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A Novel Approach of Rotor Position Detection of a Sensorless BLDC Motor with Improved Back EMF

Brij Kishore Ahirwa, Kaushik Kumar Pandey, Jitendra Singh Bhadoriya

This paper represents an improved direct back emf detection method which is used further in the rotor position detection o f a sensorless brushless dc (BLDC) motor. It is desirable in any kind of machine to use a method which is less dependable on the sensors and complex circuits, so in this paper a sensorless method is used to commutate and trigger the inverter connected to BLDC motor. Hall effect signals gives the information of the operations in the BLDC motor in this paper hall effect signals are used for the gate pulses for the inverter. Rotor position determination plays an important role in the improvement of the satisfactory operation of the motor so it is desirable to get the proper information of the rotor position or rotor angle. In this paper rotor position is determined by the Zero Crossing Detection (ZCD) of back emf. Unlike old methods of calculating Back emf of the BLDC by creating a virtual neutral point, a complimentary method is used. This method provides a wide range of speed. A pre conditioning circuit is proposed to rectify the back emf at very low speed. The rotor position can be determined even in stand still condition.