SU1262667A1 - Parallel inverter - Google Patents

Abstract

The invention relates to electrical engineering and can be used in secondary power sources, namely, valve frequency converters. The purpose of the invention is to increase the reliability of the inverter when powering a variable load. The capacitor (K) 19 is charged from the power source through choke 6. The thyristors 1 and 4, 2 and 3 of the bridge crosses are unlocked in pairs alternately shifted by 180 °. When changing the parameters of the active-inductive load, the voltage on the elements of the inverter: the switching K 7 ko and the load 8, as well as on the switching windings 9-12 and the adjusting choke 5 changes. The angle for restoring controllability changes. Due to the presence of excess circuits formed by secondary windings

Description

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double-wound chokes, the level of overvoltages on the inverter elements is limited. In the second half of each half period, when the total voltage across windings 13 and 14 or 15 n 16 exceeds the sum of the voltages on K 19 and throttle 5, valve 17 or 18 and part of the energy stored in windings 9 and 12 or 10 and 11 will open, will be returned to K 19, By varying the inductance of the droplets 5, it is possible to limit the overvoltage on the elements of the inverter. 1, Il.

The invention relates to a frequency converter HBw converter, designed to irreversibly convert direct current at the input to an alternating current of increased frequency on the receiver, and can be used to supply current of a higher frequency to a single-phase variable load, such as an induction heating plant for steel, the equivalent resistance of which in the process of heating the steel billet varies over a wide range. The aim of the invention is to increase the reliability of the inverter when. supplying a variable load by limiting overvoltages on the circuit elements and improving the conditions for restoring thyristor controllability. The drawing shows the loading scheme. The device contains: m bridge assembled on thyristors 1-4, the diagonal of the current voltage of which is connected through an adjusting choke 5 and a filter choke 6 to the input outputs and the diagonal of the alternating current to a parallel connected capacitor 7 and load 8. In series with the thyristors 1- The four windings of the bridge include the primary windings 9–12 of two winding chokes, in which the secondary windings of 13–16 cross-arms of the bridge are connected in pairs, successively and through the corresponding veins, ports 17 and 18, to the diagonal. DC bridge, to which is connected a series circuit of the capacitor 19 and the adjusting throttle 5. Inverter, works as follows. The capacitor 19 is charged from the power source through the choke 6. The thyristors 1 n 4, 2 and 3 cross-arms of the bridge are unlocked in pairs alternately shifted by 18 (When unlocking, for example, thyristors 1 and 4, a high-frequency current pulse flows through the circuit: capacitor 19 - choke 5 - winding 9 - thyristor 1 - load 8 and capacitor 7 thyristor 4 - winding 12 - capacitor 19. After natural locking of thyristors 1 and 4, thyristors 2 and 3 are unlocked and a current pulse flows through another circuit: capacitor 19 - choke 5 - winding 10 - thyristor 2 - capacitor 7 and load 8 - thyristor 3 winding 11 - capacitor 19. Then thyristors 1 and 4 are unlocked and the process is repeated. An alternating high-frequency current flows through the load 8. When the parameters of the active inductance change, the voltage on the inverter elements (switching capacitor 7 to load 8 changes and also on commutating windings 9-12 and adjusting 5 throttle) and angle to regain controllability. Due to the presence of excess energy discharge circuits formed by the secondary windings of double winding chokes, the level of overvoltages on the inverter elements is limited. It happens as follows. In the second half of each half-cycle of high-frequency current, when the total voltage on the secondary windings 13, 14 or 15, 16 exceeds

the sum of the voltages on the capacitor 19 and the adjusting choke 5, valve 17 or 18 will open and part of the energy stored in the windings 9, 12 or 10, 11 will be returned back to capacitor 19.

By changing the inductance of the choke 5, it is possible to limit the overvoltages on the inverter elements at the required level and obtain the required voltage across the load. For this, the adjustable throttle 5 can be configured with taps.

However, after turning off the thyristors, the reverse voltage is applied to them, which significantly improves the conditions for restoring the controllability of the thyristors.

Since the discharge of excess energy occurs during the half period (in the second half), the almost sinusoidal form of the current in the load is provided in the boundary mode.

Claims (1)

Invention Formula A parallel inverter containing a thyristor bridge connected to the input pins through a 4 choke choke with a switching capacitor in the diagonal of an alternating current, shunting a load circuit, as well as non-return valves, which in order to increase the reliability of operation at a variable load supply by limiting overvoltages circuit elements and improving the conditions for restoring the controllability of thyristors, it is equipped with a capacitor, an adjusting choke and four double-winding chokes, primary windings Each side of the bridge is connected in series with the thyristor, and the secondary windings of the cross-arms are connected in pairs in series and connected to the DC diagonal of the bridge through a valve, and a series of capacitors and an adjusting throttle connected between my volume and the filter choke is connected to the same bridge diagonal .