Alternating current arc welder

• US 3,995,137 A
• Filed: 03/27/1974
• Issued: 11/30/1976
• Est. Priority Date: 03/29/1973
• Status: Expired due to Term

• Current Assignee: Osaka Transformer Company Limited
• Original Assignee: Osaka Transformer Company Limited
• Inventors: Nakayama, Hiroshi, Okada, Toshiyuki, Takemoto, Tomonori
• Primary Examiner(s): Truhe, J. V.
• Assistant Examiner(s): Shaw, Clifford C.
• Application Number:
  US05/455,406
• Time in Patent Office: 979 Days
• Field of Search: 219/131 F, 219/131 WR, 219/131 R, 323/4, 323/24, 323/43.5 S, 323/45, 323/80
• US Class Current: 219/130.21
• CPC Class Codes: B23K 9/073 Stabilising the arc
• CPC Class Codes: B23K 9/0738 Stabilising of the arc by automatic re-ignition means

Abstract

An AC arc welder which comprises means for detecting the welding current, a comparison circuit for generating logical output signals by comparing the output voltage or output current of the welding current detecting means with the reference voltage or reference current from a reference voltage generating means, digital means for generating logical output signals by performing adding operation or subtracting operation in response to the logical output signal, current supplying means for supplying the output current whose common ratio becoming the geometrical series of approximately m(m = 1, 2, 3 . . . ), and switching means for on and off- controlling the output of the current supplying means in response to the logical output signals of the digital means, thus forming a current feedback loop, whereby the output current from the current supplying means can be changed minutely, thus ensuring stabilized control characteristics.

Claims

1. 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 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;

welding current zero-crossing detecting means for generating an output pulse upon detecting the approximate zerocrossing of the welding current;

current supplying means comprising a plurality of reactors or transformers whose reactance of windng is in a geometrical progression of ratio 2;

switching means comprising a plurality of switches for making and braking 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.

2. An alternating current arc welder according to claim 1, wherein said pulse generator means generates clock pulses at the same rate as the frequency of the line voltage and in synchronism with the zero-crossings thereof.

3. 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.

4. An alternating current arc welder according to claim 3, wherein said pulse generator means generates clock pulses at the same rate as the frequency of the line voltage and in synchronism with the zero-crossings thereof.

5. 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.

6. An alternating current arc welder according to claim 5, wherein said pulse generator means generates clock pulses at the same rate as the frequency of the line voltage and advanced in phase by a predetermined amount from the zero-crossings thereof, said pulse generator means comprising rectifier means to rectify the line voltage, trigger circuit means to generate trigger pulses from the recitfied line voltage, and monostable multivibrator means to generate clock pulses from the trigger pulses.

7. 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.

8. An alternating current arc welder according to claim 7, wherein said pulse generator means generates clock pulses at the same rate as the frequency of the line voltage and advanced in phase by a predetermined amount from the zero-crossings thereof, said pulse generator means comprising rectifier means to rectify the line voltage, trigger circuit means to generate trigger pulses from the rectified line voltage, and monostable multivibrator means to generate clock pulses from the trigger pulses.