Code A00912: Vdc-min Controller active
Issue Description & Safety Warning
The Siemens SINAMICS G120 CU240S Drive has triggered a critical Vdc-min Controller active alarm. Immediate attention from a qualified operator or maintenance technician is required to prevent secondary damage to the equipment or spoiled parts during the manufacturing cycle. Always ensure standard safety and LOTO procedures are followed before accessing electrical cabinets.
Official Troubleshooting Steps
Reaction: NONE Acknowledge: NONE Cause: Vdc min controller will be activated if DC-link voltage (r0026) falls below minimum level (P2172). The kinetic energy of the motor is used to buffer the DC-link voltage, thus causing deceleration of the drive! So short mains failures do not necessarily lead to an undervoltage trip. Remedy:
Source: SINAMICS G120 Control Units CU240S Faults and Alarms (Edition 05/2007)
Last reviewed: 2026-07-01 · Verified against the manufacturer’s official documentation.
About Siemens SINAMICS G120 CU240S Drive Alarms
Siemens controllers include extensive self-diagnostics that flag or halt the machine when a fault is detected. Error code A00912 on the SINAMICS G120 CU240S Drive identifies one specific fault condition — its documented cause and the official corrective steps are listed above, sourced from Siemens's service documentation. Always confirm against the manual for your exact machine configuration and follow LOTO procedures before servicing.
Complete Alarm List: 108 Siemens SINAMICS G120 CU240S Drive codes.
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