OU Overvoltage in the DC bus

What does 2020 mean?

The DC bus voltage has exceeded the switch-off threshold OU (e.g., 770V for <400V mains with C0173=0) as specified by parameter C0173, indicating excessive braking energy. The pulse inhibit is set, and a delay time (C0912) starts until the voltage falls below the switch-on threshold OU (e.g., 755V for <400V mains).

• Rapid deceleration of a high-inertia load without adequate braking resistor (R_brake) capacity or active braking module.
• Motor braking ramp time (C0013) set too short for the kinetic energy of the driven load, leading to rapid regeneration into the DC bus.
• DC bus capacitor bank degradation, reducing its ability to absorb regenerative energy and leading to voltage spikes.
• Malfunctioning or improperly sized braking resistor (e.g., open circuit, resistance value too high) that cannot dissipate regenerative energy.
• Unstable or excessively high input mains voltage (e.g., >480VAC for a 400V rated drive) causing a higher baseline DC bus voltage.

Click steps to track your progress.

1. 1

   Increase the deceleration ramp time (C0013) to allow for slower energy dissipation from the load.

2. 2

   Verify the braking resistor (R_brake) connection to terminals X5/1 and X5/2 for continuity and correct resistance value (e.g., measure with multimeter).

3. 3

   Check the braking unit's operation and ensure its switching thresholds (e.g., parameter C0173) are appropriate for the application.

4. 4

   Reduce the maximum speed (C0596) or process speed if possible, to lower the kinetic energy stored in the load.

5. 5

   Measure the input mains voltage (e.g., L1-L2, L2-L3, L3-L1 at terminals X1/L1, X1/L2, X1/L3) and verify it is within the drive's specified operating range.