Siemens SINAMICS PERFECT HARMONY GH180 Function Manual page 314

Advanced Operating Functions
8.19 Pre-charge using Dedicated I/O
Sequence of Operation
MV is maintained throughout pre-charge, therefore faulted cells are reset and bypassed once the
drive is issued a reset, and if fast bypass is enabled. Only fault messages will display on the
keypad or Drive Tool, there is no message to reset the drive, but reset is required. SOP
flag PrechargeNeedsReset_I becomes true when pre-charge is in this state. The flag is reset
once the drive receives a fault reset. You can use this as an indicator that a fault exists, but do not
use to directly issue a fault reset.
1. Drive starts with pre-charge state machine set at pre-charge faulted, and all contactors are
commanded open. When all conditions are met, it passes through pre-charge initialization.
2. After initializing all contactors and flags, it advances to pre-charge ready. M1 is checked to
ensure it is open, and the state controller waits for the pre-charge start command.
3. Drive is ready to pre-charge with all conditions met. DriveReadyToPrecharge_I is true.
4. To start pre-charge, set the StartCellPrecharge_O flag true through the SOP. This starts
the pre-charge state machine.
5. M1 is confirmed open, M2 is commanded to close.
6. With M2 closed, the drive input voltage climbs. The drive waits until 90% of rated voltage is
achieved. The pre-charge capacitors provide a resonant circuit with the input inductance
allowing a lower secondary input voltage to charge to 90% of rated drive input voltage
through the secondary.
7. When the input voltage reaches 60% of rated, cell diagnostics begins and medium voltage is
considered 'OK'.
8. Once the input voltage reaches 90% of rated input voltage (plus tap setting), M3 is
commanded to close to dampen the resonance and maintain the voltage. Failure to connect
the resistors could result in an overvoltage condition on the cells.
9. M3 is closed, M2 is commanded open.
10.M2 is open, M4 is commanded closed. M4 provides holding voltage with no resistance drop.
This lowers the power rating requirement on the pre-charge damping resistors. If parameter
ID 2633 "Prechrg M4 Holdoff time" is non-zero, then the M4 contactor will not be
commanded closed until after the hold-off time delay.
11.M4 is closed, M3 is commanded open. This sequence must complete in 30 seconds or a
timeout will occur resulting in a pre-charge fault.
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