Report on minor project

Anil Maurya

Electrical & Electronics Engineer 1

A

PROJECT REPORT

ON

OPERATION

OF

THREE PHASE INDUCTION MOTOR

THROUGH

I/O MODULE OF PLC

WITH

THREE PHASE PROTECTION CIRCUIT

BY

ANIL MAURYA

ELECTRICAL & ELECTRONICS ENGINEER

Anil Maurya


CONTENT

Contents iv

List of figures v

List of table vi

CHAPTERS

1. Introduction 2

2. Power Supply 3

2.1. DC Power Supply 3

2.2. Rectifier Operation 4

2.3. Efficiency 5

3. Programmable Logic Controller 6

3.1. Connection and Working 9

4. Three phase protection circuit and components 11

4.1 Relay 11

4.2 Contactors 12

4.3 555 Timer IC 14

4.3.1 Monostable Mode 15

4.4 Diode 17

4.5 Zener Diode 18

4.6 Transistor 19

4.7 Capacitor 21

4.4.1 Electrolytic Capacitor 22

4.8 Resistors 23

4.8.1 Fixed and Variable Resistor 24

4.9 Transformer 25

4.10 Optocoupler IC 27

5 Operation of three phase protection circuit 29

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List of Tables

4.1 Ratings of 555 timer IC 15

4.2 Operating Conditions of 555 timer IC 15

List of figures

1.1 Power supply for positive half cycle 3

1.2 Power supply for negative half cycle 3

1.3 Full wave rectifier 4

3.1 Connection scheme of module 10

4.2.1 Contactores 12

4.3.1 555 timer IC 14

4.4.1 Diode 17

4.5.1 Zener diode 18

4.6.1 Transistors 19

4.7.1 Capacitors 21

4.8.1 Resistors 23

4.9.1 Transformer 25

4.10.1 Optocoupler IC 27

5.1 Circuit diagram of 3 phase protection circuit 29

Conclusion

References

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ABSTRACT

Many of our costly appliances require three-phase AC supply for operation. Failure of any of

the phases makes the appliance prone to erratic functioning and may even lead to failure.

Hence it is of paramount importance to monitor the availability of the three-phase supply and

switch off the appliance in the event of failure of one or two phases. The power to the

appliance should resume with the availability of all phases of the supply with certain time

delay in order to avoid surges and momentary fluctuations.

It requires three-phase supply, three 12V relays and a timer IC NE555 along with 230V coil

contactor having four poles. The main advantage of this protector circuit is that it protects

three-phase appliances from failure of any of the mounted on the backside of cabinet.

Connect the appliance through external wires.

Phases by disconnecting the power supply through the contactor and automatically restores

the three-phase supply to the appliance (with reasonable time delay) when all the phases are

available. Assemble the circuit on a general- purpose PCB and enclose in a cabinet with the

relays and contactor

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CHAPTER 1 INTRODUCTION

Many of our costly appliances require three-phase AC supply for operation. Failure of any of

the phases makes the appliance prone to erratic functioning and may even lead to failure.

Hence it is of paramount importance to monitor the availability of the three-phase supply and

switch off the appliance in the event of failure of one or two phases. The power to the


delay in order to avoid surges and momentary fluctuations. The complete description of a

three phase appliance protector is described here.

User lines connected to power supply lines can be disconnected there from by a

connect/disconnect switch. An isolation rectifier circuit connected across the each phase wit

operational relays. Output of the rectifier circuit controlled by a timer and through that timer

operates the switch. The timer restores the connection in failure of any one or two phases.

1. A protection device for an electrical machine appliance or installation, comprising:

Contactor switch connected between a plurality of supply lines and respective user lines to be

protected and connectable to a load.

An each isolating rectifier circuit element having an input side connected across each phase

side point and a neutral point which can be at a ground potential, and an output side

electrically isolated from coil side of operational relay along with led and freewheeling diode.

A timer connected to an coil said operational relay and connected with contactor

switch for automatically disconnecting said user lines from said supply lines upon the failure

of any one phase or two phases, and for automatically reconnecting said user lines with said

supply lines upon presents of all the three phases with certain time delay.

