| 摘要 |
An arc retract circuit for use in a plasma arc system with a torch having an electrode and a nozzle, a power supply for providing a D.C. current, a power circuit for con necting the power supply across said electrode and a workpiece to be cut, a power switch for connecti ng the nozzle to the power supply when in a closed condition defining a pilot arc mode of operati on and for disconnecting the nozzle from the workpiece when in an open condition defini ng a cut mode of operation, amplifier means for regulating said power supply to a first set c urrent when in the pilot arc mode and a second set current when in the cut mode, and an arc retract c ircuit for shifting the power switch from the open condition to the closed condition, which arc retr act circuit includes current sensing means for creating a first signal representing the actual cu rrent applied by the power supply to the power circuit, means for creating a second signal representati ve of a current level below the second set current, and switch operations means for closing the po wer switch when the first signal is substantially equal to the second signal.
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