Overspeed Occurrence

What does E.OS mean?

The motor speed has exceeded the configured Pr.374 Overspeed detection level under encoder feedback, Real sensorless vector, Vector, or PM sensorless vector control, leading to an inverter shutdown. This protective function prevents mechanical damage from excessive speed.

• External mechanical load actively driving the motor faster than the commanded speed, exceeding the inverter's control capability.
• Incorrect Pr.374 (Overspeed detection level) setting, set too close to the operating speed or maximum speed.
• Faulty encoder feedback (e.g., loose connection, damaged cable, encoder pulse generator failure) providing incorrect speed signals.
• Inadequate motor braking torque or insufficient regenerative energy dissipation causing the motor to coast above set limits.
• PID control loop instability (if active) causing speed oscillation and transient overspeed conditions.

Click steps to track your progress.

1. 1

   1. Monitor actual motor speed via the inverter display or monitoring software and compare it to the commanded speed and Pr.374.

2. 2

   2. Increase Pr.374 (Overspeed detection level) by 5-10% above the maximum expected operating speed for the application.

3. 3

   3. Inspect encoder wiring for loose connections or damage, and verify encoder pulse output signal using an oscilloscope (expected: clean A/B/Z phase pulses).

4. 4

   4. Verify parameters Pr.30 (Braking operation frequency) and Pr.70 (Braking duty factor) are correctly configured for any external braking resistor.

5. 5

   5. Check for mechanical free play or excessive load inertia that could cause the motor to overspeed without electrical input.