Vickers, Daniels & Young
Current feedback device for electric arc welder
 In an electric arc welder including a main transformer with a primary stage coupled to a secondary stage in which is created an AC output current, a first switch opened and closed at a given rate to pass a series of first pulses of DC current in a first circuit having a first lead and through at least a portion of the primary stage in a first electrical direction, with each of the first pulses having a length determined by the time the first switch is closed, a second switch opened and closed at the given rate to pass a series of second pulses of DC current in a second circuit having a second lead through at a least a portion of the primary stage in a second electrical direction with each of the second pulses having a length determined by the time the second switch is closed, and a control circuit for rapidly closing the first and second switches in sequence to induce an AC current in the output stage, the improvement comprising: a first current transformer surrounding the first lead of the first circuit to develop a first output signal controlled by the first pulses, a second current transformer surrounding the second lead of the second circuit and developing a second output signal controlled by the second pulses and a circuit for combining the first and second output signals to provide a current signal indicative of the total current in the primary stage of the main transformer. 
Lincoln Global, Inc.
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Todd Eric Lifeng
Kooken Luo