US4071885A — Electric arc welding power supply

Claim 1

Independent Claim 111 words

In an arc welding power source including: a three phase transformer having a pair of secondaries, each including three windings; a rectifier in series with each winding; the series rectifiers and windings of each secondary being connected in a wye configuration and arranged to have a pair of DC output terminals, said output terminals being connected in parallel and arranged to supply power to external terminals of said power source, the improvement which comprises: independent inductances in series with each secondary and its output terminals, in combination with, said rectifiers having a gate responsive to an input signal to cause the rectifiers to conduct for selected portions of the AC cycle.

Claim 2

Dependent Claim 111 words

In an arc welding power source including: a three phase transformer having a pair of secondaries, each including three windings; a rectifier in series with each winding; the series rectifiers and windings of each secondary being connected in a wye configuration and arranged to have a pair of DC output terminals, said output terminals being connected in parallel and arranged to supply power to external terminals of said power source, the improvement which comprises: independent inductances in series with each secondary and its output terminals, in combination with, said rectifiers having a gate responsive to an input signal to cause the rectifiers to conduct for selected portions of the AC cycle.

Claim 3

Dependent Claim 35 words

The improvement of claim 1 wherein said inductances in series interconnect the neutral points of the wye-connection, the common connection of said inductances supplying power to one of the external terminals of said power source.

Claim 4

Dependent Claim 15 words

The improvement of claim 1 wherein said inductors comprise windings on separate magnetically permeable cores.

Claim 5

Dependent Claim 16 words

The improvement of claim 3 wherein said cores are each of a generally closed magnetic loop.

Claim 6

Dependent Claim 27 words

The improvement of claim 3 wherein said cores are each of the shell-type having three parallel legs and one of the windings is on each center leg.

Claim 7

Dependent Claim 67 words

The improvement of claim 1 wherein said inductors are comprises of a shell-type core having two side legs of one cross sectional area and a center leg of generally twice the cross sectional area of said side legs, the windings of said inductors being on said side legs and polarized so that the mmf's resulting from currents in the two windings are additive in the center leg.

Claim 8

Dependent Claim 50 words

The improvement of claim 6 wherein said center leg has an air gap and a third winding is disposed thereon, said third winding being in electrical series with an output terminal of said source, the mmf of said third winding being additive to the mmf's of said side leg windings.

Claim 9

Dependent Claim 17 words

The improvement of claim 1 including a third inductance in series with one of said output terminals.

Claim 10

Dependent Claim 21 words

The improvement of claim 8 wherein the mmf of said third inductance is additive to the mmf of the independent inductors.

Claim 11

Dependent Claim 17 words

The improvement of claim 1 wherein the independent inductors are the only inductances in said power source.

Claim 12

Dependent Claim 67 words

The improvement of claim 1 wherein said inductors are comprises of a shell-type core having two side legs of one cross sectional area and a center leg of generally twice the cross sectional area of said side legs, the windings of said inductors being on said side legs and polarized so that the mmf's resulting from currents in the two windings are subtractive in the center leg.

Claim 13

Dependent Claim 14 words

The improvement of claim 6 wherein each leg is provided with an air gap.

Claim 14

Dependent Claim 21 words

The improvement of claim 12 wherein the air gap in the center leg is greater than that on the side legs.

Claim 15

Dependent Claim 49 words

The improvement of claim 6 wherein said center leg has an air gap and a third winding is disposed thereon, said third winding being in series with an output terminal of said source, the mmf of said third winding being subtractive to the mmf of said side leg windings.

Claim 16

Dependent Claim 46 words

The improvement of claim 10 including a control circuit for supplying an input signal to said gate, said control circuit having an input proportional to the output of said source and said curcuit having a response time less than 10 cycles of 60 Hz A.C. power.

Claim 17

Dependent Claim 55 words

The improvement of claim 1 including a fault protecting circuit for de-energizing said power source due to an overload, said circuit having an input signal proportional to the output current of said source, and a trip time which decreases proportionally with the square of the current above the rated overload current of the rectifier means.

