Siemens SINAMICS S120 Manual page 42

System overview
3.4 Derating factors as a function of installation altitude and ambient temperature
Built-in devices, Chassis-2 format
At installation altitudes > 2000 m above sea level, it must be taken into account that the air
pressure, and therefore air density, decreases as the height increases. As a consequence, in
addition to the reduced cooling effect, the insulating capability of the air is also reduced.
As a result of the lower cooling effect, on the one hand, the ambient temperature must be
reduced, and on the other hand, the power loss in the chassis unit must also be reduced by
decreasing the output current; whereby ambient temperatures less than 40 °C can be
factored in as countermeasure for compensation.
The following table shows the permissible output currents as a function of installation
altitude and ambient temperature (the permissible compensation between installation
altitude and ambient temperatures of < 40 °C – supply air temperature at the air inlet of the
chassis unit – is taken into account in the specified values).
The values apply under the precondition that a cooling air flow through the devices is
ensured as specified in the technical specifications.
As a further measure at installation altitudes of 2000 m and 5000 m, the use of an isolating
transformer is required to reduce transient overvoltages in accordance with EN 61800-5-1.
Built-in devices in the Chassis-2 format and the associated system components are rated for
an ambient temperature of 45 °C and installation altitudes up to 1000 m above sea level.
The output current must be reduced for ambient temperatures > 45 °C. Ambient
temperatures above 60 °C are not permissible.
Table 3- 3 Current derating for built-in units Chassis-2 as a function of ambient temperature (air intake temperature at the
air inlet of the built-in devices) and installation altitude
Installation alti-
tude above sea
level in m
20 °C
0 ... 1000 100%
... 1500 100%
... 2000 100%
... 2500 100%
... 3000 100%
... 3500 100%
... 4000 100%
... 4500 100%
... 5000
40
Current derating factor (in % of rated current)
at an ambient temperature (supply air temperature) of
25 °C 30 °C
100% 100%
100% 100%
100% 100%
100% 100%
100% 100%
100% 100%
100% 96%
97%
98%
35 °C 40 °C 45 °C
100% 100% 100%
100% 100% 98%
100% 100% 93%
100% 96%
99%
Equipment Manual, 06/2020, 6SL3097-5AE00-0BP3
50 °C 55 °C 60 °C
83% 69% 54%
81% 67% 52%
78% 65% 50%
Air-cooled chassis power units