Sensorless control of high speed BLDC

The paper deals with brushless DC motors (BLDC) operated in high speed region without any speed or position sensor. A six-step commutation technique is used to control the BLDC motor, utilizing the disconnected motor phase for sensing the induced voltage. The main goal of the paper is to describe the limitation of the conventional 6-step commutation control in sensorless mode at high speeds and to introduce a novel approach that extends the conventional technique for high speed regions. Theoretical assumptions will be verified experimentally on a real high-speed BLDC motor.