Temperature Sensing; Blower Interface; Blowers - Compaq 4200 User Manual

The blower mounting assembly is the element for mounting the second blower. This
element has no power circuitry. It does contain a circuit board for processing signals to
and from the blower.

Temperature Sensing

The power supply uses the internal temperature of the supply to set the speed of the
blower. The power supply blank can also set the blower speed. The higher the power
supply temperature, the faster the speed of the blower. Should the power supply
temperature exceed a preset value, the power supply is shut down.

Blower Interface

The blower mounts on the rear of the power supply. A power supply connector is the
interface between the blower and the enclosure. The interface signals include:
Blower speed control to the blower
Blower speed to the EMU through the power supply
Power supply high-speed enable
Blower operating voltage

Blowers

The power supply-mounted blowers cool the enclosure by circulating air through the
enclosure and elements. The rate at which air moves, the airflow, determines the amount
of cooling. This airflow is a function of blower speed (rpm). These blower blowers, under
the control of the EMU or the associated power supply, can operate at multiple speeds.
This ensures that when the enclosure temperature changes, the blowers can automatically
adjust the airflow.
Should a blower fail
of the operational blower to high speed. Simultaneously, the error condition is reported to
the user in several ways.
NOTE: The failure of the power supply 12.5 VDC circuit disables the associated blower.
1. Operating at too low a speed or stopped.
1
, EMU and power supply circuitry automatically increase the speed
Enclosure Power and Cooling 6–3