SU741397A1 - Bridge resonant inverter - Google Patents

Description

(54) BRIDGE RESONANT INVERTER

The invention relates to a converter technique, in particular to the field of high-frequency static converters for electrical installations.

There are various versions of power circuits for resonant inverters operating at an increased frequency as the load parameters change. In some schemes, the limiting voltage on the switching elements, when operating on a variable load, is accomplished by counter-parallel switching of controlled and uncontrolled additional gates i i due to the separation of the charging circuits and the discharge of the switching capacitances Gz

Circuits are also known where the voltage limiting is realized by means of reverse current diodes, through; which is the discharge of excess reactive energy commuting inductance source 4

Each of these variants of the schemes has its own specific drawbacks, which limit the scope of their application. In particular, for circuits with reverse current diodes, this disadvantage is the instability of inversion at an increased frequency with increasing load current, the presence of significant switching overvoltages that occur in these circuits when the reverse thyristors and diodes are disconnected at the moment they are turned off. There are various measures to limit these switching overvoltages, however the use of these measures can lead to a deterioration

15 technical and economic indicators of the converter.

Closest to the invention is a bridge resonant inverter, each key of which is made in the form

20 pavement thyristor cells with a cocomotor. a capacitor and a limiting inductance connected in series with this cell, containing switching inductors, the reverse current diodes, the corresponding power electrode of which is connected to a coherent key and through said inductance is connected to the output terminal of the inverter SJ, the switching voltage in this inverter is limited by removing a part of the switching inductance from the discharge circuit of excess reactive energy and its inclusion in the form of a restrictive inductance sredstvenno series with the thyristor bridge Coy. The disadvantage of this inverter is the high level of limiting the voltage on the switching capacitors when changing the load parameters, since the limiting inductance does not enter the excess energy discharge circuit, and the process of switching the working thyristors to the corresponding reverse current diodes is delayed. With an increase in the operating purity and output power of the inverter, the switching overvoltages sharply increase, which depend on the decay rate and the amplitude of the reverse currents in the thyristors and diodes, which leads to inversion. The limitation of the amplitude of the reverse currents for switching on the semiconductor valves is carried out by connecting in series with them the saturation throttles. The effectiveness of limiting switching overvoltages will increase if, in a known device B1, we directly connect additional successive saturation throttles directly to the reverse current diodes, and the limiting inductances are also performed in the form of saturation throttles. In addition, the disadvantage is also a relatively high level of voltage limiting on the switching capacitors, the inclusion of the reverse current diodes occurs with a delay. equal to the magnetization reversal time of the saturation chokes connected in series to these diodes. The remagnetization time Re is inversely proportional to the throttle applied to the winding, which is small and equals the voltage difference across the filter capacitor and the switching capacitor, i.e., the process of switching the current of the working thyristors to the beginning of the diode does not work. This is the reason for the increase in voltage across the capacitors, which will greatly reduce the technical and economic performance of the resonant inverter. The purpose of the invention is to improve the technical and economic indicators by reducing the voltage on the switching capacitors. This goal is achieved by the fact that. additional saturation throttles are included in each arm of the inverter bridge in series with the switching inductances between the key and the output terminal of the inverter. FIG. 1 shows a circuit diagram of the proposed bridge resonant inverter; in fig. 2 - timing diagrams for s in the processes of the inverter. The device contains keys 1–4, each of which is made in the form of a bridge thyristor cell with control valves and a switching capacitor 9 connected in series with the saturation throttle 10, a comming skin inductance 11–14, and additional saturation throttles 15 -18, reverse current diodes 19-22, filter capacitor 23 and output terminals 24 and 25. The formation of one half-wave of the output load current is accomplished by simultaneously turning on the antiphase thyristors of the odd keys of the bridge resonant inverter, forming nother halfwave - simultaneous turning protivo4) ase even-numbered thyristors. keys. The reverse current diodes 19 and 21 (20 and 22), together with additional saturation points 16 and 18 (15 and 17) and the filter capacitor 23, form a circuit for discharges from each of the reactive energy commuting inductance 12 and 14 (11 and 13) to source 23- 21-12-16-25-24-18-14-19-23 (23-22-11 15.24-25-17-13-20-23). The inclusion of reverse current diodes 20 and 22, (19 and 21) occurs at that moment when the voltage at the terminals 11–15 24 25-17 13 (14-18-24-25-1612) becomes equal to or greater than the voltage across the capacitor. filter 23. At the time of switching on the reverse current diodes 22 and 22 (19 n 21), the saturation throttles (14 and 16) are already in a saturated state and therefore the switch-on delay does not occur. As a result, stiffer limiting voltages on the switching capacitors are realized.

Thus, the inclusion of the additional “bHbix” chokes on the sequential switching inductances between the key and the output terminal of the bridge resonant inverter makes it possible to improve the technical and economic performance by reducing the output capacitor capacitors and at the same time. To ensure the stable operation of the inverter when changing the parameters of the load) from nominal to short circuit.

FIG. Figure 2 shows a diagram of current 26 through the inverter thyristors and voltage switches 27 on the switching capacitor, illustrating the effect of the limitation on the switching capacitor in mode 28, when there is no limitation, in mode 29; when limiting inductances are used, in mode 30, when saturation throttles, included according to the known device scheme, are used in mode 31, when saturation throttles are included according to the scheme of the invention. The voltage across the switching capacitor is shown in relative units in the diagram. Where the base value is the voltage source of the voltage of the bridge resonant inverter.

The tests of the static 1OOW converter of the 1OOOO Hz frequency, assembled according to the proposed bridge resonant inverter scheme, confirm the reliability of its operation as a power source for the quenching plant. The voltage on the switching capacitors of the inverter does not exceed 120% of the voltage of the power source when the

ns load parameters in the process on the “detail

Claims (5)

Invention Formula A bridge resonant inverter, each key of which is made in the form of a bridge thyristor cell with a switching capacitor and a saturation throttle in series with this cell, containing commuting inductances, reverse current diodes, the corresponding seat electrode of which is connected to the corresponding switch and through the above clump with the output terminal of the inverter, as well as additional saturation chokes by the number of reverse current diodes, characterized in that, in order to improve those © A iko- con ble rates by reducing the voltage across the switching kovdensa- tori mentioned additional choke nasptseni vkgaocheny in each arm of the bridge inverter with switching consecutively tionary E inductance between the key and the output of inverter vyvodbm. Sources of information that are considered in the examination: 1. US patent Ms 321-43, 1 3406327, 1968. 2. US Patent N 321-45, b & 3487289, 1969. 3. The patent of England, N 2, NJ 1157813, 1969. 4. USSR author's certificate No. 525213, cl. H 02 M 7/515, 1976. 5. The patent of Austria 21 18, N9 255572, 1967. Yy - eS 5 o in w I „L- -I L tf 25 Ci R 2 L. R go Th  . / 2 / 6 25 0W one R J five Faye.1