Altivar ATV320 Fault Codes: What Do OCF, ObF, OLF and nSt Mean?
What ATV320 codes OCF, ObF, OLF, PHF, SCF and nSt mean, their likely cause, first check and how to clear them, based on the official Schneider manual.
What do OCF and ObF mean on an ATV320 display? OCF is overcurrent, ObF is DC bus overvoltage and OLF is motor overload. nSt is not a fault: the drive is in freewheel stop, which usually means an assigned digital input is de-energised. The tables below are written in our own words from the Schneider Electric ATV320 programming manual (NVE41295.06, 04/2025, Diagnostics and Troubleshooting, page 402 onwards). They apply to the ATV320 series only; the remedy for the same code can differ on other Altivar series.
Before touching the drive
- Disconnect all power, including external control power, and lock the disconnects open.
- Wait 15 minutes for the DC bus capacitors to discharge. The drive LEDs do not show that the DC bus is dead.
- Measure the DC bus voltage between PA/+ and PC/-. It must be below 42 Vdc.
- If the voltage does not fall, do not run or repair the drive and contact your Schneider Electric representative.
These steps come from the fault clearing procedure in the manual. Work on the power circuit must be done by qualified electrical staff.
Most common ATV320 fault codes
| Code | Meaning | Probable cause | First check |
|---|---|---|---|
| OCF | Overcurrent | Wrong SET or DRC settings, high inertia or load, mechanical locking | Parameters, motor/drive/load size and the mechanism. If needed, lower current limit CLI and raise the switching frequency |
| ObF | DC bus overvoltage | Braking too sudden, driving load, high supply voltage | Extend the deceleration time, add a braking resistor if needed, enable BRA if it suits the application, measure the supply |
| OLF | Motor overload | Excessive motor current | Motor thermal protection setting and motor load; wait for the motor to cool |
| OHF | Drive overheating | Drive temperature too high | Motor load, drive ventilation and ambient temperature; wait for the drive to cool |
| TJF | IGBT overheating | Drive overheated | Load/motor/drive size; reduce the switching frequency and let it cool |
| OSF | Mains overvoltage | Supply voltage too high or disturbed | Measure the supply voltage |
| USF | Mains undervoltage | Supply too low or a transient dip | Voltage and the USB- menu settings |
| PHF | Input phase loss | Wrong supply, blown fuse, missing phase, three-phase drive on a single-phase supply, unbalanced load | Power connection and fuses. This protection only works with the drive on load |
| OPF1 | Single output phase loss | One phase missing at the drive output | Connections from the drive to the motor |
| OPF2 | Output phase loss | Motor not connected or too small, output contactor open, unstable motor current | Connections; with an output contactor set OPL = OAC. UFR, UNS, NCR values and auto-tuning (TUN) |
| SCF1 | Motor short circuit | Short circuit or ground fault at the drive output | Motor cable and insulation; if needed motor chokes, TTR time, speed loop and brake settings |
| SCF3 | Ground short circuit | High earth leakage at the output with parallel motors | Cable and insulation; reduce the switching frequency |
| SCF4 | IGBT short circuit | Power component fault | Schneider Electric support |
| SCF5 | Motor short circuit | Short circuit at the drive output | Cable and insulation, then Schneider Electric support |
| SOF | Motor overspeed | Instability, driving load, Run command before the contactor closes; the threshold is 110 % of TFR | Gain and stability, braking resistor, sizing. TFR should be at least HSP × 1.1 |
| TNF | Auto-tuning error | Unsuitable motor, motor not connected or not stopped | Motor match and connection; keep the output contactor closed during tuning with the motor stopped |
| SSF | Torque limitation error | Switch to torque or current limit | Mechanical problems; TOL- and TID- menus |
| SPF | Encoder feedback loss | No signal on the pulse input or encoder | Wiring, encoder settings and the encoder itself |
Communication and configuration codes
| Code | Meaning | First check |
|---|---|---|
| CNF | Fieldbus module interruption | EMC, wiring, time-out; replace the option module if needed |
| COF | CANopen interruption | Bus and time-out |
| SLF1 | Modbus interruption | Bus and time-out |
| SLF2 | PC software connection lost | Connecting cable and time-out |
| SLF3 | Graphic or remote display interruption | Terminal connection and time-out |
| ILF | Internal link to option module lost | EMC and connections; replace the module if needed |
