Key takeaways
A tripped Sinamics drive stops your spindle, axis, conveyor, or pump until someone decodes the message and clears the real cause. This guide is for maintenance technicians, maintenance managers, and plant engineers working on Sinamics S120 and G120 drives who want a structured path from code to fix, without parts-swapping guesswork and without unsafe shortcuts.
Sinamics messages come in two main categories. A code starting with F is a fault: the drive executes a configured fault reaction (typically OFF1 ramp stop, OFF2 coast to stop, or OFF3 fast stop) and will not restart until the fault is acknowledged with the cause removed. Some faults additionally require a power cycle before they can be acknowledged.
A code starting with A is an alarm (warning): the drive keeps running and the message clears itself once the condition disappears. Treat alarms as free early warnings. An overtemperature alarm today is often the same fault trip next week, so investigate alarms during planned time instead of waiting for the forced stop.
The same drive event can appear in different places depending on the machine architecture. On CNC machines with a Sinumerik control, Sinamics faults propagate upward and appear as control alarms in the 300xxx range, with the underlying drive fault code embedded in the alarm text. If you work on CNC equipment, our guide to Sinumerik alarm codes and troubleshooting covers how those alarm number ranges map to the drive, PLC, and NC kernel.
On a standalone G120, you read faults directly on the BOP or IOP operator panel, over the fieldbus status words, or by going online with Startdrive in TIA Portal, which also gives you the full fault buffer and trace functions. On modular S120 systems, note which component reported the fault (Control Unit, power module, or sensor module), because that immediately narrows the physical location of the problem.
The most common troubleshooting mistake is resetting the fault, watching the machine run, and closing the job. Sinamics drives keep a fault buffer with the code, a timestamp, and a fault value (auxiliary information) for each event. That fault value is the difference between "overcurrent" and knowing which threshold tripped or which condition variant occurred.
The codes below are among the most frequently documented on S120 and G120 systems. Use them as patterns, then confirm the exact meaning in your manual.
| Code | Typical meaning | Likely causes | First check |
|---|---|---|---|
| F30001 | Power unit overcurrent | Output short or ground fault, mechanical jam, wrong motor data, ramp too aggressive | Megger motor and cable (disconnected from drive), check the mechanics for binding |
| F30002 | DC link overvoltage | Deceleration too fast for the regeneration path, braking resistor or chopper problem, high line voltage | Note whether it trips during decel; inspect braking resistor circuit and ramp times |
| F30003 | DC link undervoltage | Supply dips or sags, upstream contactor or infeed problem, loose power connections | Correlate trip times with other equipment starting; verify supply voltage at the input terminals |
| F30004 / F30024 | Overtemperature (heat sink / thermal model) | Blocked filters, failed fans, high cabinet ambient, sustained overload | Confirm fans spin and airflow is clear; measure cabinet temperature under load |
| F07900 | Motor blocked / stalled | Mechanical jam, brake not releasing, undersized drive for the load, wrong motor data | Rotate the load by hand where safe; verify the holding brake actually lifts |
| F07860 | External fault 1 | An external signal (interlock, sensor, PLC logic) commanded the fault; the drive itself is healthy | Trace the interlock chain and the PLC logic driving the external fault input |
Two of these deserve emphasis. Overcurrent diagnosis on a Sinamics follows the same discipline as on any VFD: prove the motor and cable are sound before suspecting the power unit, as detailed in our VFD overcurrent fault troubleshooting guide. And F07860 means something upstream told the drive to trip. If the PLC drives that input, check its diagnostics too; the process in our Siemens S7 PLC SF fault LED guide shows how to read the module diagnostic buffer that usually names the offending signal.
Faults in the F31xxx to F33xxx family come from the sensor module and point at the encoder or feedback path (the second digit typically identifies which encoder). Experienced troubleshooters check the cheap items first: connector seating at both ends, bent pins, cable damage in drag chains, shield termination, and coolant or oil ingress in the plugs.
Only after the cabling checks out should you suspect the encoder or the sensor module itself. Intermittent feedback faults that worsen with axis motion or vibration almost always mean cable or connector, not electronics. Feedback problems also masquerade as motor trouble, so it is worth knowing the broader servo motor failure symptoms before condemning any component.
When the drive reports Safe Torque Off (STO) active or a safety channel discrepancy, the drive is usually doing exactly what it was told. An emergency stop, an open guard door, a safety relay, or the fail-safe PLC dropped the safety circuit. Check the safety chain and both STO channels first; a discrepancy message often means one channel switched late because of a worn contact or wiring fault. Never bridge, jumper, or defeat STO, not even "just to test": it is a safety function, and bypassing it puts people at risk.
General safety applies to all drive work. Apply lockout/tagout, then wait the full discharge time marked on the drive before opening anything: the DC link capacitors hold a lethal charge after power off, and you must verify zero volts with a meter before touching terminals. Account for stored mechanical energy too (vertical axes held by brakes, chain and belt tension, pressurized hydraulics). This work belongs to qualified electricians only.
A fault that gets reset and forgotten will return. Log every occurrence as a downtime event with a cause code (for example "F30002, axis Y, during rapid decel"), and track MTBF and MTTR for the asset. Three F30004 trips in a month is not bad luck, it is a cooling problem waiting for a permanent fix such as filter schedules, fan replacement, or cabinet cooling upgrades.
This is also where drive faults connect to plant performance: every trip is an availability loss inside your OEE calculation, and the short recurring stops are usually the ones nobody writes down. Accurate loss data is what justifies the engineering hours to fix a chronic fault instead of resetting it forever.
Decoding a Sinamics fault is half the job; making sure the stop was captured, attributed, and permanently fixed is the other half. Fabrico is computer-vision-verified OEE plus closed-loop maintenance execution: cameras catch stops and micro-stops that manual logs and sensors miss, and maintenance work orders close the loop from detection to fix. If drive trips keep eating your availability and the paper log never tells the full story, book a Fabrico demo.
An F code is a fault: the drive executes a stop reaction (OFF1, OFF2, or OFF3) and must be acknowledged after the cause is removed. An A code is an alarm: the drive keeps running and the message self-clears when the condition disappears. Alarms are early warnings and worth investigating before they become faults.
First remove the cause, then acknowledge from the operator panel, via the fieldbus control word, through a configured digital input, or from Startdrive. Some faults require a full power cycle before they can be acknowledged. Always record the fault buffer, including timestamps and fault values, before resetting.
F30001 is a power unit overcurrent fault on S120 and G120 families. Common causes are a short or ground fault in the motor or cable, a mechanical jam, incorrect motor data, or overly aggressive ramp settings. Insulation-test the motor and cable with the drive disconnected before suspecting the power unit. Confirm the exact meaning and fault value in the fault list manual for your firmware.
F30002 is DC link overvoltage. During braking, the motor regenerates energy into the DC link, and if the braking resistor, chopper, or regenerative infeed cannot absorb it fast enough the voltage rises until the drive trips. Check the braking circuit, extend the deceleration ramp, or verify the drive's voltage limiting function is active.
No. Code numbering and exact meanings vary between families such as S120 and G120 and between firmware versions, and on Sinumerik machines the same event appears as a 300xxx control alarm. Always confirm the code, and especially its fault value, in the Sinamics fault list manual that matches your drive and firmware.
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