DESIGN AND FABRICATION OF SINGLE PHASE

PREVENTER

BACHELOR OF TECHNOLOGYIN

ELECTRICAL AND ELECTRONICS ENGINEERING

Submitted by

P.S.ANAND KUMAR

Regd.No:N5063A2305

SCHOOL OF CONTINUING AND DISTANCE

EDUCATION JAWAHARLAL NEHRU TECHNOLOGICAL

UNIVERSITY HYDERABAD

KUKATPALLY, HYDERABAD - 85

2009

DESIGN AND FABRICATION OF SINGLE PHASE PREVENTER

Project report submitted in partial fulfilment of the requirement For the award of the degree of B.tech.

InElectrical and Electronics Engineering

By

P.S.ANAND KUMAR

Regd.No:N5063A2305

Under the esteemed guidance of

Mr.M.V.SUBRAMANYAM

SCHOOL OF CONTINUING AND DISTANCE

EDUCATION

JAWAHARLAL NEHRU TECHNOLOGICAL UNIVERSITY HYDERABAD

KUKATPALLY, HYDERABAD-85

2009

CERTIFICATE

This is to certify that the project report entitled “DESIGN AND FABRICATION OF SINGLE PHASE PREVENTER” that is being submitted by Mr. P.S.ANAND KUMAR (N5063A2305) in partial fulfillment for the award of the Degree of Bachelor of Technology in Electrical & Electronics Engineering to the Jawaharlal Nehru Technological University is a record of bonafide work carried out by him under my guidance and supervision.

The results embodied in this project report have not been submitted to

any other University or Institute for the award of any Degree or Diploma.

Academic Supervisor Head of the department

Mr.M.V.SUBRAMANYAM Mr.Dr.K. DANWANTHRI

Associate Professor Professor

Dept. of EEE Dept.of EEE

C.V.R College of Engineering C.V.R College of Engineering,

Hyderabad Hyderabad

CHAIRMAN

PROJECT REVIEW COMMITEE

C.V.R Engineering College

Hyderabad

JAWAHARLAL NEHRU TECHNOLOGICAL UNIVERSITY

SCHOOL OF CONTINUING AND DISTANCE EDUCATION

CERTIFICATE

This is to certify that the project report entitled “DESIGN AND

FABRICATION OF SINGLE PHASE PREVENTER” that is being submitted by

Mr.P.S.ANAND KUMAR (N5063A2305) in partial fulfillment for the award of the

Degree of Bachelor of Technology (B.Tech) in Electrical& Electronics Engineering to

the Jawaharlal Nehru Technological University is a record of bonafide work

carried out by him under my guidance and supervision.

The project work has been completed and results are verified and found to

be satisfactory.

Date:

Signature of the Guide

Name : Mr. T.TRIVIKRAMA RAO

Désignation : MANAGER

Working Place : Andhra Petro chemical Limited

VISHAKAPATNAM

ACKNOWLEDGEMENT

Before we get into think of things I would like to add a few heartfelt words for

the people who guided me in bringing this entire project successfully

I acknowledge my gratitude to Academic supervisor, Mr.

M.V.SUBRAMANYAM, Associate Professor, Electrical & Electronics

Engineering Department, CVR college of Engineering Hyderabad for his valuable

recommendations and guidance throughout this project.

I sincerely express my thanks to my project guide Mr.T.TRIVIKRAMA

RAO for continuously helping me in completion of my project and for his valuable

guidance and encouragement in brining out this project.

I will be grateful to Dr.K.DANWANTHRI, Professor and Head of the

Department, Electrical & Electronics Engineering, C.V.R. College of

Engineering, Hyderabad. for his timely valuable suggestions.

A special mention goes to those who directly or indirectly helped for

successful completion of the project work.

