Siemens Sinamics G120P Operating Instructions Manual page 413

Switchover procedure between line and inverter operation
When switching over to line operation, contactor K1 is opened after the inverter pulses have
been inhibited. The system then waits for the de-energization time of the motor and then
contactor K2 is closed so that the motor is connected directly to the line supply.
When the motor is switched to the line supply, an equalizing current flows that must be taken
into account when the protective equipment is selected and dimensioned.
When switching over to inverter operation, initially contactor K2 must be opened and after
the de-excitation time, contactor K1 is closed. The inverter then captures the rotating motor
and the motor is operated on the inverter.
Inverter cabinet units
Operating Instructions, 12/2014, A5E32923362A
7.7 Application-specific functions
Functions
413