UnderVoltage

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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.

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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.