Electric heating – Metal heating – By arc
Patent
1989-04-03
1991-02-26
Paschall, M. H.
Electric heating
Metal heating
By arc
21912157, 21913031, 2191304, B23K 900
Patent
active
049964070
ABSTRACT:
The invention comprises a power transfer circuit for a plasma torch for smoothly and linearly transferring the plasma arc from the nozzle of the torch to a workpiece as cutting operation commences and vice versa as cutting operation is completed. The invention includes a switching transistor for alternately providing power to the nozzle or the workpiece and a freewheeling diode coupled between the workpiece and the power source. The transistor is responsive to the voltage differential between the workpiece and the nozzle for transferring the plasma arc therebetween. Below a specified voltage differential, the transistor is turned off such that all power is delivered to the workpiece. Above a specified upper voltage differential, the transistor is turned on and all power is delivered to the nozzle. Between the specified upper and lower voltage differentials, the transistor switches at a specified frequency, the duty cycle of the transistor (i.e., the period of each cycle during which the transistor is turned on) increasing as the voltage differential increases. In a further aspect of the invention, the level of power output is ramped from a first level to a second level as the voltage differential between the nozzle and the workpiece crosses through a third specified voltage threshold.
REFERENCES:
patent: 4692582 (1987-09-01), Mashic
patent: 4795882 (1989-01-01), Hardwick et al.
patent: 4814577 (1989-03-01), Dallavalle et al.
patent: 4839499 (1989-06-01), Kotecki et al.
HyperPower, Inc.
Paschall M. H.
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