The Down Transfer State machine consists of the following four states. It uses the same
handshaking ags as with a reactor, except that the line contactor acknowledge ag is ignored.
Table 8-3 Down Transfer States
STATE VALUE*
A – TRANSFER_INIT 0
B – WAITING_FOR_FREQUENCY_LOCK 1
D – WAITING_FOR_CONTACTOR_OPENING 5
E – TRANSFER_COMPLETE 6
* Value is the value of the state machine variable for plotting purposes.
Associated Parameters for Synchronous Transfer without Reactor
These parameters are used to select the operation with no output reactor and to set the
thresholds for detecting the line contactor status for up transfer and down transfer.
• "Down Transfer Threshold" (ID 2772) – voltage drop when the line contactor opens
• "Up Transfer Threshold" (ID 2762) – current instability when the line contactor closes
• "Sync Transfer Type" (ID 2775) – operation with or without reactor
8.17.6 Synchronous Transfer Operation For Induction Motors Up Transfer (L29)
Up Transfer of Induction Motor
Up transfer takes the motor up to speed on the VFD to match the frequency of the line, once the
drive software receives the "Up Transfer Request". The drive software uses the drive input line
frequency as a velocity reference. Once the frequency is matched the phase also needs to be
matched with a predetermined leading phase to ensure the power ow is out of the VFD while
the line contactor is closed. To match the phase with a predetermined leading phase, the drive
software uses the line frequency and phase information from the input Phase Locked Loop (PLL)
and the output phase information from the output PLL to determine a vernier adjustment to the
frequency that is added to the velocity command. When the synchronization is complete, the
drive contactor is opened and the drive coast-stopped to end the transition.
The procedures for up transfer setup are carried out during the commissioning process.
Advanced Operating Functions
8.17 Synchronous Transfer
NXGPro+ Control Manual
262 Operating Manual, A5E50491925A
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