Undervoltage

What does 8 mean?

The DC bus voltage is lower than the inverter’s 'Undervoltage limit'. The inverter will switch off until VDC recovers, but if it remains low for 1-3 seconds, it will trip with an alarm. This indicates that the incoming supply voltage is too low or unstable, potentially affecting drive operation.

• Insufficient incoming AC line voltage (L1, L2, L3) or persistent voltage sags/brownouts from the power supply.
• Overload condition causing excessive current draw and subsequent voltage drop across the input impedance of the drive or supply network.
• Blown input fuses or tripped circuit breakers on one or more phases, leading to an unbalanced or insufficient input voltage.
• Loose connections on the incoming AC power terminals (R, S, T) or in the upstream power distribution.
• Internal fault with the drive's rectifier or DC bus capacitors, causing a failure to maintain sufficient DC bus voltage.

Click steps to track your progress.

1. 1

   1. Measure the incoming AC line voltage (phase-to-phase) at terminals R, S, T with a True RMS voltmeter to confirm stable voltage within specifications (e.g., 480VAC +/- 10%).

2. 2

   2. Inspect all fuses and circuit breakers upstream of the drive for continuity and ensure they are properly rated for the application.

3. 3

   3. Power off the drive, then inspect and re-torque all incoming power connections (R, S, T) for looseness, corrosion, or signs of overheating.

4. 4

   4. Monitor the drive's DC bus voltage (A01-01) and output current (A01-04) during startup and load conditions to correlate voltage drops with current demands.

5. 5

   5. Verify the main input contactor (if present) is closing properly and all three phases are making solid contact.

6. 6

   6. If the fault persists with confirmed stable input voltage and no external load issues, consider testing the drive with a known good input power source or replacement.