ESAB MIGMASTER 250, Instruction Manual

Page: 23 / 56

23
SECTION 4 OPERATION
IV. OPERATION
4.1 CONTROLS (See Figure 4.1)
4.1.1 POWER SWITCH
A line toggle switch on the front panel energizes the
primary of the main transformer. This switch also turns on
the fan, which is connected across a portion of the
primary winding.
Two transformer secondary windings also become ener-
gized:
A. Gun trigger circuit 24 volts AC.
Wire feeder circuit 24 volts DC.
B. Main welding secondary circuit. Depending upon
the tap switch position, various secondary volt-
ages can be obtained. Then rectified, open circuit
voltages can be selected between 18 and 56 volts
DC when the secondary contactor is energized.
4.1.2 VOLTAGE CONTROL (Coarse Range Selector
and Fine Adjustment Range Selector)
Voltage control is by means of two high current tap
switches which connect the rectifier bridge to various
secondary taps.
The COARSE VOLTAGE RANGE Selector is a three-
position switch, LOW/MED/HIGH, by which the operator
selects the approximate range of voltage (or heat, that
determines the arc length) to be applied to the weld. It is
a coarse selection control and is used in conjunction with
the Fine Voltage Adjustment selector following. It must
not be switched under load.
4.1.5
2.4.2
4.2.3
4.1.3
4.1.1
4.1.2
Torch
Cable
4.1.6
4.2.2
Secondary Output Terminals
for Welding Polarity Change-
over, see 4.1.3.
10A. Fuse
Work
Cable