Input Section - Lincoln Electric PRESTO 275 Service Manual

INPUT SECTION

When the three phase input voltage 400Vac is applied
®
to the PRESTO 275 and the input switch S1 is closed
the voltage is applied to the Input EMI filter board.
EMI filter circuit prevents noise from the machine from
being transmitted along the main power line and vice
versa, necessary to be
directives and standards.
The three phases coming out from the EMI filter board
are rectified by the input rectifier bridge and the
resultant 565VDC voltage is applied to the Preload
board.
The DC BUS voltage is reaching also the Aux. Power
Board. The software loaded into the Aux. Power board
INPUT SECTION
in accordance with all relevant
monitors the input voltage and if all is correct provides
the command to the relay on the Preload board to
close bypassing the start resistors.
During this time the DC BUS capacitors on the Inverter
board started to charge throught the 4 resistors located
on the Preload board. Once the relay on the Preload
board closes the DC BUS capacitors on inverter board
complete their charge.
The Aux. Power Supply board provides all the
insulated lower power supply needed by the machine's
PCBs including the insulated 24Vdc needed to supply
the Control Board. It receives also the signal from the
NTC1 located on the primary power circuit of the
inverter board.