DC Bus Voltage Limit

What does 3211 mean?

The drive is actively limiting torque due to the intermediate circuit DC voltage being either too high or too low. This is an informative alarm indicating the drive is attempting to protect itself from potentially damaging voltage conditions, which can lead to unstable operation or component stress if the underlying cause isn't addressed.

• Over-regeneration from the motor during deceleration or overhauling load, causing DC bus voltage to rise above threshold (e.g., 800V for 400V drive).
• Insufficient braking resistor capacity or open circuit in the braking resistor circuit (e.g., resistance measurement > 100kΩ).
• Input supply voltage fluctuations or transient spikes exceeding drive's rated input (e.g., 480VAC input fluctuating to 520VAC).
• Loss of one or more input phases (for 3-phase supply) leading to DC bus ripple and potential undervoltage.
• Faulty DC bus voltage measurement circuit within the drive.

Click steps to track your progress.

1. 1

   Monitor the DC bus voltage value in the drive's actual values display (e.g., r0026) during operation and note its peak/trough values.

2. 2

   Inspect braking resistor wiring for loose connections or breaks. Measure resistance of the braking resistor across its terminals; compare to nameplate value.

3. 3

   Verify the input AC supply voltage stability using a multimeter or power analyzer at the drive's L1/L2/L3 terminals.

4. 4

   Adjust deceleration ramps (e.g., P11-01) or increase braking chopper activation voltage (e.g., P20-03) if over-regeneration is indicated.

5. 5

   Check for balanced 3-phase supply voltage at the drive input terminals (e.g., L1-L2, L2-L3, L3-L1 should be within 2% of each other).