Siemens SINAMICS G120 Operating Instructions Manual page 34

Installing
4.4 Connecting the inverter
IT supplies are fully isolated from the protective earth system, usually by an isolating
transformer. It should be noted, however, that a protective earth is still provided.
Inverters with built-in filters or external filters must not be used with IT supplies.
If the inverter connected to an IT supply is required to remain operational if an output phase
is connected to ground, then an output reactor must be fitted to prevent overcurrent tripping.
The probability of overcurrent tripping without output reactor increases with the size of the IT
supply.
Operation of the inverter without a protective earth is not permitted under any circumstances.
32
WARNING
Operating Instructions, 01/2011, FW 4.4, A5E02999804A AB
SINAMICS G120C Inverter