“Conveyor Belt Control Using Induction Motor For Industrial Application” (final year project)

Conveyor Belt Control Using Induction

Motor For Industrial Application

Submitted by:

Maham Naeem 2011-EE-61

Fatima Muhammad 2011-EE-62

Warda Gul 2011-EE-68

Sabooha Saadat 2011-EE-185

Supervised by: Dr. Syed Abdul Rahman Kashif

Department of Electrical Engineering

University of Engineering and Technology Lahore

Conveyor Belt Control Using Induction

Motor For Industrial Application

Submitted to the faculty of the Electrical Engineering Department

of the University of Engineering and Technology Lahore

in partial fulfillment of the requirements for the Degree of

Bachelor of Science

in

Electrical Engineering.

Internal Examiner External Examiner

DirectorUndergraduate Studies

Department of Electrical Engineering

University of Engineering and Technology Lahore

i

Declaration

We declare that the work contained in this thesis is my own, except where explicitly

stated otherwise. In addition this work has not been submitted to obtain another degree

or professional qualification.

Maham Naeem

2011-EE-61

Fatima Muhammad

2011-EE-62

Warda Gul

2011-EE-68

Sabooha Saadat

2011-EE-185

ii

Acknowledgments

In the name of Allah, the most Beneficent and the most Merciful! The successful ac-

complishment of any task does not solely depend on the efforts of students but also on

the guideline, encouragement and faith shown by teachers. We extend our gratitude to

Dr. Syed Abdul Rahman Kashif and all the faculty members who gave us their

undivided attention and support. Last but not least we would also like to thank our

parents and God Almighty. Without them we would not have been able to complete

any of this.

