315 / 338
D-81
Additional information
Thermal characteristics of
switchboards
Once the dissipated power of the devices has been determined and the enclosure
with its IP selected, transfer the results (sum of the dissipated power and width of the
device zone) to the chart corresponding to the enclosure IP.
DD382423.eps
Draw a line parallel to the others on the chart and read the corresponding difference
in temperature.
For the given example, the heat rise is 22 °C at mid-height in the enclosure.
The internal temperature = external temperature + heat rise
= 35 °C + 22 °C = 57 °C
57 °C < 60 °C stipulated by the standard, i.e. the result is acceptable for an IP3
cubicle.
This gives roughly: Internal temperature = 60 °C at mid-height in the enclosure for a
low IP value.
Internal temperature = 70 °C at mid-height in the enclosure for a high IP value.
Thermal management of
switchboards
Example