Delta Electronics 33W Family - Manual (Page 9)

DS_S48SA1R812_06012006
9
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 in most electronics
equipment. This type of equipment commonly uses
vertically mounted circuit cards in cabinet racks in which
the power modules are mounted.
The following figure shows the wind tunnel
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.
Note: Wind Tunnel Test Setup Figure Dimensions are in millimeters and (Inches)
10 (0.4”)
MODULE
AIR FLOW
50.8 (2.0”)
FACING PWB PWB
AIR VELOCITY
AND AMBIENT
TEMPERATURE
MEASURED BELOW
THE MODULE
Figure 17: Wind tunnel test setup
THERMAL CURVES
Figure 19: Output current vs. ambient temperature and air velocity
@V
in
< 60 V
S48SA1R812(Standard) Output Current vs. Ambient Temperature and Air Velocity
@ Vin < 60V
0
2
4
6
8
10
12
14
65 70 75 80 85 90 95 100
Ambient Temperature (℃)
Output Current(A)
Natural
Convection
100LFM
200LFM
300LFM
400LFM
500LFM
600LFM
Figure 18: Hot spot temperature measured point
＊ The allowed maximum hot spot temperature is defined at
110℃