CONTENTS

ABSTRACT

NOMENCLATURE

LIST OF TABLES

LIST OF FIGURES

1 CHAPTER INTRODUCTION

1.1.1 Brush less DC Motor

1.1.2 Advantages of BLDC Motor

1.1.3 BRUSH LESS DC MOTOR DRIVE

1.2 Sepic Converter

1.3 Unipolar Inverter

1.4 PWM Comparator

1.5 Hysteresis band current control PWM

1.6 Control strategies

1.6 Control strategies

1.7 Objective

1.8 Thesis outline

2 CHAPTER UNIPOLAR BLDC MOTOR

2.1 Introduction

2.2 CONSTRUCTION AND OPERATING PRINCIPLE

2.2.1 Stator Operation

2.2.2 Rotor Operation

2.2.2.1 ROTOR MAGNET CROSS SECTIONS

2.3 BLDC MOTOR TRANSVERSE SECTION

2.4 TORQUE/SPEED CHARACTERISTICS

2. 5 COMPARING BLDC MOTORS TO OTHER MOTOR TYPES

2.5.1 COMPARING A BLDC MOTOR TO A BRUSHED DC MOTOR

2.5.2 COMPARING A BLDC MOTOR TO AN INDUCTION MOTOR

2.6 UNIPOLAR Brush less DC Motor

3 CHAPTER PROPOSED TOPOLOGY

3.1 Proposed Topology

4 CHAPTER IMPLEMENTATION PI CONTROLLER TO SEPIC CONVERTER

4. Implementation PI controller to SEPIC Converter:

4.1 PI Controller

4.1.1 Integral and PI Controller Action

4.1.2 Function of the Proportional Term

4.1.3 Function of the Integral Term

4.1.4 Integral Action Eliminates Offset

4.1.5 Challenges of PI Control

4.1.6 Reset Time Versus Reset Rate

4.2 AC SUPPLY OPERATION

4.3 Block Diagram of Controller Ckt

5 CHAPTER RESULTS

5.1 SIMULATION

5.1.1 Comparison Of Input Current Harmonics As A Percentage Of The Fundamental

5.1.2 Comparison Of ThD And power Factor

5.2 Simulation Circuit Diagram

5.3 Simulation Results

CONCLUTIONS

REFERENCES

ABSTRACT

A new converter topology is proposed for driving a permanent magnet brushless dc

(BLDC) motor with unipolar currents. It is based on a front-end single-ended primary inductance

converter (SEPIC) and a switch in series with each phase. All the switches are ground-

referenced, which simplifies their gate drives. The available input voltage can be boosted for

better current regulation, which is an advantage for low voltage applications. For operation with

an ac supply, the SEPIC converter is designed to operate in the discontinuous conduction mode.

In this operation mode, it approximates a voltage follower and the line current follows the line

voltage waveform to a certain extent. The reduction in low-order harmonics and improved power

factor is achieved without the use of any voltage or current sensors. The simplicity and reduced

parts count of the proposed topology make it an attractive low-cost choice for many variable

speed drive applications..

NOMENCLATURE

BLDC Brushless DC motor

PFC Power Factor Correction

SEPIC Single Ended Primary Inductance Converter

EMF Electromotive Force

PI Proportional Integral

SMC Sliding Mode Control

Ckt Circuit

Vref Sinusoidal reference signal

Ma Modulation index

RMS Root Mean Square

DSP Digital Signal Processor

PWM Pulse Width Modulation

PS Periodical Sampling

HB Hysterisis Band

TC Triangular Carrier

THD Total Harmonic Distortion

Nd Neodymium

Co Cobalt

Fe Ferrite

B Boron

EMI Electro Magnetic Interference

E Back emf

Vin Input voltage

VL1 Voltage across inductor L1

VL2 Voltage across inductor L2

VC1 Voltage across capacitor C1

Wmax Maximum operating speed

Ke Phase back emf constant

Rs Phase resistance

Ls Phase inductance

I Phase current

D Duty cycle

R load resistance

T Time period

CCM Continuous Conduction Mode

CO Controller output

Cobias Controller bias or null value

e (t) Current Controller Error

SP Set Point

PV Process Variable

Kc Controller gain

ADC Analog to Digital Converter

C1, C2 Capacitors

Da, Db, Dc Diodes

Sa, Sb Turn-on and Turn-off switches

LIST OF TABLES

TABLE

NO.

TITLE PAGE NO.

2.1 Comparing a BLDC motor to a brushed dc motor

2.2 Comparing a BLDC motor to an induction motor

5.1 Comparison of Input Current Harmonics as a Percentage of the

Fundamental

5.2 Comparison of THD and Power Factor

LIST OF FIGURES

FIGURE NO.

TITLE PAGE NO.

1.1 Conventional six-switch inverter used for BLDC motor drive1.2 Simple unipolar converter for three-phase BLDC motor1.3 AC motor drive with active power factor correction stage1.4 AC motor drive with integrated PFC stage and inverter1.5 Brushless DC motor drive waveforms

1.6 Unipolar switching circuit1.7 Voltage source converter topology1.8 PWM carrier Technique1.9 Current waveforms2.1 Circular core with different magnets2.2 BLDC motor transverse section 2.3 Torque /speed characteristics2.4 Back-emf,phase current and output torque waveforms with

(a) bipolar excitation and (b) unipolar excitation

3.1 Schematic of SEPIC converter based BLDC motor drive4.1 Function of the Proportional Term4.2 Function of the Proportional Term & controller error4.3 Function of the Integral Term4.4 Schematic of the proposed converter operating from an ac supply4.5 Block diagram of the drive system5.1 Simulation Circuit Diagram SEPIC Converter Topology5.2 Power Factor Correction With SEPIC Converter5.3 Source voltage and dc output voltage at diode rectifier5.4 speed curve of induction motor drive

5.5 dc output voltage at diode rectifier

5.6 stator current of induction motor drive at load side

5.7 Torque curve of induction motor drive