Siemens SINAMICS PERFECT HARMONY GH180 - Synchronous Transfer Operation for Synchronous Motors down Transfer Preconditions (L29); Synchronous Transfer Operation for Synchronous Motors up Transfer (L29)

controller. The external controller is a separate PLC for most applications and if the analog
control signal is a 4 to 20ma current loop.
NOTICE
Potential Circuitry Damage
4 to 20ma current loops cannot be switched without potentially damaging circuitry.
An intervening PLC can digitize the signals and retransmit the signal, facilitating the switching
function.
The PLC allows for monitoring and matching between an external 󹪝eld reference source and the
drive 󹪝eld reference source during transfer.
8.17.11 Synchronous Transfer Operation For Synchronous Motors Up Transfer (L29)
Up Transfer of Synchronous Motor
Up transfers are accomplished by taking the SM up to speed on the VFD to match the frequency
and then the phase of the line. This is accomplished the same as for an IM, by using the drive
input line frequency as a velocity reference. The main di󹪜erence comes after the
synchronization and when both contactors are closed simultaneously. At this point the 󹪝eld
control has to be transferred from the drive to an external 󹪝eld controller. When the 󹪝eld transfer
is complete, the drive contactor is opened and the drive coast-stopped to end the transition.
8.17.12 Synchronous Transfer Operation For Synchronous Motors Down Transfer
Preconditions (L29)
Down Transfer of Synchronous Motor
Down transfer with synchronous motor control transfers a motor running directly connected to
a power line to the control via the VFD. The VFD output is synchronized with the line connected
to the motor, not necessarily the input to the drive. The control utilizes the connection through
the VFD output contactor with the power devices disabled to synchronize the VFD to the line.
Once synchronized, the outputs of the power devices are enabled in synchronization with the
line so that there is little or no power 󹪞ow from the drive, and none back into the drive. A 2-
quadrant cannot absorb power.
Down transfer of synchronous motors not only involves the transfer of the stator voltage source
but also the transfer of the separate 󹪝eld exciter control. This adds a level of complexity to the
logic and control.
Down transfer of synchronous motors requires an external PLC or equivalent to control the
transfer and to provide the external 󹪝eld exciter reference when the motor is on the line.
Advanced Operating Functions
8.17 Synchronous Transfer
NXGPro+ Control Manual
266 Operating Manual, A5E50491925A