bahir dar university bahir dar university institute of

Design and Implementation of Abnormal Voltage Protection System for Induction Motor

BAHIR DAR UNIVERSITY

BAHIR DAR UNIVERSITY INSTITUTE OF TECHNOLOGY

SCHOOL OF ELECTRICAL & COMPUTER ENGINEERING

Final Thesis

On

Design and Implementation of Abnormal Voltage Protection System for

Induction Motor

Prepared by:

Sebsibe Mengistu…………………0502312

Selamawit Abebe…………………0502335

Tamirat Tesema………………..…0502513

Tamiru Bedada………………….....0502514

Project Advisor

Mr. Mezgebu G.

A Project Submitted to the Faculty of Electrical and Computer Engineering of Bahir Dar

University in Partial Fulfillment of the Requirements for the Degree of Bachelor of Science in

Electrical Engineering [Power and Control Engineering]

Bahir Dar, Ethiopia

June, 2017 G.C


I | P a g e BIT, 2009 Final Thesis

Declaration

we ,the undersigned ,declare that this project shall be our original work ,and the Project work has

not been presented for a degree in this or any other universities ,and all sources of materials that

will be used for the project work will have been fully acknowledge.

Name Signature

1. Sebsibe Mengistu ________________

2. Selamawit Abebe ________________

3. Tamirat Tesema ________________

4. Tamiru Bedada ________________

This Project has been submitted for examination with my approval as a university advisor

Project Advisor Signature

Mr. Mezgebu G. ________________


II | P a g e BIT, 2009 Final Thesis

Acknowledgment

We would like to express our sincere gratitude to everyone who supported the conduct of this

project by providing us benchmark information, direction, and insights to fulfill this project. We

would like to acknowledge Faculty of electrical engineering encouraged us to dig out more about

the project. We would like to give our recognition to our project adviser Mr. Mezgebu Getnet

who extended exceptional support to the conduct of this project without which the

conceptualization of the project undertaking would not have been accomplished. Finally we would

like also to thank the electrical and computer engineering staff members helped us to attain

succession of this project.


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Table of Contents

Acknowledgment ............................................................................................................................ II

List of Figure................................................................................................................................. VI

List of Table ................................................................................................................................. VII

List of Acronyms ....................................................................................................................... VIII

Abstract ......................................................................................................................................... IX

CHAPTER ONE ............................................................................................................................. 1

1. INTRODUCTION ...................................................................................................................... 1

1.1 Background ........................................................................................................................... 1

1.3 Objective ............................................................................................................................... 2

1.3.1 Specific Objective ........................................................................................................... 2

1.4 Methodology used in this Project .......................................................................................... 2

1.5 Expected Outcomes and Significance of the Project ............................................................ 3

1.5.1 Expected Outcomes of the Project.................................................................................. 3

1.5.2 Significant of the Project ................................................................................................ 3

1.5.3 Feasibility of the Systems ............................................................................................... 3

1.5.4 Conceptual Framework................................................................................................... 3

1.5 Scope of the Project............................................................................................................... 4

1.6 The Project Organization ...................................................................................................... 4

CHAPTER TWO ............................................................................................................................ 5

2. LITERATURES REVIEW ......................................................................................................... 5

2.1 Evolution of Over Voltage and Under Voltage Control System ........................................... 5

CHAPTER THREE ........................................................................................................................ 8

3. SYSTEM COMPONENTS AND OPERATIONS ..................................................................... 8

3.1 Modeling of the Project ......................................................................................................... 8


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BIT, 2009 Final Thesis

3.2 System Components .............................................................................................................. 9

3.2.1 AC Power Supply ........................................................................................................... 9

3.2.2 Transformer: ................................................................................................................. 10

3.2.3 Diode Bridge Rectifier.................................................................................................. 11

3.2.4 Voltage Regulator – IC LM7812 .................................................................................. 12

3.3.5 Zener Diode .................................................................................................................. 13

3.3.6 Diode ............................................................................................................................ 14

3.3.7 Potentiometer ................................................................................................................ 14

3.3.8 IC LM324 ..................................................................................................................... 15

3.3.9 Transistor ...................................................................................................................... 16

3.3.10 Capacitors and Resistors ............................................................................................. 16

3.3.11 Relay ........................................................................................................................... 18

3.3 Over Voltage and Under Voltage Protection Circuit .......................................................... 20

3.3.1 Overvoltage Protection ................................................................................................. 20

3.3.2 Under Voltage Protection ............................................................................................. 21

CHAPTER FOUR ......................................................................................................................... 23

4. SYSTEM DESIGN AND ANALYSIS ..................................................................................... 23

4.1 Design of Material with Given Specifications .................................................................... 23

4.1.1 Selection of Transformer .............................................................................................. 23

4.1.2 DC Voltage Design Calculation ................................................................................... 23

4.1.3 Design Over Voltage and Under Voltage Protection Calculation ................................ 25

4.1.4 5V Power Supply using LM7805 Voltage Regulator with Design .............................. 26

4.1.5 Relay Drive Circuit ....................................................................................................... 26

4.1.6 Transistor used as Driver .............................................................................................. 27

4.2 Development of the Study ................................................................................................... 29


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CHAPTER FIVE .......................................................................................................................... 31

5. RESULTS AND DISCUSSIONS ............................................................................................. 31

5.1 The Design, Simulation and Implementation ...................................................................... 31

5.1.1 The Simulation Software .............................................................................................. 31

5.1.2 The Under Voltage and Over Voltage Control System Circuit Design ....................... 31

5.1.3 The normal voltage condition ....................................................................................... 32

5.1.4 The Under Voltage Protection Design Condition......................................................... 33

5.1.5 The Over Voltage Protection Design Condition........................................................... 34

CHAPTER SIX ............................................................................................................................. 36

6. CONCLUSION AND RECOMMENDATIONS FOR FUTURE WORK ............................... 36

6.1 Conclusion ........................................................................................................................... 36

6.2 Recommendations for Future Work ............................................................................... 37

References ..................................................................................................................................... 38


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List of Figure

Figure 1.2: Conceptual Framework of the Project [5] .................................................................... 4

Figure 3.1: Block Diagram of Protection System ........................................................................... 9

Figure 3.2: AC Source ................................................................................................................. 10

Figure 3.3: Low Voltage Stepdown Transformer ......................................................................... 11

Figure 3.4: Bridge Rectifier (positive half cycle) ......................................................................... 11

Figure 3.5: IC 7812 ....................................................................................................................... 12

Figure 3.6: Zener Diode ................................................................................................................ 13

Figure 3. 7: Diode Symbol ............................................................................................................ 14

Figure 3. 8: Rated Potentiometer ................................................................................................. 15

