SLAU927B June 2024 – November 2024 MSPM0G3507
This fault is triggered when the estimated BEMF voltage drops below the programmed Abnormal BEMF threshold percentage [ABNNORMAL_BEMF_THR]. For example, if the estimated or measured Ke is 5mV/Hz and the programmed Abnormal BEMF threshold is 40%, this fault is triggered when the estimated Ke drops below 2mV/Hz. This fault can also be triggered when the programmed Ke is inaccurate.
There are two cases for Abnormal BEMF threshold:
Case 1: Estimated BEMF voltage drops when the motor speed drops. Motor speed can drop due to load dynamics (sudden change in load). For applications with load dynamics, the speed is expected to drop and recover back. Because the speed drops, the BEMF voltage also drop and can trigger this fault. For such applications, the recommended value of 10% is to be set for the Abnormal BEMF threshold to avoid triggering this fault.
Case 2: This fault can be triggered if the programmed Ke is inaccurate. Follow steps recommended in section MOTOR_BEMF_CONSTANT to obtain accurate Ke.