Claim 18

Dependent Claim 154 words

An SCR firing control circuit including a main SCR in an A.C. circuit and having a gate which when energized moves said SCR when forward biased to conduction, a pilot SCR having a gate and effective when fired to energize said main SCR gate, a pulse transformer for energizing said pilot SCR gate, said pulse transformer having a secondary between said pilot SCR gate and a neutral point, said pulse transformer also having a primary means for energizing said primary with a pulse including a first capacitor and a transistor which when `on` discharges said capacitor through said primary, the improvement which comprises, a second capacitor in series between said secondary and said pilot SCR gate and a diode in parallel with said primary whereby the gate current of said pilot SCR does not flow in said secondary whereby to bias said transistor through said pulse transformer and prevent full discharge of said capacitor.

Claim 19

Dependent Claim 154 words

An SCR firing control circuit including a main SCR in an A.C. circuit and having a gate which when energized moves said SCR when forward biased to conduction, a pilot SCR having a gate and effective when fired to energize said main SCR gate, a pulse transformer for energizing said pilot SCR gate, said pulse transformer having a secondary between said pilot SCR gate and a neutral point, said pulse transformer also having a primary means for energizing said primary with a pulse including a first capacitor and a transistor which when `on` discharges said capacitor through said primary, the improvement which comprises, a second capacitor in series between said secondary and said pilot SCR gate and a diode in parallel with said primary whereby the gate current of said pilot SCR does not flow in said secondary whereby to bias said transistor through said pulse transformer and prevent full discharge of said capacitor.

Claim 20

Dependent Claim 199 words

In a fault protection circuit for the main SCR's in a transformer SCR electric arc welding type power source, the SCR's having a known time vs temperature and I 2 t overload curve, said fault protection circuit having a response curve generally parallel to said I 2 t overload curve comprising: a. first gain means providing a first signal proportional to said weld current, b. a plurality of first switching means which go `on` in sequence as said first signal progressively increases above a predetermined level, c. second switching means for de-energizing the input voltage to said power source including a first input which turns said second switching means `on` when energized to a predetermined voltage level and a second input which changes said predetermined voltage level, d. said first switching means energizing said first input of said second switching means at progressively faster rates as said first switching means progressively go `on`, e. second gain means producing a second signal inversely proportional to said first signal on said second switching means second input, some of said first switching means when `on` providing a signal on said second gain means to vary the gain of said second gain means.

Claim 21

Dependent Claim 199 words

In a fault protection circuit for the main SCR's in a transformer SCR electric arc welding type power source, the SCR's having a known time vs temperature and I 2 t overload curve, said fault protection circuit having a response curve generally parallel to said I 2 t overload curve comprising: a. first gain means providing a first signal proportional to said weld current, b. a plurality of first switching means which go `on` in sequence as said first signal progressively increases above a predetermined level, c. second switching means for de-energizing the input voltage to said power source including a first input which turns said second switching means `on` when energized to a predetermined voltage level and a second input which changes said predetermined voltage level, d. said first switching means energizing said first input of said second switching means at progressively faster rates as said first switching means progressively go `on`, e. second gain means producing a second signal inversely proportional to said first signal on said second switching means second input, some of said first switching means when `on` providing a signal on said second gain means to vary the gain of said second gain means.

Claim 22

Dependent Claim 175 words

The improvement of claim 18 wherein said second switching means includes: a. a PUT having a gate, an anode, and a cathode, b. means supplying said gate with a voltage normally above said anode voltage, c. a capacitor from said anode to said cathode d. a control relay, e. A normally off SCR in parallel with the operating coil of said relay and when `on` de-energizing said coil, f. means when said PUT is `on` for firing said SCR g. a plurality of triggers each normally `off` and each arranged when `on` to charge said capacitor through a resistance at a predetermined rate, said triggers being arranged to go `on` sequentially as the output voltage of said first gain means increases whereby the rate of charge of said capacitor increases with the number of triggers which are `on` whereby said capacitor is charged at more rapid rates as the current output increases above a predetermined value and the time for actuation of said second switching means decreases with increases of current above a predetermined amount.

