Alternating current arc power source having opposite polarity ignition pulse

Claim 2

An arc current supply system for establishing and maintaining an alternating current arc across an arc gap formed by an electrode and a workpiece, said system comprising: an electrode and a workpiece positioned for arc welding; first means for providing an alternating current to said electrode and to said workpiece to establish an arc therebetween; and second means for applying a voltage impulse in series with said first means during at least a portion of the alternating current cycle when said electrode is positive relative to the workpiece, said applied voltage impulse being opposite in polarity to and substantially larger than the voltage of said first means.

Claim 3

The system of claim 1 wherein: said second means includes means for timing said voltage impulse in synchronization with the alternating frequency of said first means so that said voltage impulse occurs when the voltage provided by the first means to the arc is increasing.

Claim 4

The system of claim 2 wherein: said second means includes a first capacitor, third means for charging said first capacitor to a given potential, an SCR connected to said first capacitor, a transformer having its primary coil connected in series with said first capacitor and said SCR, and having its secondary winding connected in series with said first means providing alternating current to said electrode and said workpiece, and wherein said means for timing includes means being coupled to said SCR for turning on said SCR at timed intervals to thereby periodically discharge said first capacitor to provide a voltage impulse to said arc during a portion of the period when said alternating current supplied to said electrode is positive relative to said workpiece.

Claim 5

The system of claim 3 wherein said second means includes: a power supply providing a pulsation at least twice the frequency of said alternating current, a resistor and second capacitor series timing circuit connected to be charged by said pulsating power supply, a second SCR connected in circuit with said resistor and said second capacitor in said timing circuit, and means for causing both said SCRs to conduct and thus discharge both said capacitors at least twice each cycle of said alternating current upon said second capacitor reaching a predetermined voltage.

Claim 6

The system of claim 4 wherein: said third means for charging said first capacitor is of the high frequency AC type having a frequency of at least ten times greater than the frequency of said alternating current, and rectifying means in circuit with said high frequency source and said first capacitor.

Claim 7

An arc current supply system for establishing and maintaining an alternating current arc across an arc gap formed by an electrode and A workpiece, said system comprising: an electrode and a workpiece positioned for arc welding; a transformer having at least first and second secondary windings, means for providing an alternating current to said transformer, said first secondary winding connected to provide alternating current to said electrode and said workpiece, means connected to said second secondary winding for providing an impulse in series with the alternating current output of said first secondary winding, said impulse being applied when said alternating current supplied to said electrode is positive relative to said workpiece, said applied impulse being opposite in polarity to said alternating current and of a magnitude sufficient to reignite the arc.

Claim 8

An arc current supply system for establishing and maintaining an alternating current arc across an arc gap formed by an electrode and A workpiece, said system comprising: an electrode and a workpiece positioned for arc welding; a transformer having at least first and second secondary windings, means for providing an alternating current to said transformer, said first secondary winding connected to provide alternating current to said electrode and said workpiece, means connected to said second secondary winding for providing an impulse in series with the alternating current output of said first secondary winding, said impulse being applied when said alternating current supplied to said electrode is positive relative to said workpiece, said applied impulse being opposite in polarity to said alternating current and of a magnitude sufficient to reignite the arc.