Figure 3.9: Pin Configuration LM 324 ......................................................................................... 15

Figure 3.10: Resistors ................................................................................................................... 16

Table 3.1: Resistors Used ............................................................................................................. 17

Figure 3.11: A Typical Capacitor ................................................................................................. 17

Table 3. 2 Capacitors Used ........................................................................................................... 17

Figure 3.12: Atypical Relay .......................................................................................................... 18

Figure 3.13: Circuit Diagram of Overvoltage Protection ............................................................. 21

Figure 3.14 : Circuit Diagram of Under Voltage Protection ........................................................ 22

Figure 4.1: Typical Bridge Rectifier ............................................................................................. 24

Figure 4.2: Design Over Voltage and Under Voltage Protection ................................................. 25

Figure 4.3: Typical Voltage Regulator ......................................................................................... 26

Figure 4.4: Transistor .................................................................................................................... 27

Figure 4.5: Overall System Design ............................................................................................... 30

Figure 5.1: Output of Transformer, Rectifier and Regulator ........................................................ 32

Figure 5.2: Output for Normal Voltage ........................................................................................ 33

Figure 5.3: Output for Under Voltage Protection System ............................................................ 34

Figure 5.4: Output for Over Voltage Protection System .............................................................. 35


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List of Table

Table3. 1 Resistors Used............................................................................................................... 17

Table 3. 2 Capacitors Used ........................................................................................................... 17


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List of Acronyms

AC Alternating Current

ADC Analog to Digital Converter

BJT Bipolar Junction Transistor

DC Direct Current

DG Distributed Generation

EMR Electro Magnetic Relay

IC Integrated Circuit

IPO Input, Process and Output

KVL Kirchoff’s Voltage Law

LED Light Emitting Diode

LV Low Voltage

NC Normal Close

POT Potentiometer

VO Output Voltage

VRMS Root Means Square Voltage


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Abstract

Induction motor is one of the most important motors used in industrial applications. The aim of

this project is to design an over voltage and under voltage control system to protect the induction

motor from damage. The fluctuation in AC mains supply is frequent in homes and industries. The

sensitive electronic devices in these conditions can get easily damaged. For example an induction

motor normal operating voltage is 220 volt AC. If voltage input to induction motor between 180-

240 voltages of induction motor may burn or excessive current may flow which in turn cause short

circuit in the winding of motor.

This project is designed to avoid all these issues which automatically turn on and turn off main

power supply in case of issue in AC main power supply and on one need to control it manually.

Comparator is embedded into this system to make it smart enough to handle all the issues

intelligently and to provide control signals to turn on and off AC main power supply. The over

voltage and under voltage control system of induction motor is preferable to have a tripping

mechanism to protect the induction motor from any damage. This over voltage and under voltage

control system of induction motor will trip the induction motor in the event of the input voltage

falling over or under the sated value. Comparator is used to compare under and over voltage and

send signal to switching device to trip the fault from damaging the induction motor. A switch is

then operated to cut off the induction motor for safety reasons. The hardware materials required

for this over voltage and under voltage control system of induction motor project are the

transformer, Comparator, voltage regulator, resistors, potentiometer, capacitors, diodes, switch,

and induction motor.


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CHAPTER ONE

1. INTRODUCTION

1.1 Background

Protection against fault in power systems is very essential and vital for reliable performance. A

power system is said to be faulty when an undesirable condition occurs in that power system. The

undesirable condition might be short circuits, over current, under voltage, overvoltage etc. An

Induction motor is one of the most significant electromechanical equipment, so it needs protection

against voltage instability. Power system stability is the ability of an electric power system, for a

given initial operating condition, to regain a state of operating equilibrium after being subjected to

a physical disturbance, with most system variables bounded so that practically the entire system

remains intact [5].

Voltage stability refers to the ability of a power system to maintain steady voltages at all electrical

buses in the system after being subjected to a disturbance. On the contrary, voltage instability is

mainly caused when a power system cannot meet its demand for reactive power. The dangers of

power instability are observed to be tremendously serious not only to the power grid, but also in

the mainstreams users of power utilities [4]. An overvoltage and under voltage condition is a form

of voltage instability that also may occur in the household electrical system.

Often times the aforementioned condition is detrimental to the life of electrical devices affected

by it. An overvoltage condition in an induction motor occurs when the voltage in the motor rises

above its upper design limit. Such occurrence in the system damages sensitive electronic and

electrical devices which are designed to operate within predesigned rated voltages. Consequently

during under-voltage condition, an induction motor is also heated up quickly because the torque

and the speed of the induction motor are correspondingly be reduced, hence causing an increase in

induction motor current. It is therefore desirable to protect electrical installation zones against

overvoltage and/or under voltage condition to minimize risk of damage to induction motor

connected to the electrical installation zones [7]. Now day’s high quality power is basic need of

highly automated industries and home appliances. So this high quality power may be got by the

help of this circuit and it will improve the power factor and thus power can be fully utilized.


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1.2 Statement of the Problem

The dangers of power fluctuation on electrical equipment are a serious problem. An essential

concern in an induction motor protection is the high cost of the motor and the relative downtime

cost when induction motor and other relevant equipment fails during voltage instability. Under

voltage and over voltage are the main types of voltage instability. Power fluctuations especially

in Ethiopia prompted the consumers to suffer from these inefficiencies which often times

detrimental to the life of every power utility installations aside from the discomfort of power

brown-outs.

1.3 Objective

The main objective of this project is to design and implement abnormal voltage protection system

for induction motor.

1.3.1 Specific Objective

To collect and analysis data

To design the over voltage and under voltage protection system

To select transformer , bridge rectifier, voltage sensor, voltage regulator, transistor, relay

To simulate system in accordance to the established design parameters

1.4 Methodology used in this Project

For successful completion of this project some steps will be followed to carry out different tasks.

Power fluctuation was burning issue as we saw in Ethiopian electric power utility during internship

program. So, that we were decided to solve this problem. Different literatures were revised relating

to this project and data was collected about condition and control parameter of induction motor.

The process of this system is whenever there an overvoltage or under voltage the relay sense the

input from operational amplifier and gets trip and the load is off. Thus it protects the electrical

appliance.

Figure 1.1: Methodology of the Project

Identify

problem

Revised

literature

and data

collection

System

model

design

Simulation


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1.5 Expected Outcomes and Significance of the Project

1.5.1 Expected Outcomes of the Project

The expected outcome of this project is to protect the induction motor from voltage instability by

tripping the supply voltage in the range between “180-240volt” the induction motor operate at

normal condition but when the voltage is out of the range the relay is open and the motor is safe

from damage.

