Evaluating misalignment of hall sensors in brushless DC motors

Brushless DC (BLDC) motors are used in a wide variety of applications and have been well investigated in the literature. In a typical low-cost drive the voltage source inverter is controlled by the signals produced by three Hall effect sensors that are used to detect the rotor position. These sensors are supposed to be positioned exactly 120 electrical degrees apart. However, this assumption may not always be true especially in medium- and low-precision motors. This paper demonstrates the effects of misaligned Hall sensors on stator currents and resulting torque, and presents a method for evaluating misplacement of each Hall sensor. Several industrial prototype BLDC motors are used to support the investigation and verify the developed methodology.