An each isolating rectifier circuit is connected from secondary side of each step-down

transformer. And a primary side of each step-down transformer is connected from each phase

to neutral.

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2. A protection device for an electrical machine appliance or installation, comprising:

A contactor switch connected between a plurality of supply lines and respective user

lines to be protected and connectable to a load.

An isolating rectifier circuit element having an input side connected across secondary

side of step-down transformer, and an output side electrically isolated from coil said of

operational relay.

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CHAPTER 2

POWER SUPPLY

2.1 DC POWER SUPPLY: -

An AC powered unregulated power supply usually uses a transformer to convert the voltage

from the mains to a different, now a day’s usually lower, voltage. If it is used to produce DC,

a rectifier is used to convert alternating voltage to a pulsating direct voltage, followed by a

filter, comprising one or more capacitors, resistors and sometimes inductors, to filter out

(smooth) most of the pulsating. A small remaining unwanted alternating voltage component

at mains or twice mains power frequency (depending upon whether half or full wave

rectification is used) ripple is unavoidably superimposed on the direct output voltage.

For purpose such as charging batteries the ripple is not a problem, and the simplest

unregulated mains powered DC power supply circuit consists of a transformer driving a

single diode in series with resistor.

Before the introduction of solid state electronics, equipment used valves (vacuum tubes)

which required high voltages; power supplies used step-up transformers, rectifiers and filters

to generate one or more direct voltages of some hundreds of volts, and a low alternating

voltage for filaments. Only the most advanced equipment used expensive and bulky regulated

power supplies.

2.2 RECTIFIER OPERATION: -

Transformer‘s primary is connected to main 220 volt single phase supply and secondary (12-0) is used for rectifier circuit. Since transformer’s secondary of (12-0) therefore bridge rectifier is required. It consists of four diodes which makes bridge network. When positive half cycle comes then diode D1&D3 conduct which provides positive potential at output. When negative half cycle comes then diode d2&d4 conduct and provide negative potential.

Current directions for the full wave bridge rectifier circuit are as shown in figure below

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Fig 2.1 Positive half cycle

Fig 2.2 Negative half cycle

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Fig 2.3 Full wave bridge rectifier

2.3 EFFICIENCY:-

Efficiency is the ratio of the DC output power to the AC input power.

Thus ŋ = DC output power

AC input power

= Pdc / Pac

Vdc/Rl (2Vm/π)2 8

Vrms/Rl (Vm/√2)2 π2

Ŋ = 81.2%

The maximum efficiency of a full wave rectifier is 81.2%.

2.4 Rectifier with filter

The output of the full wave rectifier contains both AC and DC components. A majority of the applications which cannot tolerate a high value ripple, necessitates further processing of the rectified output. The undesirable ac components i.e. the ripple can be minimized using filters. The output of a rectifier filter is fed as input to the filter. The output of filter is not a perfect DC, but it also contains small AC components.

CAPACITOR FILTER

A capacitor filter connected directly across the load . the property of the capacitor is that it allows AC component and blocks DC components. The operation of the capacitor filter is to short the ripple to ground but leave the DC to appear at output when it is connected across the pulsating DC voltage.

During the positive half cycle, the capacitor charges upto th peak value of the transformer secondary voltage Vm and will try to maintain this value of the full wave input drops to zero. Capacitor will discharge through the load slowly until the transformer secondary voltage gain increase to a value greater than the capacitor voltage.

The diode conducts for a period, which depends on the capacitor voltage. The diode will conduct when the transformer secondary voltage becomes more than the diode voltage. This is called the cut in voltage. The diode stops conducting when the transformer voltage becomes less than the diode voltage. This is called cut out voltage. The ripple may me decreased by increased C or RL (both) with a resulting increase in the DC output voltage.

