Brushless motor position sensor

The position sensor used in brushless motor is usually a magnetic sensor (Hall element, Hall IC). The following figure is a schematic diagram showing the motor structure and sensor layout of the brushless motor.

The motor is a three-phase brushless motor (outer rotor type). Its basic structure consists of a rotor with magnets and a stator composed of armature (winding and iron core). 

Position sensors (Hall elements, Hall IC) play an important role in accurately detecting the rotational position of the motor. Specifically, it needs to be installed at the position shown in the figure to accurately detect the magnetic flux φ g of the rotating rotor. However, in the motor, the magnetic flux of the rotor will cross the armature, and the current will flow through the armature to generate torque. Therefore, magnetic flux φ a is generated by the current flowing through the armature.

In order for the position sensor to accurately detect the magnetic flux φ g of the rotating rotor, it is necessary to avoid interference from the magnetic flux φ a as much as possible.

In addition, it also involves the hysteresis phenomenon (characteristics of Hall IC and controller) to eliminate the noise contained in the output signal of the position sensor. In any case, the layout angle accuracy of the position sensor (below) is very important.