OUTPUT SECTION AND TORCH
The output section contains a relay which, upon
receiving a pilot signal from the control board will
enable the operation of a pilot arc or a cutting arc. The
printed circuit board mounted current sensor regulates
the pilot and cutting current. The output choke, which
is in series with both the pilot circuit and the cutting
circuit, provides current filtering to enhance arc stabil-
ity.
The PCT 20 torch uses a patented touch start mecha-
nism that provides superior starting performance over
other touch start systems. The torch head consists of
3 major parts: torch body, insulator and piston. The
insulator provides an electrical barrier between the
piston and torch body. The piston provides a path for
electrical current to the electrode. The piston also dri-
ves the electrode to the nozzle for arc initiation. The
torch body contains the main torch components: the
trigger, pilot arc, cutting arc, and air flow systems are
included. See Figure F.10 & G Section for more detail.
A copper nozzle with a patented internal swirl is used
to focus the arc. A small, precise hole in the end of the
nozzle constricts the arc and increases the current
density. As the air enters the torch head, it is directed
between the electrode and nozzle for maximum elec-
trode cooling. A portion of the cooling air exits in the
chamber through vents in the side of the nozzle. A
swirl texture located inside the bottom of the nozzle
increases the plenum air swirl strength, and improves
arc start reliability and parts-in-place verification.
Plasma arc initiation occurs as follows: First, in the idle
state, a spring inside the torch head pushes the piston
and electrode forward to make continuity with the noz-
zle. When the trigger is pulled, air flow begins and cre-
ates enough back force on the electrode to overcome
the force of the spring. However, the solenoid valve
allows enough forward force on the piston to maintain
continuity between the consumables. After this
continuity has been verified, output current is estab-
lished and regulated. Once the current stabilizes, the
solenoid valve turns off, removing the forward force on
the piston. The back pressure drives the piston and
electrode away from the nozzle, creating the plasma
arc. The air stream forces the arc out the orifice of the
nozzle. This appears as a pilot arc, which can then be
transferred for cutting.
THEORY OF OPERATION
E-5 E-5
PRO-CUT 25
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FIGURE E.5 – PLASMA OUTPUT SECTION AND TORCH
