Input power circuit, Input line voltage, Main transformer – Lincoln Electric POWER MIG SVM157-A User Manual

Page 30: Voltage selector switch, Baffle mounted diode bridge, Theory of operation, Power mig 200 figure e.2 – input power circuit

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THEORY OF OPERATION

E-2

POWER MIG 200

FIGURE E.2 – INPUT POWER CIRCUIT.

INPUT LINE VOLTAGE, MAIN
TRANSFORMER, VOLTAGE
SELECTOR SWITCH AND
BAFFLE MOUNTED DIODE
BRIDGE

The single phase input power is connected to
the POWER MIG 200 through a line switch
located on the front panel.

A reconnect panel allows the user to configure
the machine for the desired input voltage. The
AC input voltage is applied to the primary of the
main transformer. The cooling fan motor
(120VAC) is powered from a portion of the
primary winding. For welding purposes, the
main transformer converts the high voltage, low
current input power to a lower voltage, higher
current output. This tapped secondary winding
is coupled to a voltage selector switch. By
selecting one of seven positions on the switch
the user can preset the desired voltage output

from a minimum setting (A) to a maximum
voltage setting (G). In addition, the main
transformer houses a 28VAC winding. This
28VAC is rectified at the baffle mounted diode
bridge and the resultant DC voltage is used to
power the electronics on the control board, the
output contactor, and the gas solenoid.

NOTE: Unshaded areas of block logic diagrams are the subject of discussion.