P.S.ANAND KUMAR

( N5063A 2305)

ABSTRACT

In India there are so many industries in different fields. For example steel

sector, Oil sector, Irrigation etc., All industries have many drives and equipment’s like

conveyor belts, pumps, Mills etc.,

All the drives of industries use electrical motors. Most of the electrical motors

are designed for three phase, 50Hz (in India) supply. These three phase motors are

less expensive than starting of DC motors. Starting of AC 3-phase induction motors is

less expensive than starting of DC motors as they require simple D.O.L or Star/delta

starters. D.O.L or Star/delta starters generally have only over load protection. Three

phase induction motors are very sensitive and get damaged, when they are subjected

to Single phasing.

For three phase induction motor, it is necessary that all the three phases of

supply should present. While it is on load when any one of the fuse goes out, or

missing, the motor will continue to run with two phases only, but it will start drawing

a huge current for the same load. This high current may run the motor unless switched

of immediately. A single phasing preventer avoids such a mishap with this circuit, the

motor will not run unless all the three phases are present.

In this context we need to design a preventer which prevents these mishaps

and protects the costly motor under such conditions. The single phase preventer

designed by my self is very less expensive and protects reliably the motor which is

very costly.

CONTENTS

Sl.NO. Description Page No.

1. INTRODUCTION 01

2. INDUCTION MOTOR 02

3. DESCRIPTION 04

4. REQUIREMENTS AND ANALYSIS 06

4.1 Transformer 07

4.2 Resisters 08

4.3 Diode 10

4.4 Zener Diode 13 4.5 Capacitors 14

4.6 Integrated Circuits 15

4.7 Transistors 20

4.8 Relay 22

4.9 LED 23

5. FEATURES 24

6. HOW TO SOLDER 25

7. FAULTS AND REMEDIES 26

8. BLOCK DIAGRAM 27

9. RESULTS 30

10. CONCLUSION 31

11. BIBLIOGRAPHY 32

LIST OF FIGURES

FIGURE No’s TITLE PAGE No’s

Fig 4.1.1 Transformer 7

Fig 4.2.1 Resistor 9

Fig.4.3.1 The symbolic representation of diode 10

Fig.4.3.2 Forward Bias 10

Fig.4.3.3 Circuit Diagram 11

Fig 4.3.4 Full wave Bridge 12

Fig 4.4.1 Zener Diode 13

Fig.4.4.2 Zener Diode Circuit 13

Fig. 4.5.1 Symbol of ceramic capacitor 14

Fig 4.5.2 Symbol of electrolytic capacitor 14

Fig 4.6.1 Integrated circuit 16

Fig 4.6.2 Pin identification of Dill type 16

Fig 4.6.3 Pin identification of Metal can type 16

Fig 4.6.4 Basical comparator 18

Fig 4.6.5 Equivalent circuit of LM741 19

Fig 4.7.1 n-p-n & p-n-p transistor structure and symbol 21

Fig: 4.8.1 Relay circuit 22

Fig: 4.9.1 Symbol of light emitting Diode (LED) 23

Fig: 8.1 Block diagram 27

Fig: 8.2 Circuit Diagram 28

Fig: 8.3 Single line diagram 29

1

CHAPTER – 1

INTRODUCTION: In India there are so many Industries in different

fields. For example Steel Sector, Oil sector, cement Sector, Irrigation Sector etc., All

the Industries have many drives and equipments like conveyor belts, Cranes, Pumps,

Mills etc.,

All the Drives of industries use Electric Motors. Most of the Electrical Motors

are designed for three phase 50Hz supply. These Three phase Motors require

maintenance compared to DC Motors. Starting of AC Three phase Induction Motor is

less expensive than starting of DC Motors as they require simple D.O.L or

STAR/DELTA Starters. D.O.L. or STAR/DELTA Starters generally have only Over

load Protection. Three phase Induction Motors are very sensitive and get damaged,

when they are subjected to SINGLE PHASING.

For Three phase Induction Motor, it is necessary that all the three phases of

supply should present. While it is on load when any one of the fuses failed, the Motor

will continue to run with two phases only, but it will start drawing a huge current for

the same load. This high current may ruin the motor unless switched off immediately.

A single SINGLE PHASING preventer avoids such a mishap with this circuit the

Motor will not run unless all the three phases are present.

