Bypass Without Synchronization - Siemens SINAMICS S120 Function Manual

Vector control
5.22 Bypass
5.22.4

Bypass without synchronization

Description
When the motor is transferred to the line supply, contactor K1 is opened (after the drive
converter pulses have been inhibited); the system then waits for the motor de-excitation time
and then contactor K2 is closed so that the motor is directly connected to the line supply.
Because the motor is not synchronized when it is connected to the line supply an
equalization current flows. This must be taken into account when designing the protective
equipment (refer to the diagram, "Circuit example, bypass without synchronization"). This is
why this type of bypass is only suitable for drives with a low power rating.
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.
A voltage sensing module VSM10 is not required for this type of bypass.
In this case, contactor K2 must be designed/selected to be able to switch inductive loads.
Contactors K1 and K2 must be interlocked so that they cannot simultaneously close.
The "flying restart" function must be activated (p1200).
Figure 5-29
290
Circuit example, bypass without synchronization
Function Manual, 11/2017, 6SL3097-4AB00-0BP5
Drive functions