Siemens SINAMICS PERFECT HARMONY GH180 Function Manual page 295

Type 2 Pre-charge circuit design
Type 2 pre-charge uses contactor M2 in addition to M1. An additional pre-charge secondary
winding is employed to be able to reach full rated voltage of the transformer primary and cell
connected secondaries.
Figure 8-17
Sequence of Operation
1. To start pre-charge, DriveReadyToPrecharge_I must be
true. PrechargeStartEnable_O is set true to start the sequence.
2. M2 is closed to begin resonance by connecting a capacitor in series with the
secondary. PrechargeM2Close_I is set equal to true.
3. When the input primary voltage reaches the max phase voltage set by the parameter
"Precharge voltage level" (2634), M2 contactor is commanded to
open.PrechargeM2Close_I is set equal to false.
4. The M2 acknowledge comes back, PrechargeM2CloseAck_O is set equal to true. M1
contactor is commanded to close, PrechargeM1Close_I is set equal to true.
NXGPro+ Control Manual
Operating Manual, A5E50491925A
Type 2 Pre-charge Component Connections
Advanced Operating Functions
8.18 Pre-charge using SOP
293