In this context we need to design a preventer which prevents this Mishap and

protects the costly Motor under such conditions. The SINGLE PHASING preventer

designed by my self is very less expensive and protects reliably the Motor which is

very costly.

2

CHAPTER – 2

INDUCTION MOTOR

The most common type of A.C.motor being used through out the world today

is the INDUCTION MOTOR. Induction motors are more rugged require less

maintenance, and less expensive than D.C.motor of equal KW and speed rating.

Induction motors are manufactured both for single phase and three phase operations.

Three phase induction motor are widely used for Industrial application such as in lifts,

cranes, pumps, line shafts Exhaust fans, lathes etc.,

.In 1891 TESLA exhibited a crude type of a three phase induction motor at an

exhibition. Subsequently an improved construction with distributed STATOR

windings and CAGE ROTOR was built. Since then a lot of improvement has taken

place on the design of Induction motor and their Protection equipments.

CONSTRUCTION MOTOR:-

An Induction motor is a rotating machine which converts the electrical energy

in to Mechanical energy. All induction motors essentially consists of the following

two main Parts.

1. STATOR

2. ROTOR

3

STATOR: - It is an outer stationary hallow cylindrical structure made of

laminations of Sheet steel having slots on the inner periphery. The insulated

conductors are placed in the Stator slots and are suitably connected to form a balanced

three phase star or delta Connected circuit.

ROTOR: - It is the rotary part of the motor. The rotor core is a laminated steel

cylinder having slots on the outer periphery. A common practice in construction the

Squirrel cage is to place the assembled core in a mould and then force the molten

conducting material Aluminum of copper in to the slots. The rotor conductors need

not be insulated from the Core since the current flow through the least resistance path

i.e., conductors. The rotor Bars are short circuited at both ends by end rings. The rotor

slots are not made parallel to the rotor shaft axis they are skewed at a certain angle to

reduce magnetic noise during working to produce a more uniform Torque and to

prevent possible magnetic locking also called as cogging of the rotor with stator.

4

CHAPTER – 3

DESCRIPTION

The SINGLE PHASING preventer consists of the following blocks

A) POWER CIRCUIT

B) COMPARATOR CIRCUIT

C) TRIPPING CIRCUIT

POWER CIRCUIT: - Basically it consists of step down Transformer, 4 no

Diodes, Shunt Resistance, Zener Diode and Filter capacitor. During the positive half

cycle of Secondary voltage Vi the circuit will appears diodes D2 and D3 are forward

biased and conducting the current through load resistance. Where as D1 and D4 are

reverse biased and are in off state. It may be observed that D2 R1 and D3 are in

series. During the Negative half cycle of secondary voltage Vi the current will appears

diodes D1 and D4 are forward biased and D2 D3 are reversed biased. Therefore the

forward biased diode conducts the current through load resistance. The most

important result is that the polarity across the load resistance R1 is same i.e. current

flowing through R1 is same direction. In this circuit the Zener diode reverse biased p-

n junction and operates only in break down region. Some times called as voltage

regulator diode because it maintains a fairly constant output voltage Zener diode must

be reverse biased operation.

COMPARATOR:-An op-amp used as a COMPARATOR. A fixed reference

voltage V ref of 1v is applied to the (pin-3) -input and the other __ varying signal V in

is applied to the (pin-2) +input. Because of this arrangement the circuit is called the

non-inverting Comparator. When V in is less than V ref the output voltage Vo is at –

5

V sat (=NEE) because the voltage at the (-) input is higher than that at the (+)

input on the other hand. When Vin is greater than V ref the (+) input becomes positive

with respect to the (-) input and Vo goes to +V sat. Thus Vo changes from one

saturation level to another. The Comparator is a type of analog-to-digital converter. At

any given time the Vo wave form shows whether Vin is greater or less than V ref.

TRIPPING CIRCUIT: - It consists of one n-p-n transistor, diode and relay. The

comparator output (pin-6) is connected to base of BD 115 and collector is connected

to voltage source. Relay and diode are connected in between emitter (BD 115) and

ground (-ve) supply. Transistor BD 115 is used as emitter follower.

