Undertorque 2 Fault

What does UL4 mean?

This fault occurs when the motor's torque output drops below the Undertorque 2 detection level (L6-05) for the set duration (L6-06). This secondary undertorque profile triggers based on L6-04 settings, causing the drive to shut down. It typically signifies a loss of mechanical load, such as a broken belt, coupling failure, or material feed issue. Unresolved undertorque can lead to runaway motor conditions, process material loss, or damage from unsupported operation.

Additional Steps

Steps 1–2 are listed in Priority Fix.

1. 3

   Ensure there are no slips or disconnections in the mechanical power transmission path.

2. 4

   Confirm the motor is properly coupled and providing the expected torque for the current operating conditions.

3. 5

   Consider if the application experiences brief, expected low-torque phases that might be falsely triggering the fault; adjust L6 parameters if necessary.