Chapter 1
Using the Mainframe
1-2
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Air Flow
The air flow into the plug-in module slots in the VXI-1501 mainframe is
significant. The mainframe supplies each of the 13 slots with enough air to
cool 60 W while maintaining only a 10 °C rise across a typically dense
module. Up to 75 W per slot may be dissipated if a 15 °C rise is acceptable
across a typically dense module. The graph of Figure 1-1 shows the air flow
volume (liters/second) versus change in pressure across the module
(mm H
2
O) for the mainframe.
Figure 1-1. Minimum Airflow Available Per Slot
The mainframe has a fan chamber with three circulation fans. The speed of
the fans is controlled by the ambient temperature of the air drawn into the
mainframe. Air from the fan chamber is forced into the compartmentalized
plenum at the bottom of the mainframe. Although the plenum does contain
a compartmentalized structure, some air flow is always present in each of
the 13 slots even if one of the three mainframe circulation fans fails to
operate. The air passes through the installed modules and escapes out the
sides and top of the mainframe.
If any plug-in module exceeds 40 W dissipation, you must provide a
minimum of 20 mm (0.8 in.) of clearance above the mainframe.
A fourth fan provides cooling for the power supply. This fan is mounted on
the side of the mainframe.
Minimum Airflow per Slot
1
2
3
4
5
6
1.0
2.0
High Fan Speed
Airflow (liters/sec)
P Across
Module
(mm H O)
2