In a three phase supply the voltage is 120 degrees apart from each other. Thus

the addition of three phases gives zero voltage. If anyone of the phases goes off

voltage present at the summing point equals half the line voltage.

In this circuit the three phases (R Y B) are connected to the line neutral, which

in turn is connected to the ground of the circuit. When all three phases are present,

voltage at point ‘D’ is zero. So potential at point 3 of IC 741 is also zero but voltage at

point 2 is nearly 4v. Here IC741 is used as comparator and the voltage at pin 6 is zero.

Hence the relay cannot operate. When phase goes out, voltage at point D goes up to

about half the line voltage. This voltage is divided by 150k and 50k resistors. The

voltage at point B is about 8V when 50k potentiometer is properly adjusted. The

voltage at point 6 is operating condition, so relay will operates when any one of the

phases goes out. This Relay when used in the control circuit of the three phase motor,

or with a circuit breaker will switch the power off on operation.

6

CHAPTER – 4

REQUIREMENTS AND ANALYSIS

4.1 TRANSFORMER

4.2 RESISTORS

4.3 DOIDES

4.4 ZENER DIODE

4.5 CAPACITORS

4.6 INTEGRATED CIRCUITS

4.7 TRANSISTORS

4.8 RELAY

4.9 LIGHT EMITING DIODE

7

4.1 TRANSFORMER

A Transformer has two are more windings of insulated copper wire over an

iron core. They are one Primary winding and one or more secondary windings. Each

winding is electrically isolated from the other, but they are magnetically coupled with

the help of a laminated iron core. Small Transformer have a shell type construction,

that is the windings are surrounded by the core as shown in fig. the power delivered

by the secondary is actually transferred from the primary, but voltage levels

determined by the turn ratio of the Transformer.

Fig.4.1.1

It consists of two inductive coils which are electrically separated but

magnetically linked through a path of low reluctance. If one coil is connected to a

SECONDARYWINDING

LAMINATED CORE

PRIMARY WINDING

source of Alternating Voltage an Alternating flux is setup on the laminated core, most

of which is linked with the other coil which it produces mutually induced e.m.f. If a

load is connected to the Secondary coil, current flows in it and so electrical energy

8

transferred from the first coil to the second coil. The first coil called primary winding

and the second coil called as secondary winding. The power transformer used in the

electronic circuit supply voltage to the voltage requirements of the circuit and is

installed before the rectifier network. It works a fixed frequency of 50HZ. It is shell

type construction with the size of the core and farmer designed to suit the

requirements. In same transformers tapings are provided on the higher voltage side so

as to obtain the desire voltage at the secondary. The Transformer used in this circuit

acts as power source of the preventer circuit.

TYPES OF TRANSFORMERS:-

1. SHELL TYPE

2. CORE TYPE

3. BERRY TYPE

4. TORROIDAL TYPE

4.2 RESISTORS:- It is element of a circuit which shows constant relation

between the voltages across it to the current through it. Normally resistors are linear

device with either +ve or –ve temperature coefficient of resistance. But non linear

resistors are also used in electronic circuit as in case of volume control. Which the

resistor value varies logarithmically for the purpose of identification of the value of

the resistor colour codes is employed.

9

VALUE TOLERANCE

COLOUR ATTRIBUTED COLOUR TOLERANCE

BLACK 0

BROWN 1

RED 2 GOLD 5%

ORANGE 3 SILVER 10%

YELLOW 4 NO COLOUR 20%

GREEN 5 PINK- HIGH STABILITY

BLUE 6

VIOLET 7 BROWN 1%

GREY 8 RED 2%

WHITE 9

YELLOW 4

VIOLET 7 ORANGE

000BROWN 1%

Fig.4.2.1

10

4.3 DIODES: It is a semiconductor device formed by joining of p-type

and n-type materials. It conducts only in one specific direction when conducted in

forward direction.

