SU812463A1 - Phase controlling circuit - Google Patents

Description

(54) PHASE REGULATING DIAGRAM OF RUNNING OF CONTROLLED DIODES IN WELDING MACHINES

I

The invention relates to welding production, in particular to phase-controlled start-up schemes of controlled diodes in welding machines, and can be used in automation and stabilization of the welding process.

A phase-controlled starting circuit for controlled diodes in welding machines is known, which contains a main charging circuit and a switching diode. The principle of operation of the circuit is based on the pre-charging of the main charging circuit from the welding arc, followed by short-circuiting it with the switching diode 1.

The disadvantage of this circuit is the low quality of its operation due to the delay in the operation of the switching diode due to the purely active nature of the diode control current circuit.

A phase-controlled starting circuit of controlled diodes in welding machines is also known, which contains, besides the main storage circuit and switching diode, an auxiliary charging circuit electrically connected to them. This circuit makes it possible to increase the reliability of operation of welding machines due to the fact that the presence of an additional charging circuit in it ensures accurate triggering of the circuit when the arc 2 is extinguished.

However, this phase-controlled start-up circuit of controlled diodes in welding machines is not adapted to stabilize the non-coherent burning of an AC arc in half-periods of direct and reverse polarity, which reduces its technological capabilities and welding quality.

The purpose of the invention is to improve the technological capabilities and quality of welding.

This is achieved by adding a rectifying bridge and resistance to the phase-controlled start-up circuit of controlled diodes in welding machines, with the main and auxiliary charging circuits connected in series and connected to the arc gap, the resistance is connected in parallel to the auxiliary charging circuit, the rectifier bridge input is connected in parallel to the main charging circuit, and a switching diode is connected to its output.

Claims (2)

The drawing shows a schematic electrical diagram of a phase-regulating circuit for driving controlled diodes in welding machines. The circuit contains a capacitor 1 entering the main charging circuit, a resistor 2 and a capacitor 3 entering the auxiliary circuit. Switching diode 4 is electrically connected to the charging circuits. Active resistance 5 connected in parallel with the auxiliary charging circuit is inserted into the circuit. , and a rectifying bridge 6, the input of which is connected in parallel to the main charging circuit and the output of which is connected to a switching diode 4. The main and auxiliary charging circuits of terminals 7 and 8 must be connected to the arc gap welding th device (not shown). The circuit also contains a shunt switching diode 4 RC-circuit consisting of a resistor 9 and a capacitor 10, a pulse transformer 11 and a diode 12. The input terminals 7 and 8 of the circuit are energized from the arc power source, namely from the arc gap. The capacitor 1 entering the main charging circuit is charged before the switching voltage of the switching diode 4. When switching diode 4 trips, capacitor 1 is discharged through the rectifying bridge 6 to the primary winding of the pulse transformer I. After switching, the switching diode short circuits the capacitor 1 along the circuit which, due to the presence of the auxiliary charge capacitor 3, is of a reactive nature. The value of the capacitor 3 resistance for a frequency of 50 Hz is selected by a much larger total circuit resistance consisting of a rectifying bridge 6, a switching diode 4 in the open state, and a primary resistance of the pulse transformer 11. Therefore, when the resistance of the adjustable resistor 2 is close to zero, the current in the circuit of the switching diode, it is ahead of the voltage at the input of the circuit by almost 90 degrees. After the input voltage passes through the maximum, the capacitor 3, charging to the maximum voltage value, begins to discharge, i.e. the current in the circuit goes through zero and reverses direction, so after closing the switching diode 4, the capacitor 1 is charged to the opposite polarity. The charging time of capacitor 1 depends on the resistance value of adjustable resistor 2. If the value of the latter is close to zero, then capacitor 1 is charged for a relatively short time and the control impulse arrives at the gate of the excitation and arc stabilization device almost at the moment the current passes through zero. Due to the rectifying bridge 6, the current through the switching diode flows in one direction regardless of the polarity of the voltage on the input and on the capacitor 1, which allows to form a control pulse in each half-period of the supply voltage with an advance in phase with respect to the moment of input voltage crossing through zero . For normal operation of the circuit and stabilization of the arc, it is necessary to fulfill the condition that the switching diode must be open during the arc, and locked only after the arc current passes through zero. Otherwise, a spurious control pulse is sent to the control electrode of the valve for the excitation and stabilization of the arc. If a voltage peak occurs at the initial moment of the arc, caused by transients in the power supply, when the value of the adjustable resistor 2 is close to zero, the circuit responds to this voltage peak. In this case, the current in the circuit of the switching diode 4 decreases to zero, however, the latter is kept in the open state due to the discharge of the capacitor 10 through the resistor-9. The capacitor 10 is pre-charged along the circuit: capacitor 3 - active resistance 5 - adjustable resistor 2 - rectifying bridge 6 - resistor 9 - primary winding of the transformer 11. The parameters of circuit 9-10 are selected so that in the initial period of the arc to form a transient current through the switching diode without zero crossing. During arc burning, the switching diode 4 is maintained in the open state by the current flowing through the circuit: capacitor 3 - active resistance 5 - adjustable resistor 2 - rectifying bridge b - primary winding of the transformer 11. If the arc voltage curve is close in shape to the capacitor 3, zaryazchis to the maximum, does not pass through itself a current, in this case, the switching element is maintained in the open state by the current flowing through the active resistance 5. When the resistance value is adjustable th resistor 2 is equal to zero, the switching diode is locked after the peak voltage at the arc extinction when the algebraic sum of the current reverse time series capacitor 3 and the direct current through the resistance 5 becomes zero. The capacitance of the capacitor 3 and the resistance 5 are selected so that the switching diode locks almost immediately after the voltage peak when the arc goes out, which corresponds to zero-crossing arc current. If the resistance value of adjustable resistor 2 is comparable to or greater than the resistance of capacitor 3 for a frequency of 50 Hz, then the phase shift angle in the circuit of switching diode 4 relative to the input voltage is less than 90 el. Degrees, i.e. the switching diode closes with a delay relative to the moment the arc current passes through zero. The magnitude of this delay, as well as the duration of the charge of the capacitor 1 to the switching voltage of the switching diode 4, is directly dependent on the resistance of the resistor 2. Additional introduction to the phase-controlled starting circuit of the controlled diodes in active resistance welders connected in parallel with the auxiliary charge circuits, and a rectifying bridge, the input of which is connected in parallel to the main charging circuit and the output of which is connected to a switching diode, as well as a serial connection nenie and connecting arc gap parallel main and auxiliary charge dnyh chains, allows to increase technological possibilities circuit and weld quality. Claims of the invention Phase-regulating circuit for driving controlled diodes in welding machines. containing electrically interconnected main and auxiliary charging circuits and a switching diode, characterized in that, in order to increase the technological capabilities and quality of welding due to the non-trivial burning of the AC arc, it additionally introduces a rectifying bridge and resistance, In this case, the main and auxiliary charging circuits are connected in series and connected to the arc gap, the active resistance is connected in parallel to the auxiliary charging circuit, the input to A switching bridge is connected parallel to the main charging circuit, and a switching diode is connected to its output. Sources of information taken into account in the examination 1. USSR author's certificate number 375760, cl. At 23 K 9/10, 1970. 2. USSR author's certificate number 448094, ..kl. At 23 K 9/10, 02.02.72.