iii

Contents

Acknowledgments iii

List of Figures vi

List of Tables viii

Abbreviations ix

Abstract x

1 Introduction 1

1.1 Problem Statement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

1.1.1 Research Problem Statement . . . . . . . . . . . . . . . . . . . . . 1

1.1.1.1 Objectives . . . . . . . . . . . . . . . . . . . . . . . . . . 1

1.2 Estimate Funding . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

1.3 Research and Experimental Period . . . . . . . . . . . . . . . . . . . . . . 2

1.3.1 Project Management . . . . . . . . . . . . . . . . . . . . . . . . . . 2

1.4 Remedy for afore mentioned problems . . . . . . . . . . . . . . . . . . . . 3

1.4.1 Why V/F control has been implemented? . . . . . . . . . . . . . . 3

1.4.2 Why has STM series been used? . . . . . . . . . . . . . . . . . . . 3

1.4.3 Conveyor Belt Usage with STM32 F3 series . . . . . . . . . . . . . 3

2 Inverters 5

2.1 Inverter Output . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

2.2 Types of Inverter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6

2.2.1 Three Phase Inverter . . . . . . . . . . . . . . . . . . . . . . . . . . 6

2.2.1.1 180 Degree Conduction . . . . . . . . . . . . . . . . . . . 6

2.2.1.2 Gating Sequence . . . . . . . . . . . . . . . . . . . . . . . 6

2.2.1.3 PWM Generation: . . . . . . . . . . . . . . . . . . . . . . 8

3 V/F Control 10

3.1 Scalar Control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10

3.2 Vector Control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10

3.3 Understanding V/F control . . . . . . . . . . . . . . . . . . . . . . . . . . 11

3.3.1 Open Loop Control . . . . . . . . . . . . . . . . . . . . . . . . . . . 12

3.4 Control Implementation . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12

3.4.1 For Voltage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12

3.4.2 For Frequency . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14

iv

Contents v

4 Hardware Implementation 16

4.1 Power Module . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16

4.2 Inverter Module . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17

4.2.1 Optocouplers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18

4.2.2 Gate Driver Circuit . . . . . . . . . . . . . . . . . . . . . . . . . . 18

4.2.3 Three Phase Inverter . . . . . . . . . . . . . . . . . . . . . . . . . . 19

4.3 Induction motor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20

4.4 Conveyor Belt . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20

5 Simulation and Hardware Results 23

6 Conclusion and Recommendations for Further Work 26

6.1 Accomplished Objective . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26

6.2 Application . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26

6.3 Recommendations for Further Work . . . . . . . . . . . . . . . . . . . . . 27

6.3.1 Current Sensing . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27

6.3.2 Voltage Sensing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27

6.3.3 Object Detection . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27

6.3.4 Speed Measurement . . . . . . . . . . . . . . . . . . . . . . . . . . 28

6.3.5 Implementation of Closed Loop Control . . . . . . . . . . . . . . . 28

References 29

List of Figures

1.1 Project Management[6] . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

2.1 Voltage Fed Inverter[5] . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

2.2 Line to neutral voltage waveform for phase a[5] . . . . . . . . . . . . . . . 7

2.3 Line to neutral voltage waveform for phase b[5] . . . . . . . . . . . . . . . 7

2.4 Line to neutral voltage waveform for phase c[5] . . . . . . . . . . . . . . . 7

2.5 Line to line voltage waveform for all phases[5] . . . . . . . . . . . . . . . . 8

2.6 Code showing Channel 1 (Reference Pulse) . . . . . . . . . . . . . . . . . 8

2.7 Code showing 120 delay . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8

2.8 120 delay . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

2.9 Code showing 240 delay . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

2.10 240 delay . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

3.1 Torque Speed Characteristic Curve[2] . . . . . . . . . . . . . . . . . . . . 11

3.2 Voltage Frequency Curve[7] . . . . . . . . . . . . . . . . . . . . . . . . . . 12

3.3 Multiplied reference pulse . . . . . . . . . . . . . . . . . . . . . . . . . . . 13

3.4 Multiplied 120 delayed pulse . . . . . . . . . . . . . . . . . . . . . . . . . . 13

3.5 Multiplied 240 delayed pulse . . . . . . . . . . . . . . . . . . . . . . . . . . 13

3.6 With Maximum Duty Cycle Of 4 KHZ Pulse . . . . . . . . . . . . . . . . 13

3.7 With Minimum Duty Cycle Of 4 KHZ Pulse . . . . . . . . . . . . . . . . . 14

3.8 Variable Frequency . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14

3.9 Variable Frequency . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14

3.10 Graph Between Voltage and Frequency . . . . . . . . . . . . . . . . . . . . 15

4.1 Project Setup . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16

4.2 AC source . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16

4.3 Bridge Rectifier And Capacitor . . . . . . . . . . . . . . . . . . . . . . . . 17

4.4 Complete Power Module . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17

4.5 Inverter Module . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18

4.6 Optocoupler[4] . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18

4.7 Gate Driver[1] . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19

4.8 Connection Diagram[1] . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19

4.9 Gate Driver Circuit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20

4.10 Pin Configuration of IRF450[3] . . . . . . . . . . . . . . . . . . . . . . . . 20

4.11 inverter pcb . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21

4.12 Induction Motor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21

4.13 Conveyor Belt . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22

5.1 Simulation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23

vi

List of Figures vii

5.2 Line to neutral Voltage Waveform(Simulation) . . . . . . . . . . . . . . . 24

5.3 Line to neutral Voltage Waveform . . . . . . . . . . . . . . . . . . . . . . 24

5.4 Line to Line Voltage Waveform . . . . . . . . . . . . . . . . . . . . . . . . 25

List of Tables

3.1 Voltage and Frequency . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15

4.1 Motor Specifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20

viii

Abbreviations

PWM Pulse Width Modulation

MOSFETS Metal Oxide Semiconsuctor Field Effect Transisitor

ix

Abstract

Experimentation and implementation, is the essence of learning in the field of engineering

that is highlighted by the final year project. The economic growth of a country depends

on a flourishing industry and betterment in its work certainly gives a boost to the

previously normal outcome. Speed control of induction motors is a major concern of

todays industry, and while different techniques are being employed for it; in this project

v/f control has been utilized. The control is executed using the STM32F3. Usage of

STM32F3 controller for such applications has not yet been dealt with at this level,

which is why our study becomes important and more elaborate. The gating sequences

for inverter switches have been tested with simple PWM pulses with varying duty cycles.

