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THERMAL CONSIDERATIONS
Thermal management is an important part of the system
design. To ensure proper, reliable operation, sufficient
cooling of the power module is needed over the entire
temperature range of the module. Convection cooling is
usually the dominant mode of heat transfer.
Hence, the choice of equipment to characterize the
thermal performance of the power module is a wind
tunnel.
Thermal Testing Setup
Delta's DC/DC power modules are characterized in
heated vertical wind tunnels that simulate the thermal
environments
encountered
equipment. This type of equipment commonly uses
vertically mounted circuit cards in cabinet racks in which
the power modules are mounted.
The
following
figure
characterization setup. The power module is mounted
on a test PWB and is vertically positioned within the
wind tunnel. The space between the neighboring PWB
and the top of the power module is constantly kept at
6.35mm (0.25'').
FACING PWB
AIR VELOCITY
AND AMBIENT
TEMPERATURE
MEASURED BELOW
THE MODULE
Note: Wind Tunnel Test Setup Figure Dimensions are in millimeters and (Inches)
Figure 20: Wind tunnel test setup
DS_L36SA3R315_02142007
in
most
electronics
shows
the
wind
tunnel
PWB
MODULE
50.8 (2.0")
AIR FLOW
12.7 (0.5")
Thermal Derating
Heat can be removed by increasing airflow over the
module. To enhance system reliability, the power module
should always be operated below the maximum
operating temperature. If the temperature exceeds the
maximum module temperature, reliability of the unit may
be affected.
THERMAL CURVES
Figure 21: Temperature measurement location
The allowed maximum hot spot temperature is defined at 130
.
L36SA3R315(standard) Output Current vs. Ambient Temperature and Air Velocity
@Vin = 48V (Either Orientation)
Output Current (A)
16
14
Natural
12
Convection
100LFM
10
200LFM
8
6
4
2
0
30
35
40
45
50
Figure 22: Output current vs. ambient temperature and air
velocity @ V
=48V (Either Orientation)
in
300LFM
400LFM
55
60
65
70
75
80
Ambient Temperature (℃)
℃
85
11
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