Thermal Considerations; Thermal Curves - Delta Electronics 33W Family Datasheet

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
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 or a heat sink is
6.35mm (0.25").
Thermal Derating
Heat can be removed by increasing airflow over the
module. Figure 18 and 19 show maximum output is a
function of ambient temperature and airflow rate. 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.
FACING PWB
AIR VELOCITY
AND AMBIENT
TEMPERATURE
MEASURED BELOW
THE MODULE
Note: Wind Tunnel Test Setup Figure Dimensions are in millimeters and (Inches)
Figure 17: Wind tunnel test setup
DS_S48SA1R812_06012006
in most
figure shows the wind
PWB
MODULE
50.8 (2.0")
AIR FLOW
10 (0.4")

THERMAL CURVES

electronics
Figure 18: Hot spot temperature measured point
tunnel
＊ The allowed maximum hot spot temperature is defined at
110
℃
Output Current(A)
14
12
10
Convection
8
6
4
2
0
65
Figure 19: Output current vs. ambient temperature and air velocity
< 60
@V
in
S48SA1R812(Standard) Output Current vs. Ambient Temperature and Air Velocity
@ Vin < 60V
Natural
100LFM
200LFM
300LFM
70 75 80 85
V
600LFM
500LFM
400LFM
90 95 100
Ambient Temperature (℃)
9