The chapters coming forth give a detailed explanation on the working of three phase

inverters, V/F control, induction motors and the conveyor belt control. Amongst the

last chapters we show the underlying software and hardware work, with their results.

Where the actual concern is implementation of speed control to conveyor belts; that are

widely used in industry, speed control may be applied for several other functions too.

Chapter 1

Introduction

1.1 Problem Statement

Controlling speed of induction motors has always been a major concern for the industry.

With the coming years, improvement in this control is a necessity.

1.1.1 Research Problem Statement

The purpose of this project is to control speed of three phase induction motors making

it simpler and easier by employing the V/F technique. Industrial processes require some

defined speed ranges of induction motors for accomplishments of various tasks. This

control has been tested and implemented using the STM32F3203VC controller. STM

series provide a much efficient and quicker on/off control for the inverter operation,

which in turns caters for a smoother operation of motor.

1.1.1.1 Objectives

Speed of control of conveyor belt via three phase induction motor

Implementation of v/f control and pulse generation by STM32F3 series

Smart conveyor belt implementation

1.2 Estimate Funding

STM32 F3 microcontroller= 1800(PKR)

PCB (Three)= 8800(PKR)

Isolated transformers = 700(PKR)

Bridge rectifiers = 150(PKR)

Driver IC (IR2103) = 700(PKR)

Opto-couplers = 700(PKR)

1

Chapter 1. Introduction 2

MOSFETS (IFR450) = 1000(PKR)

Fuses (2 Amperes) = 100(PKR)

Induction motor = 3500 (PKR)

Conveyor belt = 6000(PKR)

Display setups = 6000(PKR)

Others = 7000(PKR)

Total (approximated) = 38000(PKR)

1.3 Research and Experimental Period

Step 1: The idea was first proposed in the 6th semester. We focused on the currentindustrial needs and understood the importance of speed control and workings for

induction motors. (1-2 months)

Step 2: The next important task was to understand the implementation and work-ing of all components and features of the project, for instance studying; three phase

inverters, induction motors, techniques to control the speed and conveyor belt de-

sign. (3-4 months)

Step 3: STM32 F3 controller features; their usage and efficient implementation.(3-4 months)

Step 4: A full fledge working model/ PCB of three phase inverter. (2-3 months)

Step 5: Induction motor interfacing with the three phase inverter and its speedcontrol using the v/f technique (1-2 months)

Step 6: Design and implementation of conveyor belt. Controlling the belt withthe induction motor fixed on the side of the structure. (2 months)

1.3.1 Project Management

The concept of project management is essential for the successful completion of the target

set. The infrastructure of the whole project must be laid down and every big step must

be broken down to small ones. It is by the iterative development and accomplishment of

small tasks for a bigger and better impact on the overall outcome. The following figure

explains this concept.


Figure 1.1: Project Management[6]

1.4 Remedy for afore mentioned problems

1.4.1 Why V/F control has been implemented?

V/f control has many advantages over other speed control techniques the highlight of it

being easier and cheaper to implement. Industries require simpler and easy to imple-

ment methods for control that gives satisfactory performance too. V/f covers all these

aspects. Not only this, it also gives wider stable operating region, low starting currents

to begin with and better transient and steady state performances too. Understanding

its significance, made working on it even more important.

1.4.2 Why has STM series been used?

Usage of STM series for the purpose of speed control is not yet a widely used concept.

The STM series provides a much more efficient and reliable operation for the generation

of different PWM techniques and interfacing, enhancing control over the control belt

and setting a more stable functionality for the working of three phase inverters. Their

study and implementation for speed control in industry will prove to be a hallmark.

