Method of and power supply for electric arc welding

Claim 2

In an arc welding system having a power supply for automatic electric arc welding wherein an arc is maintained and a droplet on the end of an electrode periodically contacts the weld pool and shorts the power supply, said supply including first and second DC power sources each having a pair of output terminals with like polarities interconnected and connected one to said electrode and the other to a workpiece to be welded, the improvement which comprises said first power source having a generally constant voltage output with variations in current and a short circuit current rate of rise less than 60,000 amperes per second, said second power source having a short circuit current rate of rise in excess of 60,000 amperes per second, said first power source having a voltage output to maintain an arc between said electrode and said workpiece sufficient to melt the workpiece and the electrode, whereby a drop forms on the end of the electrode, said second power source having a generally constant voltage output with variations in current up to the maximum current such as to supply no or a minimum of current when an arc exists between said electrode and said workpiece, but sufficient to supply current to said electrode when said drop still on the end of the electrode contacts the weld pool.

Claim 3

The improvement of claim 1 wherein said second power source includes means for limiting the maximum short circuit current to less than 500 amperes.

Claim 4

The improvement of claim 1 wherein said first power source has a short circuit current rate of rise between 15,000 and 40, 000 amperes per second.

Claim 5

The improvement of claim 1 wherein said second power source has a short circuit current rate of rise between 100,000 and 1, 000,000 amperes per second.

Claim 6

The improvement of claim 1 wherein said first and second power sources have static voltage outputs which remain essentially constant as the output current is increased up to currents apProaching the maximum current rating of each.

Claim 7

The improvement of claim 1 wherein said power source is a rotating direct current generator having output terminals and a maximum open circuit voltage greater than 75 volts when excited to a saturation factor of 1.3, said second power source is a multiphase alternator on the same shaft as said rotating generator and having its output terminals connected to the input terminals of a full wave rectifier, the output terminals of said rectifier being connected to the output terminals of said generator.

Claim 8

The improvement of claim 6 wherein said first poser source includes an armature and series differential windings, and means for energizing the generator output terminals directly from said armature.

Claim 9

The improvement of claim 7 wherein a voltage regulator has output terminals connected to the field coils of said generator and sensing input terminals connected directly across said armature.

Claim 10

The improvement of claim 1 wherein said second power source is an alternator rectifier combination.

Claim 11

The improvement of claim 1 wherein said second power source is a transformer rectifier combination.

Claim 12

The improvement of claim 10 wherein means in the form of an impedance is provided in series with said combination for limiting the maximum short circuit current to the electrodes.

Claim 13

In an arc welding system having a power supply for electric arc welding wherein an arc is maintained between an electrode and a workpiece and a droplet on the end of the electrode periodically contacts the weld pool and shorts the power supply, said supply including at least a DC power source having a pair of output terminals connected one to said electrode and the other to the workpiece to be welded, said power source having a generally flat volt-ampere curve and a short circuit current rate of rise less than 60,000 amperes per second and a voltage output and current rating sufficient to melt the workpiece and form a weld pool and melt the electrode and form a drop on the end of the electrode which periodically contacts the weld pool, the improvement which comprises: a second power source having a pair of output terminals connected one to said electrode and one to said workpiece with the same polarity as said first supply and having a substantially flat volt ampere curve and short circuit current rate of rise to in excess of 60,000 amperes per second when said drop contacts said weld pool.

Claim 14

In an arc welding system having a power supply for electric arc welding wherein an arc is maintained between an electrode and a workpiece and a droplet on the end of the electrode periodically contacts the weld pool and shorts the power supply, said supply including at least a DC power source having a pair of output terminals connected one to said electrode and the other to the workpiece to be welded, said power source having a generally flat volt-ampere curve and a short circuit current rate of rise less than 60,000 amperes per second and a voltage output and current rating sufficient to melt the workpiece and form a weld pool and melt the electrode and form a drop on the end of the electrode which periodically contacts the weld pool, the improvement which comprises: a second power source having a pair of output terminals connected one to said electrode and one to said workpiece with the same polarity as said first supply and having a substantially flat volt ampere curve and short circuit current rate of rise to in excess of 60,000 amperes per second when said drop contacts said weld pool.

Claim 15

The improvement of claim 12 wherein said second power source increases the short circuit current rate of rise to an amount in excess of 100,000 amperes per second.

Claim 16

The improvement of claim 12 wherein said second power source includes means for limiting the maximum short circuit current to an amount less than 500 amperes.

Claim 17

In an arc welding system for welding a workpiece with a continuously fed electrode energized from a power supply and using drop transfer type metal transfer wherein an arc melts the workpiece and forms a drop on the end of the electrode which drop periodically contacts the weld pool and short circuits the power supply, and includes: power means for feeding said electrode toward a workpiece, said power supply for electrically energizing said electrode relative to said workpiece includes first and second DC power sources, each having a pair of output terminals with like polarities connected one to said electrode and the other to said workpiece; The improvement which comprises: said first power source having a constant voltage output which remains essentially constant as the output current is increased and a short circuit current rate of rise less than 60,000 amperes per second, said second source having a constant voltage output which remains essentially constant as the output current is increased and a short circuit current rate of rise in excess of 60,000 amperes per second, said first power source having a voltage output to maintain an arc between said electrode and said workpiece sufficient to melt the workpiece and the electrode whereby a drop forms on the end of the electrode, said second power source having a voltage output such as to supply no or a minimum of current when an arc exists between said electrode and said workpiece, but sufficient to supply a pulse of current to said electrode when said drop still on the end of the electrode contacts the weld pool.

Claim 18

In an arc welding system for welding a workpiece with a continuously fed electrode energized from a power supply and using drop transfer type metal transfer wherein an arc melts the workpiece and forms a drop on the end of the electrode which drop periodically contacts the weld pool and short circuits the power supply, and includes: power means for feeding said electrode toward a workpiece, said power supply for electrically energizing said electrode relative to said workpiece includes first and second DC power sources, each having a pair of output terminals with like polarities connected one to said electrode and the other to said workpiece; The improvement which comprises: said first power source having a constant voltage output which remains essentially constant as the output current is increased and a short circuit current rate of rise less than 60,000 amperes per second, said second source having a constant voltage output which remains essentially constant as the output current is increased and a short circuit current rate of rise in excess of 60,000 amperes per second, said first power source having a voltage output to maintain an arc between said electrode and said workpiece sufficient to melt the workpiece and the electrode whereby a drop forms on the end of the electrode, said second power source having a voltage output such as to supply no or a minimum of current when an arc exists between said electrode and said workpiece, but sufficient to supply a pulse of current to said electrode when said drop still on the end of the electrode contacts the weld pool.

Claim 19

The improvement of claim 15 wherein; said first power source has a short circuit current rate of rise less than 40,000 amperes per second, and, said second power source has a short circuit rate of rise in excess of 100,000 amperes per second.

Claim 22

The method of claim 17 wherein said first power source has a rate of rise less than 40,000 amperes per second and said second power source has a rate of rise in excess of 100,000 amperes per second.

Claim 25

The improvement of claim 19 including the step of limiting the maximum short circuit current to less than 500 amperes.