Cause : Overspeed occurrence comes when the inverter output is shut off when the motor speed exceeds the Pr.374 Overspeed detection level under encoder feedback control, Real sensorless vector control, Vector control, and PM sensorless vector control.

1. When Pr.374 = "9999 (initial value)", the inverter output is shut off when the motor speed exceeds the "maximum frequency + 20 Hz" for the induction motor (up to 420 Hz under Vector control or Real sensorless vector control), or when the motor speed exceeds the "maximum motor frequency + 10 Hz" for the PM motor.
2. Check that the Pr.374 setting is correct.
3. Check that the setting of Pr.369 Number of encoder pulses does not differ from the actual number of encoder pulses. (Under encoder feedback control or Vector control).
4. Set Pr.374 correctly.