1.5.2 Significant of the Project

The significance of the project is perceived to satisfy the household consumer’s needs for efficient

power utility, safe from detrimental power fluctuations there by offering longer service life and

quality services to electrical household equipment. The protection circuit design is also perceived

to serve as a model for induction motor protection and home safety.

1.5.3 Feasibility of the Systems

This project reduces the effect of voltage instability on induction motor safely, cheap and it gives

fast response as compared to other voltage stabilizer. So this project is more acceptable in the

society since voltage instability is currently occur in any industry, home and any organization that

uses electric power.

1.5.4 Conceptual Framework

The framework of the project covers the integration of the following electronic components that

comprise the over voltage and under voltage protection. This project utilizes the input, process,

and output (IPO) paradigm which comprises the design of the transformer, bridge rectifier, voltage

regulator, comparator, resistance, diode, potentiometer, transistor, power supply, relay, and load.

The IPO paradigm is simulated through simulation using acceptable software most preferably

Proteus software and implemented.


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Figure 1.2: Conceptual Framework of the Project [5]

1.5 Scope of the Project

The coverage of the study outlines the design, simulation and implementation of the over voltage

and under voltage protection circuit through electronic simulation using Proteus software. Physical

electronic components and other auxiliary equipment are implemented in this current study. In the

Proteus professional software have also its own limitation based on the tolerance of each

components in the over voltage and under voltage control system of single phase induction motor.

1.6 The Project Organization

The project is organized into six chapters. The contents of these chapters are summarized as:-

Chapter.1: Introduces overall background information of the system. This includes background,

problem statement, significance and objective, proposed methodology of the work and its Scope

and contribution.

Chapter.2: Focuses revision of related literatures to this system.

Chapter.3: Covers system components and operation.

Chapter.4: Focuses system design and analysis

Chapter.5: describe results and discussions

Chapter.6: Summarizes the conclusion and recommendation for future work

•Transformer

•Capacitors

•Resistors

•Transistors

•Relay

•AC motor

•Power

supply

•Diodes

•comparator

•Simulation

Software

•Over and Under

Voltage Protection

induction motor

Input

Process

Output


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CHAPTER TWO

2. LITERATURES REVIEW

2.1 Evolution of Over Voltage and Under Voltage Control System

Mohammad Shah Alamgir and Sumit Dev(2015) proposed Voltage regulators have been in

existence for some 158 years with the simple purpose of reducing or increasing voltage. Voltage

regulators are used to reduce electricity costs and CO2 emissions. This use of voltage regulators is

commonly referred to as voltage optimization, or more correctly power optimization [4]. Voltage

optimization is more in demand today than at any other time. This is because power demand is

constantly growing and now outstripping supply.

This produces a resultant deterioration of power quality irregular voltage which is mostly too high

and sometimes too low. This constant change in main voltage damages user’s electrical equipment

and causes them to pay too much for their electricity. Consumers want to protect their sites from

electrical equipment damage caused by poor power quality and the ever increasing cost of

electricity. Power optimization has become the proven method in over voltage supply areas to save

energy and electrical costs, increase the lifecycle of electrical equipment, and reduce electrical

equipment maintenance and repair of costs [9].

Causes and Effect of Voltage Unbalance Mitigation Techniques

Annette von Jouanne and BasudebBanerjee (2001) proposed on causes and effects of voltage

unbalance and to discuss related standards, definitions and mitigation techniques. Several causes

of voltage unbalance on the power system and in industrial facilities are presented as well as the

resulting adverse effects on the system and on equipment such as induction motors and power

electronic converters and drives. Standards addressing voltage unbalance are discussed and

clarified, and several mitigation techniques are suggested to correct voltage unbalance problems.

This study makes apparent the importance of identifying potential unbalance problems for the

benefit of both the utility and customer (Annette von Jouanne and Basudeb Banerjee, 2001).

The purpose of power system protection is to detect the faults or abnormal operating condition and

to initiate corrective action. Relay must be able to evaluate wide variety of parameters to establish

that corrective action is required. Obviously, a relay can’t prevent the fault. Its primary purpose is


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to detect the fault and take the necessary action to minimize the damage to the equipment or to the

system [1].

Sensitivity Analysis of Frequency and Voltage Stability in Islanded Microgrid

HannuLaaksonen, KimmoKauhaniemi (2007) describes their study on the voltage and frequency

stability of an islanded micro grid and the sensitivity of these quantities to certain changes in

system configuration. In conventional power systems the system frequency is coupled with the

rotor speed of the directly grid connected large synchronous generators and power unbalance can

be seen as changed system frequency. But in an islanded micro grid it is possible that all generation

units are connected to grid via converters and there is no inertia of rotating masses to affect the

frequency.

In that case the frequency has to be created by a power electronic device and the frequency is

more of less fixed and power unbalance cannot be detected in the classical way. The studied urban

low voltage (LV) network based micro grid consists of three converters and one synchronous

generator based distributed generation (DG) units. The studies are made with PSCAD simulation

software [2].

Voltage multi-stability in distribution grids with power flow reversal

Hung D. Nguyen, Konstantin Turitsyn (2014), describe in their study that high levels of penetration

of distributed generation and aggressive reactive power compensation with modern power

electronics may result in the reversal of active and reactive power flows in future distribution grids.

The voltage stability of these operating conditions may be very different from the more traditional

power consumption regime. Stability characteristics of distribution networks with reversed power

flow were also studied [3].

After introducing a universal algebraic approach to characterize all the solutions of the power flow

equations, we show that new solutions appear in the reversed power flow regime even in the

simplest three bus systems. Some of these solutions are shown to be stable and the system may

exhibit a phenomenon of multi-stability, where multiple stable equilibrium co-exist at the given

set of parameters, and the system may converge to an undesirable equilibrium after a disturbance.


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These predictions are validated with dynamic simulations of two different systems. Under certain

conditions the new states are viable and may be characterized by relatively high voltages.

We designed to avoid all these issues which automatically turn on and turn off main power supply

in case of issue in AC main power supply and on one need to control it manually. Comparator is

embedded into this system to make it smart enough to handle all the issues intelligently and to

provide control signals to turn on and off AC main power supply. The over voltage and under

voltage control system of induction motor is preferable to have a tripping mechanism to protect

the induction motor from any damage. This over voltage and under voltage control system of

induction motor will trip the induction motor in the event of the input voltage falling over or under

the sated value.


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CHAPTER THREE

3. SYSTEM COMPONENTS AND OPERATIONS

3.1 Modeling of the Project

In the block diagram shown below, the transformer, bridge rectifier, comparator, voltage

regulator, transistor, power supply, zener diodes, switch, and induction motor are interconnected

to perform circuit protection from over voltage and under voltage occurrence. The primary

winding of the 220v AC transformer is connected to a variable AC input voltage and the output is

connected to an induction motor.