Claim 23

Dependent Claim 260 words

In an arc welding power source fault protecting circuit, a. means producing a signal proportional to the source output current, b. a first opamp having a first and second input, means supplying an adjustable reference voltage to said second input, means supplying said signal to said first input, c. a PUT having a gate and an anode and a cathode, means supplying said gate with a voltage normally above said anode voltage, a capacitor from said anode to said cathode, said capacitor when charged to said gate voltage moving said PUT to `on` d. a normally `off` SCR which when `on` deenergizes said power source e. means when said PUT is `on` arranged to turn said SCR `on,` f. a plurality of triggers each normally`off` and energized from the output of said first opamp, each of said triggers arranged to charge said capacitor at a predetermined rate, said triggers being arranged to go `on` sequentially as the output voltage of said first opamp increases with the number of the triggers which are `on` whereby to decrease the time for said PUT to go `on`, g. a second opamp having a first input from a reference voltage less than saturation and a second input from the output of said first opamp, the output of said second opamp lowering the gate voltage on said PUT whereby said PUT fires at a lower charging level of said capacitor, h. some of said triggers when `on` raising the voltage of said second opamp first input above said reference voltage to saturate said second opamp.

Claim 24

Dependent Claim 260 words

In an arc welding power source fault protecting circuit, a. means producing a signal proportional to the source output current, b. a first opamp having a first and second input, means supplying an adjustable reference voltage to said second input, means supplying said signal to said first input, c. a PUT having a gate and an anode and a cathode, means supplying said gate with a voltage normally above said anode voltage, a capacitor from said anode to said cathode, said capacitor when charged to said gate voltage moving said PUT to `on` d. a normally `off` SCR which when `on` deenergizes said power source e. means when said PUT is `on` arranged to turn said SCR `on,` f. a plurality of triggers each normally`off` and energized from the output of said first opamp, each of said triggers arranged to charge said capacitor at a predetermined rate, said triggers being arranged to go `on` sequentially as the output voltage of said first opamp increases with the number of the triggers which are `on` whereby to decrease the time for said PUT to go `on`, g. a second opamp having a first input from a reference voltage less than saturation and a second input from the output of said first opamp, the output of said second opamp lowering the gate voltage on said PUT whereby said PUT fires at a lower charging level of said capacitor, h. some of said triggers when `on` raising the voltage of said second opamp first input above said reference voltage to saturate said second opamp.

Claim 25

Dependent Claim 229 words

In an A.C. transformer SCR type arc welding power source including: a. a plurality of SCR's which when forward biased and their gates energized, conduct to supply a source output voltage, said SCR's having a known time-current overload curve, b. means for de-energizing said source before said overload curve is exceeded, said means including: c. means producing a voltage proportional to the power source output current. d. an amplifier for said voltage, e. a plurality of switches, the first being arranged to go `on` when the output voltage of said amplifier exceeds a predetermined amount proportional to the maximum steady state current of said SCR's and the remainder going `on` sequentially with progressively higher output voltages, f. switch means which when `on` de-energize said power source and having a pair of input terminals, the energization of the first of which determines the voltage level on the second terminal which will cause said switch means to go `on,` g. said switches when on acting on energize said second input terminal to said level in decreasing amounts of time proportional to the number of switches being `on,` h. a second amplifier for the first amplifier output voltage and arranged to energize said first input terminal to lower said level, whereby the current-time curve for actuation of said switch means is a smooth curve corresponding generally to the SCR time-current overload curve.

Claim 26

Dependent Claim 229 words

In an A.C. transformer SCR type arc welding power source including: a. a plurality of SCR's which when forward biased and their gates energized, conduct to supply a source output voltage, said SCR's having a known time-current overload curve, b. means for de-energizing said source before said overload curve is exceeded, said means including: c. means producing a voltage proportional to the power source output current. d. an amplifier for said voltage, e. a plurality of switches, the first being arranged to go `on` when the output voltage of said amplifier exceeds a predetermined amount proportional to the maximum steady state current of said SCR's and the remainder going `on` sequentially with progressively higher output voltages, f. switch means which when `on` de-energize said power source and having a pair of input terminals, the energization of the first of which determines the voltage level on the second terminal which will cause said switch means to go `on,` g. said switches when on acting on energize said second input terminal to said level in decreasing amounts of time proportional to the number of switches being `on,` h. a second amplifier for the first amplifier output voltage and arranged to energize said first input terminal to lower said level, whereby the current-time curve for actuation of said switch means is a smooth curve corresponding generally to the SCR time-current overload curve.

