Starting and welding device for DC TIG welder and method of operating same
AssigneeLincoln Global, Inc.
InventorsRalph M. Samodell, Trang D. Nguyen
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Abstract
A DC TIG welder operable at a set low current level under about 5 amperes in a welding circuit including an electrode separated from a workpiece by a gap, the welder having an output welding current adjustable above the low current and driven by a constant current power supply with a first rectifier having an output current controlled by the firing phase of SCRs in an SCR network, a second rectifier settable at the low current and a sensor for sensing arc voltage. The welder further comprises: a circuit to deactivate the SCRs when the output welding current is equal to or less than the set low current and an arc starting device to cause the first rectifier to output a high pulse by operation of the SCRs of the network.
Claims51
A DC TIG welder operable at a set low current level under about 5 amperes in a welding circuit including an electrode separated from a workpiece by a gap, said welder having an output welding current adjustable above said low current and driven by a constant current power supply with a first rectifier having an output current controlled by the firing phase of SCRs in an SCR network, a second rectifier settable at said low current and a sensor for sensing arc voltage, said welder further comprising:
- a circuit to deactivate said SCRs when said output welding current is equal to or less than said set low current and an arc starting device including a high frequency generator connected in said welding circuit to pass a high frequency, high voltage current across said gap;
- a circuit for activating said high frequency generator upon starting of said welder and after said arc voltage is sensed to be greater than a first given value;
- a start pulse device activated simultaneously with the arc start by high frequency from said high frequency generator to cause said first rectifier to output a high current pulse by operation of said SCRs of said network;
- and, a termination circuit for deactivating said high frequency generator after said arc voltage is generally less than a second given value.
A method for DC TIG welding by a low current level under about 5 amperes in a power circuit including an electrode separated from a workpiece by a gap, said welder having an adjustable output welding current adjustable above said low current and driven by a constant current power supply with a first rectifier having an output current controlled by the firing phase of SCRs in an SCR network and a second rectifier settable at said low current and a sensor for sensing arc voltage, said method comprising:
- (a) deactivating said SCRs when said output current is adjusted to a value equal to or less than said low current;
- (b) passing a high frequency high voltage current across said gap;
- (c) activating said high frequency current upon starting of said welder and after said arc voltage is sensed to be greater than a first given value;
- (d) causing said first rectifier to output a high current pulse by operation of said SCRs of said network;
- and,
- (e) deactivating said high frequency current after said arc voltage is generally less than a second given value.
A DC TIG welder operable at a set low current level under about 5 amperes in a welding circuit including an electrode separated from a workpiece by a gap, said welder having an output welding current adjustable above said low current and driven by a constant current power supply with a first rectifier having an output current controlled by the firing phase of SCRs in an SCR network, a second rectifier settable at said low current and a sensor for sensing arc voltage, said welder further comprising:
- a circuit to deactivate said SCRs when said output welding current is equal to or less than said set low current and an arc starting device to output a high current pulse by operation of said SCRs of said network;
- and, a termination circuit for deactivating said SCRs during welding at said low current.
A DC TIG welder operable at a set low current level under about 5 amperes in a welding circuit including an electrode separated from a workpiece by a gap, said welder having an output welding current adjustable above said low current and driven by a constant current power supply with a first rectifier having an output current controlled by the firing phase of SCRs in an SCR network, a DC power supply settable at said low current and a sensor for sensing arc voltage, said welder further comprising:
- a circuit to deactivate said SCRs when said output welding current is equal to or less than said set low current and an arc starting device to output a high current pulse by operation of said SCRs of said network;
- and, a termination circuit for deactivating said SCRs during welding at said low current.
Dependencies are inferred from the claim text.