SU738072A1 - Ac-to-dc voltage converter - Google Patents

Description

The invention relates to the field of converter technology and can be used in thyristor converters of alternating voltage to constant. A known converter of alternating voltage into a constant, containing power thyristors, an auxiliary rectifier and a connected - at its output is a series circuit of a resistor and a capacitor. This device provides protection against external overvoltages, but it is impossible to force the switching of power thyristors. Closest to the invention in its technical essence and the effect achieved is a device that contains power thyristors associated with valve windings. power transformer and terminals for connecting a load circuit, an auxiliary rectifier, the output of which is connected to a bridge circuit, the two opposite arms of which contain uncontrolled gates, and the other two fully controlled switches and a capacitor is connected to the AC diagonal of the BRIDGE. The device is forced to com- plete power thyristors and protect p1 external overvoltages. The disadvantage of this device is that the forced switching node does not have galvanically isolated outputs, which limits its scope. The purpose of the invention is to enhance the functionality. This goal is achieved by the fact that in a converter containing power thyristors, an auxiliary rectifier whose output is connected to a bridge circuit, the two opposite arms of which contain unmanaged gates, and two other fully controllable switches, the capacitor included in the AC diagonal of the bridge circuit, In addition, a transformer was introduced, the primary winding of which is connected to the DC diagonal of the bridge circuit and shunted by a series circuit from an auxiliary capacitor and a capacitor. variable resistor, which is included vstrechnoparallelno diode, wherein an additional transformer secondary winding coupled with power thyristors through additional thyristors.

The scheme of the proposed device shown in the drawing.

The device contains power thyristors 1 connected to the valve windings 2 of the transformer and output 3 for connecting the load circuit, auxiliary rectifier 4, a bridge circuit whose two arms contain uncontrolled valves (diodes) 5 and b, and the other two are fully controllable keys 7 and 8, capacitor 9, additional transformer 10 with primary winding 11 and secondary windings 12, auxiliary capacitor 13 and thyristor 14 with diode 15, as well as additional thyristors 16 in the secondary winding circuit of the transformer 10. Keys 7 and 8 can be you oneny, e.g., in the form of analogues fully controllable, valve.

Let an open controlled converter valve b be used (for example, a single-phase, two-half-doubled converter is shown). In order to carry out artificial switching of power valves 1, the keys 7,8 and additional thyristors 16 are unlocked. The voltage of the capacitor 9 (the polarity of the voltage is indicated in the drawing) is applied to the primary winding 11 of the transformer 10, and the voltage of the secondary winding 12 to the serially connected winding 2 and power thyristor 1.

Through diode 15, capacitor 13 is charged until the voltage of the capacitor

After reducing the current of the power thyristor 1 to zero, the current of the converter passes through the winding 12 and the thyristor 16.

 . The directions of the currents in the windings 11 and 12 of the transformer 10 are opposite, and the magnetic reversal of transformer iron 10 occurs.

After locking the thyristor 1, the keys 7, 8 are locked, the thyristor 14 and the next power thyristor unlocked are unlocked.

After the discharge of the capacitor 13 to zero, its lowest recharge is due to the energy; accumulated in the converter circuit. The current in windings 11 and 12 retains the same direction, however, the main magnetic flux of the transformer 10 from this moment is created by the secondary winding 12 and the direction of the current. Going on

remagnetization of transformer 10 iron in the opposite direction.

After recharging the capacitor 13 to the voltage of the capacitor 9, the current of the terminal 11 passes through the diode 5, the capacitor 9 and the diode 6. At the moment

when the current of the winding 2 has reached a steady state, the charging of the capacitor 9 is stopped. The voltage of the capacitor 13 through the diode 15 applies it to the winding 11, the direction of the current in which in this case changes. The main magnetic flux is again created by the winding 11, and the magnetization reversal of the transformer iron 10 continues. The thyristor 16 is locked by the voltage of the winding 12.

The no-load current is a few percent of the rated current, so the capacitance of the capacitor 13 can be quite small.

By virtue of the capacitor 13, the rate of increase of the direct voltage on the lockable controlled valve is reduced.

Instead of a transformer 10, an autotransformer can be used 5.

The capacitance of the capacitor 9 is large enough and it also performs the functions of overvoltage protection.

Claims (1)

Invention Formula AC to DC converter containing power thyristors connected to the valve windings of the transformer and an output for connecting the load circuit, an auxiliary rectifier whose output is connected to a bridge circuit whose two opposite arms contain uncontrollable valves and the other two are fully controllable keys, and the diagonal is variable The bridge circuit current is switched on capacitor, characterized in that that, in order to extend the functionality, the primary winding of the additionally inserted transformer is connected to the DC diagonal of the bridge circuit, which is bridged by a series circuit of auxiliary capacitors and thyristors, the diode is connected in parallel with the secondary windings of the additional transformer connected to the power thyristors through additional thyristors.