Claim 27

Dependent Claim 36 words

The improvement of claim 21 wherein said first mentioned amplifier is an opamp having a feedback circuit which is frequency sensitive to lower the gain of the amplifier to rapidly changing voltages on the input thereof.

Claim 28

Dependent Claim 35 words

The improvement of claim 21 wherein at least some of said switches after the first switch goes `on,` energize said first input terminal to lower the voltage level at which said switch means goes `on.`

Claim 29

Dependent Claim 29 words

The improvement of claim 21 wherein said first and second amplifiers are each opamps, each having a second input terminal and means supplying a reference voltage to said terminals.

Claim 30

Dependent Claim 79 words

The improvement of claim 21 wherein said first and second amplifiers are each opamps, each having a second input terminal and means supplying a reference voltage to said terminals, said some of said switches energizing said second input terminal of said second opamp whereby to override its said reference voltage and change the output voltage of said second opamp as the overload current increases whereby to lower the firing level on the first input terminal of said switch means.

Claim 31

Dependent Claim 248 words

In an A.C. transformer SCR type arc welding source including: a. a plurality of SCR's which when forward biased and their gates energized conduct to supply a source output voltage, b. a firing circuit for the SCR's having a nominal input voltage at which said gates are energized at 0° phaseback, c. a control circuit for said firing circuit having an input voltage proportional to the current output of said source, d. said control circuit including a plurality of amplifiers for said input voltages, e. means limiting the amplifier output voltage when the current proportional voltage is zero to not more than said firing circuit nominal input voltage, f. a manually adjustable reference voltage for determining the desired output current of said source, g. said amplifiers comparing the current proportional voltage with said adjusted reference voltage and when the amplified current proportional voltage exceeds said reference voltage, increasing their output voltage to said firing circuit to phaseback said SCR's, h. the gain of said amplifiers being such as to vary the output voltage of the source by phasing back the SCR's to hold the output current constant, i. the improvement which comprises means comparing the source output voltage with a fixed reference voltage and when said output voltage drops to less than a predetermined value due to short circuits on said source, changing said manually adjusted reference voltage to decrease the phaseback of the SCR's and increase the current beyond that determined by the manually adjusted reference voltage.

Claim 32

Dependent Claim 248 words

In an A.C. transformer SCR type arc welding source including: a. a plurality of SCR's which when forward biased and their gates energized conduct to supply a source output voltage, b. a firing circuit for the SCR's having a nominal input voltage at which said gates are energized at 0° phaseback, c. a control circuit for said firing circuit having an input voltage proportional to the current output of said source, d. said control circuit including a plurality of amplifiers for said input voltages, e. means limiting the amplifier output voltage when the current proportional voltage is zero to not more than said firing circuit nominal input voltage, f. a manually adjustable reference voltage for determining the desired output current of said source, g. said amplifiers comparing the current proportional voltage with said adjusted reference voltage and when the amplified current proportional voltage exceeds said reference voltage, increasing their output voltage to said firing circuit to phaseback said SCR's, h. the gain of said amplifiers being such as to vary the output voltage of the source by phasing back the SCR's to hold the output current constant, i. the improvement which comprises means comparing the source output voltage with a fixed reference voltage and when said output voltage drops to less than a predetermined value due to short circuits on said source, changing said manually adjusted reference voltage to decrease the phaseback of the SCR's and increase the current beyond that determined by the manually adjusted reference voltage.

Claim 33

Dependent Claim 41 words

The improvement of claim 26 wherein a portion of said source output voltage is simultaneously fed to said amplifiers whereby to obtain a small increase in the output current with drops in source output voltage to compensate for line voltage variations.

