Alternating current arc welder

An alternating current arc welder, operating from an A.C. line source, for producing an arc between an electrode and a workpiece comprising:

• welding current detecting means for detecting welding current and for generating a detection signal;
• wave form converting means for rectifying and smoothing the detection signal and for generating a feedback voltage;
• reference voltage source means for generating a reference voltage;
• comparing means for comparing the reference voltage with the feedback voltage and for generating a first logical output signal in accordance with the comparison;
• pulse generator means for generating clock pulses of constant frequency having a period equal to one of the period of the line frequency of the A.C. line source and of an integral multiple of the period of the line frequency of the A.C. line source, the clock pulse being in synchronism with zero-crossings of the line voltage of said A.C. line source;
• digital means for receiving the clock pulses from said pulse generator means and for generating a plurality of second logical output signals by adding or subtracting pulses having the same period as the clock pulses of constant frequency and the same polarity as the first logical output signal;
• arc voltage zero-potential detecting means for generating an output pulse upon detecting the approximate zero-potential of the arc voltage;
• current supplying means comprising a plurality of reactors or transformers whose reactance of winding is in a geometrical progression of ratio 2;
• switching means comprising a plurality of switches for making and breaking electrical connections between more than one reactor or transformer and one of the A.C. line source and a welding current output lead connected with one of the electrode and workpiece;
• and
• gate circuit means for connecting said digital means with said switching means, said gate circuit means passing a plurality of said second logical output signals to a plurality of switches of said switching means, respectively, only when the output pulse of said arc voltage zero-phase detecting means is applied thereto, said switching means increasing or decreasing the output current at each clock pulse by a predetermined constant low current value with respect to the output current value immediately prior to the clock pulse.

An alternating current arc welder, operating from an A.C. line source, for producing an arc between an electrode and a workpiece comprising:

• welding current detecting means for detecting welding current and for generating a detection signal;
• wave form converting means for rectifying and smoothing the detection signal and for generating a feedback voltage;
• reference voltage source means for generating a reference voltage;
• comparing means for comparing the reference voltage with the feedback voltage and for generating a first logical output signal in accordance with the comparison;
• pulse generator means for generating clock pulses of constant frequency having a period equal to one of the period of the line frequency of the A.C. line source and of an integral multiple of the period of the line frequency of the A.C. line source, the clock pulses being advanced in phase by a predetermined amount from zero-crossings of the line voltage of said A.C. line source;
• digital means for receiving the clock pulses from said pulse generator means and for generating a plurality of second logical output signals by adding or subtracting pulses having the same period as the clock pulses of constant frequency and the same polarity as the first logical output signal;
• welding current zero-crossing detecting means for generating an output pulse upon detecting the approximate zero-crossings of the welding current;
• current supplying means comprising a plurality of reactors or transformers whose reactance of winding is in a geometrical progression of ratio 2;
• switching means comprising a plurality of switches for making and breaking electrical connections between more than one reactor or transformer and one of the A.C. line source and a welding current output lead connected with one of the electrode and workpiece, and
• gate circuit means for connecting said digital means with said switching means, said gate circuit means passing a plurality of second logical output signals to said switches of said switching means, respectively, only when the output pulse of said welding current zerocrossing detecting means is applied thereto, said switching means increasing or decreasing the output current at each clock pulse by a predetermined constant low current value with respect to the output current value immediately prior to the clock pulse.

An alternating current arc welder, operating from an A.C. line source, for producing an arc between an electrode and a workpiece comprising:

• welding current detecting means for detecting welding current and for generating a detection signal;
• wave form converting means for rectifying and smoothing the detection signal and for generating a feedback voltage;
• reference voltage source means for generating a reference voltage;
• comparing means for comparing the reference voltage with the feedback voltage and for generating a first logical output signal in accordance with the comparison;
• pulse generator means for generating clock pulses of constant frequency having a period equal to one of the period of the line frequency of the A.C. line source and of an integral multiple of the period of the line frequency of the A.C. line source, the clock pulses being advanced in phase by a predetermined amount from zero-crossing of the line voltage of said A.C. line source;
• digital means for receiving the clock pulses from said pulse generator means and for generating a plurality of second logical output signals by adding or subtracting pulses having the same period as the clock pulses of constant frequency and the same polarity as the first logical output signal;
• arc voltage zero-potential detecting means for generating an output pulse upon detecting the approximate zero-potential of the arc voltage;
• current supplying means comprising a plurality of reactors or transformers whose reactance of winding is in a geometrical progression of ratio 2;
• switching means comprising a plurality of switches for making and breaking electrical connections between more than one reactor or transformer and one of the A.C. line source and a welding current output lead connected with output terminals of the welder, and
• gate circuit means for connecting said digital means with said switching means, said gate circuit means passing a plurality of said second logical output signals to a plurality of switches of said switching means, respectively, only when the output pulse of said arc voltage zero-phase detecting means is applied thereto, said switching means increasing or decreasing the output current at each clock pulse by a predetermined constant low current value with respect to the output current value immediately prior to the clock pulse.