Technical Reference Notes (TRN)

AK45C 100W Series

36 Vdc to 75 Vdc Inputs, 100 W

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ASTEC POWER - Andover

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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

(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:

Determine minimum airflow (Figure 14): v = 1.0 m/s (200 ft/min)

Figure 14. Forced Convection Power Derating

* longitudinal airflow, transverse airflow is more efficient and extends

calculated maximum ambient by 5 °C

AK45C SERIES

Power Derating Curve*

0

2

4

6

8

10

12

14

16

18

20

25

30

35

40

45

50

55

60

65

70

75

80

85

90

95

100

Ambient Temperature (ºC)

2.0 m/s (400 ft/min)

1.5 m/s (300 ft/min)

1.0 m/s (200 ft/min)

0.5 m/s (100 ft/min)

Nat. Conv.