1.4.3 Conveyor Belt Usage with STM32 F3 series

Conveyor belts are chiefly meant for the purpose of conveying or carrying/transporting

objects from one place to another. The belts act as a medium of transportation, residing

on two or more pulleys for accomplishing its purpose. The pulleys are named as the

powered and empowered pulleys also known as drive pulleys and idler pulley respectively.

Industrial applications vary widely, and so does the conveyor belt type. It maybe used


either for simple transporting boxes within store rooms of a factory or even handling

bulk material movement (longer conveyor belts are used for this purpose). In our project

the conveyor belt is driven with the help of two pulleys, where the drive is provided by

the induction motor which is in turn controlled by the inverter.

Chapter 2

Inverters

The conversion of dc input to required magnitude and frequency of ac output is called

inversion. Inverters are solid state devices that can be given dc input in the form of

current or voltage; to be converted to respective ac output. Based on inputs; there are

different type of inverters namely voltage fed inverters, current fed-inverters, resonant

pulse inverters etc. The type of inverter widely used in the industry is the voltage

fed inverter, which has been implemented in the project for conveyor belt control. In

this type, the dc voltage being fed is kept constant, while output depends on the gating

sequence of the switches used. Output current is dependent on the value of load.

Figure 2.1: Voltage Fed Inverter[5]

2.1 Inverter Output

Output voltage of Inverter can be changed by two methods

1. Keeping the dc input voltage constant; while varying the gain of the inverter that

employs the technique of pulse width modulation for its gating sequence.

2. Keeping the gain of the inverter constant, varying the input dc voltage of the

inverter.

5

Chapter 2. Inverters 6

2.2 Types of Inverter

1. Single Phase Inverter

2. Three Phase Inverter

2.2.1 Three Phase Inverter

Three phase inverters can be made by either using three single phase inverters together,

that is, the whole inverter shall have twelve switching devices. But the exceeding number

of components and their control not only reduces efficiency but also makes it a tedious

task. We can in turn use the configuration shown below, which employs only six switches

fulfilling the same task. 3-phase inverters are frequently used for high-power applications.

They are also used for supplying 3-phase load particularly in AC motor drives. These

inverters can be operated in different modes such as 60 degree conduction, 120 degree

conduction and 180 degree conduction. We shall describe 180 degree conduction further

on.

2.2.1.1 180 Degree Conduction

Three phase inverter consists of six MOSFETs and six diodes. The diodes are parallel

to the switches and prevent the opposite flow of current. The three phase inverter

employs six MOSFETs as the switching devices. The on off control of these MOSFETs

via gate pulses determines the output voltage waveform. The switching control decides

how long one switch remains on or conducts. In 180 degree conduction every MOSFET

conducts for 180 degrees, or the gate pulse applied keeps the MOSFET in ON state for

180 degrees. At any given time only three of them remain ON while the rest are off.

Two switches of the same phase are never turned on simultaneously otherwise the DC

input provided would be short circuited.

2.2.1.2 Gating Sequence

Three PWM pulses generated from the micro-controller were applied to the opto-couplers

(they help in providing the electrical isolation and save the microcontroller from damage

in case a fault occurs) which in turn were fed to the gate drivers. The pulses applied

were 120 degrees out of phase with one another, which the gate drivers (IR2103) then

change to six pulses that is, the original pulses with their complements or 180 degree

shifted pulses.


Line to neutral and line to line voltages are shown below

Figure 2.2: Line to neutral voltage waveform for phase a[5]

Figure 2.3: Line to neutral voltage waveform for phase b[5]

Figure 2.4: Line to neutral voltage waveform for phase c[5]


Figure 2.5: Line to line voltage waveform for all phases[5]

2.2.1.3 PWM Generation:

Three pulses are generated with 120 and 240 degree delays with respect to the first pulse.

The inverted pulses are generated by the gate driver IC (IR2103).

