the second half-wave of the output current, i.e. In two stages of the inverter operation, a full period of the output current is formed. Symmetric recharge of the load with high-frequency current can significantly reduce the level of harmonic components in the output current, which ensures stable operation of the inverter in conditions of low quality factor of the load or its non-linear nature. In subsequent cycles of operation, when the thyristors 3,4 and 7, 8 open, the inverter operates as described

With an increase in the equivalent load resistance, the output diode 15 - capacitor 30 - dros 25 increases. - primary winding 33 16 inductor 23; inductor diode 15 - primary winding inductor 26 - capacitor 29 16 - inductor 22, In the second voltage and voltage on the primary windings of the output transformer, which is applied to the bridges of the inverter. The critical value of the amplitude of this voltage at a finite filter capacitor multiplicity, when the time provided for restoring the control properties of thyristors., Sharply decreases, is 0.8-0.9 of the supply voltage. To limit the voltage on the primary windings at a given level, additional valves ^ 41-44 are connected to the boost windings of these windings. This connection allows you to limit the amplitude of the voltage on the primary winding with boost turns at a level equal to the supply voltage, while the current recovery of energy stored in the load flows along the contours: primary winding 31 - capacitor 27 - valve 41; primary winding 32 - valve 42 capacitor 28; primary winding 33- valve 43 - capacitor 29; the primary winding 34 is a capacitor 30 is a valve 44. In this case, the voltage that is applied to the bridges of the inverter, is only part of the supply voltage, which can be adjusted by the ratio of the turns of the primary winding and boost boost coils.

Claims (3)

The invention relates to a converter technique and is intended for induction heating, as well as for powering ultrasonic process plants. The known circuit of a series inverter with anti-parallel connection valves l. Such a circuit is capable of operating in a region of small equivalent load resistances, since excess reactive energy stored in the switching circuit is accumulated by means of counter-parallel switching valves. However, in the region of high values of load resistance, there is a sharp decrease in the time allowed to restore the controllability of direct gates, which reduces the stability of the inverter. In addition, at a specified time interval, a small reverse voltage is applied to the direct valves, which leads to an increase in the time required to restore the controllability of the direct voltage and to a decrease in the inversion frequency limit. There is also an iwustnd circuit of a successive inverter 2, which contains two valve bridges with switching capacitors in alternating current diagonals. The excess reactive energy in this circuit is reset directly from the switching throttle to the auxiliary capacitors connected between the output terminals and the tapes of the filter chokes connected to the positive input terminal. In a number of cases, when it is necessary to coordinate the parameters of the load, an output transformer is used, the primary winding of which is connected to the output terminals of the inverter. The disadvantage of this circuit is that in order to achieve the greatest effect of limiting the voltage on the inverter elements, it is necessary to remove the entire commutating choke from the inverter bridge and cover the recovery circuit, while the full voltage of the commutator end is applied to the forward valves when the antiphase valves are turned on. a densator that is still high. In addition, to carry out the recovery of excess reactive energy from the commutating throttle, it is necessary to install auxiliary capacitors that are not involved in the generation of a current pulse by the inverter bridge, which leads to an increase in the cost of installed equipment and an increase in its dimensions, voltage on auxiliary capacitors at a finite value of their capacitance, is not enough, which leads to a sharp decrease in the time provided for the restoration of control direct gate valves. The closest to the proposed inverter is a standalone inverter, containing two tiristor bridges with two TIOCs connected via input filter throttles connected through commutating throttles connected to the diagonals of the alternating current of the opposing valve bridges and switching capacitors in the diagonal of the alternating current, two filter capacitors, the first lining of each of which is connected to the anode group of the corresponding thyristor bridge, and the second - to the anode group of the opposing veins