IGBT Short Circuit (SCF) Fault in Schneider Altivar Drives

SCF (IGBT Short Circuit) in Schneider Electric Altivar Drives indicates that the drive has detected a short circuit in the inverter output stage (IGBT power module) or a severe short circuit on the motor output. To protect the inverter and motor, the drive immediately disables the output and trips with the SCF fault.

This fault can be caused by a short circuit in the motor, motor cable, output wiring, or by a failed IGBT power module inside the drive.

Possible Causes

• Short circuit between motor output phases.
• Ground (earth) fault in the motor.
• Ground fault in the motor cable.
• Damaged motor cable insulation.
• Incorrect motor wiring.
• Motor winding short circuit.
• Failed IGBT power module.
• Internal power board failure.
• Moisture or contamination inside the motor terminal box.
• Output contactor switching while the drive is running.

Solutions

1. Disconnect the motor cable and inspect it for short circuits or insulation damage.
2. Check the motor windings for phase-to-phase and phase-to-ground faults.
3. Measure the insulation resistance of the motor and motor cable using a megohmmeter.
4. Verify that the motor wiring is correct.
5. Ensure there are no contactors or switches operating between the drive and motor while the drive is running.
6. Check the drive output terminals for signs of damage or loose connections.
7. If the fault remains with the motor disconnected, check the IGBT module using a multimeter.
8. Repair or replace the drive if the IGBT power module is defective.

Additional Information

Schneider Altivar drives continuously monitor the inverter output current and the condition of the IGBT power stage.

An SCF fault is generated when the drive detects:

• A phase-to-phase short circuit.
• A phase-to-ground fault.
• An internal shorted IGBT.
• Excessive current caused by an output-stage failure.

If the SCF fault occurs immediately after power-up or with the motor disconnected, the cause is typically an internal IGBT or power board failure.

Common Symptoms

• Drive displays SCF (IGBT Short Circuit).
• Motor does not start.
• Drive trips immediately after the Run command.
• Fault cannot be reset.
• Output voltage is not generated.
• Repeated trips even with the motor disconnected.
• Burnt smell or visible damage inside the drive (in severe cases).
• Production stops unexpectedly.

Recommended Troubleshooting Sequence

1. Verify that the displayed fault is SCF.
2. Disconnect power and follow lockout/tagout procedures.
3. Disconnect the motor from the drive.
4. Inspect the motor cable for damage or short circuits.
5. Measure the insulation resistance of the motor and motor cable.
6. Check the motor windings for phase-to-phase and phase-to-ground continuity.
7. Restore power with the motor disconnected and check if the fault persists.
8. If the fault remains, test the IGBT power module with a multimeter.
9. Repair or replace the drive if the power module is defective.
10. Reconnect the motor only after confirming that both the drive and motor are fault-free.

SCF IGBT Short Circuit Check Table

Check Point	Action
Motor cable	Inspect for short circuit or insulation damage
Motor windings	Check for phase-to-phase and earth faults
Insulation resistance	Measure motor and cable insulation
Output wiring	Verify correct connections
Output contactors	Ensure they are not switching during operation
Drive output terminals	Inspect for damage or loose connections
IGBT module	Test with a multimeter if the fault persists
Power board	Inspect for visible damage
Drive operation	Verify normal operation after repair

Preventive Maintenance Tips

• Periodically inspect motor cables for insulation wear or damage.
• Measure motor insulation resistance during scheduled maintenance.
• Keep motor terminals clean and dry.
• Do not operate contactors between the drive and motor while the drive is running.
• Ensure the motor is correctly sized for the drive.
• Tighten power terminals regularly.
• Maintain adequate drive cooling to prevent IGBT overheating.
• Protect the drive from moisture, dust, and conductive contaminants.
• Record recurring SCF faults to identify developing electrical problems.
• Follow Schneider Electric preventive maintenance recommendations for the specific Altivar drive model.

Proper inspection of the motor, motor cable, output wiring, insulation resistance, and IGBT power module will help prevent recurring SCF (IGBT Short Circuit) faults in Schneider Altivar drives, ensuring reliable operation, protecting the inverter power stage, and extending the service life of both the drive and motor.