The output wave form the full wave rectifier with filter and without filter is shown:

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CHAPTER 3

PROGRAMMABLE LOGIC CONTROLLER

A Programmable controller is a solid state user programmable control system with

functions to control logic, sequencing, timing, arithmetic data manipulation and counting

capabilities. it can be viewed as an industrial computer that has a central processor unit,

memory ,input, output interface and a programming device. the central processing unit

provides the intelligence of the controller .it accepts data ,status information from various

sensing devices like limit switches ,executes the user control to a program store in the

memory and give appropriate commands to devices like solenoid valves, switches etc. Input

output interface is the communication link between field devices and the controller ; field

devices are wired to the input output interfaces.

Fig 3 connection scheme of input module

I/O module system of a PLC consist of different I/O pins i.e. 16 pin, 32 pin, but in this

project only two I/O pins will be configured. Two buttons will be used to turn on and

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turn off the motor. For this I/O module wiring is made to connect the field appliance.

Here the controller will not be used therefore input module is connected to the output

module which provides 12 volt dc supply to energize the relay coil.

Here controller will not be used so the above ladder logic will be converted into a

hardware scheme, and it takes place of the controller.

Start Motor

Motor

Stop

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Electrical & Electronics Engineer

Hardware scheme of Input module:

Fig 3.2

The field device contact is a push button. When it is get pushed, input circuit would be

completed. Here optocoupler IC is intermediate device between input module and controller.

Optocoupler IC contains infrared led & t

gets activated and the signal goes to controller.

The controller is a hardware which consists of relay. If the push button is

pressed field device get turn on but after re

Therefore to maintain continuous output below circuit is used:

ctrical & Electronics Engineer

Hardware scheme of Input module:

Fig 3.2 connection scheme of output module



Optocoupler IC contains infrared led & transistor. When light falls on the base of transistor, it

gets activated and the signal goes to controller.


pressed field device get turn on but after release the push button, field device will be off.

Therefore to maintain continuous output below circuit is used:-

13

Hardware scheme of Input module:-



ransistor. When light falls on the base of transistor, it


lease the push button, field device will be off.

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After getting the continuous output from the relay, signal goes to optocoupler IC of the

output module and further the light falls on the base of the transistor, it gets turn on & the 12

volt dc supply appears on the relay coil so it get energized and the field appliance will be on.

3.1 CONNECTION AND WORKING

An optocoupler ic has a two part i.e. input & output, input side consists of an infrared

led and the output side consists of a transistor. A 5V dc supply is connected to input of

optocoupler ic through push button (s1) and 220ohm resistor. Resistor limits the input

current. The voltage drop across the input side (across the led) is 1.5v therefore, led glows

,when the light falls on the base of transistor it conducts . the collector terminal of a transistor

is connected to 12V DC supply and emitter is connected to the next optocoupler (input side)

of the controller through 1kohm resistor therefore light falls on the base of transistor and it

get activated . a 12V relay is connected in series with the transistor so relay contacts would be

changed. The middle point of relay consists of 5V DC supply when it get energized 5V

appears on the N/O terminal of relay and a connection is made from N/O to input module (as

a feedback) to maintain the connection after the push button get released. the 5V supply at

N/O also connected to the output module (input side) through 220ohm resistor and again

lights falls on the base of transistor and it get activated ,12V DC supply appears on the relay

coil which the first field device. A 220V AC supply is connected to the middle point of relay

and the N/O terminal is connected to the 3- phase contactor coil .

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Fig 3.3 Connection of I/P-O/P Module

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CHAPTER 4

PHASE PROTECTION CIRCUIT

Many of costly electrical appliances require three phase power supply for operation.

Failure of any of the erratic functioning and may even lead to failure. The power to the


delay in order to avoid surges and momentary fluctuations.

The complete circuit of a three phase appliance protector is described here. It

requires three phase supply three 12 volt relays and a timer IC NE555 along with 230V coil

contactor having four poles. Here 555 timer IC triggers only when all the phases (R, Y, B) are

available. It provides a delay of approximately four second, which energizes relay RL3 and

its N/O contact, closes to connect the line to the energizing coil of four pole contactor relay

RL4.

COMPONENTS OF PROTECTION CIRCUIT

4.1 RELAY

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

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

applications where it is necessary to control a circuit by a low-power signal, or where several

circuits must be controlled by one signal. The first relays were used in long distance telegraph

circuits, repeating the signal coming in from one circuit and re-transmitting it to another.

