Siemens SINAMICS S120 Function Manual page 284

Vector control
6.22 Bypass
● Since the bit is set while the converter is running, the "Transfer motor to supply"
synchronization process is started.
● After the motor has been synchronized to the line frequency, line voltage and line phase, the
synchronizing algorithm reports this status (r3819.2).
● The bypass mechanism evaluates this signal and closes contactor K2 (r1261.1 = 1). The
signal is internally evaluated - BICO wiring is not required.
● After contactor K2 has signaled back the "closed" state (r1269[1] = 1), contactor K1 is
opened and the drive converter inhibits the pulses. The drive converter is in the "hot
standby" state.
● If the on command is withdrawn in this phase, the drive converter changes into the basic
standby state. If the appropriate contactors are being used, the drive converter is isolated
from the line supply and the DC link is discharged.
Retrieving the motor from power system operation
Retrieving the motor from mains operation is done in the following order:
● Initial state:
– Contactor K2 is closed.
– Contactor K1 is opened.
● The "Command bypass" control bit is canceled (e.g. by the higher-level automation).
● The bypass function sets the control word bit "synchronizing".
● Pulses are enabled. Since "Synchronize" is set before "Pulse enable", the converter
interprets this as a command to retrieve a motor from the supply and to take it over.
● After the motor has been synchronized to the line frequency, line voltage and line phase, the
synchronizing algorithm reports this status.
● The bypass mechanism evaluates this signal and closes contactor K1. The signal is
internally evaluated - BICO wiring is not required.
● Once contactor K1 has reported "closed" status, contactor K2 is opened and the motor
returns to operation on the drive.
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Function Manual, 06/2019, 6SL3097-5AB00-0BP2
Drive functions