SU836741A1 - Ac-to-unipolar current pulse converter - Google Patents

Description

(54) AC CONVERTER UNIPOLAR

PULSE CURRENTS

the capacitor and the zero point are the stars of the secondary windings, and the anode with the first output terminal, the cathode rupture of the bridge thyristors and the cathode of the second diode connected by an anode to the second plate of the separating capacitor and the cathode of the third iodine, the anode of which is connected to the second output terminal and the anode rupture ,

In the converter, as the load resistance increases, the first diode turns on, connecting a capacitor in parallel with the load. As a result, a loop is closed through which the oscillating current of the inverter passes with increased load resistance. In this case, the capacitor is recharged, and the constant component of its discharge current is able to flow to the rectifier through the zero output of the secondary winding of the transformer. Therefore, the converter becomes operational at any value of load resistance, which increases its reliability.

Figure 1 shows a circuit diagram of a converter; 2, timing diagrams of a switching current circuit of a voltage on a load Oc, a current of an additional diode ig, and a voltage on an additional capacitor I. A thyristor converter of alternating current to unipolar current pulses (Fig. 1) contains a power transformer 1, a bridge rectifier 2, a successive inverter bridge 3 with counter-diodes and a load 4 connected to the pole of the rectifier 2. The inverter bridge 3 contains the rectifier 2 connected to the pole through the choke 5 of the coupling capacitor 6 and the inverter bridge, with remaining from thyristors 7-10, counter diodes 11-14, and commuting LC-chain 15, 16. Load 4 is connected between the cathodes of thyristors 9, 10 and the pole of the rectifier 2, shunted by a chain of diodes 17 and 18, the common point of which is connected to the capacitor plate 6. In parallel with the load 4, a circuit is included consisting of a diode 19 and an additional capacitor 20, the connection point of which is connected to the zero output of the secondary winding of the transformer 1 ..

The converter works as follows

By connecting the capacitor SO to the zero point of the transformer secondary winding, the voltage on this capacitor is approximately half the input voltage of the inverter. When the load resistance is low, the voltage value on the load 4 does not exceed the voltage value on the capacitor 20, Therefore, the diode 19 is locked and ok

through it does not go. When turning on the thyristors 7, 10, the oscillating current of the recharge of the capacitor 16 of the switching LC circuit. The loop is closed: load 4, diode 18, splitter capacitor 6, thyristor 7, LC circuit 16, 15 thyristor 10. After that, counter diodes 11 and 14 turn on and the current closes along the loop: isolation capacitor 6, diode 17, load 4, diode 14, -С-п п; 15, 16 diode 11, В, as a result, a unipolar current impulse flows through load 4, consisting of two half-waves of oscillatory currents thyristor 7, 10 and diodes 11, 14. The processes when turning on thyristors 8, 9 and diode 12, 13 With an increased load resistance 4 some time after switching on The thyristors 7, 10, the voltage on the load 4 will exceed half of the input voltage of the inverter 3. At the same time, the diode 19 will begin to conduct and the oscillating current of the inverter 3 will also be closed along the circuit: thyristor 7, LC circuit 15, 16, thyristor 10, diode 19, the capacitor 20, the diode 18, the coupling capacitor 6. The greater the load resistance, the earlier the diode 18 turns on and the greater the percentage of the oscillating current of the inverter 3 thyristors, is closed through the capacitor 20. When the thyristors and counter diodes of the inverter are inoperative, through diode 17 and the choke 5 current flows through charge capacitor 6. With an increase in load resistance increases the average voltage across it. Therefore, by turning on the diode 17, the voltage on the capacitor 6 decreases. At a certain resistance value, the loads of the counter diodes of the inverter 3 cease to turn on. The inverter continues to operate without counter diodes and without increasing the amplitude of the thyristor currents, since this amplitude is determined by the voltage difference across the capacitors 6 and 20;

Thus, connecting parallel to the load of the circuit from the capacitor and the diode, the connection point of which is connected to the zero output of the secondary winding of the power transformer, provides a circuit for the flow of the oscillating current of the inverter with an increased load resistance,

. The specified inclusion of the circuit of the capacitor and the diode ensures the operation of the inverter and the converter as a whole with any load resistance, from the mode. short circuit to idle mode. This increases the reliability of the thyristor converter of alternating current into unipolar current pulses with variable load resistance.

Claims (3)

1. USSR author's certificate number 462688, cl. B 23 P 1/02, 1972. 2.Certificate of the USSR 5 № 563258, cl. B 23 P 1/02, 1975. 3. Thyristor frequency converters for induction heating of materials. Works AIM, vol. 64, Sat 4, Ufa, 1974, p.93, Fig.2. I g t J i. -.ja; s #, tzl l: t / od T g V