Claim 34

Dependent Claim 57 words

The improvement of claim 26 wherein a first zener diode limits the minimum voltage from said amplifiers to said firing circuit to said nominal voltage, and the difference between the voltage of said first zener diode and a second zener diode limits the maximum voltage to said firing circuit and thus the maximum phaseback of said SCR's.

Claim 35

Dependent Claim 23 words

The improvement of claim 26 wherein said amplifiers have a frequency sensitive feedback circuit to reduce the gain thereof to rapid voltage changes.

Claim 36

Dependent Claim 24 words

The improvement of claim 26 wherein said control and firing circuits have a response time less than 10 cycles of 60 Hz A.C. power.

Claim 37

Dependent Claim 227 words

In an A.C. transformer SCR type arc welding source including: a. a plurality of SCR's which when forward biased and their gates energized conduct to supply a source output voltage, b. a firing circuit for the SCR's having a nominal input voltage at which said gates are energized at 0° phaseback, c. a control circuit for said firing circuit having an input voltage proportional to the current output of said source, d. said control circuit including a plurality of amplifiers for said input voltages, e. means limiting the amplifier output voltage when the current proportional voltage is zero to not more than said firing circuit nominal input voltage, f. a manually adjustable reference voltage for determining the desired output current of said source, g. said amplifiers comparing the current proportional voltage with said adjusted reference voltage and when the amplified current proportional voltage exceeds said references voltage, increasing their output voltage to said firing circuit to phaseback said SCR's, h. the gain of said amplifiers being such as to vary the output voltage of the source by phasing back the SCR's to hold the output current constant, i. the improvement which comprises means simultaneously feeding a portion of said source output voltage to said amplifiers whereby to obtain a small increase in the output current with drops in source output voltage to compensate for line voltage variations.

Claim 38

Dependent Claim 227 words

In an A.C. transformer SCR type arc welding source including: a. a plurality of SCR's which when forward biased and their gates energized conduct to supply a source output voltage, b. a firing circuit for the SCR's having a nominal input voltage at which said gates are energized at 0° phaseback, c. a control circuit for said firing circuit having an input voltage proportional to the current output of said source, d. said control circuit including a plurality of amplifiers for said input voltages, e. means limiting the amplifier output voltage when the current proportional voltage is zero to not more than said firing circuit nominal input voltage, f. a manually adjustable reference voltage for determining the desired output current of said source, g. said amplifiers comparing the current proportional voltage with said adjusted reference voltage and when the amplified current proportional voltage exceeds said references voltage, increasing their output voltage to said firing circuit to phaseback said SCR's, h. the gain of said amplifiers being such as to vary the output voltage of the source by phasing back the SCR's to hold the output current constant, i. the improvement which comprises means simultaneously feeding a portion of said source output voltage to said amplifiers whereby to obtain a small increase in the output current with drops in source output voltage to compensate for line voltage variations.

Claim 39

Dependent Claim 237 words

In an A.C. transformer SCR type arc welding source including: a. a plurality of SCR's which when forward biased and their gates energized conduct to supply a source output voltage, b. a firing circuit for the SCR's having a nominal input voltage at which said gates are energized at 0° phaseback, c. a control circuit for said firing circuit having an input voltage proportional to the output of said source, d. said control circuit including a plurality of amplifiers for said input voltages, e. means limiting the amplifier output voltage when the current proportional voltage is zero to not more than said firing circuit nominal input voltage, f. a manually adjustable reference voltage for determining the desired output of said source, g. said amplifiers comparing the proportional voltage with said adjusted reference voltage and when the amplified proportional voltage exceeds said reference voltage, increasing their output voltage to said firing circuit to phaseback said SCR's, h. the gain of said amplifiers being such as to vary the output of the source by phasing back the SCR's to hold the output constant, i. the improvement which comprises a first zener diode which limits the minimum voltage from said amplifiers to said firing circuit said nominal voltage, and the difference between the voltage of said first zener diode and a second zener diode limits the maximum voltage to said firing circuit and thus the maximum phaseback of said SCR's.

