Overvoltage During Deceleration

What does ObF mean?

This fault occurs when the DC bus voltage rises above its safe limit during motor deceleration, typically due to kinetic energy being regenerated back to the drive from a sudden stop or an overhauling load. Without proper energy dissipation, this can damage the drive's DC bus components.

• Deceleration ramp time (Parameter P0-12) set too short for the load's inertia, causing rapid energy regeneration.
• Overhauling load condition (e.g., gravity-fed conveyor, fan stopping) generating kinetic energy back to the drive.
• Dynamic Braking Resistor (DBR) is not connected, undersized, or has failed (open circuit).
• Dynamic Braking Chopper (internal or external) is faulty or not enabled (Parameter P1-10 or similar).
• Excessive regeneration due to frequent starts and stops with high inertia loads.

Click steps to track your progress.

1. 1

   1. Increase deceleration ramp time (Parameter P0-12) by 20% and retest.

2. 2

   2. Verify the dynamic braking resistor (DBR) connection between terminals BR+ and BR- (or similar) is secure.

3. 3

   3. Measure the resistance of the DBR (power off) and compare it to the specified value in the drive manual.

4. 4

   4. Confirm the braking function is enabled in drive parameters (e.g., P1-10 for braking resistor type or chopper enable).

5. 5

   5. Check for overhauling load conditions; consider mechanical brakes or larger braking resistor if load is inherently regenerative.