This book is all about running a brushless DC motor using a sensorless technique. The target of the work was to make a very simple operating method for a brushless motor and formulate a speed control mechanism. Initially the work was started with both considering back-EMF and without considering back-EMF. Because of more complexity in the back-EMF sensing method, and as our intention was to make a simpler and cost effective operation, so finally we assembled our project the without back-EMF sensing. Even though being a simple and inexpensive machine, the performance was quite good. However adding back-EMF sensing in this machine can give it more dependability.TABLE OF CONTENTS: DECLARATIONIAPPROVALIIACKNOWLEDGEMENTIIILIST OF FIGURESVIIABSTRACTIXCHAPTER 1INTRODUCTION101.1.Introduction101.2.Historical Background101.3.Advantage over Traditional Method111.4.Objective of this Work121.4.1.Primary objectives121.4.2.Secondary Objectives121.5.Introduction to this Thesis12CHAPTER 2BRUSHLESS DC MOTOR142.1.Introduction142.2.Comparison of Brushless motor with brushed motors152.3.Structure of a BLDC152.3.1.Stator162.3.2.Rotor172.4.Operating Principle182.4.1.Sensored Commutation192.4.2.Conventional Control Method Using Hall-effect Sensors202.4.3.Sensorless Control222.5.Applications232.6.Summary24CHAPTER 3MOTOR DRIVE SYSTEMS253.1.Introduction253.2.Components of Drive Electronics253.3.Inverter263.3.1.Three-Phase Inverter263.3.1.1.120-Degree Conduction273.3.1.2.180-Degree Conduction293.4.Speed Control Techniques303.4.1.Open Loop Speed Control313.4.2.Closed Loop Speed Control313.4.2.1.Proportional-Integral (PI) Controller323.5.PWM based Methods333.5.1.Conventional 12