4535 612 10261 HD11 Service Manual Page 75
CSIP Level 1 Theory of Operation: Functional Description
System Cooling
Bottom-mounted fans provide forced-air cooling:
• Airflow: The system fans (12 V/0.6 A) blow air through the bottom of the unit and exhaust
through the top with sufficient airflow to keep the exhaust air temperature less than +7°C
(+44.6°F) above the intake air. The exhaust cools the system electronics. The system pre-
sents a back pressure of 0.1mm H
2
O and requires at least 100 CFM of airflow that’s uniform
to within 10% and has a worse case temperature gradient of +10°C (+50°F).
• Cooling: If the signal N_PWR ON is active, the fans will always be on with a minimum fan
voltage up to an external temperature of +25°C ±2°C (+77°F ±35.6°F). At higher external
temperatures, the supply will slowly vary the speed of the fans to a maximum fan voltage
when the external temperature is at +35°C ±2°C (+95°F ±35.6°F). If N_PWR ON is off, the
fans will normally be off, and if needed, only turn on at the minimum voltage to cool the PFC
and AC Regeneration.
To Next Page
Loading...