Tweco 6000 CE Merlin - Manual (Page 17)

Manual 0-2601 2-3 INTRODUCTION & DESCRIPTION
12. Secondary Water
Tap water can be used as a secondary gas and must be
capable of delivering the following minimums:
• Water pressure of 50 psi (3.5 bar)
• Flow of 8 gph (35.2 lph)
NOTES
Tap water should only be used as a secondary gas
on machine torches.
The tap water source does not need to be deionized,
but in water systems with extremely high mineral
content a water softener is recommended.
13. Power Supply Dimensions
Enclosure Only -
Width: 24.12 in (0.61 m)
Height: 38.38 in (0.98 m)
Depth: 34.25 in (0.87 m)
Fully Assembled -
Width: 28.50 in (0.72 m)
Height: 43.38 in (1.10 m)
Depth: 43.75 in (1.11 m)
14. Weight of Power Supply Only
678 lbs (308 kg)
2.04 Theory Of Operation
A. Plasma Arc Cutting and Gouging
Plasma is a gas which is heated to an extremely high tem-
perature and ionized so that it becomes electrically con-
ductive. The plasma arc cutting process uses this plasma
gas to transfer an electric arc to a workpiece. The metal
to be cut is melted by the intense heat of the arc and then
blown away by the flow of gas. Plasma arc gouging uses
the same process to remove material to a controlled depth
and width.
With a simple change of torch parts, the system can also
be used for plasma arc gouging. Plasma arc gouging is
used to remove material to a controlled depth and width.
B . Input and Output Power
The Power Supply accepts input voltages of 380/415V,
50 or 60 Hz, three-phase. The unit converts AC input
power to DC power for the main cutting arc. The nega-
tive output is connected to the torch electrode through
the negative torch lead, and the positive output connects
to the workpiece through the work cable.
C. Pilot Arc
When the torch is activated there is a two second gas pre-flow,
followed by a uninterrupted DC pilot arc established between
the electrode and tip. The pilot arc is initiated by a momentary
high frequency pulse from the Arc Starter Box. The pilot cre-
ates a path for the main arc to transfer to the work. When the
main arc is established, the pilot arc shuts off. The pilot auto-
matically restarts when the main arc stops, as long as the torch
remains activated.
NOTE
For the arc to restart automatically, AUTO RE-
START must be enabled at switch settings inside
the Power Supply (Refer to Section 4.07).
D. Main Cutting Arc
The Power Supply accepts 50 or 60 Hz three-phase line
input. The power supply converts AC input power to
DC power for the main cutting arc. The negative output
is connected to the torch electrode through the negative
torch lead. The positive output is connected to the work-
piece via the work cable and ring lug connection.
E. RF Shielding
All machine torch systems are shielded to minimize ra-
dio frequency (RF) interference which results from the
high frequency arc initiation. These shielded systems are
designed with features such as a wire for establishing an
earth ground and shielded torch and control leads.
F. Interlocks
The system has several built-in interlocks to provide safe
and efficient operation. When an interlock shuts down
the system, the fault condition must be remedied and the
system recycled using the applicable control device.
1. Parts-In-Place (PIP) Interlock
The Power Supply has a built-in parts-in-place inter-
lock that prevents accidental torch starting when
torch parts are not properly installed. A flow switch
on the coolant return lead detects reduced coolant
flow caused by improper torch assembly. If not sat-
isfied, the switch interrupts power to the tip and elec-
trode.
2. Gas Pressure Interlock
A pressure switch acts as an interlock for the plasma
gas supply. If the supply pressure falls below mini-
mum requirements the pressure switch will open,
shutting off the power to the contactors, and the GAS
indicator will go out. When adequate supply pres-
sure is available the pressure switch will close, al-
lowing power to be resumed for cutting.