Figure 2.6: Code showing Channel 1 (Reference Pulse)

The pulse with 120 delay is shown in figure below:

Figure 2.7: Code showing 120 delay

The pulse with 240 delay is shown in figure below:


Figure 2.8: 120 delay

Figure 2.9: Code showing 240 delay

Figure 2.10: 240 delay

Chapter 3

V/F Control

Induction motor controls are of two types

Scalar Control

Vector Control

3.1 Scalar Control

Scalar Control is an easily implemented control, in which only the magnitude and phase

of the variable quantities or parameters are to be set. For instance, in case of induction

motors we may control the parameter of flux via voltage or frequency to control the

torque. Even though these parameters affect each other too, that is, voltage by frequency

and torque by flux, we neglect it. This control is not as fast as or efficient as vector

control its simple and economical factors which make its use widespread.

3.2 Vector Control

Vector control is although a more complicated approach, but it is still a more precise and

faster control. What happens in this case is that each of the stator current, in the three

phases of motor, parameter is broken down or decoupled into two vectors; one vector

that controls magnetic flux and the other which is responsible for torque and then each

of this vector parameter is controlled separately.

Speed Control of Motors can be done by different methods such as follows:

Varying parameters of stator such as

1. Voltage

2. Current

3. Frequency

V/f Control

10

Chapter 3. V/F Control 11

Slip Control

Changing Poles

Varying rotor resistance

Vector Control

Amongst these controls V/f control is the most commonly used control. This is because

not only it is easier to implement, it also gives a good speed range for which an induction

motor can work.

3.3 Understanding V/F control

In case of V/f control our major concern is, as the name indicates, keeping the ratio

a constant. Why that is necessary, is explained as follows: Stator voltage is directly

proportional to both supply frequency and the flux in the air gap. It can be given by

the following equation:

If we ignore the resistance of the stator, the same could be considered for the voltage that

appears at its terminals. If the voltage is kept constant while decreasing frequency the

air gap flux would increase. This increase is unwanted and is the reason for iron losses

and decrease in the motor efficiency, which is why whenever the frequency is changed,

so is the voltage so that the ratio and in turn the flux remains a constant. With this

approach maximum torque of the induction machine remains a constant for different

speed ranges. This can be viewed through the following graph.

Figure 3.1: Torque Speed Characteristic Curve[2]

Another graph that follows can help better in the understanding of this concept: The

v/f control graph can be divided into three portions.


Figure 3.2: Voltage Frequency Curve[7]

When the induction machine just starts the voltage is not zero but the frequency is,

so the voltage is kept at such a value that, there is a certain drop across the stator

resistance. The value of voltage is increased gradually up to cut off frequency for a

linear relation to establish between the two parameters. From cut off frequency to rated

frequency both the parameters increase at the same rate (within the maximum limits

of the machine), keeping the flux value constant and in turn the torque that would be

independent in such a way.

After the rated value of voltage of the machine is achieved increasing frequency any

further would only cause a disturbance in the ratio maintained and the flux would

decrease. Increasing voltage will damage the insulation of the stator windings and

therefore it is preferred to remain within the linear region.

3.3.1 Open Loop Control

The V/f control used here in the project is an open loop control, which is why even if

the output speed is a little varied from the theoretically calculated, it would not affect

the overall outcome as such. Feedback or closed loop control is needed for places where

high accuracy is required.

3.4 Control Implementation

3.4.1 For Voltage

Step 1: In order to vary the output voltage we generated 4KHZ PWM pulse.

Step 2: 4 KHz PWM pulse is multiplied with the reference pulse, of 50 Hz fre-quency.

Step 3: 4 KHz PWM pulse is multiplied with the 120 delayed pulse, of 50 Hzfrequency.

Step 4: 4 KHz PWM pulse is multiplied with the 240 delayed pulse, of 50 Hzfrequency.


Figure 3.3: Multiplied reference pulse

Figure 3.4: Multiplied 120 delayed pulse

Figure 3.5: Multiplied 240 delayed pulse

Step 5:The duty cycle of the 4 KHz PWM pulse is varied to change the outputvoltage. The duty cycle is changed by a variable resistor, which is fed to ADC of

the microcontroller.

