UnderVoltage

What does F4 mean?

The drive has detected that the DC bus voltage has dropped below its predefined minimum operating threshold. This condition typically occurs due to low incoming AC line voltage, a momentary power interruption, or excessive voltage sag from the utility supply. Sustained undervoltage can prevent the drive from operating correctly, cause nuisance trips, or indicate a problem with the main power supply, potentially halting equipment operation.

• Incoming AC line voltage consistently below the drive's minimum operating threshold (e.g., 340V for a 400V class drive).
• Momentary power interruption (brownout) or significant voltage dip on the utility supply.
• Overloaded input transformer or upstream circuit causing an excessive voltage drop under load.
• Loose or corroded electrical connections at the drive's main power terminals (L1, L2, L3) increasing resistance.
• Incorrectly set undervoltage trip level parameter (e.g., P0-03) too high for the nominal supply voltage.

Click steps to track your progress.

1. 1

   Measure incoming AC line voltage at terminals L1, L2, L3 for phase-to-phase values under no-load and full-load conditions.

2. 2

   Verify that the supply voltage consistently falls within the drive's specified input voltage range (e.g., 380-480VAC).

3. 3

   Check all fuses and circuit breakers in the power path for proper continuity and correct rating.

4. 4

   Inspect and retorque all main power connections at the drive (L1, L2, L3) and upstream power sources.

5. 5

   Increase the undervoltage trip delay time (e.g., Parameter P1-30) if momentary sags are expected and tolerable for the application.