Kindly ask for some help, I make some research on a problem with BLDC motor which is driven by PWM signal by a control unit. BLDC Motor is driving an impeller type pump element. Unfortunately the impeller is being found blocked after some hundreds of hours with damage. I have some doubts whether the control unit losing the back EMFsignal and causing jitter on the motor/ impeller.
What happens actually if the back EMF is lost and motor starts jittering ? And what could also cause EMF signal lost ?
This depends if your BLDC motor is controlled using internal hall sensors or with sensorless trapezoidal commutation. From what you described, it seems that most probably no hall or other sensors are used on the motor to tell the controller when to switch the phases, the rotor position is detected using the motor’s back EMF voltage.
Since this control method depends on the presence of Back EMF (which is the voltage generated inside the motor windings as the rotor rotates in the permanent magnets field), the position can only be sensed if the rotor is spinning. Therefore, the rotor position cannot be know when the motor is stalled or rotating at slow RPM. If, for some reasons, the motor is stalled or if your application requires that the motor will rotate at low RPMs, the back EMF signal will be lost and the motor will start to jitter.
If stall is what caused the back EMF signal to be lost and the motor to jitter, you will need to investigate why the motor is stalling and if the motor you are using is appropriate for the kind of torque you are applying. In case, your system requires the motor to rotate at slow speed, you will need a BLDC motor controlled with hall sensors instead of sensorless commutation.
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