Technical Reference Notes (TRN)

BK60C-H Series

36 Vdc to 75 Vdc Inputs, 150 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 13 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 13 is shown in the

following example.

Example

What is the minimum airflow required for an 033F40H operating at 48 V, an output current of 25

A, and maximum ambient temperature of 55 ºC.

Solution:

Determine airflow (Figure 16): v = 1.0 m/s (200 ft/min)

Figure 13. Forced Convection Power Derating

BK60C SERIES

Power Derating Curve

0

5

10

15

20

25

30

25

30

35

40

45

50

55

60

65

70

75

80

85

90

95 100 105 110

Ambient Temperature (ºC)

Nat. Conv.

0.5 m/s (100 ft/min)

1.0 m/s (200 ft/min)

2.0 m/s (400 ft/min)