Figure 3.6: With Maximum Duty Cycle Of 4 KHZ Pulse


Figure 3.7: With Minimum Duty Cycle Of 4 KHZ Pulse

3.4.2 For Frequency

Voltage is changed by a variable resistor and correspondingly frequency is calculated so

that flux of the motor remains constant.

Figure 3.8: Variable Frequency

Figure 3.9: Variable Frequency


Proceeding step by step, we first derive a relation between output voltage and voltage

across the variable resistor.

Vo = K*Va

where Vo = output voltage

Va = Voltage across variable resistor

and K is the constant of proportionality.

Kf = Vo/F-rated =220/50= 4.4

And Kf =Vo/f =K*Va /f

f = (K*Va)/4.4

We calculated the value of K by hit and trial so that the ratio output voltage and fre-

quency comes out to be constant, K= 20

The graph is obtained from the following readings

Frequency Voltage

50 73

45 66

40 58

35 51

30 40

Table 3.1: Voltage and Frequency

The graph between frequency and voltage shows that the ratio remains constant.

Figure 3.10: Graph Between Voltage and Frequency

Chapter 4

Hardware Implementation

The entire project set up is shown in the figure below. Each of its part is explained as

follows:

Figure 4.1: Project Setup

4.1 Power Module

The power module consists of a 220V AC source, which is rectified by a three phase

bridge rectifier; the pulsating DC is then smoothed out by a capacitor and fed as an

input DC source to the inverter. The complete power module is shown in Figure 4.4

Figure 4.2: AC source

16

Chapter 4. Hardware Implementation 17

Figure 4.3: Bridge Rectifier And Capacitor

Figure 4.4: Complete Power Module

4.2 Inverter Module

The three phase inverter is made of several different components working in a well

defined sequence. The pulses generated by the microcontroller can not be directly fed

into the MOSFETs. This is because the pulses generated have a very small magnitude

of voltage which is not sufficient to switch ON these devices. Also the microcontroller

needs to be protected in case of short-circuiting or any other fault that occurs in the

circuit. The components described below are in the sequence of usage in this module.


Figure 4.5: Inverter Module

4.2.1 Optocouplers

The pulses are fed to optocouplers instead. The ones used here are TLP250. These

provide electrical isolation to the microcontroller. We have used six of them. The pin

configuration of the isolator has been shown.

Figure 4.6: Optocoupler[4]

4.2.2 Gate Driver Circuit

The isolators send the signal to gate drivers IR2103. These are responsible for not only

inversion of the three pulses being fed but also add a dead band of about 520 nanoseconds

in them. This helps greatly as the pulses of two MOSFETs in the same phase, while


switching do not overlap and create a short circuit. These signals, that is, inverted and

no inverted pulses are fed to the MOSFETs. The connections, pin configuration and

description of the IC are given below:

Figure 4.7: Gate Driver[1]

HIN: Logic input for high side gate driver output(HO), in phase LIN: Logic input for

low side gate driver output (LO), out of phase VB: High side floating supply HO: High

side gate drive output Vs: High side floating supply return Vcc: Low side and logic fixed

supply LO: Low side gate drive output COM: Low side return

Figure 4.8: Connection Diagram[1]

At pins HIN and LIN we give the non-inverted pulses generated by microcontroller via

optocoupler. From pins HO and LO we receive the inverted and non-inverted output

ready to be given to the power MOSFETs. Three of them were used to cater for the six

power MOSFETs utilized.

4.2.3 Three Phase Inverter

Six power MOSFETs, IRF450, have been used to implement the three phase inverter

configuration. Each phase consists of two ICs, with complementing pulses.

These power MOSFETs have a large voltage rating approximately 500 V and a maximum

current rating of 14 Amperes, which allows us to vary DC input voltage for a wider range

The PCB of the module is shown in the figure below:

The fuses at the end of the three phases are to save the motor from burning due to short

circuiting or overcurrent.