Claim 40

Dependent Claim 237 words

In an A.C. transformer SCR type arc welding source including: a. a plurality of SCR's which when forward biased and their gates energized conduct to supply a source output voltage, b. a firing circuit for the SCR's having a nominal input voltage at which said gates are energized at 0° phaseback, c. a control circuit for said firing circuit having an input voltage proportional to the output of said source, d. said control circuit including a plurality of amplifiers for said input voltages, e. means limiting the amplifier output voltage when the current proportional voltage is zero to not more than said firing circuit nominal input voltage, f. a manually adjustable reference voltage for determining the desired output of said source, g. said amplifiers comparing the proportional voltage with said adjusted reference voltage and when the amplified proportional voltage exceeds said reference voltage, increasing their output voltage to said firing circuit to phaseback said SCR's, h. the gain of said amplifiers being such as to vary the output of the source by phasing back the SCR's to hold the output constant, i. the improvement which comprises a first zener diode which limits the minimum voltage from said amplifiers to said firing circuit said nominal voltage, and the difference between the voltage of said first zener diode and a second zener diode limits the maximum voltage to said firing circuit and thus the maximum phaseback of said SCR's.

Claim 41

Dependent Claim 203 words

In an A.C. transformer SCR type arc welding source including: a. a plurality of SCR's which when forward biased and their gates energized conduct to supply a source output voltage, b. a firing circuit for the SCR's having a nominal input voltage at which said gates are energized at 0° phaseback, c. a control circuit for said firing circuit having an input voltage proportional to the output of said source, d. said control circuit including a plurality of amplifiers for said input voltages, e. means limiting the amplifier output voltage when the current proportional voltage is zero to not more than said firing circuit nominal input voltage. f. a manually adjustable reference voltage for determining the desired output of said source, g. said amplifiers comparing the proportional voltage with said adjusted reference voltage and when the amplified proportional voltage exceeds said reference voltage, increasing their output voltage to said firing circuit to phaseback said SCR's, h. the gain of said amplifiers being such as to vary the output of the source by phasing back the SCR's to hold the output constant, i. the improvement which comprises said amplifiers having frequency sensitive feedback circuits effective to reduce the gain thereof to rapid voltage changes.

Claim 42

Dependent Claim 203 words

In an A.C. transformer SCR type arc welding source including: a. a plurality of SCR's which when forward biased and their gates energized conduct to supply a source output voltage, b. a firing circuit for the SCR's having a nominal input voltage at which said gates are energized at 0° phaseback, c. a control circuit for said firing circuit having an input voltage proportional to the output of said source, d. said control circuit including a plurality of amplifiers for said input voltages, e. means limiting the amplifier output voltage when the current proportional voltage is zero to not more than said firing circuit nominal input voltage. f. a manually adjustable reference voltage for determining the desired output of said source, g. said amplifiers comparing the proportional voltage with said adjusted reference voltage and when the amplified proportional voltage exceeds said reference voltage, increasing their output voltage to said firing circuit to phaseback said SCR's, h. the gain of said amplifiers being such as to vary the output of the source by phasing back the SCR's to hold the output constant, i. the improvement which comprises said amplifiers having frequency sensitive feedback circuits effective to reduce the gain thereof to rapid voltage changes.

Claim 43

Dependent Claim 24 words

The improvement of claim 33 wherein said control and firing circuits have a response time less than 10 cycles of 60 Hz A.C. power.

Claim 44

Dependent Claim 19 words

The improvement of claim 6 wherein said side legs have an air gap and said center leg has none.

Annuity Stage	Window Opens	Payment Deadline	Surcharge Period Until	Estimated Fee	Status
3.5 Years (Year 4)	1981-01-30	1981-08-01	1982-01-31	$2000.00	Window Closed / Lapsed
7.5 Years (Year 8)	1985-01-30	1985-08-01	1986-01-31	$3760.00	Window Closed / Lapsed
11.5 Years (Year 12)	1989-01-30	1989-08-01	1990-01-31	$7700.00	Window Closed / Lapsed

Electric arc welding power supply

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