Underload Min Alarm Trip

What does Min Alarm mean?

This fault indicates that the motor load has dropped below a predefined minimum threshold, typically signaling an underload condition. This can occur if a belt breaks, a pump runs dry, a conveyor jams causing a sudden load drop, or other process failures. It protects the driven equipment from damage caused by low-load or no-load operation (e.g., pump cavitation). Ignoring this can lead to equipment damage or process inefficiency.

• Mechanical power transmission failure such as a broken drive belt, coupling shear, or shaft disconnect.
• Loss of process material or fluid for the driven equipment (e.g., pump running dry, material flow interrupted on a conveyor).
• Overly sensitive underload detection threshold (e.g., Parameter P1-30) configured too high for the application's minimum operating load.
• Intermittent blockage clearing, leading to a sudden and sustained drop in mechanical load below the set threshold.
• Malfunctioning current or torque sensor providing a falsely low feedback signal to the drive's underload monitoring function.

Click steps to track your progress.

1. 1

   1. De-energize and mechanically inspect the driven equipment (e.g., pump, fan, conveyor) for broken belts, disengaged couplings, or mechanical disconnection. Verify shaft integrity.

2. 2

   2. Confirm the presence of process material or fluid. For pumps, check fluid levels in the reservoir and confirm intake valve position. Measure pump suction pressure at port A1 if applicable.

3. 3

   3. Access the drive's programming and verify Parameter P1-30 (Underload Threshold) and P1-31 (Underload Delay Time) are correctly set for the minimum expected operating load current.

4. 4

   4. Using a clamp-on ammeter, measure the actual motor phase currents (L1, L2, L3) during both no-load and minimum-load conditions. Compare readings to the drive's reported current.

5. 5

   5. Inspect wiring for current transducers or load cells. Perform continuity and insulation resistance tests on signal cables connected to drive analog input (e.g., AI1, AI2).

6. 6

   6. Observe the drive's load feedback (e.g., percentage of full load current) via the HMI or diagnostic software during various operating conditions to identify consistent low load values.