Relays found extensive use in telephone exchanges and early computers to perform logical

operations. A type of relay that can handle the high power required to directly drive an

electric motor is called a contactor. Solid-state relays control power circuits with no moving

parts, instead using a semiconductor device to perform switching. Relays with calibrated

operating characteristics and sometimes multiple operating coils are used to protect electrical

circuits from overload or faults; in modern electric power systems these functions are

performed by digital instruments still called "protection relays".

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Fig 4.1 Small relay as used in electronics

4.2 CONTACTORS

In semiconductor testing, contactor can also refer to the specialized socket that

connects the device under test. In process industries a contactor is a vessel where two streams

interact, for example, air and liquid. A contactor is an electrically controlled switch used for

switching a power circuit, similar to a relay except with higher current ratings. A contactor is

controlled by a circuit which has a much lower power level than the switched circuit.

Contactors come in many forms with varying capacities and features. Unlike a circuit

breaker, a contactor is not intended to interrupt a short circuit current. Contactors range from

those having a breaking current of several amperes to thousands of amperes and 24 V DC to

many kilovolts.

The physical size of contactors ranges from a device small enough to pick up with one

hand, to large devices approximately a meter (yard) on a side. Contactors are used to control

electric motors, lighting, heating, capacitor banks, thermal evaporators, and other electrical

loads. Construction Albright SPST DC contactor, sometimes used in EV conversions

Powerful DC contactor with electro- pneumatic drive A contactor has three components. The

contacts are the current carrying part of the contactor. This includes power contacts, auxiliary

contacts, and contact springs. The electromagnet ("coil") provides the driving force to close

the contacts.

The enclosure is a frame housing the contact and the electromagnet. Enclosures are

made of insulating materials like Bakelite, Nylon 6, and thermosetting plastics to protect and

insulate the contacts and to provide some measure of protection against personnel touching

the contacts. Open-frame contactors may have a further enclosure to protect against dust, oil,

explosion hazards and weather. Magnetic blowouts use blowout coils to lengthen and move

the electric arc. These are especially useful in DC power circuits. AC arcs have periods of

low current, during which the arc can be extinguished with relative ease, but DC arcs have

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continuous high current, so blowing them out requires the arc to be stretched further than an

AC arc of the same current. The magnetic blowouts in the pictured Albright contactor (which

is designed for DC currents) more than double the current it can break, increasing it from 600

A to 1,500 A. Sometimes an economizer circuit is also installed to reduce the power required

to keep a contactor closed; an auxiliary contact reduces coil current after the contactor closes.

A somewhat greater amount of power is required to initially close a contactor than is required

to keep it closed.

Such a circuit can save a substantial amount of power and allow the energized coil to

stay cooler. Economizer circuits are nearly always applied on direct-current contactor coils

and on large alternating current contactor coils. A basic contactor will have a coil input

(which may be driven by either an AC or DC supply depending on the contactor design). The

coil may be energized at the same voltage as a motor the contactor is controlling, or may be

separately controlled with a lower coil voltage better suited to control by programmable

controllers and lower-voltage pilot devices. Certain contactors have series coils connected in

the motor circuit; these are used, for example, for automatic acceleration control, where the

next stage of resistance is not cut out until the motor current has dropped.

Operating principle unlike general-purpose relays, contactors are designed to be directly

connected to high-current load devices. Relays tend to be of lower capacity and are usually

designed for both normally closed and normally open applications. Devices switching more

than 15 amperes or in circuits rated more than a few kilowatts are usually called contactors.

Apart from optional auxiliary low current contacts, contactors are almost exclusively fitted

with normally open contacts. Unlike relays, contactors are designed with features to control

and suppress the arc produced when interrupting heavy motor currents.