The symbolic representation of diode is

Fig.4.3.1 BIASING OF DIODE:-

Forward bias:- When Anode of diode is connected to positive terminal and Cathode

is connected to Negative terminal of supply is called Forward bias. The diode

conducts only forward bias.

Fig.4.3.2IN4007 DIODE:The Diode used as rectifier in rectifier circuit

Specification of Diode

Peak inverse voltage : 1000 V

ANODE

+ _

CATHODEE

Current at forward voltage: 1 A

Forward voltage : 1.1 V

Maximum reverse current: 10 micro A11

DIODE AS RECTIFIER: When an AC supply is given to rectifier circuit shown in

Fig. during positive half-cycle of input, the diode is forward biased and starts

conducting current through load resistance. Thus positive half-cycle of input appears

across R1. S shown in output wave. During negative half cycle of input, the diode

becomes reverse-biased and prevents the flow of current.

CIRCUIT DIAGRAM

Fig.4.3.3

FULL WAVE BRIDGE RECTIFIER

The most commonly used full-wave rectifier for electronic d.c.power supply is

shown in fig. it eliminates the centre-tap transformer and uses four diodes in a bridge

configuration.

AC

INPUT OUTPUT

12

WORKING: During the positive half-cycle of secondary voltage (vi) the

circuit will appear as shown in fig. diodes D2 and D3 are forward-biased and conduct

the current through load resistance as shown in arrows. Where as D1 and D4 are

reverse biased and are in off state. It may be observed that D2 R1 and D3 are in series.

During the negative half-cycle of secondary voltage (vi) the circuit will appear as

shown in fig. diodes D1 and D4 are forward-biased and D2 and D3 are reverse-biased.

Therefore the forward biased diodes conduct the current through load resistance as

shown by arrows. The most important result is that the polarity across the load

resistance R1 is same.i.e. Current flowing through R1 is in same direction,

establishing a secondary positive plus.

.

V1

13

4.4 ZENER DIODE: Zener diodes are also known as voltage reference

diodes. They are named after C A Zener who analysed the voltage break down of

insulators. Zener diodes are designed for a specific reverse break down voltage,

typically 3 to 200 volts. Series diodes can be used for a higher rating. A heavily doped

p-n junction diode which has a sharp break down voltage known as a Zener diode.

Fig.4.4.1

APPLICATION

Used in voltage regulator circuits

D1D2

D3 D4

CIRCUIT DIAGRAM

OUTPUT OF D2 AND D3

OUTPUT OF D1 AND D2

TOTAL OUTPUT

V1

V1

V1

0

0

t

t

t

t

ANODECATHODE

SYMBOL

Fig4.3.4

Used in stabilizer circuits

14

4.5 CAPACITORS: Capacitors are components, which can store electrical

charge, when a voltage is applied across them and get discharged when a load is

connected across them.

TYPES OF CAPACITORS

CERAMIC CAPACITORS: Ceramic feed through capacitors are available for

de-coupling at very high frequencies (e.g. about 30 MHz) such components may be

soldered directly onto a bulk head on screening enclosure and are typically rated at in

farads 350V.

ELECTROLYTIC CAPACITORS: Electrolytic capacitors exhibits a fairly

wide tolerance and hence in the majority of smoothing and de-coupling applications.

It is usually quite permissible to substitute one value for another. Providing the

working voltage of the substitute capacitor is of the same or higher value.

+

-

R1

Z1 R2

Fig.4.4.2

Fig.4.5.1 Fig.4.5.2

15

4.6 INTEGRATED CIRCUIT: The IC is a combination of components such

as transistors, diodes, resistors, capacitors and other inter connection formed in one or

more complete circuits designed to perform one or more specific functions. These

components are produced on a small common base mounted on standard packages.

Since this method of fabrication combines both active and passive components in a

monolithic structure. The complete unit is called integrated circuit.

An operational amplifier is a direct coupled high gain amplifier usually

consisting of one or more differential amplifiers and usually followed by a level

translator and an out stage. The output stage is generally a push-pull or pull-contary

symmetry pair. An operational amplifier is available as a single integrated circuit (IQ)

package.

