Siemens SINAMICS S120 Manual page 258

Cabinet Modules
5.8 Auxiliary Power Supply Modules
Note
Supply infeed
The same rated voltage must be fed into the supply infeed of the Auxiliary Power Supply
Module as for the connected Cabinet Modules, as the voltage fed into the Auxiliary Power
Supply Module supplies the entire system with auxiliary voltage via the auxiliary power
supply system.
If a different voltage than that of the connected Cabinet Modules is fed in, there is a risk of
an insufficient energy supply to the device fans or too high a voltage, which can cause
damage to the system.
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Cabinet Modules
Manual, 03/2013, A5E03263538A