Electric heating – Metal heating – By arc
Patent
1998-11-06
2000-10-17
Walberg, Teresa
Electric heating
Metal heating
By arc
21912162, B23K 900
Patent
active
061335436
ABSTRACT:
A system for controlling a plasma arc torch circuit uses two different current thresholds to control pilot current, thereby reducing nozzle wear while maintaining a reliable arc and an adequate transfer height. Specifically, by using a Hall effect current sensor to monitor low levels of current in the lead that normally carries high current, it is possible to determine more accurately (1) when there is a low level of pilot arc current that can be ramped to a higher level, and (2) when the level of transferred current is capable of reliably sustaining a transferred arc such that the pilot arc can be extinguished. Thus, the current can be removed from the nozzle, at the precise moment in time that the torch can reliably sustain the transferred arc, thereby saving wear on the nozzle. In addition, the system of the present invention can save nozzle wear when used in combination with circuits that compensate for discontinuities in the workpiece by decreasing the current to the workpiece to a pilot arc level. Applicants have found the invention to be particularly advantageous when employed in a hand-held plasma arc torch system.
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Borowy Dennis M.
Lindsay Jon W.
Ren Tianting
Hypertherm, Inc.
Van Quang
Walberg Teresa
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