Overvoltage Due to Deceleration

What does Overvolt D mean?

This fault occurs when the DC link voltage rises above a safe threshold during motor deceleration. This is typically caused by regenerative energy from the motor feeding back into the VSD faster than it can be dissipated, often in applications with high inertia loads or short deceleration times. Sustained overvoltage can damage the VSD's DC bus capacitors and IGBTs, risking drive failure.

• Deceleration ramp time (e.g., P1-03) set too short for the mechanical load's inertia, causing excessive regenerative energy.
• Missing, incorrectly sized (e.g., ohmic value too high, power rating too low), or faulty braking resistor.
• Failure of the internal braking chopper circuit (e.g., IGBT fault, control signal issue).
• Rapid stop command from the control system or a process requiring very quick deceleration with a high inertia load.
• Incorrect DC link overvoltage threshold parameter (e.g., P3-12) set too low in the VSD.

Click steps to track your progress.

1. 1

   Increase the VSD's deceleration ramp time parameter (e.g., P1-03) by 20% and observe the DC link voltage (UDC) during deceleration.

2. 2

   Verify the braking resistor connections at terminals (e.g., R+, R-). Measure the actual resistance of the braking resistor with a multimeter.

3. 3

   Check braking chopper functionality by monitoring DC link voltage and current into the resistor during deceleration (requires specialized diagnostic tools).

4. 4

   Review the application's deceleration requirements. Implement a slower ramp, or a coast-to-stop function if suitable for the process.

5. 5

   Confirm that the VSD's DC link overvoltage trip threshold parameter (e.g., P3-12) is set to the manufacturer's recommended default value.