Undertorque Detection 2

What does UL4 mean?

Similar to UL3, this fault indicates the drive's output current was below the L6-05 threshold for longer than L6-06, with L6-04 set for undertorque detection. It signifies a motor running under an unexpectedly light load condition, potentially indicating a process issue or mechanical failure that needs investigation.

• Mechanical decoupling of the motor from its load (e.g., broken shaft, slipped coupling, loss of fluid in a pump).
• Process material flow stoppage or significant reduction in demand (e.g., valve closure, fan duct blockage).
• Undertorque detection level (L6-05) set too high for the second detection stage's intended low-load scenario.
• Undertorque detection delay time (L6-06) set too short, leading to nuisance trips for brief current dips.
• Temporary drop in system pressure or flow, causing the motor to momentarily operate at a lighter load.

Click steps to track your progress.

1. 1

   1. Visually inspect the driven equipment for signs of mechanical load loss, such as a broken shaft, slipped coupling, or loss of fluid in a pump.

2. 2

   2. Observe the process for any conditions that would naturally lead to a sustained reduction in motor load and current draw.

3. 3

   3. Use a clamp-on ammeter to accurately measure the motor's actual output current under the specific light-load conditions intended for UL4 detection.

4. 4

   4. Adjust parameter L6-05 (Undertorque Detection Level 2) to a value below the measured minimum operating current for the expected light-load scenario.

5. 5

   5. Increase parameter L6-06 (Undertorque Detection Time 2) to provide a longer delay, preventing immediate fault trips during brief current dips.