Cause : Tachometer dn/dt comes when the permissible change value of the speed encoder signal P215 dn(actual, permissible) was exceeded.

1. Check tachometer cables for interruptions.
2. Check earthing of tachometer shield.
3. The shield must be connected both at the motor and the converter side.
4. The encoder cable must not be interrupted.
5. The encoder cable must not be laid together with the power cables