Tweco A120 CutMaster - Manual (Page 20)

CUTMASTER A120
INTRODUCTION Manual 0-4989 2T-2
E. Type Cooling
Combination of ambient air and gas stream through torch.
F. Torch Ratings
Automated / Machine Torch Ratings
Ambient
Temperature
104° F
40° C
Duty Cycle
100% @ 100 Amps @ 400 scfh
80% @ 120 Amps @ 400 scfh
Maximum Current 120 Amps
Voltage (V
peak
) 500V
Arc Striking Voltage 7kV
Manual Torch Ratings
Ambient
Temperature
104° F
40° C
Duty Cycle 100% @ 120 Amps @ 400 scfh
Maximum Current 120 Amps
Voltage (V
peak
) 500V
Arc Striking Voltage 7kV
G. Gas Requirements
Automated, Manual and Machine Torch Gas
Specifications
Gas (Plasma and Secondary) Compressed Air
Operating Pressure
Refer to NOTE
60 - 95 psi
4.1 - 6.5 bar
Maximum Input Pressure 125 psi / 8.6 bar
Gas Flow (Cutting and
Gouging)
300 - 500 scfh
142 - 235 lpm
!
WARNING
This torch is not to be used with oxygen (O
2
).
NOTE
Operating pressure varies with torch model, operat-
ing amperage, and torch leads length. Refer to gas
pressure settings charts for each model.
H. Direct Contact Hazard
For standoff tip the recommended standoff is 3/16 inches
/ 4.7 mm.
2T.04 Options And Accessories
For options and accessories, see section 6.
2T.05 Introduction to Plasma
A. Plasma Gas Flow
Plasma is a gas which has been heated to an extremely
high temperature and ionized so that it becomes electri-
cally conductive. The plasma arc cutting and gouging
processes use this plasma to transfer an electrical arc to
the workpiece. The metal to be cut or removed is melted
by the heat of the arc and then blown away.
While the goal of plasma arc cutting is separation of the
material, plasma arc gouging is used to remove metals to
a controlled depth and width.
In a Plasma Cutting Torch a cool gas enters Zone B, where
a pilot arc between the electrode and the torch tip heats and
ionizes the gas. The main cutting arc then transfers to the
workpiece through the column of plasma gas in Zone C.
A-08331
Workpiece
Power
Supply
+
_
C
B
A
Typical Torch Head Detail
By forcing the plasma gas and electric arc through a small
orifice, the torch delivers a high concentration of heat to a
small area. The stiff, constricted plasma arc is shown in
Zone C. Direct current (DC) straight polarity is used for
plasma cutting, as shown in the illustration.
Zone A channels a secondary gas that cools the torch. This
gas also assists the high velocity plasma gas in blowing
the molten metal out of the cut allowing for a fast, slag -
free cut.