Underfrequency

What does LF mean?

This fault occurs when the frequency of the incoming mains power supply falls below the specified operating range. By default, this critical condition triggers a full TRIP, inhibiting all ignition pulses and resetting the Ready signal to prevent damage to the drive and motor that could result from operation at an incorrect frequency. Manual reset is required after the frequency stabilizes.

• Unstable or overloaded utility grid supplying power to the facility, causing frequency drop.
• Faulty or undersized generator supplying the drive, struggling to maintain output frequency under load.
• Incorrectly set minimum frequency trip threshold parameter (e.g., P0-11) in the drive, triggering prematurely.
• Issues with the drive's internal mains frequency measurement circuit (uncommon, usually indicates a hardware fault).
• Sudden heavy load applied to the mains supply, causing a transient frequency dip.

Click steps to track your progress.

1. 1

   Measure the actual incoming mains frequency at the drive's input terminals (L1, L2, L3) using a true RMS multimeter or power analyzer; compare to expected 50 Hz or 60 Hz.

2. 2

   Check the drive's underfrequency trip threshold parameter (e.g., P0-11) and adjust if it is set too high (e.g., typically 47 Hz for 50 Hz system).

3. 3

   Monitor the utility grid's frequency stability over time using a data logger if the issue is intermittent.

4. 4

   Verify the capacity and stability of the local power generator if it is the primary power source.

5. 5

   Check for any significant load changes or faults in other equipment connected to the same mains supply that could impact frequency.