| 摘要 |
Upon energization of the control unit, it operates a switch to supply air in a gap between the cutting nozzle and the electrode of a plasma torch, a second switch to apply a high voltage from a high voltage DC (direct current) power supply unit at the gap to initiate a starting arc, a third switch to energize a low voltage direct current power supply unit, and a fourth switch in circuitry for applying from the low voltage power supply unit, a low voltage across the cutting nozzle and the electrode to establish a pilot arc after the high voltage has been applied across the gap and after the establishment of the pilot arc and upon moving the head of the torch sufficiently closely adjacent to the a workpiece, establish a main arc between the electrode and the workpiece. Preferably the high voltage is applied for only about 0.25-0.5 seconds and the low voltage applied across the cutting nozzle and the electrode for about 3 second. The high and low voltage supply units are connected in parallel with the fourth switch, a pilot resistor and a high voltage diode connect in series across the positive terminals of the high and low voltage units.
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