Cause : Mld n(set)- This fault comes due to several reasons, check below table:

• Permissible phase sequence
• Max. frequency, 
• Min. speed, 
• Changeover frequency between V- and I model, 
• Start of field weakening frequency, 
• Frequency suppression bandwidth, it was not possible to determine a permissible frequency range for the rotating measurement.

There must be a 10% frequency range which lies above 1.1 times the changeover frequency and below 0.9 times the start of field- weakening frequency.

Possible counter-measures following as:

- Permit both phase sequences
- Increase maximum frequency
- Reduce minimum speed,
- Reduce changeover frequency between the V and I model.
- Reduce or remove the frequency suppression bandwidth.