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GENERAL DESCRIPTION
The SA-250 is a heavy duty, engine driven DC arc
welding power source capable of providing constant
current output for stick welding or DC TIG welding.
Also, a total of 3000 watts of auxiliary power is available
at the 115 or 230VAC receptacles.
BATTERY, STARTER, ENGINE
ALTERNATOR, AND PROTECTION
CIRCUITS
The 12VDC battery powers the starter motor and,
through the ignition switch, the engine protection cir-
cuitry. In the event of a low oil pressure or a high
coolant temperature condition, the engine protection
system shuts the engine off. The protection relay mon-
itors the oil pressure switch and the coolant tempera-
ture sensor. If either sensor “faults,” the protection relay
deactivates the fuel injection pump, and the engine
shuts down. The engine alternator supplies “charging”
current for the battery circuit.
THEORY OF OPERATION
E-2 E-2
SA-250
FIGURE E.2 – BATTERY, STARTER, ENGINE ALTERNATOR, AND PROTECTION CIRCUITS
NOTE: Unshaded areas of Block Logic Diagram are the subject of discussion.
NEGATIVE
OUTPUT
TERMINAL
POSITIVE
OUTPUT
TERMINAL
115 & 230VAC
RECEPTACLES
CURRENT
TRANSFORMER
FIELD
RECTIFIER
FLASHING
RESIDUAL
MAGNETISM
ALTERNATOR STATOR
ROTOR
SLIP
RINGS
ARMATURE
SHAFT
GENERATOR
ARMATURE
BRUSHES
&
COMMUTATOR
GENERATOR
FRAME
SERIES
COILS
INTERPOLE
COILS
SHUNT
WINDINGS
GENERATOR
FIELD CONTROL
FIELD
MECHANICAL
COUPLING
REED
RELAY
CR2
SELECTOR
SWITCH
IDLER
BOARD
IDLER
SOLENOID
OIL
PRESSURE
TEMPERATURE
FUEL
ENGINE
ALTERNATOR
STARTER
MOTOR
BATTERY
ENGINE
PROTECTION
RELAY
IGNITION
SWITCH
INJECTION
PUMP
GAUGE
SWITCH