Lincoln Electric RANGER 305 D Service Manual page 54

RANGER 305D
ENGINE
PROTECTION
LIGHT
ENGINE
PROTECTION
CIRCUIT
FUEL
PUMP
FUEL
SOLENIOD
HOLD COIL
PULL COIL
START
BUTTON
GLOW
PLUG
BUTTON
12V.
BATTERY
RUN
STOP
SWITCH
WELD POWER ND CONTROL
WELD POWER:
Approximately 90VDC power, as described earlier under the heading
"Generating Power", is supplied to the IGBT's, (See IGBT Operation)
and to the control circuitry in the power module, as well as the weld
control PC board.
The IGBT's control the weld output by switching the weld power on
and off using a 20 Khz PWM (Pulse Width Modulation) signal from the
control PC board. This PWM signal varies the ratio of on and off time,
thereby controlling the power passing through to the welding arc.
(See Pulse Width Modulation )
FIGURE E.5 – WELD POWER & CONTROL
CHARGING
SYSTEM LIGHT
(CODE 10926 ONLY)
ENGINE
GLOW
ENGINE
SENSORS
PLUGS
ALTERNATOR
ENGINE
STARTER
IDLE
SOLENOID
PULL HOLD
COIL COIL
FLASHING
PULL COIL
PC BOARD
The DC power that is being controlled by the IGBT's is now applied to
the choke. The choke is a heavy conductor wound around an iron
core. This device stores power and tends to resist any change to
current flow. During the IGBT off cycle, the choke begins to discharge
through a freewheeling diode, on the power module. This diode
provides the necessary current path, allowing the choke to use its
stored power to maintain a smooth flow of current to the welding arc
during the IGBT's off times. (See Chopper Technology
Fundamentals )
WELD CONTROL ND FEEDB CK:
The operator provides input to the weld control circuitry by means of
the output control and arc control potentiometers, and the mode
switch. These operator inputs are used by the microprocessor,
together with pre-programmed internal parameters, current feedback
from the shunt, and voltage feedback from the output studs, to control
the IGBT's via the PWM signal discussed earlier.
E 5
POWER
MODULE
WELD
WINDING
ROTOR
STATOR
ER 120/240 VAC 42 VAC
EXCIT
WINDING
WINDING AUX.WINDING
CURRENT
SENSOR
14
240
PIN
VAC
120
AMPHENALS
6
vac
RECEPTACLES
PIN
OUTPUT
CONTROL
THEORY OF OPERATION
SHUNT
+
IGBTs
-
CHOKE
AMP
DISPLAY
WELD CONTROL
VOLT
P.C. BOARD
DISPLAY
IDLE
SWITCH
MODE
WELDING
SWITCH TERMINAL
SWITCH
ARC
CONTROL