Theory of operation, Precharge (soft start) – Lincoln Electric INVERTEC POWER WAVE 450 SVM112-B User Manual
Page 51
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.
THEORY OF OPERATION
E-3
E-3
POWER WAVE 450
FIGURE E.3 – PRECHARGE CIRCUIT
NOTE: Unshaded areas of Block Logic Diagram are the subject of discussion.
CONTROL
BOARD
DISPLAY
BOARD
PROTECTION
BOARD
AUX.
TRANS
POWER
BOARD
CT
CONTACTOR
INPUT
INPUT
RECTIFIER
AND
RECONNECT
SWITCH
BOARD
FET
ASSEMBLY
SWITCH
BOARD
FET
ASSEMBLY
MAIN
TRAMSFORMER
OUTPUT
RECTIFIER
SHUNT
CHOKE
POSITIVE
NEGATIVE
SNUBBER
AND
LEADS
SENSE
LCD
DISPLAY
KEYPAD
OVERLAY
WATER
COOLER
PC
INTERFACE
INPUT
LINE
SWITCH
FAN
WF1
WF2
THREE
PHASE
INPUT
POWER
LEFT
RIGHT