Theory of operation, Input line voltage and main transformer – Lincoln Electric SQUARE WAVE TIG 255 SVM100-A User Manual
Page 34
SQUARE WAVE TIG 255
E-1
THEORY OF OPERATION
INPUT LINE VOLTAGE AND MAIN TRANSFORMER
LINE
SWITCH
R
E
C
O
N
N
E
C
T
MAIN
TRANSFORMER
X2
X1
POWER
FACTOR
CAPACITORS
FAN
115VAC
PROTECTION
SNUBBER
BOARD
ARC START
115 VAC
GATE SIGNALS
HI-FREQ
115 VAC
CONTROL
BOARD
LCD DISPLAY
KEYPAD
LED
BOARD
KEYPAD
HIGH VOLTAGE
TRANSFORMER
CIRCUIT
115 VAC
115 VAC
REMOTE
RECEPTACLE
115 VAC
RECEPTACLE
CONTROL
TRANSFORMER
24 VAC
18 VAC
16 VAC
HIGH FREQUENCY SPARK
WORK
ELECTRODE
HI-FREQ
TRANSFORMER
BY-PASS
BOARD
POLARITY
SWITCH
CHOKE
FEED BACK
GATE SIGNALS
AC
AC
DC+
DC-
SCR
BRIDGE
SHUNT
The desired single-phase input power is connected to
the TIG 255 through a line switch located on the front
panel.
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. Power factor correction capacitors are incor-
porated in the primary circuit of the main transformer
to help balance the inductive nature of the TIG 255.
The transformer changes the high voltage, low current
input power to a low voltage, high current output. In
addition, the main transformer also has an isolated
115vac auxiliary winding, that supplies 115vac to
operate the cooling fan and offers 10 Amps of auxil-
iary power at the 115vac receptacle. This 115vac is
also applied to the control board and the control trans-
former via the protection/snubber board. The 115vac
also powers the high voltage circuit. The secondary
voltages that are developed in the control transformer
power the control board. On 50/60 Hz machines
the main transformer also has a 220vac auxiliary
winding that provides power to the 220vac receptacle.
This 220vac winding is not isolated from the 115vac
winding.