Synchronous Transfer; Synchronous Transfer_Introduction (L29) - Siemens SINAMICS PERFECT HARMONY GH180 Function Manual

8.17

Synchronous Transfer

8.17.1

Synchronous Transfer_Introduction (L29)

The synchronous transfer feature is used to avoid line-start mechanical and electrical strain in
constant-speed applications. The VFD soft starts the motor(s), and then the control matches line/
load electrical characteristics, allowing "bumpless" synchronous transfer.
Note
Additional hardware requirements
Synchronous transfer requires hardware in addition to the drive: output reactor and switchgear.
Siemens recommends using a PLC for multi-motor applications.
• Up transfer is the process of transferring a VFD-controlled motor to the line, and then
decoupling the motor from the drive.
• Down transfer is the process of transferring a line-energized motor to VFD control, and then
decoupling the motor from the line.
To achieve successful up and down transfers, the output voltage of the VFD must match or
exceed the amplitude of the line. If the line is unstable with frequency and/or voltage variations,
the VFD may not be able to synchronize, and therefore transfer is inhibited.
Note
Applications that use a synchronous motor
In transfer applications where a synchronous motor is used, the VFD must have control of the
field supply with smooth transition of the field control to an external source via a PLC.
Note
Control modes
Synchronous up and down transfer is not available in control modes V/Hz or OLTM.
Fire Hazard
Improper phase sequence may result in a synchronous transfer related VFD fault, which could
lead to shorted phase to phase connections on the MV source and become a fire hazard. This
may result in death, serious injury or damage to equipment.
Ensure that input and output phases are properly wired to match the sequence.
NXGPro+ Control Manual
Operating Manual, A5E50491925A
WARNING
Advanced Operating Functions
8.17 Synchronous Transfer
257