Figure 4.9: Gate Driver Circuit

Figure 4.10: Pin Configuration of IRF450[3]

4.3 Induction motor

The inverter output is used to drive the three phase induction motor. The motor is

connected to the inverter, as the motor is driven the conveyor belt attached to it moves

as well. The motor specifications are given in table.

Phase 3

Frequency 50Hz

Voltage 220V

Current 2A

Power 10W

rpm 1450

Table 4.1: Motor Specifications

4.4 Conveyor Belt

The conveyor belt designed has a length of about 3 feet and width of 4.7 inches. The

entire structure is made of aluminum and supported on a wooden sheet by two aluminum

cases. The pulleys and bearings were designed in accordance to the conveyor size. There

are two pulleys, one controlled by the motor and the other is the idler that moves by


Figure 4.11: inverter pcb

Figure 4.12: Induction Motor

the movement of belt. The belt itself is made of flex sheet of about 80 inches in size and

3.5 inches width that is wrapped around the structure uniformly


Figure 4.13: Conveyor Belt

Chapter 5

Simulation and Hardware Results

Prior to hardware implementation we simulated the three phase inverter onto Proteus

8.0. The circuit simulation is as follows:

Figure 5.1: Simulation

In the circuit shown above: Pulses marked one, two and three show the input to the

upper three MOSFETs marked Q1, Q2 and Q3. Also a dc input of twenty volts has

been given to their collectors that are common. Even though IRF230 is used as power

MOSFET, when actually implemented we employed IRF450 to cater for higher values

of voltage and current. The three pulses are shifted at 120 degrees from one another,

inverted by NOT gate and given to the lower three MOSFETs marked Q4, Q5 and Q6.

In such a way each phase has two MOSFETs, one driven by non-inverted input and the

other by the inverted pulse. No two MOSFETs of the same phase are ON at a certain

time otherwise it short circuits the dc input voltage, which is undesirable. The three

phases A, B and C have been given to a resistive load at the end and output waveform

is seen by the oscilloscope which is as follows:

23

Chapter 5. Simulation and Hardware Results 24

Figure 5.2: Line to neutral Voltage Waveform(Simulation)

The hardware results in comparison to these were as follows

Figure 5.3: Line to neutral Voltage Waveform

Chapter 5. Simulation and Hardware Results 25

Figure 5.4: Line to Line Voltage Waveform

Chapter 6

Conclusion and

Recommendations for Further

Work

6.1 Accomplished Objective

The major objective this project was to control speed of a conveyor belt using an in-

duction motor. This goal was successfully met by implementation of this control using

the STM series, that is, STM32F1 and STM32F3 controller. The pulses generated were

through the microcontroller, 120 degrees displaced from each other, and then comple-

mented. The six pulses, three inverted and three non-inverted were achieved by the gate

drivers used IR2103. These were utilized, to drive the six MOSFET configuration of the

three phase inverter. By controlling the duty cycle of these pulses, that is the originally

generated 50 Hz frequency pulses multiplied with 4 KHz PWM, consequently giving a 50

Hz pulses with varying duty cycle. This variation was controlled by a variable resistor.

The output of inverter was fed to induction motor. This drove the conveyor belt and

varied its speed as desired. This was the successful implementation of V/f control; an

easy, simple and economical technique which gives a wider range of speed too.

6.2 Application

Conveyor belt control has multiple applications. Industrial processes such as moving

around goods, collection, packaging etc. all involve controlling the speed of conveyor

belts for the overall smooth functioning of manufacturing or supplying a final product.

Conveyor belts are also used for

Security purposes in airports.

A good example in case of health and fitness is the usage of the belt in treadmills

Washing machines26

Chapter 6. Conclusion and Recommendations for Further Work 27

Smaller cranes

Robot Arm of Injection Machine (clamp)

Elevator

Grinding Machine

Drilling Machine

Wood Machine

Webbing Loom

Air Conditioner for Large Buildings

Water Supply System for Large Buildings

Collection and separation of solid wastes. For instance, the speed of conveyor beltcould be slowed down so that glass maybe be picked out carefully by manual labor.

