Lincoln Electric INVERTEC V300-PRO SVM105-B Service Manual page 27

E-5
1˘ OR 3˘ DETETCTION (H5)
INPUT
LINE
RECTIFIER
SWITCH
1
AC1
2
AC2
3 AC3
3A
A-LEAD
24VDC
AUXILIARY
FAN
TRANSFORMER
18VAC
24VAC
TO
WIREFEEDER
OUTPUT AND CONTROL CIRCUITS
The AC output of the transformer is changed to DC by
the Output Rectifier. The Output Choke between the
negative side of the rectifier and the negative output
stud provides the necessary filtering for DC welding.
The two smaller chokes and their series diodes are the
OCV boost circuit used to help provide good weld
starts.
Current feedback to the Control Board is provided by
the shunt in the negative output circuit. It is used for
weld control, overcurrent protection and actual amme-
ter readings. The Voltage feedback lead at the positive
output stud also provides information for weld control
and actual voltmeter readings.
The Control Board monitors input from the front panel
controls (output, arc control, mode switch, etc..). The
software on the board processes these inputs, sets up
the proper weld information and sends the "set" para-
meter information to the meter.
NOTE: Unshaded areas of block logic diagram are the subject of discussion
THEORY OF OPERATION
FIGURE E-5 --OUTPUT & CONTROL CIRCUITS
POWER SWITCH
SECTIONS
20KHZ
LEFT SWITCH BOARD
FET MODULES
CAP
FET MODULES
PRE-CHARGE
DRIVER
BOARD
CR1
PROTECTION
PULSE
BOARD
TRAIN
CR2
PRE-CHARGE
RIGHT SWITCH BOARD
2ND STEP PWM
FET MODULES
CAP
POWERBOARD
FET MODULES
<1 VDC
LOCAL
METER MODE POT
REMOTE
1ST STEP PWM VOLTAGE
15VDC-CONTROL BOARD FUNCTION VOLTAGE
24VAC-THERMOSTATS-GUN TRIGGERING
V300-PRO
MAIN
TRANSFORMER
TOP
CURRENT
TRANSFORMER
CONTROL
BOARD
BOTTOM
Y-Y FEEDBACK
TOP
VOLTAGE FEEDBACK
POT
CURRENT FEEDBACK-PROTECTION
When weld output is requested, the Control Board
compares the input information to the feedback signals
and provides the correct PWM signals to the Switch
Boards for optimum welding. The Mode Switch setting
determines which feedback signal (voltage or current)
will have the most relevance. However, both signals
are used in all modes.
The Control Board also monitors signals from the ther-
mostats and the Protection Board and if necessary,
shuts off the weld output. The protection circuit infor-
mation is discussed in more detail later in this section.
E-5
RECTIFIER
CHOKE
HEATSINK
1 DIODE
5 DIODES
5 DIODES
1 DIODE
CHOKE
CHOKE
SHUNT