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INPUT VOLTAGE AND MAIN TRANS-
FORMER
Single-phase input power is brought into the rear of the
Power MIG 350MP through a three-prong plug and
input cable. A reconnect panel, also located on the rear
of the machine, allows the user to configure the Power
MIG 350MP for either 230V, 460V, or 575V input sup-
ply power. An ON/OFF line switch is located on the
front panel. When the line switch is ON, AC input volt-
age is applied to the primary winding of the main trans-
former. The main transformer converts the high volt-
age, low current input power to a low voltage, high cur-
rent output. The main transformer also has two isolat-
ed auxiliary windings. One supplies 30 VAC to a Diode
Control Rectifier, which converts the 30 VAC to 40 VDC
to supply the Power Board and the Spool Gun Board.
The Power Board in turn supplies 20
VDC to the Chopper Board and +15 VDC, -15 VDC and
+5 VDC to the Weld Control Board circuitry. The other
auxiliary winding provides 115 VAC to operate a ther-
mostatically controlled fan motor through a relay, which
also receives signals from the Weld Control Board.
The fan is designed to come on automatically when the
trigger is pulled. The fan will stay on as needed for a
minimum of six minutes after the weld arc is terminat-
ed. The fan will also stay on when the machine's weld-
ing and feeding are disabled during thermostatic over-
temperature protection. The 115 VAC winding also
supplies power to the 115 VAC auxiliary receptacle
located on the back of the machine. This offers 15
amps of auxiliary power. (See Thermal and Overload
Protection)
THEORY OF OPERATION
E-3 E-3
POWER MIG 350MP
FIGURE E.3 – INPUT VOLTAGE AND MAIN TRANSFORMER
NOTE: Unshaded areas of Block Logic Diagram are the subject of discussion.
