Ap1 Power Board - ESAB Caddyt Arc 150i Service Manual

15

AP1 Power board

WARNING!
Dangerous voltage - - mains voltage.
Never make any measurements on this
board when the machine is connected to
the mains supply.
The power module is a single forward converter, operating at a switching frequency of
65 kHz. IGBT transistors are used as the switching elements. See page 49 and 50 for
screen traces of waveforms and measurement instructions.
If the power board has failed, a replacement board must be mounted in accordance with the
instructions on page 51.
The power board carries the mains rectifier, the charging circuit, the switching circuit and the
gate circuit.
The mains rectifier and the switching transistors are integrated in a semiconductor module,
PM1, which is part of the power board.
Charging circuit
When the mains power supply is turned on, the rectified mains voltage charges smoothing
capacitor 15C1 via resistor R31. Thyristor TY1 short--circuits charge resistor R31 when the
machine is loaded. If TY1 did not conduct, resistor R31 would burn out when the power
source is on load.
ct27d_15
- - 20 - -
S0740 800 161/E061205/P66