yl bridge, its cathode connected to said first electrode group with the filter additional capacitor, the second plate of which is connected to the cathode of this group zhe.tiristornoto bridge. . The disadvantage of such an inverter is the large capacitance of the capacitors, which increases the size and cost. The aim of the invention is to reduce the cost of the inverter. To achieve this, the inverter 3 is equipped with four switches and an output transformer with four primary windings, two of them. each end of which is connected at one end with the first plate of the additional filter capacitor, and at the other end through one of the indicated drain channels to the anode group of the corresponding thyristor bridge, and the other primary windings are connected, each end with the second plate of the filter capacitor, and to another through another of the indicated chokes - with the cathode group of the corresponding thyristor Mofijra; In addition, to increase stability while expanding the functionality of the inverter, it is equipped with four additional volts, and the primary windings of the output transformer are supplied with additional voltage windings ,. the first ends of which are connected to the other ends of the primary windings, and the second ends of the two of them through an additional valve connected in the opposite direction are connected, kgikdy, with the second plate of the additional filter capacitor, forming a closed loop, and the second ends of two additional voltage windings through another additional valve is connected, each with the first lining of the corresponding filter capacitor. 1 shows a diagram of the invertropa; figure 2 - the same, single-bridge version. InverterFfig. 1) contains two thyristor bridges, assembled on thyristors 1-8, two opposing valve bridges. on diodes 9-16. In the diagonal of the thyristor bridges, switching capacitors 17–20 and switching inductors 21, 22 are connected, each valve bridge being bridged by two chains consisting of switching inductors 23–26, filter capacitors 27–30, primary windings 31–34, to the secondary winding 35 the output transformer is connected to the load 36. The thyristor bridges are connected to the input terminals through filter chokes 37, 38, and the output bridges from the filter chokes 39, 4 €, and each primary winding and filter capacitor are bridged by additional valves and 41-44. The scheme shown in Fig., Works as follows. In the first cycle, the thyristors 1.2 and the current flow through the circuits: thyristor 1 - capacitor 17 choke 21 - capacitor 18 - thyristor 2 - choke 24 - primary winding 32 - capacitor 28 - tyrist.or 1; thyristor 1 - capacitor 17 choke 21 - capacitor 18 - thyristor 2 - capacitor 27 - primary winding 31 - choke 23 - thyristor 1. Two filter capacitors 27, 28 are involved in generating a current pulse through the inverter bridge, the current of which flows through the primary windings of the output transformer and summed in load 36. Since the current through the commutating chokes 23, 24 is summed in the diagonal commutating choke 21, the inductance value of the latter must be two times less than the inductance of the commutating chokes included therefore with. filter capacitors, while the voltages on the specified chokes are equal and at the moment of turning on the thyristors 1.2, the counter diodes 9, 10 will be closed, because in the loop: choke 21 - diode 9 - capacitor 27 - choke 24 - primary winding 32 diode 10 - choke 21 and loop: choke 21 - diode 9. - primary winding 31 - choke 23, capacitor 28 - diode 10 - choke 21 of the voltage across the switching chokes x {polarity is indicated in Fig. 1) are mutually switched to diodes 9 and 10 applies a reverse voltage equal to the supply voltage to which the charge is charged. s filter capacitors 27, 28 In the second half of the current half-period when the voltage on the commutating chokes x 21, 23 takes the polarity indicated in Figure 1 (in brackets), and the sum of these voltages exceeds the voltage on the filter capacitors and primary In the windings of the output transformer, the counter diodes 11, 12 open. As a result, the current of the inverter bridge stops, the recharging of the switching capacitors 17 18 stops at a predetermined level and the discharge current of the excess reactive energy stored in the switching switches of x n loops: inductor 21 - diode 11, the primary winding 31 - choke 23, capacitor 28 - diode 12 - choke 21; choke 21 — diode 11 — capacitor — 27 — choke 24 — primary winding 32 — diode 12 — choke 21. A reset current flows through the primary windings of the output transformer in the same direction as the inverter bridge current, which reduces the harmonic components in the output current. In the second cycle, the thyristors 5.6 open and the current flows through the circuits: capacitor 29 — thyristor .5 capacitor 19 — choke 22 — capacitor 20 — thyristor 6 — choke 25 — primary winding 33 — capacitor 29, capacitor 30 primary winding 34 - choke 26 - thyristor 5 - capacitor 19 - droplet 22 - co-sensor 20 - thyristor 6.. capacitor 30, In the second half of the current half-cycle, the diodes 15, 16 and the excess reactive energy discharge current are opened under the effect of voltage across the droplets x 22, 25, 26 in the specified throttle x flows along the contours; choke 22 t diode 15 - capacitor 30 - cores 25 .