CERAMIC

ELECTROLYTIC

The operational amplifier is a versatile device that can be used to amplify

d.c.as well as a.c. input signals and was originally designed for computing such

mathematically operations as addition, subtraction, multiplication and integration.

Thus the name operational amplifier is abbreviated as op-amp. With the addition of

external feedback, the modern op-amp can be used to obtain desired gain and band

width, such as A.C and D.C. signal amplification active filters, oscillators,

comparators and others.

BLOCK DIAGRAM OF TYPICAL OP-AMPV1 = Voltage at the non-inverting inputV2 = voltage at the inverting input

OUTPUT VOLTAGEAll these are measured with respect to groundA = large signal voltage gain

16

TYPES OF IC PACKAGES

1. The flat pack

2. The metal can or transistor pack

3. the dual-in-line package

Fig.4.6.1PIN DIAGRAM OF LM 741PIN NO.

1. – OFF SET NULL

2. – IN

3. + IN

4. – VE

_

+

INVERTING INPUT

NON INVERTING INPUT

OUTPUT

5. + OFF SET NULL

6. OUT

7. +VE

8. NC

PIN IDENTIFICATION OF LM 741 

                                     

      

                  

                                                    

   Fig.4.6.2      Fig.4.6.3               

                          

17

TEMPARATURE RANGES

1. Military Temperature range -55 to +125 c (or -55 to +85c)

2. Industrial Temperature -20 to +85 c (or -40 to +85c)

3. Commercial Temperature range 0 to +70 c (or 0 to +75c)

LA 741 T C

Device type package type Commercial Temperature range (op-amp) mini DIP ( o to 70c )

NOTCH

1

2

3 4

8 7

6

5

DIL PACK

1

2

3 4 5

6

7

TAB

METAL CAN TYPE 4th pin connected to case

8

BASICAL COMPARATOR: The fig.shows and op-amp used as a

comparator. A fixed reference voltage V ref it IV is applied to (-) input and the other

time varying signal voltage V in is applied to the (+) input. Because of this

arrangement, the circuit is called the non-inverting comparator.

18

                

                                                                                                                                                                                           

LM 741

F 80 16

Fairchild Year Week of the year

Device Type

+ _

V ref

R1

R4 10 ohms

V0 R0

D1 D2 +

_

Protective Diodes

                                                                    

Fig.4.6.4When V in is less than V ref the o/p voltage Vo is at –V sat Vee. Because the

voltage at the (-) input is higher than that (+) input. On the other hand, when V in is

greater than V ref (+) input becomes positive w.r.t. (-) input and Vo goes to +ve sat

Vcc. Thus Vo changes from one saturation level to another whenever Vin = V ref. in

short the comparator is a type of analog to digital converter. The comparator is some

times also called voltage level detector, because for a desired value of V ref, the

voltage level of the input V in can be detected.

The Diodes D1 and D2 protect the op-amp from the damage due to excessive

input voltage V in. there are some op-amp with built in input, protection in such op-

amps the input diodes D1 $ 132 are unnecessary. The resistance R in series with V in

is used to limit the current through D1 and D2 to reduce offset problems a resistance

Ro=R is connected between input V ref.

Comparator characteristics

The important characteristics of a comparator are1. Speed of operation2. Accuracy3. Compatibility of output

19

EQUILENT CIRCUIT OF THE LM741 OP-AMP                   

     

 

         

 

                                                                

V in

O6

O8 O9

O1

0

O12 O13 O14

R722 ohms

R627 ohms

C130uF

V+

offsetnull

Inverting input

noninvertinginput

                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                

             

 

                                 Fig.4.6.5              

         

           

                 20

4.7 TRANSISTOR: On the 23rd December 1947 Walter H.Brattain

(W.H.Brattain) and john Bardeen of Bell Telephone Laboratory in America

announced the invention of a new electronic device called a Transistor or Junction

Transistor. Now the transistor becomes the heart of many electronic applications.

