Undervoltage
Vacon · NX All-in-One Application
What does 9 mean?
The DC-link voltage is lower than its operational limits during run, specifically subcode S1 indicates the DC-link is too low. This condition can be caused by an insufficient supply voltage, an internal AC drive fault, a defective input fuse, or an external charge switch that is not closed. Subcodes S2 (No data from power unit) and S3 (Undervoltage control supervision) also relate to general undervoltage conditions.
Common Causes
- Input voltage to the drive is below the acceptable operating range (e.g., P4-01).
- Low mains voltage condition.
- Faulty AC input power supply.
- Loose or damaged power wiring to the drive.
- Internal power supply regulation failure.
Repair Steps & Checklist
Click steps to track your progress.
- 1
If a temporary supply voltage interruption occurred, reset the fault and attempt to restart the drive.
- 2
Measure the supply voltage at the drive's AC input terminals (L1, L2, L3) — verify it is within the specified nominal voltage range (e.g., 380-480VAC for 400V drives).
- 3
Inspect all input fuses for continuity using a multimeter and ensure their current rating is appropriate for the drive.
- 4
Verify the external charge switch, if present, is correctly closed and its contacts are making good connection.