Siemens SINAMICS S120 Function Manual page 287

Figure 6-28
When the converter retrieves the motor from the line supply, initially contactor K2 is opened,
and after the excitation time has expired, contactor K1 is closed. The drive converter then
connects to the rotating motor and the motor is fed from the drive converter.
Features
The function is characterized by the following features:
● Operation without Voltage Sensing Module (VSM10)
Activating the function
To be able to activate the function, the following requirements must be satisfied:
● Contactor K2 must be designed for switching an inductive load.
● Contactors K1 and K2 must be interlocked against closing at the same time.
● The "flying restart" function must be activated (p1200).
Activation of the bypass function without synchronization (p1260 = 3) can be triggered via the
following signals (p1267):
● Bypass using control signal (p1267.0 = 1):
Activation of the bypass is triggered by a digital signal (p1266) e.g. from a higher-level
control system. If the digital signal is withdrawn, a changeover to converter operation is
initiated once the bypass delay time (p1263) has expired.
● Bypass at speed threshold (p1267.1 = 1)
Once a certain speed is reached, the system changes over to bypass, i.e. the converter is
used as a start-up converter. The precondition for activating the bypass is that the speed
setpoint is greater than the bypass speed threshold (p1265).
Switching back to converter operations is initiated by the setpoint (at input of ramp
generator, r1119) falling below the bypass speed threshold (p1265). The setpoint >
comparison value condition prevents the bypass from being reactivated straight away if the
actual speed is still above the bypass speed threshold (p1265) after switching back to
converter operations.
Drive functions
Function Manual, 06/2019, 6SL3097-5AB00-0BP2
Circuit example, bypass without synchronization
Vector control
6.22 Bypass
285