SU817940A1 - Self-sustained voltage inverter - Google Patents

Description

(54) AUTONOMOUS VOLTAGE INVERTER

one

The invention relates to electrical engineering and can be used for any variant of a thyristor voltage inverter with single-phase and three-phase loads.

Known circuits of inverters with switching nodes, built on the basis of the switching circuit of the capacitor and the throttle 1.

In such schemes, an increase in load phasing leads to an increase in the number of switching capacitors and chokes, a decrease in reliability, and an increase in the mass and dimensions of the device. The number of switching reactive elements can be reduced by transforming the switching circuit and the main thyristors ViHBepTOpa 2.

The closest to the technical essence is a three-phase autonomous inverter circuit containing a bridge of basic HpifCTOpoB connected to input pins, reverse-coupled diodes connected by input} 1, the common point of which is connected through toric windings of a switching transformer with one electrodes of two-operation thyristors united by other electrodes into anode one the cathode group, a single-phase commutating thyristor bridge, the thyristors of the anodic group of which are backed up by reverse diodes, and in the diagonal alternating current in lyucheny serially connected commuting LC-chain and the primary winding of the switching transformer, schuntirovanna oppositely series-connected zener diodes.

The potential of unplugging the switching circuit from the main thyristors with the help of a pulse transformer and two-operation thyristors in the inverter allows, with a minimum number of bulky reactive switching elements, to provide phased switching of the main thyristors. Another advantage of the inverter is the ability to control the voltage on the switching capacitor without introducing a special regulated power source. Such regulation allows changing the amplitude of the switching current of the load, thereby maintaining the high efficiency of the device at low load currents of the inverter, for example, when the induction motor 3 is idling.

One of the drawbacks of the device should be considered as the fact that in the inverter there is a phase switching of the main thyristors, which in a number of cases does not provide such a harmonic composition of the output voltage of the inverter, which is achieved when the thyristors turn in the switch direction 4.

Another disadvantage is the local overheating of the structure of commuting two-stage thyristors at the stage of their shutdown, which is associated with the process of squeezing the anode current into a narrow cord and narrowly localized heat generation when the control current pulse is locked 5.

Local overheating, reaching temperatures in the order of 400 ° C, leads to a large thermal overload of two-stage thyristors.

The purpose of the invention is to expand the functional capabilities of the device, namely, the implementation of the povtile switching of the main thyristors of the inverter, while at the same time increasing the reliability by reducing the thermal overload of the dual-operation thyristors.

The goal is achieved by the fact that an autonomous voltage inverter containing a bridge of main thyristors connected to the input pins, shunted by reverse diodes and sequential chains consisting, each, of a secondary winding of a switching transformer and a two-operation thyristor and a single-phase switching thyristor bridge, anodic group thyristors which are bridged by reverse diodes, and the switching circuit of the LC circuit is connected to the diagonal of the alternating current, in series with the reverse diodes, shunting and property | ican anode group switching bridge, including the primary winding of the switching transformer.

FIG. 1 is a schematic diagram of an autonomous voltage inverter in a three-phase bridge version; in fig. 2 - timing diagrams explaining the operation of the device on the switching interval.

A three-phase inverter with main thyristors 1-6, shunted reverse diodes 7-12 and successive circuits consisting of secondary windings 13-18 of a pulse transformer 19 of two-stage thyristors 20-25 operates on a three-phase load 216 and contains a single-phase thyristor bridge 27-30, thyristors 27 and 28 of which are shunted by reverse diodes 31 and 32.

The bridge DC diagonal is connected to the inverter’s power supply, and the AC diagonal contains a switching circuit 33 consisting of a capacitor 34 and a throttle 35. To extend the functionality of the circuit while reducing the thermal overload of the dual-operation thyristors 20-25

in series with the diodes bypassing the thyristors of the anode group of the switching bridge, the primary windings 36 and 37 of the switching transformer 19 are included. The inverter works as follows.

Let the thyristors 1, 3, 5 be open at the initial moment of time to, and the switching capacitor 34 is charged with positive polarity on the right plate. At time t-i, the process begins.

switching thyristor 1. To lock thyristor 1, positive control pulses are applied to thyristors 27 and 20. Capacitor 34 begins to recharge along circuit 34-35-36-32-27-34 (Fig. 2a), and current i flows through thyristor 1 (Fig. 2c),

equal to the difference between the load current of phase A-1d and the current of the indicated oscillatory circuit i, given through the transformation ratio to the secondary winding 13 of the transformer 19 (current i in Fig. 26).