- primary winding 33 diode 16 choke 23; choke 22 - diode 15 - primary winding 34 - choke 26 - capacitor 29 diode 16 - choke 22,. In the second cycle, the second half-wave of the output current is formed, i.e. The two steps of the inverter operation form the full period of the output current. Symmetrical feeding of the load with high frequency current makes it possible to significantly reduce the level of harmonic components in the output current, which ensures stable operation of the inverter under conditions of low quality of the load or its nonlinear nature, in subsequent clock cycles when the thyristors open 3,4 and 7, 8 the inverter is working as described above, with an increase in the equivalent load resistance, the output voltage and voltage on the primary windings of the output transformer, which is applied to the bridges, increases. PTOP. The critical value of the amplitude of this voltage at the final multiplicity of filter capacitors, when the time allowed for the restoration of the thyristor control properties, decreases sharply, is 0.8-0.9 times the supply voltage. To limit the voltage on the primary windings at a predetermined level, additional valves 41-44 are connected to the additional voltage windings of these windings. This connection allows you to limit the voltage amplitude on the primary winding with additional voltage at the same voltage level as the supply voltage energy stored in the load flows along the circuits: the primary winding 31 - capacitor 27 - valve 41; primary winding 32 - valve 42; capacitor 28; primary winding 33 — valve 43 — capacitor 29; Primary winding 34 — capacitor -30 — valve 44. In this case, the voltage that is applied to the inverter bridges is only a fraction of the supply voltage, which can be adjusted by the ratio of the turns of the primary winding and the booster turns. Claim 1. Sequential autonomous iverter containing two thyristor bridges connected to input pins via filter chokes with two series-connected through switching commutators connected to the diagonal m of alternating-current oncoming valve bridges, switching capacitors in diagonals of alternating current, two filter capacitors , the first facing of each of which is connected to the anode group of the respective thyristor bridge, and the second - to the anode group of the oncoming valve bridge a, connected by its cathode group to the first plate of an additional filter capacitor, the second plate of which is connected to the cathode group of the same thyristor bridge, characterized in that, in order to reduce the cost, it has four throttles and an output transformer with four primary windings, two of which are connected, each, at one end with the first lining of an additional Iltre capacitor, and the other end through one of the indicated chokes, with the anode group of the corresponding thyristor bridge, and e other primary windings are connected, each at one end with the filter capacitor second electrode and the other through the other of ukazannyhdrosseley - cathode of thyristor bridge group. 2. The inverter according to claim 1, in accordance with the fact that, in order to increase the stability of the operation while expanding the functionality, it is equipped with four additional valves, and the primary windings of the output transformer are equipped with additional voltage windings, the first ends of which connected to the other ends of the primary windings, and the second ends of two of them through an additional valve connected in the opposite direction are connected, each with the second lining of the additional filter capacitor, and the second ends of the two The other booster windings are connected through another auxiliary valve, each with the first lining of the filter capacitor. Sources of information taken into account in the examination -one. USSR Author's Certificate No. 486439, cl. H 02 M 7/537, 1971. 2. USSR author's certificate number 647817, cl. H 02 M 7/515, 1979. 3. USSR author's certificate 5 according to application number 2730527, cl. H 02 M 7/515, 1979, pg rm TO at " g "  6i7 H1tn W l -) 24 W 3S .37 a a 4 39 HI Th " gu ut