AK45C Datasheet, PDF (13/17 Pages) Astec America, Inc – 36 Vdc to 75 Vdc Inputs, 100 W

Technical Reference Notes (TRN)
AK45C 100W Series
36 Vdc to 75 Vdc Inputs, 100 W
Thermal Considerations
The power converter operates in a variety of thermal environments: however, sufficient cooling
should be provided to help ensure reliable operation of the converter. Heat-dissipating
components are thermally coupled to the case. Heat is removed by conduction, convection, and
radiation to the surrounding environment. Proper cooling can be verified by measuring the case
temperature.
Heat Transfer Characteristics
Increasing airflow over the converter enhances the heat transfer via convection. Figure 14 shows
the maximum power that can be dissipated by the converter without exceeding the maximum
case temperature versus local ambient temperature (T_A) for natural convection through 2.0 m/s
(400 ft/min).
Systems in which these converters are used generate airflow rates of 0.25 m/s (50 ft/min) due to
other heat dissipating components in the system. Therefore, the natural convection condition
represents airflow rates of approximately 0.25 m/s (50 ft/min). Use of Figure 14 is shown in the
following example.
Example
What is the minimum airflow required for an 033F20 operating at 48 V, an output current of 15 A,
and maximum ambient temperature of 50 ºC.
Solution:
Given: Vi = 48 V, Io = 15 A, T_A = 50 ºC.
Determine P_D (Figure 17): P_D = ~8 W.
Determine minimum airflow (Figure 14): v = 1.0 m/s (200 ft/min)
AK45C SERIES
2.0 m/s (400 ft/min)
Power Derating Curve*
1.5 m/s (300 ft/min)
1.0 m/s (200 ft/min)
0.5 m/s (100 ft/min)
Nat. Conv.
20
18
16
14
12
10
8
6
4
2
0
25 30 35 40 45 50 55 60 65 70 75 80 85 90 95 100
Ambient Temperature (ºC)
Figure 14. Forced Convection Power Derating
* longitudinal airflow, transverse airflow is more efficient and extends
calculated maximum ambient by 5 °C
_____________________________________________________________
ASTEC POWER - Andover
13 of 17