DC Link Voltage Ripple Exceeds Maximum

What does DC link error mean?

This fault occurs when the DC link voltage ripple within the variable speed drive exceeds its maximum permissible level. This often indicates an issue with the incoming mains supply, the rectifier stage, or an unbalance in the input phases. Unaddressed, it can lead to unstable operation, premature component wear, and potential damage to the VSD's internal circuitry.

• Missing input AC phase (phase loss) due to fuse blown or contactor failure.
• Unbalanced input AC supply voltage (e.g., L1-L2=400V, L2-L3=380V, L3-L1=360V).
• Rectifier bridge (diode module) internal short or open circuit in one or more diodes.
• Degraded DC link capacitors (reduced capacitance or increased Equivalent Series Resistance (ESR)).
• Transient voltage dips or spikes on the incoming mains supply exceeding drive's ride-through capability.

Click steps to track your progress.

1. 1

   Measure incoming AC supply voltages at terminals L1, L2, L3 (phase-to-phase) and verify they are balanced within 2% and within drive's rated input voltage.

2. 2

   Check all input fuses for continuity and proper rating.

3. 3

   Power down the drive, discharge DC link, then measure resistance across drive's input terminals (L1, L2, L3) to verify rectifier diode integrity.

4. 4

   Inspect DC link capacitors for bulging, leakage, or signs of overheating.

5. 5

   Use a power quality analyzer to monitor incoming AC supply for transient events or voltage sags.