20Ap1:2 Fan Control - ESAB Arc 4000i Service Manual

Uan 5 V internal reference voltage on 20AP1.
Uref 2.5 V internal reference voltage on 20AP1.
20AP1:2 Fan control
When the mains power supply is turned on, the fans are off. After about 4
seconds they start and run at full speed, for a short moment, before shutting
down until welding starts.
The fan speed depends on the welding current. For loads up to 146 A, the fans
run at low speed, supplied at about 18 V. At load currents above 146 A, the
fans are supplied at 24 V and run at full speed. On conclusion of welding, the
fans continue to run for 6.5 minutes.
If the welding current is above 146 A and then is recuced to a lower value, the
fans continue to run at full speed for 6.5 minutes, before dropping to the lower
speed.
If overtemperature is detected, the fans run at high speed until the power
source has cooled down to normal temperature.
S0740 800 191/E080229/P78
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