Hello -
I am designing custom hardware, and have a question regarding 2 vs 3 current sensors. I understand that to achieve maximum motor speed, overmodulation needs to be implemented. I also understand that full overmodulation requires 3 current sensors in order to reconstruct current during high-speed operation.
I have done some experimentation with this using a DRV8301-69M board. Using Lab 5a/5b, I am able to achieve nearly maximum motor speed using only 2 current sensors (3 physically on the board, but only 2 selected in user.h). I have simply set the USER_MAX_VS_MAG_PU to (2.0/3.0) and can achieve nearly the same maximum speed achievable using 3 current sensors and full overmodulation (lab 10). I do, however, hear a bit of noise at this speed with only 2 current sensors, where I do not hear the same noise using 3 current sensors.
Can someone shed some light here? I am trying to make a decision whether to add a 3rd current shunt + amplifier to my board vs designing using only 2 current sensors.
I should probably also add that my application requires zero-speed startup under load. Not sure if 2 vs 3 current sensors and overmodulation matter much for this requirement, but figured I'd add that detail.
As always, any advice is much appreciated!
Best,
-asifjahmed
