Hypertherm MAX42, Service Manual

Page: 35 / 100

THEORY OF OPERATION
MAX42 Service Manual Page 2-5
• Output Rectifier Circuit
The output rectifier circuit (PCB8 and PCB9) converts the high frequency AC
signal back to a pulsating DC signal for output to filter L1.
• Pilot Arc Controller Board PCB15
This circuit provides a path from the electrode to the nozzle for the pilot arc. As
the arc is brought closer to the workpiece more current is diverted to the work-
piece and less to the nozzle. When the voltage between the workpiece and the
nozzle reduces to the preset level, the pilot arc controller turns off the current
path to the nozzle and arc transfer is complete.
During cutting, the pilot arc controller monitors the workpiece-to-nozzle voltage.
If this voltage increases past the preset level, the current path is turned on and
current is diverted to the nozzle. A gradual transition occurs from the cut mode
to the pilot arc mode of operation. The pilot arc controller also signals the control
board PCB14 to reduce the current to 20 amps whenever the unit is in pilot arc
operation.