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Thermal management system
Method of determining the thermal solution
H = Height
W = Width
D = Depth
Position of Location
Formula for
the enclosure according to IEC 890 ratio
calculating S (m
2
)
Accessible from every side
S = 1.8 H (W + D) + 1.4 W D
Placed against a wall
S = 1.4 W (H + D) 1.8 D H
On the end when suited
S = 1.4 D (H + W) + 1.8 W H
On the end when suited,
S = 1.4 H (W + D) + 1.4 W D
placed against a wall
In the middle when suited
S = 1.8 W H + 1.4 W D + D H
In the middle when suited,
S = 1.4 W (H + D) + D H
placed against a wall
In the middle when suited,
S = 1.4 W H + 0.7 W D + D H
placed against a wall with the top covered
Max. internal temperature: Ti max = Pd
KxS + Te max
Min. internal temperature: Ti min = Pd
KxS + Te min
or
K = 5.5 W/m
2
/°C for an enclosure made of painted sheet steel
K = 3.5 W/m
2
/°C for a polyester enclosure
K = 3.7 W/m
2
/°C for a stainless-steel enclosure
K = 12 W/m
2
/°C for an aluminium enclosure
1
Characteristics of the enclosure
Example
Spacial reference
NSYSF20840
H
= 2000
W
= 800
D
= 400
Installation method:
Suitable enclosure placed against a wall.
2
Thermal power dissipated by the operational components
Calculated as the sum of the power dissipated by each of the
installed components.
If these are not known, use the ProClima software and
page
8/115
, which shows the average values.
3
Characteristics of the environment air
Maximum ambient temperature
Minimum ambient temperature
Average relative humidity
Dew point temperature. Calculation of resistance heater power.
4
Average desired internal temperatures
The temperature conditions are as follows:
5
Final temperature inside the enclosure with no thermal system
Ti
max
= 70 °C
Ti
min
= 50 °C
They are defined by the nature of the components and the
characteristics of the environment air.
Maximum internal temperature
Minimum internal temperature
(maximum value between the dew point temperature and the
minimum operating temperature of the devices)
Assume that the switchgear dissipates
800 W
S = 4.13 m
2
Pd = 800 W
Ts
max
= 40 °C
Ts
min
= 29 °C
The heat balance, which consists of comparing the power released by the devices with the power exchanged spontaneously through the wall
of the enclosure, allows us to calculate the internal temperature obtained in the enclosure, with no thermal accessories, and thus to determine
whether it is necessary to install any, bearing in mind the desired internal and external temperatures.
Below we have presented a simple method for implementing this choice.
S =
m
2
Pd =
W
Te
max
=
°C
Te
min
=
°C
RH =
%
Tr =
°C
Ts
max
=
°C
Ts
min
=
°C
Ti
max
= °C
Ti
min
=
°C
Te
max
= 35 °C
Te
min
= 15 °C
RH = 70 %
Tr = 29 °C
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