SLVSDN2E January 2018 – March 2021 DRV10974
If the motor is in normal operation, the motor BEMF is always less than the voltage applied to the phase. The sensorless-control algorithm of the DRV10974 device is continuously updating the value of the motor BEMF based on the speed of the motor and the motor Kt as shown in Figure 7-11. If the calculated value for motor BEMF is 1.5 times higher than the applied voltage on phase U (VU) for an electrical period then an error is present in the system, and the calculated value for motor BEMF is wrong or the motor is out of phase with the commutation logic. When this condition is detected, a lock is triggered.