SU1668068A1 - Device for welding by alternating current - Google Patents

Abstract

The invention relates to arc and plasma welding, in particular, to alternating current power sources with pulse stabilization, and can be used in welding with non-consumable electrode in inert gases of aluminum and its alloys. The purpose of the invention is to improve the quality of the welded joint with low-stable arcs. The device contains a thyristor transformer of discontinuous current with a pulse stabilization. In order to excite the arc without contact of the electrode with the product being welded, a step-up transformer is inserted into the device, connected in series to the welding circuit, the primary winding of which is connected to the midpoint of the bipolar DC source and the point of connection of the series-connected thyristors connected by pole poles bipolar dc source. The stability of the amplitude of the stabilizing pulse, regardless of the moment of its generation, is achieved by switching on a stabilizing circuit consisting of a series-connected capacitor and an additional winding of the welding transformer between the connection point of the switching thyristors and the midpoint of the bipolar DC source. 1 il.

Description

The invention relates to the field of arc and plasma welding, in particular, to AC power sources with Pulsed arc stabilization.

The purpose of the invention is to improve the quality of a welded joint with low-stable arcs by providing non-contact initial excitation of the arc and increasing the reliability of its repeated excitations in an extended range of welding currents.

The drawing shows the electrical circuit of the proposed device for welding with alternating current.

The device contains an adjustable single-phase welding transformer 1, together with the secondary winding 2 of which additional winding 3 is placed. A series connection of the additional winding 3 and capacitor 4 constitutes a pulse stabilization circuit which is connected between the connection point of switching thyristors 5 and 6 and the midpoint of bipolar source 7 direct current. The switching thyristors 5 and 6 are connected in series and in agreement between the poles of the bipolar direct current source 7.

In addition, between the connection point of the switching thyristors 5 and 6 and the midpoint of the bipolar DC source 7 is connected a circuit consisting of

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hence the connected feed-through capacitor 8 and the primary winding of the step-up transformer 9, the secondary winding of which is included in the welding circuit in series with the electrode. The device includes a protective capacitor 10 and a thyristor control unit 11.

The device for welding with alternating current works as follows.

At the moment of time corresponding to the beginning of the welding current half-period, the control signal from control unit 11 is fed to the switching thyristor 5, the switching on of which causes a charge from the bipolar direct current source 7 and the capacitor A. At the flow of charge current through the capacitor 8 through the primary winding of the step-up transformer on its secondary winding form c a pulse of high voltage, which through a protective capacitor 10 butts aets to the arc gap and causes it to impact ionization. Due to the flow of the charge current of the capacitor 4 through the additional winding 3 of the welding transformer 1, a stabilizing voltage pulse is applied to its secondary winding 2, which is also applied to the arc gap. Since the inductive resistance of the welding transformer 1 is much higher than the inductive resistance of the step-up transformer 9, the duration of the voltage stabilizing pulse is sufficient to ensure the increase in current from the welding transformer 1 to the value required for a stable arc. At the end of the charge of the pass-through capacitor 8 and the capacitor 4, the switching thyristor 5 is locked. The current in the welding circuit is determined by the selected external current-voltage characteristic of the welding transformer 1.

In the negative half-voltage of the supply voltage, at the time point corresponding to the beginning of the next half-cycle of the welding current, the control signal from the control unit 11 is supplied to the switching thyristor 6, which switching on causes recharge of the passage capacitor 8 and the capacitor 4. At the secondary winding of the step-up transformer 9 an impulse of increased voltage is formed, which is applied to the arc gap and causes its impact ionization, and on the secondary winding 2 of the welding transformer 1 is induced voltage stressing pulse, also

applied to the arc gap. Upon completion of the recharge of the pass-through capacitor 8 and the capacitor 4, the switching thyristor 6 is turned off.

Further, all processes in the device for

AC welding is repeated as described above.

The connection for alternating current welding of a pulse stabilization circuit between the connection point of switching thyristors and the midpoint of a bipolar DC source ensures the stability of the amplitude of the stabilizing pulse regardless of the moment of its generation, as well as the possibility of contactless arc in the case of a non-melting electrode.

Claims (1)

Claims An alternating current device comprising an adjustable single-phase welding transformer, parallel to the secondary winding of which a protective capacitor is switched on, a step-up transformer whose primary winding The secondary winding is connected to the welding circuit, in series with the electrode, two series-connected thyristors with a control unit, a bipolar DC source with a midpoint, characterized in that, in order to improve the quality of the welded connection in low-stable arcs, by providing contactless initial excitation arc and increase the reliability of its re-excitations in an extended range of welding currents, a capacitor and an additional winding are additionally introduced into it in series the welding transformer, forming the impulse stabilization circuit, the thyristors are connected according to the poles of a bipolar DC source, the midpoint of which is connected to the second output of the primary winding of the step-up transformer, the second output of the flow capacitor is connected to the thyristor connection point, thyristor connections and the midpoint of a bipolar power source.