Fan And Liquid Cooling - BONFIGLIOLI active Installation Manual

4.2
The size of the heat sinks can be reduced if fans are installed or a liquid cooling system
is used in addition to the "Cold Plate" technology.
The size of the heat sink can be reduced proportionally to the increase in the flow rate
of the cooling medium.
In the following a fan cooling system is described as an example. For calculating the
maximum permissible heat resistance R
portionality factor is introduced. This factor describes the increase of the max. permis-
sible thermal resistance at increasing flow rate of the cooling air.
The max. permissible thermal resistance R
lated as follows:
R : max. permissible thermal resistance with free circulation of air; calculate according to the
th
formula for R
factor
The relation is shown, as an example, in the following table for the ACT401-27 fre-
quency inverter.
R
th
11/06

Fan and liquid cooling

in the previous chapter or use the value indicated in the table, α: proportionality
th
Thermal resistance for enforced air cooling
[K/W] V [m/s]
air
0.08
0.08
0.08
0.08
0.08
for cooling by means of a fan, a pro-
th enforced
for enforced air cooling can be calcu-
th enforced
R
th
R =
th enforced
α
α
0 1
1 0.65
2 0.45
4 0.28
6 0.20
R [K/W]
th enforced
0.08
0.12
0.18
0.29
0.40
13