Type 2 (Open) Pre-Charge (6Sr325) - Siemens SINAMICS PERFECT HARMONY GH180 Function Manual

Advanced Operating Functions
8.18 Pre-charge using SOP
6. The M1 acknowledge comes back, PrechargeM1CloseAck_O is set equal to true. M3
contactor is commanded to open, PrechargeM3Close_I is set equal to false.
7. The M3 acknowledge comes back, PrechargeM3CloseAck_O is set equal to false. Pre-
charge is complete, PrechargeComplete_I is set equal to true. The pre-charge request
can be removed, PrechargeStartEnable_O is set equal to false.
8. After the pre-charge request is removed, the drive is now able 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.
8.18.5

Type 2 (Open) Pre-charge (6SR325)

Type 2 pre-charge uses a resonant circuit. Type 2 pre-charge avoids inrush into the cells; it
does not prevent input transformer inrush.
• This pre-charge type has a break-before-make (open) contactor sequence that does not
require close synchronization between the input voltage to the pre-charge circuit and the
input voltage to the transformer primary. Breaking the connection to the pre-charge source
after the cells are fully charged, causes the flux in the transformer to collapse almost
immediately. So, when the main input contactor is closed, the only inrush is for magnetizing
the transformer itself, and not for charging the cell capacitors.
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