An innovative usage of conveyor belts is in the restaurant business. The idea is simple.

Food is placed onto conveyor belts that move around the entire service lounge. Speed

can be controlled manually and orders are placed accordingly. Customers can self-pick

what they ordered for as it approaches towards them on the belt.

6.3 Recommendations for Further Work

With the limited time span allotted for a final year project, there are many areas which

could always be improved or worked more thoroughly on. A few recommendations for

further work are as follows

6.3.1 Current Sensing

As the load on the conveyor belt varies, the current drawn also varies and so does the

speed of the belt. Work can be done in order to sense and measure the value of current

and change the conveyor belt control parameters accordingly.

6.3.2 Voltage Sensing

Value of output voltage can be sensed by using potential divider rule and then displaying

it on the LCD. The implementation would include configuring ADC (Analog to Digital

Converter) in the STM microcontroller.

6.3.3 Object Detection

Another possibility could be the detection of objects placed on conveyor belt such that

the belt moves only when an object is placed onto it and when it reaches the required

destination the belt stops automatically.

Chapter 6. Conclusion and Recommendations for Further Work 28

6.3.4 Speed Measurement

Induction motor speed varies according to the load on it. The same holds true for the

load onto conveyor belt. What can be done is different speed ranges can be set and

defined for the maximum and minimum amount of load that can be put with respect to

the DC input voltage applied.

6.3.5 Implementation of Closed Loop Control

Speed may not increase or decrease according to the theoretical calculations which is why

a feedback or closed loop control would be more suitable in case of some applications.

A reference speed can be set and others can be measured and corrected to its respect.

References

[1] http://pdf1.alldatasheet.com/datasheet-pdf/view/84682/IRF/IR2103.html.

[2] http://ethesis.nitrkl.ac.in/5016/1/109EE0039.pdf.

[3] http://www.jameco.com/Jameco/Products/ProdDS/670135-DS01.pdf.

[4] http://pdf1.alldatasheet.com/datasheet-pdf/view/32418/TOSHIBA/TLP250.

html.

[5] books.google.com.pk/books/about/Power_Electronics.html?id=

-WqvjxMXClAC&redir_esc=y.

[6] http://open-services.net/bin/view/Main/PmHome.

[7] http://www.ti.com/lit/an/sprabq8/sprabq8.pdf.

29

AcknowledgmentsList of FiguresList of TablesAbbreviationsAbstract1 Introduction1.1 Problem Statement1.1.1 Research Problem Statement1.1.1.1 Objectives

1.2 Estimate Funding1.3 Research and Experimental Period1.3.1 Project Management

1.4 Remedy for afore mentioned problems1.4.1 Why V/F control has been implemented?1.4.2 Why has STM series been used?1.4.3 Conveyor Belt Usage with STM32 F3 series

2 Inverters2.1 Inverter Output2.2 Types of Inverter2.2.1 Three Phase Inverter2.2.1.1 180 Degree Conduction2.2.1.2 Gating Sequence2.2.1.3 PWM Generation:

3 V/F Control3.1 Scalar Control3.2 Vector Control3.3 Understanding V/F control3.3.1 Open Loop Control

3.4 Control Implementation3.4.1 For Voltage3.4.2 For Frequency

4 Hardware Implementation4.1 Power Module4.2 Inverter Module4.2.1 Optocouplers4.2.2 Gate Driver Circuit4.2.3 Three Phase Inverter

4.3 Induction motor4.4 Conveyor Belt

5 Simulation and Hardware Results6 Conclusion and Recommendations for Further Work 6.1 Accomplished Objective6.2 Application6.3 Recommendations for Further Work6.3.1 Current Sensing6.3.2 Voltage Sensing6.3.3 Object Detection6.3.4 Speed Measurement6.3.5 Implementation of Closed Loop Control

References

Documents

“Conveyor Belt Control Using Induction Motor For Industrial Application” (final year project)