At the primary side of the transformer is a step down transformer and which is step down from

220v to 12v AC. By the helping of bridge rectifier it is converted to a pure 12v DC at the secondary

side of the transformer. While monitoring the induction motor parameters, whenever the induction

motor voltage exceeds high voltage, a comparator compare the voltage drop on potentiometer and

zener diode and it sends a trip signal to the switch, thereby protecting the induction motor from

damage. Moreover, when the supply voltage is decreased from its specified voltage, the

comparator compare the voltage drop on potentiometer and zener diode and it sends a trip signal

to the switch and the induction motor will be protected from damage.


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Figure 3.1: Block Diagram of Protection System

3.2 System Components

3.2.1 AC Power Supply

This over voltage and under voltage control system project the AC power supply typically takes

the voltage from the main supply and lowers it to the desired voltage. An AC powered unregulated

power supply usually uses a transformer to convert the voltage from the wall outlet to a different

measurement of voltages by the helping of step down transformer on this over voltage and under

voltage control system project. If it is used to produce DC, a bridge rectifier is used to convert

alternating voltage to a pulsating direct voltage, followed by a filter, comprising by the capacitor,

and resistor, to filter out (smooth) most of the pulsation. Figure 3.2 shows the AC power supply

electronic symbol.

Step

down

Transform

er

Bridge

Rectifier

Power

supply

Voltage

Regulato

r

Pot.

Preset 2

Zener diode

Pot.

Preset 1

Zener

diode

Comparato

rs

IC LM324

Relay

Load


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3.2.2 Transformer:

Specification:

Step down transformer 230V/12V

Operating frequency is 50HZ

Voltage is converted from 230 V to 12 V

Current rating is 1A

Low voltage power is described as power supplied from a transformer of 30 volts or

less. The transformer actually steps down and converts 230 volt power to 30 volts or less.

Transformers are normally mounted on a junction box. Sometimes transformers have more than

one voltage connection point, called a multi-tap transformer.

Transformers are constructed of two tightly wound coils encased in a metal cover. Since the two

coils are placed closely together in the case, current flows through the primary winding (the 120-

volt side) and as it does this, it produces a magnetic flow. This flow produces current in the second

coil winding (secondary winding) that produces the low voltage output.

The primary coil has more windings than the secondary coil. Because of the reduced

number of windings in the secondary coil, the voltage output is much less. Secondary windings

usually produce voltages between 8 and 24volts.An electronic low voltage transformer also

contains an electronic device, called an inverter, which allows the size of the low voltage

transformer to be substantially smaller. An inverter and a small transformer make up the main

components of what we normally call an electronic low voltage transformer.

Figure 3.2: AC Source


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Characteristics:

Used for indoors

Low voltage ripple noise

Green energy saving chip

Design double insulate

Figure 3.3: Low Voltage Stepdown Transformer

3.2.3 Diode Bridge Rectifier

A bridge rectifier is an arrangement of four or more diodes in a bridge circuit configuration which

provides the same output polarity for either input polarity. It is used for converting an alternating

current (AC) input into direct current (DC) output. The primary application of bridge rectifiers

which is used for the purpose of converting an alternating current (AC) input into direct current

(DC) output. All electronic devices require direct current, so bridge rectifiers are used inside the

power supplies of almost all electronic equipment. The signal may be amplified before it is detected; if it is

not then a very low voltage drop diode or a diode biased with a fixed voltage must be used.

Figure 3.4: Bridge Rectifier (positive half cycle)


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3.2.4 Voltage Regulator – IC LM7812

The LM7812 series of three-terminal positive regulators are available in the VO=DVs and with

several fixed output voltages, making them useful in a Wide range of applications. Each type

employs internal current limiting, thermal shutdown and safe operating area protection, making it

essentially indestructible. If adequate heat sinking is provided, they can deliver over 1A output

Current. Although designed primarily as fixed voltage regulators, these devices can be used with

External components to obtain adjustable voltages and currents.

A voltage regulator is an electrical regulator designed to automatically maintain a

constant voltage level. A voltage regulator is an example of a negative feedback control loop. It

may use an electromechanical mechanism, or electronic components. Depending on the design,

it may be used to regulate one or more AC or DC voltages.

Figure 3.5: IC 7812

Electronic voltage regulators operate by comparing the actual output voltage to some

internal fixed reference voltage. Any difference is amplified and used to control the regulation

element in such a way as to reduce the voltage error. This forms a negative feedback control

loop; increasing the open-loop gain tends to increase regulation accuracy but reduce stability

(avoidance of oscillation, or ringing during step changes).

There will also be a trade-off between stability and the speed of the response to changes. If the

output voltage is too low (perhaps due to input voltage reducing or load current increasing),

the regulation element is commanded, up to a point, to produce a higher output voltage - by


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dropping less of the input voltage (for linear series regulators and buck switching regulators),

or to draw input current for longer periods (boost-type switching regulators); if the output

voltage is too high, the regulation element will normally be commanded to produce a lower

voltage. However, many regulators have over-current protection; so that they will entirely stop

sourcing current (or limit the current in some way) if the output current is too high, and some

regulators may also shut down if the input voltage is outside a given range.

Specification:

Output current in excess of 1A.

Output Voltages of 12V.

Current internal thermal overload protection.

No external components required.

Output transistor safe area protection.

Internal short circuit limit.

3.3.5 Zener Diode

A Zener diode is a type of diode that permits current not only in the forward

direction like a normal diode, but also in the reverse direction if the voltage is larger than the

breakdown voltage known as "Zener knee voltage" or "Zener voltage".

Figure 3.6: Zener Diode

A conventional solid-state diode will not allow significant current if it is reverse-biased below its

reverse breakdown voltage. When the reverse bias breakdown voltage is exceeded, a

conventional diode is subject to high current due to avalanche breakdown. Unless this current is

limited by circuitry, the diode will be permanently damaged. In case of large forward bias

(current in the direction of the arrow), the diode exhibits a voltage drop due to its junction built in


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voltage and internal resistance. The amount of the voltage drop depends on the semiconductor

material and the doping concentrations.

A Zener diode exhibits almost the same properties, except the device is specially

designed so as to have a greatly reduced breakdown voltage, the so-called Zener voltage. By

contrast with the conventional device, a reverse-biased Zener diode will exhibit a controlled

breakdown and allow the current to keep the voltage across the Zener diode at the Zener voltage.

For example, a diode with a Zener breakdown voltage of 3.2 V will exhibit a voltage drop of 3.2V

if reverse bias voltage applied across it is more than its Zener voltage. The Zener diode is therefore

ideal for applications such as the generation of a reference voltage (e.g. for an amplifier

stage), or as a voltage stabilizer for low-current applications.

