DRV10983-Q1: Current waveform distortion

Hey Jeff,

Let me see if I can answer your questions:

1.  Why some motor phase current have is beautiful sinusoidal waveform, but some motor phase current is distortion. Which motor parameter will cause that.
   1. There's 3 factors that usually cause distortion in the current
   2.  BEMF of the motor: Sensorless algorithms in the DRV10x (and many other devices) require good information about the BEMF. The algorithm expects a sinusoidal BEMF. If the BEMF is not sinusoidal, then the information gathered from the BEMF might not be ideal for the algorithm to make good decisions when driving the current. Remember, BEMF shape comes from the physical construction of the winding (trapezoidal vs. sinusoidal vs. "bad" or "prototype" windings for example)
   3. Inductance and resistance of the motor might be very low which would result in the decay of the current in between PWM signals on the motor phase. Sometimes, the decay is small which result in distortion, and sometimes, the decay is very large which prevents the algorithm from driving the motor at all
   4. Changing inertia or load (e.g. swinging ceiling fan or unevenly manufactured blades) might cause some distortion on the current waveform. This can be explained because more load requires higher current and less load requires lower current.
2. Why some motor very easy to tuning. For example it can follow the speed command in many Kt value.  And some motor just can run in specific Kt value...
   1. i find Tcontrol (or Lead Time or Commutation Angle or Lead angle), in addition to correct Phase Resistance and Kt, result in robust motor operation. As a result, I cannot comment why some Kt motors may be easier than others. I would say the combination of these factors result in easy tuning
   2. Tcontrol tuning can be found in the tuning guide. Generally speaking, Tcontrol is usually somewhere between 5us and 400us. The more inductance, the higher Tcontrol time and vice versa.
3. My customer have a motor need to spin in 300RPM  and  the speed cmd is 10%.  The motor is used for lidar the inertia is high. In production line they found when force shake the motor, It will cause BMEF fail. Whether DRV10983 suite  this kind  application scenario.
   
   1. I'm not surprised by this result. In a ceiling fan application (which is usually high inertia), turning off the motor during vigorous shaking would be beneficial. It might not be useful in your application.
   2. I'd recommend disabling the Lock and  ensuring a different lock catches any other application situation you're interested in. For example, Abnormal BEMF is the best lock for capturing lock rotor on start up, ensure it is caught by the Current Limit Lock or Closed Loop Stuck Lock.

Best,

-Cole