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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_E24SR05012_01032008
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
temperature. If the temperature exceeds the maximum
module temperature, reliability of the unit may be affected.
THERMAL CURVES
Figure 21: Hot spot temperature measured point
The allowed maximum hot spot temperature is defined at 118
E24SR05012(Standard) Output Current vs. Ambient Temperature and Air Velocity
Output Current(A)
@Vin = 24V (Transverse Orientation)
12
10
8
6
4
2
0
25
30
35
40
45
50
Figure 22: Output current vs. ambient temperature and air velocity
@V
=24V (Transverse Orientation)
in
the
maximum
operating
Natural
Convection
100LFM
200LFM
55
60
65
70
75
80
Ambient Temperature (℃)
℃
85
10
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