D. C. power supply for arc welding with SCR controlling three-phase power

Claim 2

A D.C. arc welding power supply utilizing three-phase power comprising a three-phase transformer having primary windings for receiving three-phase power and secondary windings for delivering power in three phases to three respective power conductors, a three-phase rectifier bridge including three unidirectionallyconductive thyristors each having a power circuit and a gate electrode, with the power circuit serially connected to a respective one of said power conductors and conductive of current unidirectionally upon receipt of a firing signal at the respective gate electrode, and direct current output conductors for receiving said unidirectional current and applying said current to a welding torch, a timing pulse generator having a reference terminal, an input terminal, and an output terminal, said input terminal being coupled to all of said three power conductors to supply phase reference signals and power to said timing pulse generator, said reference terminal being coupled to one of said output conductors, said timing pulse generator being responsive to said phase reference signals for producing timing pulses on said output terminal following respective phase reference signals, said timing pulse generator including variable control means for controlling the phases of said timing pulses relative to the respective phases of the voltages on said power conductors, a firing signal generator including a separate amplifying means for each phase, each such amplifying means having an input coupled to said output terminal and being responsive to said timing pulses by generating temporally corresponding firing signals and including means for applying such firing signals to a respective one of said gate electrodes, whereby the current through the respective thyristors is controlled by said control means, and torch switch means having an off condition and an on condition, said torch switch means being coupled to said timing pulse generator for normally inhibiting said firing signals when in said off condition even though full voltage is applied to said primary windings, and when actuated to said on condition pErmitting the generation of said firing signals.

Claim 3

A power supply according to claim 1 for hot starts wherein said torch switch means includes means responsive to actuation of said torch switch means to its on condition for operating said control means to advance the phase of said timing pulses for a predetermined period.

Claim 4

A power supply according to claim 1 for spot welding wherein said torch switch means includes means for automatically returning said torch switch means to its off condition at a predetermined time after it is actuated to its on condition.

Claim 5

A D.C. arc welding power supply utilizing three-phase power comprising a three-phase transformer having primary windings for receiving three-phase power and secondary windings for delivering power in three phases to three respective power conductors, a three-phase rectifier bridge including three unidirectionally-conductive thyristors each having a power circuit and a gate electrode, with the power circuit serially connected to a respective one of said power conductors and conductive of current unidirectionally upon receipt of a firing signal at the respective gate electrode, and direct current output conductors for receiving said unidirectional current and applying said current to a welding torch, a timing pulse generator having a reference terminal, an input terminal, and an output terminal, said input terminal being coupled to all of said three power conductors through respective similarly poled diodes to supply phase reference signals and power to said timing pulse generator, said reference terminal being coupled to one of said output conductors, said timing pulse generator including a Zener diode connected to said reference terminal and coupled through first resistance means to said input terminal, capacitance means and variable resistance means serially connected across said Zener diode whereby upon application of voltage to said input terminal voltage builds up upon said capacitance means at a rate dependent upon the resistance of said variable resistance means, and pulse generating means coupled to said capacitance means for producing timing pulses on said output terminal upon the voltage on said capacitance means reaching a predetermined level, a firing signal generator including a separate amplifying means for each phase, each such amplifying means having an input coupled to said output terminal and being responsive to said timing pulses by generating temporally corresponding firing signals and including means for applying such firing signals to a respective one of said gate electrodes, whereby the current through the respective thyristors depends upon the resistance of said variable resistance means, and torch switch means having an off condition and an on condition, said torch switch means being coupled to said timing pulse generator for normally inhibiting said firing signals when in said off condition even though full voltage is applied to said primary windings, and when actuated to said on condition permitting the generation of said firing signals.

Claim 6

A D.C. arc welding power supply utilizing three-phase power comprising a three-phase transformer having primary windings for receiving three-phase power and secondary windings for delivering power in three phases to three respective power conductors, a three-phase rectifier bridge including three unidirectionally-conductive thyristors each having a power circuit and a gate electrode, with the power circuit serially connected to a respective one of said power conductors and conductive of current unidirectionally upon receipt of a firing signal at the respective gate electrode, and direct current output conductors for receiving said unidirectional current and applying said current to a welding torch, a timing pulse generator having a reference terminal, an input terminal, and an output terminal, said input terminal being coupled to all of said three power conductors through respective similarly poled diodes to supply phase reference signals and power to said timing pulse generator, said reference terminal being coupled to one of said output conductors, said timing pulse generator including a Zener diode connected to said reference terminal and coupled through first resistance means to said input terminal, capacitance means and variable resistance means serially connected across said Zener diode whereby upon application of voltage to said input terminal voltage builds up upon said capacitance means at a rate dependent upon the resistance of said variable resistance means, and pulse generating means coupled to said capacitance means for producing timing pulses on said output terminal upon the voltage on said capacitance means reaching a predetermined level, a firing signal generator including a separate amplifying means for each phase, each such amplifying means having an input coupled to said output terminal and being responsive to said timing pulses by generating temporally corresponding firing signals and including means for applying such firing signals to a respective one of said gate electrodes, whereby the current through the respective thyristors depends upon the resistance of said variable resistance means, and torch switch means having an off condition and an on condition, said torch switch means being coupled to said timing pulse generator for normally inhibiting said firing signals when in said off condition even though full voltage is applied to said primary windings, and when actuated to said on condition permitting the generation of said firing signals.

