Fundamental Principles and System Description
Engineering Information
SINAMICS Engineering Manual – November 2015
Ó Siemens AG
214/528
The coolant temperature setpoint T
set
is thus calculated from the measured ambient temperature T
a
and the
measured relative air humidity Φ according to the diagram below.
Irrespective of the input quantities "ambient temperature" and
"relative air humidity", the minimum coolant temperature
setpoint should be approximately 10°C. It is absolutely
essential to limit the maximum setpoint to 50°C. With high
relative air humidity, however, this means that the maximum
ambient temperature is limited to 46°C.
Coolant temperature control solely as a function of ambient temperature
It is basically not essential to measure the relative air humidity in order to calculate the temperature difference ΔT
L
that must be added to the ambient temperature T
a
so as to ensure that the setpoint T
set
for the coolant temperature
always remains higher than the dew point of the ambient air. In this case it is necessary to know the maximum
potential relative humidity of the ambient air.
If the maximum potential relative air humidity is assumed to be between 95 % and 100 % in the worst-case scenario,
then the diagram on the previous page (which specifies the temperature difference ΔT
L
as a function of relative air
humidity Φ) indicates that the temperature difference ΔT
L
must be set to the value ΔT
L
= +4°C. The coolant
temperature setpoint T
set
is then calculated solely on the basis of the measured ambient temperature T
a
as shown in
the diagram below. When the relative air humidity is low, however, this method results in a significantly higher coolant
temperature setpoint than the method previously described that takes in account both, the measured ambient
temperature T
a
and the measured relative air humidity Φ.
Irrespective of the input quantity "ambient temperature", the
minimum coolant temperature setpoint should be
approximately 10°C. It is absolutely essential to limit the
maximum setpoint to 50°C. This means, however, that the
maximum ambient temperature is limited to 46°C.
1.16.7 Information about cooling circuit configuration
Permissible current as a function of the coolant temperature and ambient temperature
Liquid-cooled SINAMICS S120 units in Chassis format are rated for a coolant inlet temperature and an ambient
temperature of 45 °C, and for an installation altitude of up to 2000 m above sea level. Current derating must be
applied if liquid-cooled SINAMICS S120 units in Chassis format are operated at coolant inlet temperatures and/or
ambient temperatures in excess of 45 °C. It is not permissible to operate liquid-cooled SINAMICS S120 units in
Chassis format at coolant inlet temperatures and ambient temperatures in excess of 50 °C. The following charts
indicate the permissible current as a function of the coolant inlet temperature and the ambient temperature.
Note:
The derating factors of the two charts must not be multiplied. For dimensioning purposes, it is the least favorable
derating factor of the two charts that applies which means that a total derating factor of 0.9 is applicable under worst-
case conditions.
Current derating as a function of coolant inlet temperature Current derating as a function of ambient temperature
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