Red-D-Arc D502K 5+4 Technical Manual page 37

PART NAME
FAN MOTOR This device provides cooling of the internal
parts of a welding power source.
VARISTOR A protection device whose resistance is
dependent on the voltage applied to it. In
normal operation it has a high resistance;
however, a surge of voltage (voltage spike)
will cause its resistance to go way down and
absorb the spike. These devices are most
often found in rectifying circuits, where they
are used to protect the diodes.
GAS OR WATER These are electromechanical devices used to
SOLENOID start or stop the flow of shielding gas or
(VALVE) water.
RELAY––COIL AND This is an electromechanical device whose
CONTACTS, contacts change state (the normally open
NORMALLY OPEN points close and the normally closed points
AND NORMALLY open) when proper voltage is applied to the
CLOSED coil. These contact points in turn may control
a fan motor, gas solenoid, contactor, etc.
Circuit diagrams (schematics) always show
the contact points in the power off state.
THERMOSTAT, This is a switch that closes its normally open
NORMALLY OPEN contacts (or opens its normally closed
AND NORMALLY contacts) when a preset temperature is
CLOSED reached. When the temperature goes back
down, it will reset itself. Uses of these
devices include turning on a fan motor when
needed and shutting off the output of a
welding power source if it is overheating.
CONTACTOR A heavy duty relay. Usually used to make
and break the welding arc or primary power.
PILOT LIGHT A light located on the front panel which
indicates if the machine is on or off.
STABILIZER/ When placed in a DC circuit, the inductor or
REACTOR stabilizer as it is usually called, will oppose
any change in existing current. It is therefore
widely used to "stabilize" the welding arc.
When the inductor is placed in an AC circuit it
is referred to as a reactor where it now acts
to restrict the flow of current. A "tapped
reactor" is used to create current ranges for
welding.
D502K 5+4
FUNCTION PICTURE CIRCUIT SYMBOL
CR1
NRM OPEN
POINTS
TP1
NRM OPEN NRM CLOSED
W
NRM OPEN
POINTS
FM
VR1
GS1
OR
WS1
COIL
CR1
NRM CLOSED
POINTS
TP1
COIL
W
1
PL
Z1
L1
TM-4412 Page 33