Siemens SINAMICS S120 Function Manual page 246

Vector control
4.25 Bypass
The motor is transferred to the line supply
(the drive converter controls contactors K1 and K2):
● The initial state is as follows: Contactor K1 is closed, contactor K2 is open and the motor
● The control bit "bypass command" (p1266) is set (e.g. from the higher-level automation).
● The bypass function sets the control word bit "synchronizing" (r1261.2).
● Since the bit is set while the converter is running, the "Transfer motor to supply"
● After the motor has been synchronized to the line frequency, line voltage and line phase,
● The bypass mechanism evaluates this signal and closes contactor K2 (r1261.1 = 1). The
● After contactor K2 has signaled back the "closed" state (r1269[1] = 1), contactor K1 is
● If the on command is withdrawn in this phase, the drive converter changes into the basic
Retrieving the motor from supply mode functions the same but in reverse:
At the start of the process, contactor K2 is closed and 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
● After the motor has been synchronized to the line frequency, line voltage and line phase,
● The bypass mechanism evaluates this signal and closes contactor K1. The signal is
● Once contactor K1 has reported "closed" status, contactor K2 is opened and the motor
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is fed from the drive converter.
synchronization process is started.
the synchronizing algorithm reports this status (r3819.2).
signal is internally evaluated - BICO wiring is not required.
opened and the drive converter inhibits the pulses. The drive converter is in the "hot
standby" state.
standby state. If the appropriate contactors are being used, the drive converter is isolated
from the line supply and the DC link is discharged.
interprets this as a command to retrieve a motor from the supply and to take it over.
the synchronizing algorithm reports this status.
internally evaluated - BICO wiring is not required.
returns to operation on the drive.
Function Manual, (FH1), 01/2013, 6SL3097-4AB00-0BP3
Drive functions