Fig 4.2 CONTACTOR

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4.3 555 TIMER IC

FIG 4.3

The 555 Timer IC is an

multivibrator applications. The IC was designed by

market in 1971 by Signetics (later acquired by

The original name was the SE555 (metal can)/NE555 (plastic

as “The IC Time Machine”. It has been claimed that the 555 gets its name from the three 5

resistors used in typical early implementa

arbitrary. The part is still in wide use, thanks to its ease of use, low price and good stability. As of

2003[update], it is estimated that

Table 4.1 Absolute maximum time


FIG 4.3 555 TIMER IC

The 555 Timer IC is an integrated circuit (chip) implementing a variety of

applications. The IC was designed by Hans R. Camenzind in 1970

(later acquired by Philips).

The original name was the SE555 (metal can)/NE555 (plastic DIP) and the part was described

. It has been claimed that the 555 gets its name from the three 5

resistors used in typical early implementations, but Hans Camenzind has stated that the number was


it is estimated that 1 billion units are manufactured every year.

19

(chip) implementing a variety of timer and

1970 and brought to

) and the part was described

. It has been claimed that the 555 gets its name from the three 5 kΩ

tions, but Hans Camenzind has stated that the number was


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Ultra-low power versions of the 555 are also available, such

7555 requires slightly different wiring using fewer external components and less power.

Fig 4.4 circuit diagram of 555 timer IC

4.4 The 555 has three operating modes:

Monostable mode: In this mode, the 555 functions as a "one

missing pulse detection, bouncefree switches, touch switches, frequency d

measurement, pulse-width modulation (PWM) etc

Monostable mode


low power versions of the 555 are also available, such as the 7555 and TLC555.


Fig 4.4 circuit diagram of 555 timer IC

operating modes:

n this mode, the 555 functions as a "one-shot". Applications include timers,

missing pulse detection, bouncefree switches, touch switches, frequency d

width modulation (PWM) etc

FIG 4.5 555 IN MONOSTABLE

20

as the 7555 and TLC555.[5] The


shot". Applications include timers,

missing pulse detection, bouncefree switches, touch switches, frequency divider, capacitance

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Schematic of a 555 in monostable mode

The relationships of the trigger signal, the voltage on

mode

In the monostable mode, the 555 timer acts as a “one

begins when the 555 timer receives a signal at the trigger input that falls below a third of the voltage

supply. The width of the pulse is determined by the time constant of an RC network, which consists

of a capacitor (C) and a resistor

supply voltage. The pulse width can be lengthened or shortened to the need of the specific

application by adjusting the values of R and C.

The pulse width of time t, which is the time it takes to charge C to 2/3 of the supply voltage,

is given by


Schematic of a 555 in monostable mode

The relationships of the trigger signal, the voltage on C and the pulse width in monostable

In the monostable mode, the 555 timer acts as a “one-shot” pulse generator. The pulse


pulse is determined by the time constant of an RC network, which consists

resistor (R). The pulse ends when the charge on the C equals 2/3 of the


application by adjusting the values of R and C.[6]


21

C and the pulse width in monostable

shot” pulse generator. The pulse


pulse is determined by the time constant of an RC network, which consists

e ends when the charge on the C equals 2/3 of the



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4.5 DIODE

In electronics, a diode is a two

in only one direction. The term u

today. This is a crystalline block of

vacuum tube diode (now little used except in some high

two electrodes; a plate and a cathode

The most common function of a diode is to allow an electric current to pass in one direction

(called the diode's forward direction) while blocking current in the opposite direction (the reverse

direction). Thus, the diode can be thought of as an electronic version of a

unidirectional behaviour is called

current, and to extract modulation

However, diodes can have more complicated behaviour than this simple on

to their complex non-linear electrical characteristics, which can be tailored by varying t

construction of their P-N junction

different functions. For example, specialized diodes are used to regulate volta

electromechanically tune radio and TV receivers (

oscillations (tunnel diodes), and to produce light (

semiconductor electronic devices

physicist Ferdinand Braun in 1874. The first semiconductor diodes, called


FIG 4.6 DIODE

, a diode is a two-terminal electronic component that conducts

in only one direction. The term usually refers to a semiconductor diode, the most common type

today. This is a crystalline block of semiconductor material connected to two electrical terminals. A

(now little used except in some high-power technologies) is a

cathode.


ode's forward direction) while blocking current in the opposite direction (the reverse

direction). Thus, the diode can be thought of as an electronic version of a

idirectional behaviour is called rectification, and is used to convert alternating current

modulation from radio signals in radio receivers.