01 02

O3 O4

O5

O7

O11

O15

O16

O17

O18

O19

O2

0

021

O22

O23

O24 R11 K

R250K

R31K

R45K

R540K

R8100

R1050K

300 ohms

V-

10 K offsetnull

output

R1150K

A transistor consists of two p-n junctions by sandwiching either p type or n type

semi-conductor between a pair of opposite types. There are two types of transistors

namely, n p n transistor and p n p transistor.

It has section of doped semiconductors. The section on one side is the emitter that

supplies carriers (electrons or holes). The section on the opposite side is the collector

that collects the charges. The middle section which forms two p-n junctions between

the emitter and collector is called the base.

CODE SYSTEM FOR DIODES AND TRANSISTORS

(As approved by rpoelectron standardization authority in Belgium)

Every semiconductor device is a number by 5 alpha-numeric symbol. Comprising

two letters and 3 numbers (used for industrial equipment) or three letters and 2

numbers (used for entertainment equipment).First letter indicates nature of

semiconductor material as A-Germanium, B-Silicon, C- Gallium arsenide R-

Compound material. The second letter indicates the device and circuit function

Ex: - A=Diode B=AF-low power transistor

F=HF-low power transistor Z=Zener

21

                 

                                                             

P

N

P

N

P

N e

b

c

p-n-p Transistor structure n-p-n Transistor structure

SYMBOL SYMBOL

e

b

c

(N-P-N) (P-N-P)

              

                                                 

   Fig.4.7.1    

                 TRANSISTOR BD 115The characteristics and rating of BD 115

1. collector to base break over voltage (emitter o/c) ---- 50 V

2. collector to base break over voltage (base o/c) ---- 45 V

3. maximum collector (or emitter) current ---- 2 A

4. Maximum power dissipation ---- 3 W

5. Maximum working temperature ---- 120 c

6. Collector-base cut-off current ---- 1 mA

7. Minimum and Maximum dc current gain or AC current gainMin – 30

Max – 150

Le - 1 A

Vce – 2V

8. Switching rise or fall time=switching time/falling time

9. Manufactures: MSP (Motorola Semiconductors Products)

22

4.8 RELAY

A relay is a sensitive device which is used to make and break a circuit a relay

mainly consists of a coil two fixed contacts and one moving contact.

Coil: - the coil is made of a thin copper wire which was insulated by enamel

painting which was wounded in the form of rings on a metal core

e

b

c

e

b

c

Fixed contacts:-These are two fixed contacts, when the moving contact

touches the position 1 contact the circuit is open when the contact is in position 2

the circuit is closed.

Moving contacts:-which is attracted by the magnet, which was magnetized by

energizing the coil, so it moves from position 1 to position 2.

Working:-when there was no supply at the primary coil, so the core is

demagnetized so the contact is not attracted by the core. Then the fixed contact

touches contact1, so the circuit opened. When the coil is energized by supply the

flux links with the core and it gets magnetized. So the core attracts the moving

contact so it change the position from 1 to 2. so the circuit is closed and current

passes from circuit to relay and to operate the external circuit.

                           

 

 

   Fig.4.8.1          23

4.9 LIGHT EMITING DIODE (LED)

When a p-n junction is forward biased, free electrons cross the junction and

fall in holes. As the electrons fall from higher energy level to a lower energy level,

they radiate energy. In typical p-n junction diode this radiated energy goes off in

the form of heat. But in case if light emitting diode (LED), as name implies, the

12V 200 ohms

NC

NO

MOVING

CONTACT TO EXT. CIRCUIT

radiated energy gives of visible light. In Germanium and Silicon the great

percentage of energy given up in the form of heat and some in the form of photon

or emitted light which is insignificant. Where as is other materials made of

Gallium compounds, such as Gallium arsenide phosphide (GaAsp) or Gallium

phospide (GaPo). The number of photons of light energy emitted will create a

visible light.

SYMBOL

Fig.4.9.1

24

Chapter -5

FEATURES

1. Circuit is so simple

2. Easily available components

3. It has more efficiency

                                                                                                                     

K

A

4. It is low component equipment but it protects heavy costly three phase equipment

5. It is most useful for Agriculture motors and Industrial.

25

Chapter – 6

HOW TO SOLDER

There are four essential points to be remembered for successful soldering.