3.3.6 Diode

The most common function of a diode as shown in bridge rectifier figure above is to allow an

electric current in one direction (forward direction) while blocking current in the opposite direction

(reverse direction). In electronics a diode is a two terminal electronic component that conducts

electric current in only one direction.

Figure 3. 7: Diode Symbol

3.3.7 Potentiometer

A potentiometer (colloquially known as a "pot") is a three- terminal resistor with a

sliding contact that forms an adjustable voltage divider. If only two terminals are used (one side

and the wiper), it acts as a variable resistor or rheostat. This component acts much like a

tapped/split resistor, except that you can adjust its resistance. The variability of the potentiometer

allows flexibility in the resistance as it resists the flow of current into a particular branch.


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Potentiometers are commonly used to control electrical devices such as volume controls on audio

equipment. Potentiometers operated by a mechanism can be used as position transducers, for

example, in a joystick. Potentiometers are rarely used to directly control significant power.

Figure 3. 8: Rated Potentiometer

3.3.8 IC LM324

Specifications:

Internally frequency compensated for unity gain

Large DC voltage gain 100 Db

Wide bandwidth (unity gain) 1 MHz

Wide power supply range

Very supply current drain (700 µA)

Low input biasing current 45 mA (temperature compensated)

Low input offset voltage 2 mV and offset current 5 mA

Input common mode voltage range includes ground

Figure 3.9: Pin Configuration LM 324


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The LM324 series consists of four independent, high gains; internally frequency compensated

operational amplifiers which were designed specifically to operate from a single power supply

over a wide range of voltages. Operation from split power supplies is also possible and the low

power supply current drain is independent of the magnitude of the power supply voltage.

3.3.9 Transistor

A transistor is a semiconductor device used to amplify and switch electronic signals

and electrical power. It is composed of semiconductor material with at least three terminals for

connection to an external circuit. A voltage or current applied to one pair of the transistor's

terminals changes the current through another pair of terminals. Because the controlled (output)

power can be higher than the controlling (input) power, a transistor can amplify a signal. Today,

some transistors are packaged individually, but many more are found embedded in integrated

circuits.

3.3.10 Capacitors and Resistors

Resistors:

Resistors are used to maintain a constant relation between current flow and voltage. Resistors are

used to step up or lower the voltage at different points in a circuit and to transform a current signal

into a voltage signal or vice versa, among other uses. The electrical behavior of a resistor obeys

Ohm's law for a constant resistance; however, some resistors are sensitive to heat, light, or other

variables. Variable resistors, or rheostats, have resistance that may be varied across a certain range,

usually by means of a mechanical device that alters the position of one terminal of the resistor

along a strip of resistant material.

Figure 3.10: Resistors


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Rating of Resistor Required Numbers

33kΩ 3

6.8Ω 4

10kΩ 4

1kΩ 4

Table 3.1: Resistors Used

Capacitors:

Capacitor stores and release electrical charge. A capacitor or condenser is a passive electronic

component consisting of a pair of conductors separated by a dielectric. When a potential difference

exists across the conductors, an electric field is present in the dielectric. This field stores energy

and produces a mechanical force between the conductors. They are used for filtering power supply

lines, tuning resonant circuits, and for blocking DC voltages while passing AC signals, among

numerous other uses. The effect is greatest when there is a narrow separation between large areas

of conductor; hence capacitor conductors are often called plates. Figure 3.7 shows a capacitor

electronic symbol.

Figure 3.11: A Typical Capacitor

Rating of Capacitor Required Numbers

470 µF 3

0.1 µF 4

Table 3. 2 Capacitors Used


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3.3.11 Relay

A relay is an electrically operated switch. Many relays use an electromagnet to

operate a switching mechanism mechanically, but other operating principles are also used.

Relays are used where it is necessary to control a circuit by a low-power signal (with complete

electrical isolation between control and controlled circuits), or where several circuits must be

controlled by one signal. The relay is an electrically controllable switch widely used in industrial

controls, automobiles, and appliances.

It allows the isolation of two separate sections of a system with two different voltage sources. For

example, an induction motor can be isolated from a 220V system by placing a relay in between

them. One such relay is called an electromechanical or electromagnetic relay EMR. The EMRs

have three components: the coil, spring and contacts. In figure 3.13, a digital +3V can control a

220Vac induction motor without any physical contact between them. When current flows through

the coil, a magnetic field is created around the coil (the coil is energized), which causes the

armature to be attracted to the coil. The armature’s contact acts like a switch and closes or opens

the circuit. The relay serves as the protective device of the entire system.

Figure 3.12: Atypical Relay

A simple electromagnetic relay consists of a coil of wire surrounding a soft iron

core, an iron yoke which provides a low reluctance path for magnetic flux, a movable iron

armature, and one or more sets of contacts (there are two in the relay pictured). The armature is

hinged to the yoke and mechanically linked to one or more sets of moving contacts. It is held in


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place by a spring so that when the relay is de-energized there is an air gap in the magnetic circuit.

In this condition, one of the two sets of contacts in the relay pictured is closed, and the other set

is open.

When an electric current is passed through the coil it generates a magnetic field that

attracts the armature and the consequent movement of the movable contact either makes or

breaks (depending upon construction) a connection with a fixed contact. If the set of contacts

was closed when the relay was de-energized, then the movement opens the contacts and breaks

the connection, and vice versa if the contacts were open. When the current to the coil is switched

off, the armature is returned by a force, approximately half as strong as the magnetic force, to its

relaxed position. Usually this force is provided by a spring, but gravity is also used commonly in

industrial motor starters. Most relays are manufactured to operate quickly. In a low-voltage

application this reduces noise; in a high voltage or current application it reduces arcing.

When the coil is energized with direct current, a diode is often placed across the coil

to dissipate the energy from the collapsing magnetic field at deactivation, which would otherwise

generate a voltage spike dangerous to semiconductor circuit components. Some automotive

relays include a diode inside the relay case. Alternatively, a contact protection network

consisting of a capacitor and resistor in series (snubber circuit) may absorb the surge. If the coil

is designed to be energized with alternating current (AC), a small copper "shading ring" can be

crimped to the end of the solenoid, creating a small out-of-phase current which increases the

minimum pull on the armature during the AC cycle.

A solid-state relay uses a thyristor or other solid-state switching device, activated by the control

signal, to switch the controlled load, instead of a solenoid. An opt coupler (a light-

emitting diode (LED) coupled with a photo transistor) can be used to isolate control and

controlled circuits.


