Siemens SINAMICS S150 NEMA, Operating Instructions Manual

Page: 615 / 862

Functions, monitoring and protective functions
9.4 Extended functions
Enclosed Drives
Operating Instructions, 12/2018, A5E36652151A
613
9.4.2.1 Bypass with synchronizer with degree of overlapping (p1260 = 1)
Description
The "Bypass with synchronization with degree of overlapping" is used for drives with a low
moment of inertia. These are drives for which their speed would sink very fast when the K1
contactor opens.
When "bypass with synchronization with overlap (p1260 = 1)" is activated, the motor is
transferred, synchronized to the line supply and is also retrieved again. During the change-
over, both contactors K1 and K2 are closed at the same time for a period (phase lock
synchronization).
This bypass type requires a VSM10 Voltage Sensing Module that measures the line voltage
for the drive to be synchronized.
A reactor is used to decouple the converter from the line supply; the uk value for the reactor
is 10% (±2).
Figure 9-21 Typical circuit diagram for bypass with synchronizer with degree of overlapping
Note
As a result of the overlap, when synchronizing back to the converter, the DC link voltage can
increase; in the worst case scenario this can result in a fault trip. It is possible to activate an
overvoltage protection function, which, when a Vdc max threshold (r1242) is reached, the
pulses are inhibited; as a consequence, the DC link voltage stops increasing. When the
pulses are inhibited, the motor coasts down, which is why it must be restarted on the fly.
As a consequence, overvoltage protection is only active if the "Flying restart" function was
activated (p1200 = 1).