Cleanliness: Be sure that the surfaces to be soldered are perfectly cleaned.

Scrap the surface with a knife, blade or sand paper which ever possible.

Flux: Use resin flux, an acid flux may corrodes the wires. After soldering wide

off any excess flux.

Heat: Heat the surface to be soldered until the solder flows over there. If

possible keep the hot iron on the joint even after the solder has flowed so as to sure

that there is enough heat. Keep the soldering iron bit clean by removing any oxide that

may form on it. DI use resin-cored solder which quickly melts at low temperature.

26

Chapter – 7

FAULTS AND REMIDIES

Input supply 12V missing - Check the Transformer and connections.

Relay coil burnt - Check and replace the relay coil.

Diodes short circuited - Check and replace the diode.

Resistor open circuited - Check and replace the resistor.

Capacitor leak or short circuited - Check and replace it.

LM 741 IC not working - Check and replace the IC.

150K resistance open circuited - Check and replace it.

50K variable resistor miss aligned - Check and aline properly.

Relay contacts dirty - Clean properly.

Neutral link disconnecting - Check and connect the disconnected line.

BD 115 defective - Check and replace the Transistor BD 115.

27

Chapter – 8

BLOCK DIAGRAM

Fig.8.1.

28

CIRCUIT DIAGRAM OF SINGLE PHASING PREVENTER

                        

SINGLE PHASING PREVENTER

POWER CKT

COMPARATORCKT

TRIPPINGCKT

STARTER

MOTOR

TRANSFORMER

P

N D2 D1 D3 D4 D1…D4 IN 4007

12.1ZEN

ER

1000mfd25V

R Y B 150k 150k 150k 150k

D

B BY 127 10K 1K 1K

+ _ 2

4

3

7

6

B

C E 3.8K

50K

32mfd15v

IN 4148

RELAY +12V

LM741

N

                                        

Fig.8.229

LINE DIAGRAM

         

                                    

R

FUSE

                                                                                                                                                                                                                                                                                                         

Fig.8.3

30

Chapter – 9

RESULTS

OFF

OLR

SPP

ON HOLDING

CONTACTOR COIL

LINK FUSE

When all 3 phases are present the voltage at D is zero. Voltage at point

2 is nearly 4V and at pin 3 is zero. At pin 6 of the comparator is also zero

voltage. When any phase goes out at point D the voltage is half the line

voltage. When any phase goes out at the point B the voltage is

approximately 8 V. when any phase or two phases goes out then the

indicator LED shows red colour. If there is all phases are present healthy

then the indicator shows green colour.

31

Chapter – 10

CONCLUTION

The rule of electricity in modern technology is that of an extremely

versatile intermediately. The chief advantage of this energy is Electrical

form can be transmitted, controlled and utilized with relative simplicity,

reliability and efficiency.

The primary objective of presenting this project named “DESIGN

AND FABRICATION OF SINGLE PHASE PREVENTER TO

PROTECT THE 3-PHASE INDUCTION MOTOR AGAINST SINGLE

PHASING”.

This is designed as per our above mentioned requirements. This project

states clearly how it is functioning. In addition to that we discussed about

the faults and remedies of the circuit also.

Every care has been taken to design this project and we expect that this

project is very useful for avoiding SINGLE PHASING problem for A.C.

3-phase induction motors and saved equipment from damage.

32

BIBLIOGRAPHY

Name of the Book Authors Date of published

A TEXT BOOK OF Year 2000 ELECTRICAL TECHNOLOGY B.L.Theraja.VOLUME-II s.chand and company

A.K.TherajaNew Delhi-110055

LINEAR INTEGRATED Ramakanth CIRCUITS Prentice Hall of India

AGyakwad Private LimitedNew Delhi-110001Year 1990 Annual

Electronics for you Rashmi Bhushan EditionS.Das Gupta ratna offsetNew Delhi-110020