Red-D-Arc D502K 5+4 Technical Manual page 39

PART NAME
SCR A Silicon Controlled Rectifier (SCR) is an
electrical device with three connections,
anode, cathode, and gate. It will allow current
to flow in only one direction and will only do
so after receiving a signal on the gate lead.
SCR's are used to change AC to DC and to
control the output to a load such as a welding
arc.
THERMISTOR A thermally sensitive resistor. The resistance
of a thermistor changes with a change in
temperature. Primarily used for "Fan on
Demand" and "Thermal Shutdown" circuits.
TRANSFORMER A device that changes AC voltage from one
magnitude to another. Typically used to
reduce high primary voltages to lower
welding voltages.
INTEGRATED An arrangement of four diodes used to
BRIDGE change AC to DC.
RECTIFIER
SPARK GAP The arrangement of two electrodes between
which a discharge of electricity will occur.
Typically used to produce " high frequency"
which can be used for arc starting when TIG
welding.
CURRENT A transformer that produces an AC voltage
TRANSFORMER used for measuring purposes. The primary
winding is in series with the circuit carrying
the current to be measured. Its main use in
engine-driven equipment is to activate the
"Automatic Idle" circuit by sensing welding
current or auxiliary power current.
D502K 5+4
FUNCTION PICTURE
AC
+
–
AC
CIRCUIT SYMBOL
K
G
A
RT1
OR
TH1
T1
+
AC
_
AC
G
CT1
OR
CT1
TM-4412 Page 35