SU1292144A1 - Self-excited free-running parallel inverter - Google Patents

Abstract

The invention relates to a converter technique and can be used in electrothermia for induction heating and melting of metals. The goal is to increase the reliability of the start-up to the load with varying parameters. The device contains a bridge on controlled valves 2–5. A generator 7 of excitation current pulses is connected to the output of a bridge and consists of controlled valves B and 9 and switching circuit 10, 11. AC voltage from load 6 is connected to the input of the starting control unit 12, which provides the leading phase shift of the output voltage relative to {INPUT, and supplies it to the input of the pulse shaper 13. One of the outputs of the shaper 13 delivers control pulses to the valve 9 connected to the output of the generator 7, and to the valves 2, 3 m hundred. The frequency of the generator is determined by the natural frequency of the load 6. 1 sludge. i (L Yul1 with N9 i 4

Description

The invention relates to electrical engineering, in particular, to converter technology, and can be used in electrothermal induction heating and melting of metals, heat treatment, and other technological processes.

The aim of the invention is to improve the reliability of the start-up to the load with varying parameters by automatically synchronizing the operating frequency of the gate bridge of the parallel inverter and the generator of the excitation current with the natural frequency of the load.

The drawing shows the scheme of the inventor.

The inverter contains a bridge 1 consisting of two pairs of common-mode arms performed on controllable gates 2-5, a load 6 representing the RLC circuit, a generator 7 of excitation current pulses with controllable valves 8, 9 and a switching LC- circuit 10, 11, start control unit 12 and control pulse driver 13.

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The scheme works as follows.

When power is supplied to the generator 7 of the excitation current pulses and the control pulse shaper 13, the control pulse arrives at the valve 8, which is unlocked and charges the resonant switching LC circuit 10-11, the valve 8 is locked by reverse voltage through the half-period of natural oscillations of this circuit and the 10-11 LC circuit remains charged. Then, after a specified time, a trigger pulse is applied to the valve 9. In this case, the circuit 10-11 is recharged through the load 6 of the parallel interval, after which the valve 9 is closed. Since the load 6 is a resonant oscillating RLC circuit, natural oscillations with a given frequency occur in it. AC voltage from the load is fed to the input of the starting control unit 12, which provides the leading phase shift of the output voltage relative to the input and supplies it to the input of the driver 13 pulses, against

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shoulders 2 and 3 of the bridge 1 parallel inverter. The other output of the imaging unit 13 provides control pulses to the input valve 8, which sets the switching frequency of the generator 7, and to another pair of common-mode arms 4 and 5 of bridge 1. At the same time, the generator 7 enters self-excitation along the circuit 7-6-12-13-7 i.e. the frequency of generator 7 is determined by the natural frequency of load 6, and at the same time control pulses are applied to bridge 1 with the same frequency. After completion of the transient process in the specified self-excitation circuit, power is supplied to the input diagonal of bridge 1. At the same time, the parallel inverter is started at load 6, since gates 2–5 of bridge 1 are switched by the load, the frequency of the control pulses corresponds to the natural frequency of the load, and the phase of these The pulses are set by the start-up control unit. com, i.e. The necessary conditions for switching the gates 2-5 of the bridge 1 of the parallel inverter are provided, corresponding to the steady state operation of the parallel inverter.

When changing the parameters of the load 6 (R, L, s), the natural frequency of the oscillating circuit changes. This, in turn, leads to a change in the frequency of the control pulses applied to the valves 2–5 and 8–9, both in steady state operation and during start up.

Due to the fact that in the first switching of the inverter valves conditions are created for their normal locking, the start-up process takes place steadily over the entire range of variation of the load parameters characteristic of installations for heating, melting and heat treatment of various metals and alloys.

Claims (1)

Invention Formula 50 A self-stimulating autonomous parallel inverter to supply the load, in the form of a resonant RLC circuit, containing a bridge on controllable valves, which are combined into two pairs of phase outputs of which are formed by common-mode oscillations, a diagonal of variable-control pulses. One of the output current of which is connected to the output of the shaper supplies the control terminals, the forwarder controls the pulses to the valve 9 connected to the pulses to the two anti-phase outputs of the generator 7 and to the in-phase ones. mi exits, each of which is under five 0 five 0 five 0 five shoulders 2 and 3 of the bridge 1 parallel inverter. The other output of the imaging unit 13 provides control pulses to the input valve 8, which sets the switching frequency of the generator 7, and to another pair of common-mode arms 4 and 5 of bridge 1. At the same time, the generator 7 enters self-excitation along the circuit 7-6-12-13-7 i.e. the frequency of generator 7 is determined by the natural frequency of load 6, and at the same time control pulses are applied to bridge 1 with the same frequency. After completion of the transient process in the specified self-excitation circuit, power is supplied to the input diagonal of bridge 1. At the same time, the parallel inverter is started at load 6, since gates 2–5 of bridge 1 are switched by the load, the frequency of the control pulses corresponds to the natural frequency of the load, and the phase of these The pulses are set by the start-up control unit. com, i.e. The necessary conditions for switching the gates 2-5 of the bridge 1 of the parallel inverter are provided, corresponding to the steady state operation of the parallel inverter. When changing the parameters of the load 6 (R, L, s), the natural frequency of the oscillating circuit changes. This, in turn, leads to a change in the frequency of the control pulses applied to the valves 2–5 and 8–9, both in steady state operation and during start up. Due to the fact that in the first switching of the inverter valves conditions are created for their normal locking, the start-up process takes place steadily over the entire range of variation of the load parameters characteristic of installations for heating, melting and heat treatment of various metals and alloys. Invention Formula keys, respectively, to the control electrodes of the first and second pair of common-mode arches of the bridge, and an input connected to the output of the starting control unit, whose input is connected to the output diagonal of the bridge, and a frequency controlled excitation pulse generator, characterized in that start-up to the load with varying parameters by automatically synchronizing the operating frequency of the valve bridge of the parallel inverter and the generator of the excitation current pulses with the natural frequency of the load, g he generator The excitation current pulses are made according to the scheme of an asymmetrical resonant inverter on controllable gates, one of which, connected to one of the output pins of an unbalanced inverter, is connected by a cathode to the first output terminal of the bridge on the controllable gates, and the control electrode to the control the output terminal of the bridge, another output terminal of the unbalanced inverter is connected to the second output terminal of the bridge; a parallel inverter, and the second output; the course of the control pulse former is connected to the control input at excitation current pulse generator