Position sensorless starting method of BLDC motor based on SVPWM and stator magnetomotive force control

In open-loop starting process of Brushless DC motor without position sensors, pulsations of torque and speed are large and motor cannot even start successfully. In order to solve those problems, Space Vector Pulse Width Modulation control schema of three-phase inverter employing 180° switch-on mode is analyzed. Moreover, relationship between the composed stator magnetomotive force and current maximum phase´s magnetomotive force is derived with windings in Y connection. Hence, this paper proposes a new starting control strategy combing stator magnetomotive force regulation with SVPWM. Furthermore, calculation of the composed stator magnetomotive force is simplified. The proposed starting algorithm is independent of saliency or initial position of rotor. It can also effectively suppress ripples of speed and torque, so its starting performance is greatly improved compared with conventional variable-frequency open-loop start. Finally, validity of the presented algorithm is verified by simulation and experiment.