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S7-300 Automation System, Hardware and Installation: CPU 31xC and CPU 31x
A5E00105492-03
5-13
2YHUYLHZRIW\SLFDOFDELQHWW\SHV
The table below gives you an overview of the commonly used cabinet types. It
shows you the applied principle of heat dissipation, the calculated maximum power
loss and the degree of protection.
Table 5-5 Types of cabinet
2SHQFDELQHWV &ORVHGFDELQHWV
Enclosed
ventilation via
natural convection
Increased
enclosed
ventilation
Natural convection Forced convection
with rack fan,
improvement of
natural convection
Forced convection
with heat
exchanger, internal
and external
auxiliary ventilation
Mainly inherent
heat dissipation,
with a small portion
across the cabinet
wall.
Higher heat
dissipation with
increased air
movement.
Heat dissipation
only across the
cabinet wall; only
low power losses
permitted. In most
cases heat
concentration
develops at the top
of the cabinet
interior.
Heat dissipation
only across the
cabinet wall.
Forced convection
of the interior air
improves heat
dissipation and
prevention of heat
concentration.
Heat dissipation by
heat exchange
between heated
internal air and
cool external air.
The increased
surface of the
pleated profile of
the heat exchanger
wall and forced
convection of
internal and
external air provide
good heat
dissipation.
Degree of
protection IP 20
Degree of
protection IP 20
Degree of
protection IP 54
Degree of
protection IP 54
Degree of
protection IP 54
Typical power dissipation under following marginal conditions:
• Cabinet size: 600 mm x 600 mm x 2,200 mm
• Difference between the outer and inner temperature of the cabinet is 20 °C (for other temperature
differences refer to the temperature charts of the cabinet manufacturer)
up to 700 W up to 2,700 W (with
fine filter up to
1,400 W)
up to 260 W up to 360 W up to 1,700 W
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