Derating Factors As A Function Of Installation Altitude And Ambient Temperature - Siemens SINAMICS S120 Manual

3.4 Derating factors as a function of installation altitude and
ambient temperature
Chassis format units
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. This reduces the
cooling effect as well as the insulating strength of the air.
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.
Chassis units and the associated system components are rated for an ambient temperature of
40 °C and installation altitudes up to 2000 m above sea level.
At ambient temperatures > 40 °C, the output current must be reduced. Ambient
temperatures above 55 °C are not permissible.
Table 3- 2 Current derating for chassis units as a function of ambient temperature (air intake temperature at the air inlet
of the chassis unit) and installation altitude
Installation altitude
above sea level in m
0 ... 2000
... 2500
... 3000
... 3500
... 4000
... 4500
... 5000
Air-cooled chassis power units
Equipment Manual, 06/2020, 6SL3097-5AE00-0BP3

3.4 Derating factors as a function of installation altitude and ambient temperature

Current derating factor (in % of rated current)
at an ambient temperature (supply air temperature) of
20 °C 25 °C
100% 100% 100%
100% 100% 100%
100% 100% 100%
100% 100% 100%
100% 100% 96.3%
100% 97.5%
98.2%
30 °C 35 °C 40 °C
100% 100%
100% 96.3%
98.7%
System overview
45 °C 50 °C
93.3% 86.7% 80.0%
55 °C
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