Type 3 Pre-Charge (Parallel Drives) (6Sr325) - Siemens SINAMICS PERFECT HARMONY GH180 Function Manual

Advanced Operating Functions
8.18 Pre-charge using SOP
5. The M1 acknowledge comes back, PrechargeM1CloseAck_O is set equal to true. Pre-
charge is complete, PrechargeComplete_I is set equal to true. The pre-charge request
must be removed, PrechargeStartEnable_O is set equal to false.
6. With the removal of the pre-charge request, the drive is now ready to
run. PrechargeDriveEnable_I is set equal to true.
Note
Pre-charge faults
The following conditions will result in a pre-charge fault:
• failure to follow the sequence
• failure to leave a minimum of 250 msec between receiving a response and issuing the
• removal of pre-charge start enable before the cycle completes.
All handshaking must follow the sequence of operation.
8.18.6

Type 3 Pre-charge (Parallel Drives) (6SR325)

Pre-charge in parallel drives, or other selected drives, is known as type 3 pre-charge. It may use
either an exciter controller or a fixed source with a resistive element instead of the resonant
capacitor, to increase the cell voltage gradually.
Pre-charge of this type requires that the input source, i.e. output of exciter power supply or
independent source, be rated with high enough voltage to reach the level set by the parameter
"Precharge voltage level" (2634) of rated input voltage under all conditions, without exceeding
the pre-charge trip voltage. Two input sources can be used, each is addressed according to its
constraints:
• Exciter power supply source In this case, a resistor may not be required. This depends on the
current needed from the source to charge the capacitors and also on any stability issues with
the current loop of the exciter power supply. The only real requirement is that it is able to
charge the cell capacitors in the timeframe allotted.
• Independent / constant source Contactor status M2 represents the contactor status in
series with the exciter power supply and the enable signal to the exciter power supply. In this
case, the M2 contactor is connected to the pre-charge secondary winding through the series
resistor.
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