Methods and apparatus for improved low current AC/DC TIG welding and starting
AssigneeLincoln Global, Inc.
InventorRalph Samodell
Life of this patent
Estimating the term…
Abstract
A TIG welder and methodologies for providing an output welding current in a welding circuit. The welder has main and background power supplies. The main supply has an SCR network which selectively connects a transformer secondary winding to the welding circuit according to SCR control signals. The background supply is connected to the SCR network, which selectively connects the second power supply to the welding circuit according to the SCR control signals. The SCR network may have first and second SCRs operating according to first and second SCR control signals from a control circuit, where the control circuit is connected to the SCR network and the second power supply and selectively connects the SCR control signals to the SCR network according to the setpoint current value.
Claims39
A TIG welder operable to provide an output welding current through a gap in a welding circuit between an electrode and a workpiece according to a setpoint current value, said welder comprising:
- a first power supply comprising a first transformer secondary winding;
- an SCR network connected to said first transformer secondary winding, said SCR network being operable to selectively connect said first transformer secondary winding to said welding circuit according to SCR control signals so as to provide a first current to said welding circuit;
- a second power supply connected to said SCR network, said SCR network being operable to selectively connect said second power supply to said welding circuit according to said SCR control signals so as to provide a second current to said welding circuit through at least one SCR in said SCR network of said first power supply;
- a control circuit connected to said SCR network and to said second power supply and operable to selectively connect said SCR control signals to said SCR network according to said setpoint current value;
- and
- an AC/DC switch with a first switch condition and a second opposite switch condition;
- wherein said welder is operable in an AC mode to provide an AC output welding current through said gap in said welding circuit according to said setpoint current value when said AC/DC switch is in said first switch condition, and is operable in a DC mode to provide a DC output welding current through said gap in said welding circuit according to said setpoint current value when said AC/DC switch is in said second switch condition;
- wherein said SCR network is operable in said AC mode to provide current of a first polarity to said welding circuit from at least one of said first and second power supplies in a first half-cycle, and to provide current of a second polarity to said welding circuit from at least one of said first and second power supplies in a second half-cycle according to said setpoint current value;
- and
- wherein said SCR network is operable in said DC mode to provide current of one of said first and second polarities to said welding circuit from at least one of said first and second power supplies according to said setpoint current value.
A TIG welder operable to provide an output welding current through a gap in a welding circuit between an electrode and a workpiece according to a setpoint current value, said welder comprising:
- first power supply means for supplying welding current comprising an SCR network connected to a first transformer secondary winding, said SCR network being operable to selectively connect said first transformer secondary winding to said welding circuit according to SCR control signals to provide a first current to said welding circuit;
- second power supply means for supplying welding current being connected to said SCR network, said SCR network being further operable to selectively connect said second power supply means to said welding circuit through at least one SCR in said SCR network according to said SCR control signals to provide a second current to said welding circuit through said first power supply means;
- and
- control means for controlling said SCR network being connected to said SCR network and said second power supply means and operable to selectively connect said SCR control signals to said SCR network according to said setpoint current value,
- wherein said SCR network comprises:
- a first SCR operating in one of a conductive state and a nonconductive state according to a first SCR control signal from said control means, and
- a second SCR operating in one of a conductive state and a nonconductive state according to a second SCR control signal from said control means;
- and
- wherein said second power supply means comprises:
- a first background power supply connected to said SCR network, said first SCR being operable to selectively connect said first background power supply to said welding circuit according to said first SCR control signal so as to provide said second current to said welding circuit, and
- a second background power supply connected to said SCR network, said second SCR being operable to selectively connect said second background power supply to said welding circuit according to said second SCR control signal so as to provide said second current to said welding circuit.
A TIG welder for providing a welding current to a welding circuit, said welder comprising:
- a main supply comprising:
- a transformer secondary winding, and
- an SCR network including first and second SCRs connected between said transformer secondary winding and said welding circuit;
- a control circuit connected to said first and second SCRs and operable to provide a gating signal to one of said first and second SCRs in said SCR network to connect said transformer secondary winding to said welding circuit so as to provide main supply current to said welding circuit during a portion of a power half-cycle;
- and
- a background supply connected to said control circuit, said background supply comprising first and second DC power supplies connected to said first and second SCRs, respectively, wherein said background supply is operable to provide background current to said welding circuit through said one of said first and second SCRs in said SCR network during said portion of said power half-cycle and to latch said one of said first and second SCRs in a conductive state thereafter so as to provide background current to said welding circuit after said power half-cycle until said control circuit provides a gating signal to another of said first and second SCRs in said SCR network.
Dependencies are inferred from the claim text.