| CFF | Incorrect configuration | Module or control block may have changed; factory settings or a valid backup |
| CFI / CFI2 | Invalid configuration or transfer error | Loaded configuration; load a compatible one |
| CSF | Switch to an invalid channel | Function parameters |
| LFF3 | AI3 4-20 mA signal loss | Analog input connection |
| EPF1 / EPF2 | External or network-triggered fault | The triggering device or network |
Brake, contactor and process codes
| Code | Meaning | First check |
|---|---|---|
| ANF | Load slipping | Motor, gain and stability; braking resistor; sizing; encoder coupling |
| ASF | Angle measurement error | Motor phases and the maximum drive current |
| BLF | Brake control error | Drive/motor connection, windings, IBR, IRD and BEN settings |
| BRF | Brake feedback error | Feedback and brake control circuits, brake condition, linings |
| DLF | Abnormal load variation | Whether the load is blocked |
| FCF1 / FCF2 | Output contactor stuck closed / stuck open | Contactor, wiring and feedback circuit |
| LCF | Input contactor error | Contactor, wiring, LCT time, mains connection |
| OLC / ULF | Process overload / underload | Cause of the load change; OLD- and ULD- menus |
| OTFL / PTFL | PTC overheat on DI6 / PTC probe fault | Motor load and cooling; probe and wiring |
| SAFF | Safety function error | Safety settings and the ATV320 Integrated Safety Functions manual |
| FBE / FBES | Function block error | FBFT and FBSM settings |
Internal fault codes
CRF1 is the precharge circuit, EEF1 / EEF2 internal memory, HCF board pairing, HDF IGBT desaturation, and INF1, INF2, INF3, INF4, INF6, INF9, INFA, INFB and INFE are internal board, measurement, temperature sensor or processor faults. For HDF check the drive-to-motor cable and motor insulation first; for INF6 check the option module reference and seating. For INF codes that remain after a power cycle the manual points to Schneider Electric support.
How do you clear an ATV320 fault code?
| Clearing method | Codes |
|---|---|
| Power off and on after removing the cause | ANF, ASF, BLF, BRF, CRF1, EEF1, EEF2, FCF1, HDF, ILF, INF1, INF2, INF3, INF4, INF6, INF9, INFA, INFB, INFE, SAFF, SOF, SPF |
| Automatic restart (ATR) or an input assigned to RSF | CNF, COF, EPF1, EPF2, FBES, FCF2, LCF, LFF3, OBF, OHF, OLF, OLC, OPF1, OPF2, OSF, OTFL, PTFL, SCF4, SCF5, SLF1, SLF2, SLF3, SSF, TJF, TNF, ULF |
| Clears by itself once the cause is gone | CFF, CFI, CFI2, CSF, DLF, FBE, HCF, PHF, USF |
| RSF if HRFC = YES, otherwise a power cycle | OCF, SCF1, SCF3 |
The manual's summary table and its code pages differ for ASF, BRF, SOF and SPF: the summary says power cycle, the code pages say ATR or RSF. If RSF does not clear the fault, power cycle the drive after removing the cause.
Why does it show nSt and not run?
- Freewheel or fast stop input: if these functions are assigned to a digital input, the drive will not start while that input is de-energised. It shows nSt in freewheel stop and FSt in fast stop. This is normal, because these functions act at zero so a wire break stops the drive.
- Run command: check that the run input suits the control mode set in TCC and TCT.
- Limit switch: if an input assigned to the limit function is at zero, the drive can only start in the opposite direction.
- Network: if the reference or command channel is on a network, the drive shows nSt until the network sends a command.
Products these tables apply to
The tables cover the ATV320 family, for example compact ATV320U15N4C and ATV320U75N4C, book ATV320U15N4B and single-phase ATV320U07M2C. See variable frequency drives for replacements, braking resistors for ObF, and the frequency inverter selection guide for sizing.
Frequently asked questions
What is the difference between OCF and SCF1?
OCF is overcurrent; the manual lists wrong settings, high inertia or load, and mechanical locking as causes. SCF1 is a short circuit or ground fault at the drive output. With SCF1, check the motor cable and motor insulation before the parameters.
Is a braking resistor required for an ATV320 ObF fault?
No. The manual starts with a longer deceleration time and a check of the supply voltage. A braking resistor is added when needed, and BRA is enabled only if it suits the application.
Can PHF be disabled?
It can be set with IPL = NO, but that only turns the protection off and does not fix a lost phase. Check the power connection and fuses first.
Is the OCF fix the same on the ATV12?
The code is the same but the advice is not. The ATV320 manual says to raise the switching frequency, while the ATV12 manual says to reduce it and add line chokes. Always use the manual for your series.