ESAB fabricator 141i Service Manual page 65

ESAB FABRICATOR 141i
The mains supply voltage is connected via a double pole switch to the input rectifier BR1 &BR2. Overvoltage protection is provided by
varistor CY1.
The rectifier output charges the main capacitor bank (C16, C18, C18-1) to high voltage. Inrush current limiting is provided by a PTC
which is then bypassed by relay J1 after a few seconds.
The primary igbt transistors (T1, T2, T4, and T5) switch the transformer primary at high frequency and varying duty cycle.
Secondary output voltage from the transformer is rectified by the output diodes (T13-1, T14-1, T15-1, T16-1, T17-1, T18-1) to DC.
This DC is controlled by the PWM of the primary side igbt transistors, and is filtered by an inductor before connecting to the welding
output terminals.
A thermal overload device (thermistor) is fixed to the rectifier heatsink. When an over temperature occurs, the control circuit inhibits
the trigger, gas solenoid, wire drive system and the welding output. The thermal overload indicator LED on the front panel is illumi-
nated.
The current transformer TR8 provides a signal to the control circuit to indicate both transformer primary current, and also detect
transformer saturation. The Hall effect current sensor is powered from regulated + & - 15VDC supplies and provides a voltage signal
proportional to the output DC welding current to allow the control circuit to regulate welding current.
Manual 0-5448 6-23 TROUBLESHOOTING