SU1283918A1 - Self-excited inverter - Google Patents

Abstract

The invention relates to a converter technique. The goal is to reduce the installed power of the inverter elements with an extended range of parameters of the complex load. The device contains thyristors 1-4 bridge cells. A direct current choke (DHOT) 10 is connected in parallel to the bridge cell through a capacitor (K) 9. Load 7 together with the choke 6 is bridged by a chain of diode (D) 11 and K 9. At the moment of equal voltage on the switching capacitor 5 to the total voltage on K 9 and the filter capacitor 8 turn on D 11, which limits the voltage on the capacitor 5. Only current flowing through DPP 10 is due to the flow of reactive energy. 1, il. (I

Description

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The invention relates to converter technology and can be used in the development of high frequency thyristor converters for induction heating of metals, quenching and melting, operating in a wide range of variation of load impedance with a lower installed power of active and passive elements.

The purpose of the invention is to reduce the installed power of the inverter elements with an extended range of variation of the parameters of the complex load,

The drawing shows an example implementation of the device.

The self-contained inverter contains common-mode thyristors 1-4 of the bridge cell with switching capacitor 5, switching choke 6 and complex load 7, filter capacitor B connected to the input terminals, capacitor 9 connected to the direct current choke, current 10 and cathode of the uncontrolled diode 11, positive and a negative 12,13 DC power source.

As the inverter load, for example, a compensated loop of the induction heating unit of a higher frequency is used. On the capacitors 8 and 9 during the operation of the inverter, the voltage has an average value equal to the inverter supply voltage, and the choke 10 in a steady state flows proportional to the equivalent inverter load resistance.

Consider the operation of the inverter in one cycle of turning on the thyristors of the inverter cell.

When the thyristors 1 and 2 are turned on, the switching capacitor 5, the choke 6 and the load 7, the capacitor of the filter 8, oscillates, the amplitude of which is determined by the initial voltage across the circuit and its characteristic impedance.

Perezar d switching capacitor 5 is limited at the time of switching on unmanaged diode 11, which closes the current to the moment in the inductor 6 and the load 7 on the capacitor 9.

Turning on diode 11 changes the flow along the inverter.

The voltage on the capacitor 5 is fixed at the moment of turning on the diode 11 at the level of the total voltage on the capacitors 9 and 8, i.e. will be

equal to twice the voltage of the inverter power supply. The throttle current 6 is terminated after the accumulated stock of electromagnetic energy has been consumed. After this point

the diode 11 is turned off and the load circuit 7, the droplet 6, the capacitor 9 and the droplet 10 are flowing back current, the discharging capacitor 9.

After a short pause since

turning off the diode 1 1, the thyristors 3 and 4 are turned on. In this case, the switching capacitor 5 is recharged along a circuit consisting of 6 Drossel 6, switched on thyristors 3 and 4, the load

7 and the filter capacitor 8.

At the moment of equality of the voltage on the capacitor 5 to the total voltage on the capacitors 8 and 9, the diode 11 is turned on again, limiting the increase in voltage on the capacitor 5.

After turning off the thyristors 3 and 4 and then diode 11 and a short pause, the introduction of which improves the harmonic composition of the output current generated by the inverter and increases the amplitude of its first harmonic, the thyristors 1 and 2 of the bridge cell turn on again and the considered processes cyclically repeat, forming output pulses in the load current. The load 7, which is a compensated circuit, for example, an electrothermal installation for induction heating of metals by high-frequency currents is tuned to

resonance with the first harmonic of the inverter output current.

By changing the pause between the time the diode 11 is turned off and the next bridge cell thyristors are turned on, the frequency of the inverter output current is adjusted.

The ratio between the resonant frequency of the impedance

the load oscillating circuit and the frequency of the main harmonic of the output current of the inverter determines the equivalent load impedance of a capacitive or inductive nature, which in both specified cases is less than the resonance value. Nevertheless, in this scheme, the inverter voltage amplitude

J

The capacitor must therefore be limited and stabilized at variable load on the thyristors of the bridge cell.

In this inverter circuit, a current flows through the direct current choke, due to the circulation of reactive energy in the inverter, so the choke can be made to a much smaller current.

Claims (1)

Invention Formula A self-contained inverter containing a filter capacitor connected to the input terminals, a thyristor bridge cell with a switching capacitor in the alternating current diagonal, the anode group of which is connected to the first output drossel constant 839184 a current, a series circuit connected from a capacitor, a switching throttle and a load circuit connected to the negative input 5, as well as a diode, the cathode of which is connected to the second terminal of a drossel of direct current, characterized in that, in order to reduce the installed power of the elements at JO extended range of parameters of the complex load, the free output of the capacitor of the series circuit is connected to the junction point of the second output of the throttle 15 DC with the cathode of the diode, the anode of which is connected to the negative input terminal, and the cathode group of the bridge cell is connected to the junction point of the switching cell. 20 drossel with chain capacitor. P