Control of PMBLDC motor using third harmonic back emf sensing with zigzag transformer

This paper presents a significant improvement in sensorless control technique of PMBLDC motor drive by making use of third harmonic component of back EMF to enable the drive to work satisfactorily over a wide range of speed efficiently. The resistance bank used in extracting the third harmonic component in the conventional technique results in high loss and requires rigorous filtering. Creating a virtual neutral using a zigzag transformer is proposed in the present paper. The use of grounding transformer results in a significant improvement in the efficiency of the drive and also a reduction in the noise level while inferring the rotor position of the drive.