ESAB ESP-150 Manuel D'instruction page 251

SECTION 5
3. Place Gas Mode Switch (OSS) to "CUT" position.
a. Gas solenoid valves (CGSV) energize. Gases flow to permit setting of
pressures and to purge system.
4. Place OSS to "Operate" position.
a. Gas valves (PGSV and CGSV) deenergize to stop gas flows.
5. Depress torch switch.
a. SHSV and SGSV (shield and start) gas solenoid valves open to allow
gases to flow to torch.
b. Pilot Arc Contactor (PAC) closes.
c. High Frequency (HF) energizes.
d. Pressure Switches (PGPS & CGPS) close (provided gas pressures are
set above 19 psig on PGPS and 22 psig on CGPS).
e. Two seconds later, Main Contactor (MC) closes to establish pilot arc.
f. Pilot arc will transfer to cutting arc within 6 seconds as long as torch is
close enough (1/8 —1/4-in.) to work.
g. HF and PAC deenergizes immediately when cutting arc is established,
or after 6 seconds of continuous pilot arc. If cutting arc is not established
after six seconds, MC will open but the HF will remain energized. MC
and pilot arc will then cycle on and off every 3 seconds, MC will open but
the HF will remain energized. MC and pilot arc will then cycle on and off
every 3 seconds until torch switch is released. WARNING: Dangerous
high voltage (over 300 volts) exists a the torch front end whenever MC is
closed; therefore, release torch switch when cutting is not established
and repeat step 5.
6. Release torch switch.
a. MC opens and the cutting arc shuts off.
b. Gases continue to flow (postflow) for approximately another 10 seconds
at which time the PGSV and CGSV will close, opening PCPS and CGPS.
NOTE: A new cutting cycle can be started anytime during the postflow. As soon
as the torch switch is depressed, the remaining postflow time will cancel
and the normal preflow time will start.
7. Control circuit will not energize or can deenergize during a cutting cycle
when:
a. PGPS or CGPS is open due to insufficient gas pressure (at least 15 psi
required).
b. Thermal Switches (TS) are open due to overheating of unit. TS should
open at 180° C (356° F).
8. Place ROS to "OFF" position.
a. Control circuit deenergizes.
b. Fan motor (FM) deenergizes.
c. Low Gas light on status board will go out.
9. Open primary disconnect switch.
a. Input power unit shut off.
PREFLOW & HF****
2 sec.
Push
Torch Switch
PGSV/CGSV opens
* HF and MC remain on for approximately 6 sec. unless a main arc is established. If a main arc is not established the MC will open
PAC closes
after 6 sec. but HF stays on. If torch switch is not released MC will cycle on and off every 3 sec. until torch switch is released.
HF energizes
* * Cutting arc actually starts during the HF phase when the arc transfers to the workpiece anywhere between 2 and 6 seconds; Pilot arc
PGPS/CGPS closes
circuit and high-freq. generator will then shut off immediately.
FS closes * * * A new cycle may be started anytime in the Postflow phase, which will cancel remaining postflow time and start again with the normal
preflow time.
* * * * On units made for Advance Systems cutting machines, HF activates when MC closes at end of 2 second preflow.
HF and MC*
CUTTING ARC**
6 sec.
PAC opens
MC closes
HF deenergizes
Fig. 26 - Torch Operation Sequence Diagram
245
MAINTENANCE
POSTFLOW***
10 sec.
Release Torch
PGSV/CGSV closes
Switch
PGPS/CGPS opens
MC opens
FS opens