SU955457A2 - Two-cell series inverter - Google Patents

Description

(54) TWO-STYLE SEQUENTIAL INVERTER

one

The invention relates to a converter technique and can be used in induction heating installations for billets of powders in other high frequency installations.

According to the main author. St. No. 526052 is a two-cell serial inverter, containing a control and protection unit, two thyristor bridges connected in series through the commutation capacitors in diagonals connected through a filter choke to a power source, while the load is bridged by a compensating capacitor and a series of additional diodes and commuting Drossel, and the separation capacitor of each cell is connected to the input terminal of a thyristor bridge by one plate, the other to the common point Comm connectors of the commutating throttle and the corresponding electrodes of the additional diodes 1.

The disadvantages of this inverter include the following; if the load parameters change, the voltage on the elements of the inverter circuit can significantly increase, which can lead to a breakdown of the inversion and failure of its elements; When additional diodes fail, the switching capacitor of each bridge begins to recharge along the circuit,

5 in which there is no inductance, which leads to high rates of increase in the current of the thyristors and a breakdown of the inversion, reducing the reliability of the inverter as a whole.

0 The purpose of the invention is to increase the reliability of operation by eliminating the inversion failures.

The goal is achieved by the fact that the two-cell series inverter is equipped with an optocoupler, a resistor and a current sensor, the primary windings of which are connected according to between the same electrodes of the respective diode and bridge valves, each, and the secondary winding through a resistor connected to the input of the optro2Q on, the output connected to the control unit and protection.

The drawing is a diagram of the inverter. The two-cell serial inverter contains a control and protection unit 1, two valve bridges 2 and 3 connected in series through the load 4 (thyristors 5-8 of bridge 2 and thyristors 9-12 of bridge 3) with switching capacitors 13 and 14 in diagonals connected via filter choke 15 to the power supply 16, while the load 4 is clamped by the switching capacitor 17 and a series of diodes 18, 19 and the switching throttle 20, and the separation capacitors 21 and 22 of each cell are connected to the input terminal with one plate of the resistor bridge (thyristors 5 and 6 of bridge 2 and thyristors 11 and 12 of bridge 3), another plate to the common connection points of the switching throttle 20 and the corresponding electrodes of the diodes 18 and 19, current sensor 23, the input of the optocoupler is connected to the secondary winding 24 of which 26, and the primary windings 27 and 28 are connected mutually in series with the anode circuit of one (19) and cathode circuit of another (18) diodes 18 and 19, with the output of the optocoupler 26 connected to the control and protection unit 1 of the inverter.

In the quasi-reducing mode, the inverter operates as follows.

Let isolating capacitors 21 and 22 be normally charged to half the voltage of power supply 16 through a filter choke 15 and a switching choke 20. And let switching capacitors 13 and 14 have the polarity of the voltage shown on the drawing.

When the thyristors 5 and 7 are turned on (and the control pulses are supplied by the control and protection unit 1), the oscillating overcharge of the switching capacitor 13 through the circuit 13-7-4-28--19-20-21-5- 13 starts. As soon as the current of the thyristors 5 and 7 passes through the maximum value, the polarity of the voltage on the switching choke 20 changes to the opposite and, as soon as the voltage across it is higher than the load voltage 4, the diode 18 turns on, releasing excess electromagnetic energy from the throttles 20 to the load 4. The current of the thyristors 5 and 7 decreases and they are turned off, limiting the growth of the voltage across the switching capacitor 13.

Similar processes occur and with the next turn on the thyristors 9, 11, then the thyristors 6, 8 and then the thyristors 10, 12.

As follows from the principle of the inverter, through the primary windings 27 and 28 of the current sensor 23, the current flows in the direction in which the optocoupler 26 does not operate.

When at least one of the diodes 18 and 19 breaks down, which takes place in the process

0 operating an inverter, for example, 18, a current begins to flow through the primary winding 27 of the current sensor 23 (the next time the thyristors 5, 7 or 6, 8 are turned on) along circuit 27-21-5-13-7-27, in which there is no inductance, a greater rate of increase, causing the inversion to fail and the thyristors to go out of line, if you do not turn off the inverter.

In this inverter, as soon as the current passes through the circuit 27-21-5-13-7-27, the optocoupler 26 is triggered, starting the protection unit, which also turns off the inverter before the inversion fails, increasing its reliability.

Thus, by inserting a current sensor into the circuit of 5 diodes, it is possible to significantly increase the reliability of the inverter.

Claims (1)

Invention Formula Two-cell serial inverter auth. St. No. 526052, characterized in that, in order to increase reliability by eliminating the inversion failures, it is provided with an optocoupler, a resistor, a sensor current, the primary windings of which are connected according to each other by the same electrodes of the respective diode, and the bridge gates, each, and the secondary side through a resistor connected to the input of the optocoupler, the output connected to the control unit and protection. Sources of information taken into account during the examination 1. USSR Author's Certificate No. 526052, cl. H 02 M 7/515, 1973.