Siemens SINAMICS PERFECT HARMONY GH180 Function Manual page 282

Advanced Operating Functions
8.17 Synchronous Transfer
13.When cell diagnostics is complete, M4 is commanded to open, resulting in a drop in input
voltage, although the cell capacitors are completely charged.
Note
Pre-charge in Service Mode
If Service Mode is selected, pre-charge completes at this point with M4 closed and MV stays
on through the pre-charge source.
14.M4 is open, M1 is enabled to close through two separate digital outputs: M1 close permissive
(M1 DOUT) on the system interface board and Precharge Complete M1 Close (DO-9) on user
I/O board #1.
15.The drive waits for the M1 contactor to close, via the digital input for the M1 Acknowledge
(DI-2E). The M1 contactor closes to prevent discharge of the cell capacitors, and must be
closed before a low cell bus voltage alarm is received.
16.Once the M1 acknowledge is received, pre-charge is complete and the drive is connected to
the MV source and ready to run. The pre-charge state machine is exited and the exit state is
recorded in the event log along with all other recorded pre-charge events in the sequence.
Note
The drive run is inhibited until pre-charge completes successfully.
On a successful pre-charge, the state machine remains in PC_COMPLETE until reset. It will cycle
back to pre-charge faulted (without fault) to begin again.
See also
Pre-charge using Dedicated I/O (Page 269)
Type 4 Pre-charge (resonant-open transfer-capacitors only) (Page 269)
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NXGPro+ Control Manual
Operating Manual, A5E50491925A