After the moment of time tjTOK, Lzi becomes larger than the current 1 d and the current equal to their difference goes into diode 7, and the thyristor 1 is under reverse anodic voltage and restores non-conductive properties. On the time interval tj, -1stock 1d increases to a maximum and begins to subside. At time i, before the current iji drops to a current value 1 /, a unlocking control impulse is supplied to the thyristor 30 and a locking negative control current impulse to the dual-operation thyristor 20. When the thyristor 30 is unlocked, the winding 36 through this thyristor and diode 32 conducting for some time in the opposite direction, it is connected to the power source of the inverter and a voltage pulse with amplitude Ec1Ctr appears on the winding 13. where CTD is the transformation ratio, equal to the ratio of the number of turns of the winding 13 to the number of turns in the winding 36. If QTP 1, then the thyristor 20 is under reverse anode voltage of EC | (Ktr-1) which, together with a negative control current pulse, leads to the combined switching off of a two-stage thyristor 20.

Claims (5)

Essentially equivalent circuit given to the winding 13 of the transformer 19 at the stage of turning off the thyristor 20 (interval tj-tj), is a sequential chain consisting of the source of the supply voltage E, the source of the pulse voltage Ktr, directed opposite to the first source and exceeds its magnitude, conducting in the forward direction of the thyristor 30 and diode 10, through which current 1 begins to flow and conducting in the interval tj-tz, in the opposite direction of the thyristor 20 and diode 32; Moreover, diode 32 is chosen so that the lifetime of minority carriers in its base (this time determines the magnitude of the excess charge accumulated in the diode 32 base and the rate of its decay) is longer than the lifetime of minority carriers in the p-base of the thyristor 20. Therefore, the thyristor 20 is first at time i restores the non-conductive properties in the opposite direction (Fig. 2e) and it is to him that at the given moment almost all the voltage EeL (Ctr. 1) is applied in the opposite direction (Fig. 2g), since the diode 32 at the moment tj, still has a significantly smaller. than uchi Ristor 20, resistance, in reverse Hianp-Alenia because of the excess charge remaining in it. Thus, the pulse of the reverse anode voltage is maintained on the thyristor 20 until the moment tg, when the process of reducing to an equilibrium value the charge of minority carriers in the base of the diode 32 accumulated during the flow of the direct anode current through the diode (see the interval ti tj in Fig. 26). At the moment 15, the resistance of the diode 32 in the opposite direction increases sharply and the winding 13 ceases to induce the voltage Ed KTP, which leads to the appearance of a direct voltage Ed on the thyristor. (Fig. 2g). Simultaneously with the process of turning off the thyristor 20, when unlocking the thyristor 30, the process of charging the capacitor 34 along the loop 34-35-30 begins. - Inverter power supply 27-34. Availability of voltage source c. This circuit allows to compensate for the energy losses in the switching LC chain occurring at the time interval At time t to the current ij O and thyristors 27 and 30 are turned off, after which, in principle, the next main inverter thyristor can be switched. In the next switching cycle, the thyristor 28 and a two-stage thyristor shunting the next lockable main thyristor of the inverter are first unlocked, and then, after a delay time tjao, the thyristor 29 is unlocked and a negative control current is applied to the dual-operation thyristor, which is locked in a combined way, as the two-step thyristor 20 is locked at the previous switching cycle. Adjustable time tja allows regulating the voltage on the capacitor 34, and hence the current amplitudes in the commutating circuit 33, This provides minimal switching losses when the inverter operates for varying loads. The claims autonomous inverter voltage, comprising connected to the input terminals of the bridge main thyristors schuntirovannyh reverse diode and successive chain comprising conductive, each of the secondary winding kommutiruyuts its transformer and dvuhoperatsionnogo thyristor and a single-phase commutating thyristor bridge thyristors anode group which zaschuntirovany inverses diodes, and in the diagonal of the alternating current is included a switching circuit LC, characterized in that, in order to extend the functionality minutes and increasing reliability, the primary windings of the pulse transformer connected in series with diodes, thyristors anode shunt .odnofaznogo group of said bridge. Sources of information taken into account in the examination 1. Zabrodin Yu. S. Nodes of forced capacitor switching thyristors M., “Energie, 1974. 2. The patent of the USA, 4060757, cl. 363-57, 3. USSR author's certificate number 564698 cl. H 02 M 7/515 1975. 4.Labuntsov V.A. .. Analysis and synthesis of autonomous thyristor voltage invertors, Dis. on the competition uch. Art. D.T.N. MEI, 1973. 5.Azn R. E. and others. On the limitation of switching power in pnpn structures that are turned off by a control current pulse. “Physics and Technology of Semiconductors, 1971, vol. № 5 № 1, p. 141 - 143. + eJto te