Claim 7

A power supply according to claim 4 wherein said torch switch means comprises means coupled to said capacitance means for normally limiting the voltage on said capacitance means to less than said predetermined voltage in said off condition even though full voltage is applied to said primary windings, and wherein actuation of said torch switch means to said on condition permits said voltage on said capacitance means to rise to generate said timing pulses.

Claim 8

A power supply according to claim 5 wherein said timing pulse generator includes secondary timing pulse generating means for normally producing secondary timing pulses just prior to 120* of each timing cycle, and means responsive to said secondary pulses for discharging said capacitance means, and said torch switch means comprises means for reducing the period of said secondary pulses to discharge said capacitance means before the voltage tHereon reaches said predetermined level.

Claim 9

A power supply according to claim 4 for hot starts wherein said torch switch means includes means responsive to actuation of said torch switch means to its on condition for reducing the resistance of said variable resistance means for a predetermined period.

Claim 10

A power supply according to claim 7 for spot welding wherein said torch switch means includes means for returning said torch switch means to its off condition at a predetermined time after it is actuated to its on condition.

Claim 11

A D.C. arc welding power supply comprising a transformer having a primary winding for receiving power and a secondary winding for delivering power to a power conductor, a rectifier bridge including a unidirectionally conductive thyristor having a power circuit and a gate electrode, with the power circuit serially connected to the power conductor and conductive of current unidirectionally upon receipt of a firing signal at the gate electrode, and direct current output conductors for receiving said unidirectional current and applying said current to a welding torch, a timing pulse generator having a reference terminal, an input terminal, and an output terminal, said input terminal being coupled to said power conductor to supply phase reference signals and power to said timing pulse generator, said reference terminal being coupled to one of said output conductors, said timing pulse generator including a Zener diode connected to said reference terminal and coupled through first resistance means to said input terminal, capacitance means and variable resistance means serially connected across said Zener diode whereby upon application of voltage to said input terminal voltage builds up upon said capacitance means at a rate dependent upon the resistance of said variable resistance means, and pulse generating means coupled to said capacitance means for producing timing pulses on said output terminal upon the voltage on said capacitance means reaching a predetermined level, a firing signal generator coupled to said output terminal and responsive to said timing pulses by generating temporally corresponding firing signals and including means for applying them to the gate electrode, whereby the current through the thyristor depends upon the resistance of said variable resistance means, and torch switch means having an off condition and an on condition, said torch switch means including means coupled to said capacitance means for normally limiting the voltage on said capacitance means to less than said predetermined voltage when in said off condition even though full voltage is applied to said primary winding, and when actuated to said on condition permitting said voltage on said capacitance means to rise to generate said timing pulses.

Claim 12

A D.C. arc welding power supply comprising a transformer having a primary winding for receiving power and a secondary winding for delivering power to a power conductor, a rectifier bridge including a unidirectionally conductive thyristor having a power circuit and a gate electrode, with the power circuit serially connected to the power conductor and conductive of current unidirectionally upon receipt of a firing signal at the gate electrode, and direct current output conductors for receiving said unidirectional current and applying said current to a welding torch, a timing pulse generator having a reference terminal, an input terminal, and an output terminal, said input terminal being coupled to said power conductor to supply phase reference signals and power to said timing pulse generator, said reference terminal being coupled to one of said output conductors, said timing pulse generator including a Zener diode connected to said reference terminal and coupled through first resistance means to said input terminal, capacitance means and variable resistance means serially connected across said Zener diode whereby upon application of voltage to said input terminal voltage builds up upon said capacitance means at a rate dependent upon the resistance of said variable resistance means, and pulse generating means coupled to said capacitance means for producing timing pulses on said output terminal upon the voltage on said capacitance means reaching a predetermined level, a firing signal generator coupled to said output terminal and responsive to said timing pulses by generating temporally corresponding firing signals and including means for applying them to the gate electrode, whereby the current through the thyristor depends upon the resistance of said variable resistance means, and torch switch means having an off condition and an on condition, said torch switch means including means coupled to said capacitance means for normally limiting the voltage on said capacitance means to less than said predetermined voltage when in said off condition even though full voltage is applied to said primary winding, and when actuated to said on condition permitting said voltage on said capacitance means to rise to generate said timing pulses.

Claim 13

A power supply according to claim 9 for hot starts wherein said torch switch means includes means acting upon actuation of said torch switch means to its on condition to reduce the resistance of said variable resistance means for a predetermined period.

Claim 14

A power supply according to claim 10 for spot welding wherein said torch switch means includes means for returning said torch switch means to its off condition at a predetermined time after it is actuated to its on condition.