F30003 Siemens — DC Bus Undervoltage Fault
At a glance
- Severity
- FAULT STOP
- Domain
- DRIVES
- Reference standard
- IEC 61800-5-1
- Product / context
- Power unit DC link undervoltage
What it means
DC bus undervoltage on the drive. The DC bus voltage level has dropped below the minimum allowed threshold. This can be caused by a mains voltage dip, a momentary power interruption, a faulty capacitor precharge circuit, or degraded DC bus capacitors.
Probable causes
- Mains voltage dip or micro-interruption
- DC bus capacitor precharge circuit faulty
- DC bus electrolytic capacitors degraded or dried out
- Three-phase supply with missing or unbalanced phase
Reference values
| undervoltage trip V | {"230V_class":200,"400V_class":370,"690V_class":640} |
|---|---|
| dc bus capacitor check | Measure DC bus discharge time: with drive off, voltage must drop below 50V within < 5 min. If it drops too fast (< 30s), capacitors are degraded. |
Where to start
Does the fault occur at drive power-up or during operation?
Full guided diagnosis in the app
The diagnostic tree for this fault has 7 guided steps with measurements, checks and resolutions. You'll find it in ElectraIQ, one of the five IndexOS apps: free, works offline.
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The same fault on other brands
More Siemens codes
- F07900 — Motor Stall / Locked Rotor
- F30001 — Overcurrent Fault
- F30002 — DC Bus Overvoltage Fault
- F30004 — Drive Overtemperature Fault
- F30021 — Ground Fault
- 0xE900 / 0xE901 — IO-Link communication lost (device not responding)
- 6EP1333-4BA00 — Unstable PLC power supply — cyclic restarts
- 6ES7521-1BL00-0AB0 — Digital input module — input not reading (stuck at 0)