Theory Of Operation; General Description; Input Line Voltage, Contactor And Main Transformer - Lincoln Electric IDEALARC R3R-300 Service Manual

E-2
FIGURE E.2 – INPUT LINE VOLTAGE, CONTACTOR AND MAIN TRANSFORMER
CONTROL
TRANSFORMER
MOTOR
POWER
THERMOSTATS SWITCH
R
E
C
O
N
N
E
C
T
INPUT
CONTACTOR

GENERAL DESCRIPTION

The Idealarc R3R welder is a three-phase transformer
rectifier type constant current power source designed
for DC manual welding and air carbon arc cutting. Its
power system is SCR controlled with solid state elec-
tronic circuitry. Minimum to maximum output is
obtained with a single potentiometer control.
INPUT LINE VOLTAGE,
CONTACTOR AND MAIN
TRANSFORMER
The desired three-phase input power is connected to
the R3R through an input contactor, located in the
input box at the rear of the machine. Two phases of
the input line are also connected to the primary of the
NOTE: Unshaded areas of Block Logic Diagram are the subject of discussion.

THEORY OF OPERATION

OPTIONAL
OPTIONAL
POCKET
POCKET
AMPTROL
AMPTROL
TRANSFORMER
PC BOARD
AMPHENOL
TERMINAL
STRIP
REMOTE
SWITCH
FAN
MAIN
TRANSFORMER
IDEALARC R3R
OUTPUT
CONTROL
DIAL
ARC FORCE
SELECTOR
CONTROL
SWITCH
CONTROL BOARD
G S
A I
G
T
N
E
A
L
S
SNUBBER
BOARD
SHUNT
SCR DIODE /
HYBRID BRIDGE
control transformer.
transformer supplies 120VAC power, via the power
switch and thermostats, to activate the input contac-
tor.
A reconnect panel allows the user to configure the
machine for the desired input voltage. This AC input
voltage is applied to the primary of the main trans-
former.
The transformer changes the high voltage, low current
input power to a lower voltage, higher current output.
The finishes or "neutrals" of the main secondary coils
are connected together, and the three starts of the
secondary windings are connected to the rectifier
bridge assembly.
angle windings are housed in the main transformer
assembly. These windings provide power and "timing"
for the control board.
120VAC for the fan motor.
FEEDBACK
OPTIONAL
POLARITY
F
SWITCH
OUTPUT
E
E
CHOKE
D
B
A
C
K
TERMINAL
The secondary of the control
In addition, three 66VAC phase
Two of these coils provide
E-2
NEGATIVE
OUTPUT
TERMINAL
POSITIVE
OUTPUT