Position Sensorless Speed Control of Brushless DC Motor

Abstract

This project work presents the position sensor less speed control of brushless DC motor, brushless DC motors has the similar speed and torque characteristics of conventional DC motors, instead of commutating brushes brushless DC motor uses an electronic commutation system. To obtain the commutation instants the position of permanent magnet rotor position should detect, normally we use a position sensor to detect the position. instead of using the position sensor to detect the rotor position here in this project we are using the zero crossing instances of the back EMF to get commutation instances, when we use the phase back EMF wave forms for detecting the commutation instances there will be a 30-degree electrical phase shift between the commutation instances and the zero crossing points. To avoid this 30-degree phase shift between the commutation instances and zero crossing points instead of using the phase back EMF wave forms we uses the line to line back EMF wave forms.