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3.3 Over Voltage and Under Voltage Protection Circuit

3.3.1 Overvoltage Protection

In overvoltage protection system of single phase induction motor, protects the motor from

overvoltage, the voltage which is higher than the rated voltage. In circuit diagram of overvoltage

protection it consists the comparator which compare two voltages one is supply and another one

is drop across the variable resistance. Operational amplifier IC LM324 (IC2) is used here as a

comparator. IC LM324 consists of four operational amplifiers, of which only two operational

amplifiers (N1 and N2) are used in the circuit. The unregulated power supply is connected to the

series combination of resistors R1 and R2 and potentiometer VR1. The same supply is also

connected to a 6.8V Zener diode (ZD1) through resistor R3.

Preset VR1 is adjusted such that for the normal supply of 180V to 240V, the voltage at the non-

inverting terminal (pin 3) of operational amplifier N1 is less than 6.8V. Hence the output of the

operational amplifier is zero and transistor T1 remains off.

The relay, which is connected to the collector of transistor T1, also remains de-energized.

As the AC supply to the electrical appliances is given through the normally closed (N/C)

terminal of the relay, the supply is not disconnected during normal operation.

When the AC voltage increases beyond 240V, the voltage at the non-inverting terminal

(pin 3) of operational amplifier N1 increases. The voltage at the inverting terminal is still

6.8V because of the zener diode.

Thus now if the voltage at pin 3 of the operational amplifier is higher than 6.8V, the output

of the operational amplifier goes high to drive transistor T1 and hence energize relay RL.

Consequently, the AC supply is disconnected and electrical appliances turn off.

Thus the appliances are protected against over-voltage.


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Figure 3.13: Circuit Diagram of Overvoltage Protection

3.3.2 Under Voltage Protection

In under voltage protection of single phase induction motor provides the protection from the under

voltage. When supply system has low voltage less than the rated of induction motor then under

voltage protection section of protection supply is provided to motor. Single phasing works.

When the line voltage is below 180V, the voltage at the inverting terminal (pin 6) of operational

amplifier N2 is less than the voltage at the non-inverting terminal (6V). Thus the output of

operational amplifier N2 goes high and it energizes the relay through transistor T1. The AC supply

is disconnected and electrical appliances turn off.

Thus the appliances are protected against under-voltage. IC1 is wired for a regulated 12V

supply.

The relay energizes in two conditions: first, if the voltage at pin 3 of IC2 is above 6.8V,

and second, if the voltage at pin 6 of IC2 is below 6V.

Over-voltage and under-voltage levels can be adjusted using presets VR1 and VR2,

respectively.


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Figure 3.14 : Circuit Diagram of Under Voltage Protection


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CHAPTER FOUR

4. SYSTEM DESIGN AND ANALYSIS

4.1 Design of Material with Given Specifications

4.1.1 Selection of Transformer

Secondary winding calculation of transformer

The 220v AC: 12v AC step down transformer is used to supply the reduced voltage for induction

motor over voltage and under voltage control system. The voltage transformer will pass through

rectification process before fed to a 12v DC. Assume the transformer has 120 turns of coil in the

primary, therefore secondary winding turns calculated as:

N1

N2=

V1

V2 (1)

120

N2= 220Vv/12v

N2 =12

220∗ 120 = 𝟕turns

Transformer primary current calculation The step down transformer is a transformer that has

low voltage in the secondary than the voltage in the primary. But in case of current it would step

up i.e. the current at the primary is lower than the current at the secondary side of the transformer.

Assume the secondary current is 1A, and then the primary current can be calculated as:

N1

N2=

I2

I1 (2)

N1

N2=

V1

V2=

I2

I1=

220

12

I1 =12

220∗ 1 = 𝟎. 𝟎𝟓𝟒𝟓𝐀 = 𝟓𝟒. 𝟓𝐦𝐀

The above calculation shows that the step down transformer has step up the primary current from

54.5mA to 1A at the secondary.

4.1.2 DC Voltage Design Calculation

The over voltage and under voltage protection circuit is capable of measuring and monitoring

voltages from 200 to 240v AC. In this project the voltage can be increased or decreased by using

the autotransformer and the output of the voltage monitoring circuit is fed to ADC convertor,


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whenever the voltage is varied to 200v AC, the comparator will detect under voltage fault,

consequently the comparator sends a trip signal to the relay, and the relay cuts the induction motor

from the AC mains, thereby protecting the motor automatically. The secondary voltage of the

transformer is 12v AC and connected to the bridge rectifier, therefore the DC output is

approximated as:

𝐃𝐃𝐂 = 𝐕𝐀𝐂 ∗ √𝟐 − (𝟐 ∗ 𝟎. 𝟕) (𝟑)

VDC = 12 ∗ √2 − 1.4 = 15.57𝑉

The rms transformer voltage and the 0.7v is voltage drop across the rectifier. As there are two

Diodes conducting for each half cycle, therefore there will be two rectifier voltage drops.

Figure 4.1: Typical Bridge Rectifier

Design bridge rectifier with given specifications

Given data:

VDC = 15.57V

IDC = 1A

Assume;VON = 1V, VR < 0.15𝑉

V =VP

√2=

VDC

√2+

2VON

√2=

15.57v

√2+

2 ∗ 1

√2= 12.42Vrms

According to various sources, the ripple voltage of a full wave bridge rectifier is calculated as:

VR =IDC ∗ T

2C (4)


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C =Idc ∗ T

2VR= 1A ∗

66μS

2 ∗ 0.15V= 220.3μF

Where:

T =is the time taken

C= is the capacitor

R =the resistor of motor.

4.1.3 Design Over Voltage and Under Voltage Protection Calculation

By applying the analog signal to comparator + input called “non-inverting” and – input called

“Inverting”, the comparator circuit will compared this two analog signal, if the analog input on +

input is greater than the analog input on – input (inverting) then the output will swing to the logical

“1” and this will make the open collector transistor.

Figure 4.2: Design Over Voltage and Under Voltage Protection

𝑉− =𝑅𝑣2 + 𝑅4

𝑅𝑣2 + 𝑅4 + 𝑅6∗ 𝑉𝐶𝐶 (5)

Assume R6 = 10KΩ

𝑉𝐶𝐶 is the voltage which activities comparator

When 𝑉− = 𝑉+ the output of comparator is zero

V− = V+ = 6.8v , which drop on the zener diode

So, 6.8v = (RV2+R4

RV2+R4+10KΩ) ∗ 5.2V


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6.8V

5.2V=

RV2 + R4

RV2 + R4 + 10KΩ= 1.307

1.307(RV2 + R4) + 13.07KΩ = RV2 + R4

0.307(RV2 + R4) = −13.07KΩ

RV2 + R4 = −13.07KΩ

0.307= 42.6KΩ

In case of our design we choose 10𝐾Ω resistance and 47KΩ potentiometer adjust to32.6KΩ.

