Cooling Requirements - Motorola MVME177P Installation And Use Manual

Specifications
A

Cooling Requirements

A-2
The Motorola MVME177P VME Embedded Controller is specified,
designed, and tested to operate reliably with an incoming air temperature
range from –5° to 55° C (23° to 131° F) with forced air cooling of the entire
assembly (base board and mezzanine, if present) at a velocity typically
achievable by using a 100 CFM axial fan. Temperature qualification is
performed in a standard Motorola VME system chassis. Twenty-five-watt
load boards are inserted in two card slots, one on each side, adjacent to the
board under test, to simulate a high power density system configuration.
An assembly of three axial fans, rated at 100 CFM per fan, is placed
directly under the VME card cage. The incoming air temperature is
measured between the fan assembly and the card cage, where the incoming
airstream first encounters the module under test. Test software is executed
as the module is subjected to ambient temperature variations. Case
temperatures of critical, high power density integrated circuits are
monitored to ensure that component vendors' specifications are not
exceeded.
While the exact amount of airflow required for cooling depends on the
ambient air temperature and the type, number, and location of boards and
other heat sources, adequate cooling can usually be achieved with 10 CFM
and 490 LFM flowing over the module. Less airflow is required to cool the
module in environments having lower maximum ambients. Under more
favorable thermal conditions, it may be possible to operate the module
reliably at higher than 55° C with increased airflow. It is important to note
that there are several factors, in addition to the rated CFM of the air mover,
which determine the actual volume and speed of air flowing over a
module.
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