I have a BLDC motor with HALL sensors. Datasheet reads the motor is 4 pole technology. Somewhere else it says "Number of pole pairs = 2". I can only assume that they both mean the same thing. It also features 3 HALL sensors at 120°
My question is, what would be fundamentally different in commutation of a BLDC motor with respect to the number of poles, like sequence or number of switching on/off for driver transistors?
For example, If I have a fully working code for a 6 pole or 8 pole motor, what would I need to do to make it work with 4 pole as well?
Best Answer
'Pole pairs' is the number of North and South magnet pole pairs. 'Poles' is the number of individual North and South poles (always an even number).
Unless it has a separate rotation sensor, The controller cannot tell how many poles the motor has or what mechanical speed it is doing. From the controller's point of view all motors have 2 poles and 3 phases, which requires 6 commutation steps per 'electrical' revolution. So you could have a 4 pole motor that needs 12 steps per revolution, and the controller will think it has done a full revolution when the rotor has only gone half way around.
All else being equal, a controller which works with 6 or 8 poles should also work with 4 or 2 poles. Secondary factors might have an effect, eg. 2 pole inrunners often have very low inductance and are designed for high rpm, which might not suit a controller designed for high torque outrunners.