A novel starting method for BLDC motors without the position sensors

This paper presents a novel method to estimate the rotor position of a brushless dc (BLDC) motor at standstill. Moreover, a method for startup and acceleration of the motor up to a certain speed is introduced. The principle of the estimation method is based on the variation of the BLDC motor current in the magnetic axis due to the magnetic saturation of the stator core. An advantage of this method is that the maximum estimated error of the initial rotor position is 6°. Therefore, the motor starting torque is increased significantly. However, to implement this method, a current sensor at the dc link of the inverter is needed.