4. To start pre-charge, set the StartCellPrecharge_O ag true through the SOP. This
starts the pre-charge state machine.
5. M1 is conrmed 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/ holding resistors. If
parameter ID 2633 "Prechrg M4 Holdo time" is non-zero, then the M4 contactor will not be
commanded closed until after the hold-o 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.
12.The drive then waits for cell diagnostics to complete. If a cell is faulted, pre-charge waits for
a fault reset. The fault reset only acknowledges the fault and cell diagnostics exits so that pre-
charge can continue. Any faulted cells will be bypassed on exit if bypass is enabled.
Note
Cell Faults
A detected cell fault will display on the keypad. No other indication is given that a reset is
required.
The drive trips if any of the following conditions occur:
• overvoltage fault
• cell under-voltage fault
• input protection fault
• pre-charge is aborted
• MV falls below 60%, as read through the input attenuators.
The drive waits until the cell fault is reset.
Note
Fatal Fault SOP Flag
Any cell fault is a fatal fault and will set the FatalFault_I SOP ag.
Do not use this ag to:
• remove the pre-charge enable ag, StartCellPrecharge_O
• set the MainInputVoltageDisable_O ag
Doing so during pre-charge will abort pre-charge with a pre-charge fault.
Advanced Operating Functions
8.19 Pre-charge using Dedicated I/O
NXGPro+ Control Manual
Operating Manual, A5E50491925A 307
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