SU900387A1 - Self-sustained inverter - Google Patents

Description

(5) AUTONOMOUS INVERTER

one

The invention relates to static CMI frequency converters, which are the power sources of installations for high-frequency heating of metals and ultrasonic technological installations.

There are known autonomous inverters containing a series circuit from the load and a filter capacitor connected to the input terminals, in parallel with which a thyristor bridge is connected, switching LC circuit 13 and C2.

The closest to the present invention is an inverter containing a series circuit from a load and a filter capacitor connected to the input terminals via a filter choke, in parallel through which a thyristor bridges with switching LC circuits are connected via a switching choke, as well as two additional diodes, one of which is connected counter-parallel to one another chains

From the load and the filter capacitor, and the other counter-parallel to the filter capacitor and the switching choke 3.

The disadvantage of the known inverter is the absence of damping of the switching overvoltages on the thyristors of the circuit, which is usually carried out by connecting parallel to the thyristors of the chains of capacitors

10 diodes and resistors.

The purpose of the invention is to increase the reliability of damping switching overvoltages while simultaneously stabilizing with varying

15 ruzke.

To achieve this goal, a standalone inverter containing a series connected to the input outputs through a filter choke

A chain of a filter capacitor and output pins, parallel to which a thyristor bridge with a switching LC circuit in the diagonal and two diodes is connected via a switching choke, is equipped with two resistors, two capacitors and two additional diodes connected in series and connected anti-parallel to the bridge, one the end of the diagonal of the alternating current through a series-connected resistor and capacitor is connected to the common point of two additional diodes, and the other end of it across the other wires Torr and a capacitor the common point of these two diodes connected in series and connected in anti-parallel bridge. The drawing shows the scheme of the inverter. The inverter contains a filter choke 1, through which a series circuit from the filter capacitor 2 and the load 3 is connected to the input terminals. Parallel to this circuit, a bridge consisting of thyristors is connected through commuting choke k. The bridge bridge is connected to the LC circuit from the switching capacitor 9 and the second switching throttle 10. Two circuits are connected in parallel to the bridge from diodes 11 and 12 and additional diodes 13 and I. The connection points of each pair of diodes are connected through a capacitor 15 and 16 the diagonal of the AC bridge. The inverter works as follows. When the next pair of thyristors of the bridge is unlocked, for example, 7 and 8, an oscillating recharge of the switching capacitor 9 along the contour 9-8-3-2-4-7-10-9 occurs. Simultaneously, the capacitors of the damping circuits are discharged along circuits 15-17-8-12 and 16-13-7-18-16, discharged in the previous half-period. By the end of the half-cycle of the natural frequency of the recharge circuit of the switching capacitor 9, the current in the circuit drops to zero, and the voltage on the switching capacitor 9 changes its polarity, as a result of which the thyristors 7 and 8 are locked. For a short period of time while the thyristors 7 and 8 are locked, the reverse current flows through them. When thyristors 7 and 8 are locked, the current in the circuit is abruptly interrupted and, due to the presence of inductances 4 and 10, large impulses of overvoltages can occur on the thyristors. The presence of damping ORC circuits eliminates these overvoltages, since at the time of shutting down thyristors 7 and 8, the current in the circuit with inductances does not drop abruptly, but smoothly as the capacitors 15 and .16 charge along the circuit 9-10-18-16- 13- 2-3-12-15-17-9,. Then there is a pause, equal to the half-period of the natural frequency of the switching circuit, during which the electrical state of all circuit elements does not change, except that a constant input current flows through the (+) - 1-2-3 -. (-) circuit. the inverter, and the direction of this current in the load is opposite to the half-wave of the current formed in the range of conductance of thyristors 7 and 8. In the next half-period, another pair of thyristors of bridge 5 and 6 is unlocked, the reverse recharge of the switching capacitor 9 occurs along circuit 9-10-6-3- 2-5-9. At the same time, the capacitors 15 and 16 of the damping circuits are discharged along circuits 15-11-5-17-15 and, 16-18-6-1 -16, preparing the circuits for damping. After half a period, the voltage on the capacitor 9 will change polarity, the current in the circuit will drop to zero, trying to change its direction. After the thyristors 5 and 6 are locked, the overvoltage is damped along the circuit 9-17-15-11 2-3-1-1-18-18-10-9. Further, the processes in the circuit are repeated. In the design mode of operation, the parameters of the elements are chosen such that the amplitude of the total voltage on the choke 4 and the load 3 does not exceed the voltage on the filter capacitor 2. Under the effect of the last circuit voltage from the diodes 11, 12 and 13, 1 are in the locked state . As the load resistance decreases, the quality factor increases, and the voltages on the elements, including the choke, increase. As soon as the amplitude of the sum of the voltages on the choke and the load 3 exceeds the voltage on the capacitor 2 of the filter, the circuits from the diodes 11, 12 and 13-,

image additional switching circuits;

/ 2-1Ч

9-8-3-2-i -7-10-9

Additional circuits, shunt choke reduce the resulting inductance, and hence the quality of the switching circuit. As the load resistance 3 increases, the voltage across it increases, and as soon as the amplitude of the sum of this voltage from the voltage across the choke exceeds the voltage of the filter capacitor 2, the diode circuits forming the same additional switching circuits will again be unlocked. The formation of these circuits, in principle, ensures the switching stability of the inverter until the load is broken.

Thus, in the proposed inverter, the same device performs the stabilization of the mode when changing the load parameters and damping overvoltages on the thyristors of the inverter.

Claims (3)

1. USSR Author's Certificate No. 89186, cl. H 02 M 7/515, 1973. 2. USSR author's certificate number 515228, cl. H 02 M 7/515, 1973. 3. USSR author's certificate number 700905, cl. H 02 M 7/515, 1978.