Filter
Top Products
315889-002 45
Environmental Conditions
8 Environmental Conditions
The VRM/EVRD design, including materials, should meet the environmental
requirements specified below.
8.1 Operating Temperature - PROPOSED
The VRM/EVRD shall meet all electrical requirements when operated at the Thermal
Design Current (Icc
TDC
) over an ambient temperature range of 0ºC to +45ºC with a
minimum airflow of 400 LFM (2 m/s). The volumetric airflow (Q) can be measured
through a wind tunnel. For testing, the baseboard should be mounted in a duct. (A VRM
should be mounted on a PCB, and then mounted in a duct.) The recommended duct
cross-section, assuming the PCB is horizontal and flush with the bottom of the duct, is
as follows:
• Y direction duct width (perpendicular to flow, horizontal) = 0.3 m
• Z direction duct height (perpendicular to flow, vertical) = 0.15 m
• Minimum X direction duct length in front of VRM = 6 hydraulic diameters = 1.2 m
• Minimum X direction duct length behind VRM = 2 hydraulic diameters = 0.4 m
• Velocity (v) is calculated from the volumetric flow and cross-sectional area at the
inlet as:
• v = Q/(0.3 x 0.15)m
2
Operating conditions shall be considered to include 10 cycles
between min and max temperature at a rate of 10ºC/hour and a dwell time of 30
minutes at extremes. Temperature and airflow measurements should be made in
close proximity to the VRM.
8.2 VRM Board Temperature - REQUIRED
To maintain the connector within its operating temperature range, the VRM board
temperature, at the connector interface, shall not exceed a temperature equal to 90ºC.
At no time during the operation is the board permitted to exceed 90ºC within a distance
of 2.54 mm [0.100”] from the top of connector (0.4 in. from board edge). In order not
to exceed 90ºC, it is recommended that the board be constructed from 2-ounce copper
cladding. Temperature and airflow measurements should be made in close proximity to
the VRM.
8.3 Non-Operating Temperature - PROPOSED
The VRM/EVRD shall not be damaged when exposed to temperatures between –40ºC
and +70ºC. These shall be considered to include 50 cycles of minimum to maximum
temperatures at 20ºC/hour with a dwell time of 20 minutes at the extremes.
8.4 Humidity - PROPOSED
85% relative – operating
95% relative – non-operating