Precharge (Soft Start - Lincoln Electric INVERTEC POWER WAVE 450 SVM112-B Service Manual

E-3
THREE
PHASE
INPUT
POWER
INPUT
LINE
SWITCH
PROTECTION
BOARD

PRECHARGE (SOFT START)

The Protection Board contains a "soft Start" circuit,
which is powered by the Auxiliary Transformer. During
precharge or "soft start" only two phases of the input
power, with current limiting, are connected to the input
rectifier. This AC input voltage is rectified, and the DC
voltage is applied through the Reconnect Switches to
the input capacitors located on the Switch Boards.
The Protection Board monitors the voltage across the
capacitors. When the capacitors have charged to an
acceptable level, the Protection Board energizes the
Main Input Contactor, making all three phases of input
power available to the input capacitors. At this point
the Power Wave is in the "Run Mode" of operation. If
the capacitors become under- or overvoltaged, the
Protection Board will de-energize the Main Input
Contactor, and the machine output will be disabled.
NOTE: Unshaded areas of Block Logic Diagram are the subject of discussion.
THEORY OF OPERATION
FIGURE E.3 – PRECHARGE CIRCUIT
INPUT
RECTIFIER
INPUT AND
CONTACTOR RECONNECT
LEFT
SWITCH
BOARD
FET
ASSEMBLY
AUX.
TRANS
RIGHT
SWITCH
BOARD
FAN
FET
ASSEMBLY
POWER
BOARD
WATER
COOLER
PC
INTERFACE
POWER WAVE 450
MAIN
OUTPUT
TRAMSFORMER RECTIFIER
CT
SNUBBER
SENSE LEADS
CONTROL
BOARD
LCD
DISPLAY
DISPLAY
BOARD
KEYPAD
OVERLAY
WF1 WF2
E-3
CHOKE POSITIVE
NEGATIVE
SHUNT
AND