Theory Of Operation - Lincoln Electric POWER MIG SVM167-A Service Manual

E-2
FAN
MOTOR
LINE
SWITCH
RECONNECT
PANEL
TRANSFORMER
INPUT LINE VOLTAGE, MAIN
TRANSFORMER, VOLTAGE
SELECTOR SWITCH AND
BAFFLE MOUNTED DIODE
BRIDGE
The single phase input power is connected to
the POWER MIG® 215 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 low voltage, high current
output. This tapped secondary winding is
coupled to a voltage selector switch.
selecting one of seven positions on the switch
the user can preset the desired voltage output
NOTE: Unshaded areas of block logic diagrams are the subject of discussion.

THEORY OF OPERATION

FIGURE E.2 – INPUT POWER CIRCUIT.
GAS
SOLENOID
CONTROL BOARD
RECTIFIER
DIODE
BRIDGE
TAP SELECTOR
SWITCH
CONTACTOR
MAIN
By
POWER MIG® 215
WIRE
SPEED
CONTROL
WIRE
DRIVE
MOTOR
TRANSFORMER
TACH
THERMOSTAT
GUN TRIGGER
OUTPUT DIODE
BRIDGE
+
+
OUTPUT
POSITIVE
CHOKE
TERMINAL
OUTPUT
CAPACITORS
- -
NEGATIVE
TERMINAL
from a minimum setting (A) to a maximum
voltage setting (G). In addition, the main
transformer also has a 28VAC winding. This
28VAC is rectified at the baffle mounted diode
bridge. The resultant DC voltage (approx.
35VDC) is used to power the electronics on the
control board.
E-2
OUTPUT BRIDGE
THERMOSTAT
GUN
ASSEMBLY