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General Information
1
Cooling Requirements
1-4
Motorola VMEmodules are specified, designed, and tested to operate
reliably with an incoming air temperature range from 0 degrees C to 55
degrees C (32 degrees F to 131 degrees F) with forced air cooling.
Temperature qualification is performed in a standard Motorola
VMEsystem 1000 chassis. Twenty-five watt load boards are inserted in the
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 71 CFM per fan, is placed directly under the MVME
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 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 5 CFM
flowing over the module. Less air flow 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 degrees C with increased air flow. 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 of air flowing
over a module.
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