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D-78
Additional information
Thermal characteristics of
switchboards
Calculation of the internal
temperature
Calculation of the temperature is the means to check that the enclosure can
evacuate the dissipated power of the installed devices.
Important note
Correct thermal management of the switchboard depends on compliance with
the installation requirements for the distribution system (power circuits).
Incorrect installation will have major consequences on the connected device, but
almost none on the internal temperature of the enclosure.
Once the circuit has been correctly sized, it is necessary to check whether the
assembly (devices + distribution system + cables) have a level of dissipated power
P(W)
y
the P(W) that the enclosure can handle.
Dd381401.eps
Method defined by IEC 890 technical report
This IEC guide for switchboards proposes a calculation method to determine three
levels of internal temperature, depending on the dissipated power of the devices and
distribution blocks installed in the switchboard.
Users can consult this document when it is necessary to determine precisely the
internal temperature in view of optimising the switchboard.
On request, Schneider Electric can carry out a thermal study to check that the
installed assembly and the thermal capacity of the enclosure are compatible.
DD381350.eps
Comparative method
A number of qualified and tested configurations serve as the basis for indicating the
thermal capacity of Prisma P enclosures.
This is en empirical means to check whether the dissipated power of the desired
configuration is close to that of a tested configuration.
DD382422.eps
Method using charts taking into account enclosure characteristics
To speed up calculations, Schneider Electric produces charts based on the
company’s experience and a number of assumptions on the installation.
They can be used sufficiently precisely to determine the variations in temperature
and the dissipated-power levels for the different types of wall-mounted enclosures,
floor-standing enclosures and cubicles.
For details on the calculation of the dissipated power in the device zone, see page
D-80.
Thermal management
of switchboards
General