Overspeed

What does SOF mean?

The motor has exceeded its programmed maximum speed or the drive has detected an unstable speed condition, possibly due to a driving load that forces the motor beyond its setpoint. This can lead to mechanical damage or loss of control.

• Driving load (e.g., conveyor on incline, centrifuge) overhauling the motor, forcing it to rotate faster than the commanded speed.
• Incorrectly set maximum frequency (Parameter P1-09) or maximum speed limit (P1-10) in the drive, causing a trip when motor speed exceeds this value.
• Faulty speed feedback device (e.g., encoder, resolver) providing erroneous high-speed signals to the drive.
• Unstable control loop (e.g., PID regulator, speed controller gains P2-10, P2-11) allowing speed oscillations that momentarily exceed the overspeed threshold.
• Mechanical fault in the driven equipment causing uncontrolled acceleration (e.g., broken gearbox, detached coupling, free-wheeling load).

Click steps to track your progress.

1. 1

   1. Monitor the actual motor speed or frequency (e.g., r0.3, r1.5) via the drive's diagnostic display and compare it to the commanded speed and the maximum frequency setting (P1-09).

2. 2

   2. If an encoder is used for speed feedback, verify encoder pulse count and direction on a diagnostic display; check wiring of encoder signals (A, /A, B, /B) at drive terminals.

3. 3

   3. Adjust the maximum frequency parameter (P1-09) and the maximum motor speed parameter (P1-10) to match the application's true operational limits with a safety margin.

4. 4

   4. If a regenerative load is suspected, lengthen deceleration ramps (P1-12) or install/verify an external braking resistor (Parameter bC1) to absorb excess energy.

5. 5

   5. Inspect the mechanical connection between the motor and the load for any slippage, broken components, or free-wheeling conditions.

6. 6

   6. Review and fine-tune the drive's speed control loop gains (e.g., P-gain P2-10, I-gain P2-11) to improve stability and prevent overshoot during transient conditions.