4.1.4 5V Power Supply using LM7805 Voltage Regulator with Design

In most of our electronic products or projects we need a power supply for converting mains AC

voltage to a regulated DC voltage. For making a power supply designing for each and every

component is essential. Here we select LM7805 voltage regulator type because in our design we

need 5v dc output and have an input 12v dc. As we require a 5v we need LM7805 voltage regulator

IC.LM7805 IC Rating:

Input voltage 7v-35v

Current rating 𝐼𝐶 = 1𝐴

Output voltage rang 4.8v-5.2v

Figure 4.3: Typical Voltage Regulator

4.1.5 Relay Drive Circuit

The 3v relay‘s coil needs around 30mA to be energized, the current is obtained by V/R

expression. The coil is 3v DC and the coil resistance is 200ohm, (3v/200ohm) is needed to energize

the relay; therefore a transistor was used as relay driver which is placed between the comparator

and the relay.


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4.1.6 Transistor used as Driver

The transistor is used as the driver and the basic function of the driver circuit is to provide the

necessary current to energize the relay coil. It’s important that the transistor is driven in to

saturation so that the voltage drop across the transistor is minimum thereby dissipating very little

power. The protection diode in the circuit is used to protect the transistor from the reverse current

generated from the coil of the relay during the switch off time. When the base voltage is zero, BJT

will be in cut off IC =0, VOUT=VCC (open switch) When base voltage is 5V DC, BJT can be in

saturated (closed switch) with VOUT=VCE=Vsat~0.2v.

Figure 4.4: Transistor

Cut off condition

A transistor is said to be in cut-off region when the base emitter BE junction is not forward biased.

When IB is near to zero IC approaches zero in a non-liner manner this is known as a cut off region

of operation and in this case the transistor acts as open or off switch.

Saturation condition

The transistor is said to be in a saturated condition when the BE base emitter junction is in forward

biased, and there is an enough base current to produce high collector current. In this case the

transistor is said to be closed or on. The collector current can be calculated as:

VBE = 0.7V, IB > 0A

IC =VCC − VCE

RC (6)


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Verification of transistor base resistor value

The output from the comparator is required to energize the relay with a 240 ohm coil. The

supply voltage to the transistor is 5V. The comparators supply a maximum current of

2mA.Calculating the base resistance RB. Therefore:

𝑅𝐵 =𝑉𝐶𝐶 ∗ ℎ𝐹𝐸

3 ∗ 𝐼𝐿 (7)

To find the load current,

IL =VS

RL=

3V

200Ω= 15mA

To find the resistor current gain,

hFE = 5 ∗IL

Iinput= 3 ∗

15mA

8.24mA= 9.1v

Finally the 𝑅𝐵 is calculated since all the variables are known:

RB =3 ∗ 9.1V

3 ∗ 15mA= 0.6068KΩ

With the RB=0.6068Kῼ, the closest resistor value of 1kῼ choose as RB

Verification of transistor VCE in saturated region (closed) by voltage divider

Voltage divider rules states that the voltage across the resistor in series circuit is equal to the value

of the resistor multiply by the total impressed voltage across the series elements divided by the

total resistance of the series elements.

VCE =RE

RC + RE∗ VCC (8)

RE = 0KΩ, RC = 200Ω, VCC = 5V and VCC =?

VCE =0

200Ω∗ 5V

𝑉𝐶𝐸 = 0𝑉

Calculating base current IB using Kirchhoff’s voltage law (KVL)

The base current IB can be calculated as:

IBRB + VBE − VBB = 0 (9)

IB =VBB − VBE

RB=

5V − 0.7V

1KΩ= 4.3mA

Calculating Collector current IC using Kirchhoff’s voltage law (KVL)

The collector current Ic can be calculated as:


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𝑉𝐶𝐶 = 𝐼𝐶𝑅𝐶 + 𝑉𝐶𝐸 (10)

IC =VCC − VCE

RC=

5V − 0V

0.2KΩ= 2.5mA

Verification of transistor VCE in cut off region (open)

In cut off region IC=IE≈0, therefore the collector current can be reckoned as:

VCE = VCC (11)

IC =VCC − VCE

RC

ICRC = VCC − VCE

0 ∗ 0.2KΩ = 5V − VCE

0 = 5 − VCE

VCE = 5V

4.2 Development of the Study

The design of over voltage and under voltage control system or tripping mechanism section

describes the process of developing the operational circuit design based on the stipulated block

diagram. However, the implementation of this protection circuit will only be simulated using the

acceptable electronic circuit Proteus professional software. The purpose of the simulation

approach is to save financial resources during the development process. Circuit integration of

components according to their specific functionality will be undertaken through simulation. The

overall design of over voltage and under voltage control system of the project is looks like the

circuit in Figure 4.5.


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Figure 4.5: Overall System Design

The inclusion of comparator makes the circuit operations many accurate and tripping points

adjustable to any levels as desired by the input supply. The voltage regulator gives a constant dc

5v to the comparator to energize it. The bridge rectifier converts 12v ac supply to 15.5v dc and the

capacitor used to make smooth the output voltage from rectifier. The comparator compare the

voltage level from zener diode and potentiometer and sends a signal to the transistor and the

transistor is used as a drive circuit for the relay.

Transistor (Q1)’s base is connected to the above diode junction, and as long as the comparator

output remain low, transistor (Q1) is allowed to conduct by getting the biasing voltage through R7

and R8. However at the moment of comparator output goes high or which may happen during

abnormal voltage conditions, restricting transistor (Q1) from conducting. Relay resistance

instantly switches off itself and the connected motor. The protection diode (D5) in the circuit is

used to protect the transistor from the reverse current generated from the coil of the relay during

the switch off time.


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CHAPTER FIVE

5. RESULTS AND DISCUSSIONS

5.1 The Design, Simulation and Implementation

The design of over voltage and under voltage control system of induction motor analysis depends

upon the values of the given electronics circuit of the over voltage and under voltage in the Proteus

professional software. In this project the design of over voltage and under voltage control system

of induction motor is automatically protected from the effect of over voltage and under voltage by

using the circuit concept of the study through the Proteus software. This Proteus professional

software is properly functional when the proper designing calculation is correct.

5.1.1 The Simulation Software

The electronic circuit ancillary components that comprised the complete control circuit were

chosen in such a way that they are completely available in the simulation software list of

components. The choice of components was undertaken based on its availability in the software

package because there are electronic components that are not available and that it is difficult to

implement simulation without the appropriate electronic components, however, the researchers

were able to find alternative components after a series of benchmarking on its cross reference using

the internet.

