DC-link Ripple

What does A00525 mean?

A large ripple in the DC-link voltage has been detected, which can indicate issues with the input power supply, filter capacitors, or excessive harmonic distortion. This condition can affect inverter performance, efficiency, and potentially lead to premature component failure.

• Degradation or failure of DC-link filter capacitors (e.g., electrolytic capacitors), reducing their capacitance and ripple filtering capability.
• Unstable or distorted AC input supply voltage (e.g., high harmonic content, phase imbalance, voltage sag) exceeding rectifier tolerance.
• Excessive regenerative braking energy without sufficient braking resistor capacity, leading to rapid DC-link voltage fluctuations.
• Internal rectifier bridge fault (e.g., damaged diode) causing only half-wave rectification and increased DC-link ripple.
• Heavy dynamic loads causing large current swings that overwhelm the DC-link's ability to maintain a stable voltage.

Click steps to track your progress.

1. 1

   1. Measure the AC input line voltages (L1-L2, L2-L3, L3-L1) at the drive input terminals (e.g., R, S, T) for phase imbalance and harmonic distortion.

2. 2

   2. Using an oscilloscope, measure the DC-link voltage (e.g., at terminals DC+/DC-) to observe the ripple magnitude and frequency.

3. 3

   3. Inspect the drive's internal DC-link capacitors for physical swelling, leakage, or signs of overheating.

4. 4

   4. Verify the braking resistor connection (e.g., terminals R+, R-) and its resistance value (e.g., P0231) against specifications if regenerative braking is active.

5. 5

   5. Check the drive's input rectifier bridge (if accessible) for signs of damage or overheating by measuring individual diode voltage drops.

6. 6

   6. Reduce the drive's acceleration/deceleration ramps (e.g., P1120, P1121) to minimize sudden current demands and observe ripple reduction.