5.1.2 The Under Voltage and Over Voltage Control System Circuit Design

The circuit design stipulated in the methodology is utilized in the simulation of the corresponding

under-voltage and over-voltage protection parameters. Specifically, simulations for under-voltage

and over-voltage are conducted to determine the range and level of protection were observed.

The output of the entire system was checked separately. As we designed previously the output of

the transformer, rectifier and voltage regulator is similar with designed values as shown in the

figure 5.1 below.


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Figure 5.1: Output of Transformer, Rectifier and Regulator

The overall design of under and over voltage protection system for an induction motor is obtained

by combining the above circuit including comparator, relay and transistor. The expected output of

transformer, bridge rectifier, and regulator are checked and satisfy the desired output. Comparator

is to isolate the motor from under voltage and over voltage by sending tripping signal to the relay.

5.1.3 The normal voltage condition

During normal voltage condition where the AC voltage supply is within the interval from 175V to

245V, the output component represented by the motor performed its normal function without any

treat of damage or possible burnout. Figure 5.2 reflects the circuit in the normal voltage condition

where the relay contact is triggered to provide current continuity to power the motor as indicated

by the encircled relay.


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Figure 5.2: Output for Normal Voltage

5.1.4 The Under Voltage Protection Design Condition

When the supply voltage is below 180 V, the comparator IC LM324 checks the voltage at the

inverting terminal of operational amplifier N2 is less than the voltage at non-inverting terminal

(6V). Thus the output of operational amplifier goes high and it energizes the relay.

When relay is get energized the protection circuit act as open circuit and it disconnect the AC

supply and load get off. The below picture depicts the working of protection circuit in under

voltage supply is 171 V. Thus, when there is under voltage, the protection circuit automatically

switched off the load and protects the load.


34 | P a g e

Figure 5.3: Output for Under Voltage Protection System

5.1.5 The Over Voltage Protection Design Condition

The over voltage limit is selected by the variable resistor 2 i.e. potentiometer 2. So, the beyond

245 voltage level the protection circuit will remain open and load is off.

When the line voltage increases above 245V, the comparator IC check the voltage at the non-

inverting terminal (pin 3) of operational amplifier increases and the voltage at inverting terminal

remain same 6.8V due to zener diode. Thus output of operational amplifier goes high and relay

gets energized through transistor. As the relay gets energized the AC supply gets disconnected and

load is turned off and thus, load is protected from over voltage.


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Figure 5.4: Output for Over Voltage Protection System


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CHAPTER SIX

6. CONCLUSION AND RECOMMENDATIONS FOR FUTURE WORK

6.1 Conclusion

In this project, the induction motor protection using comparator is proposed. For induction

motor voltage sensing circuits were designed and the results have been verified with Proteus

simulation. Through the induction motor voltage analysis in Figure 5.2, Figure 5.3 and Figure 5.4

the current of the induction motor is either zero (open circuit) in under and over voltage condition

but close circuit at normal condition as voltage varies in the system. Whenever the supply voltage

goes above the induction motor rated voltage, the comparator compare the voltage drop on

potentiometer and zener diode and it sends a trip signal to relay thereby protecting the induction

motor from burning. As the supply voltage goes below the minimum voltage of the induction

motor, and then the comparator compare the voltage drop on potentiometer and zener diode and

sending a signal to the relay in order to protect the induction motor from over loaded.

When the supply voltage is at normal condition which is from 175V to 245V, then the induction

motor is working its proper function without damage. The over voltage and under voltage control

system is very important, in order to protect induction motor from unbalanced voltage and also the

purpose of design system is to solve the problems that takes place due to unbalanced voltage. Based

on the simulation results, the system has fast response, better isolation and accurate detection under

the abnormal condition and economically efficient. Hence, the design and simulation on over

voltage and under voltage protection circuit satisfies the technical parameters requirements.


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6.2 Recommendations for Future Work

Based on the results and findings of the study, the recommendations are anchored on the least

significant result of the study. The following recommendations are proposed:

Since there were difficulties encountered during the conduct of the study relative to the use

of legitimate simulation software, it was observed that with the use of a limited edition

software not all electronic components are available thus simulation sometimes fail. As

such, the purchase of licensed simulation software in electronics and electrical engineering

is highly recommended.

Since the simulation of the circuit design on abnormal voltage protection has been proven

to be successful, it is recommended that this circuit design shall be physically implemented

by fulfilling all required materials to test its actual functionality in real world problem.

Based on the work done in this project which protecting induction motor using comparator

some modifications need to be made in the future work, instead of relay it will be changed

by Cycloconverter. Because the relay needs some amount of time to sense a trip signal to

protect the induction motor from damage, but using Cycloconverter the induction motor

can get rated voltage without interruption.


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References

[1]. Annette von Jouanne and BasudebBanerjee, “Causes and Effect of Voltage Unbalance

Mitigation Techniques”, 2001.

[2]. HannuLaaksonen, KimmoKauhaniemi, “Sensitivity Analysis of Frequency and Voltage

Stability”, in Islanded Microgrid, 2007, retrieved from http://www.researchgate.net/publication,

accessed 6/4/2014.

[3]. Hung D. Nguyen, Konstantin Turitsyn, “Voltage multi-stability in distribution grids With

power flow reversal”,2014, retrieved from http://www.researchgate.net/publication, accessed

6/10/2014.

[4]. Mohammad Shah Alamgir and Sumit Dev, “Design and Implementation of an Automatic

Voltage Regulator with a Great Precision and Proper Hysteresis”, Vol.75, year 2015, pp,

“IJAST”.

[5]. C.H.Vithalani, “Over-Under Voltage Protection of Electrical Appliances”, August 2003,

Electronics for You.

[6]. Badri Ram and D N Vishwakarma, “power system protection and switch gear”, New Delhi:

Tata McGraw hill, 1995.

[7]. Frank D. Petruzella, “Electric motors and control systems”, New York: McGrawHill, 1st Ed,

2010.

[8]. Article, “Over voltage Under voltage load Protection”, website:

http://www.nevonprojects.com/Over-voltage-Under-voltage-load-protection.html , last Accessed

27 September 2015.

[9]. LAMARCHE, Paper, “Controlled Ferroresonant Technology”, Volume 1, Issue 2, November

2006.

[10]. Endeavour Energy Power Quality & Reliability Centre, “Voltage Sag Mitigation”,

Technical Note 11, August 2012.

[11]. Math H.J.Bollen, “Understanding Power Quality Problems - Voltage Sags and

Interruptions”, 2000, New Jersey, John Wiley & Sons.

[12]. All about Circuits, Voltage Regulation, Available from:

http://www.allaboutcircuits.com/vol_2/chpt_9/6.html, last Accessed 29 September 2015.

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