However, diodes can have more complicated behaviour than this simple on

electrical characteristics, which can be tailored by varying t

N junction. These are exploited in special purpose diodes that perform many

different functions. For example, specialized diodes are used to regulate voltage (

nically tune radio and TV receivers (varactor diodes), to generate

), and to produce light (light emitting diodes).Diodes were the first

semiconductor electronic devices. The discovery of crystals' rectifying abilities was made by German

in 1874. The first semiconductor diodes, called cat's whisker diodes

22

that conducts electric current

sually refers to a semiconductor diode, the most common type

material connected to two electrical terminals. A

power technologies) is a vacuum tube with


ode's forward direction) while blocking current in the opposite direction (the reverse

direction). Thus, the diode can be thought of as an electronic version of a check valve. This

alternating current to direct

However, diodes can have more complicated behaviour than this simple on-off action, due

electrical characteristics, which can be tailored by varying the

. These are exploited in special purpose diodes that perform many

ge (Zener diodes), to

), to generate radio frequency

).Diodes were the first

abilities was made by German

cat's whisker diodes were

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made of crystals of minerals such as galena. Today most diodes are made of silicon, but other

semiconductors such as germanium are sometimes used.

4.6 ZENER DIODE

It is the p-n junction diode with heavily doping. Always operate in reverse bias condition. It

can be used as a voltage regulator. This reverse break-down can be occur in junction diode by

two different mechanism. They are zener breakdown and avalanche breakdown. Zener

breakdown occur due to high electric field (9V – 12V). Voltage in reverse bias is low and

doping is very high.

Avalanche breakdown occur due to impact ionization doping is low compared with zener is

very high as compared with ordinary p-n junction. Zener breakdown occurs at relatively low

voltage where as avalanche breakdown occurs at relatively high voltage.

Applications:

Radio demodulation, Power conversion, Over-voltage protection, Logic gates, Ionizing

radiation detectors, Temperature measurements, Current steering.

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4.7 TRANSISTOR

FIG 2.6.1 TRANSISTOR

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

It is made of a solid piece 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 flowing through another pair of terminals. Because the controlled (output) power can

be much more than the controlling (input) power, the transistor provides amplification of a

signal. Today, some transistors are packaged individually, but many more are found

embedded in integrated circuits.

The transistor is the fundamental building block of modern electronic devices, and its

presence is ubiquitous in modern electronic systems. Following its release in the early 1950s

the transistor revolutionised the field of electronics, and paved the way for smaller and

cheaper radios, calculators, and computers, amongst other things.

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The NPN is one of the two types of bipolar transistors, in which the letters "N" and

"P" refer to the majority charge carriers inside the different regions of the transistor. Most

bipolar transistors used today are NPN, because electron mobility is higher than hole mobility

in semiconductors, allowing greater currents and faster operation.

NPN transistors consist of a layer of P-doped semiconductor (the "base") between two

N-doped layers. A small current entering the base in common-emitter mode is amplified in

the collector output. In other terms, an NPN transistor is "on" when its base is pulled high

relative to the emitter.

The arrow in the NPN transistor symbol is on the emitter leg and points in the

direction of the conventional current flow when the device is in forward active mode. One

mnemonic device for identifying the symbol for the NPN transistor is "not pointing in"[5] or

"never points in".

The other type of BJT is the PNP with the letters "P" and "N" referring to the majority

charge carriers inside the different regions of the transistor.

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4.8 CAPACITORS

A capacitor (formerly known as condenser) is a passive electronic component

consisting of a pair of conductors separated by a dielectric (insulator). When a potential

difference (voltage) exists across the conductors, an electric field is present in the dielectric.

This field stores energy and produces a mechanical force between the conductors. The effect

is greatest when there is a narrow separation between large areas of conductor; hence

capacitor conductors are often called plates.

An ideal capacitor is characterized by a single constant value, capacitance, which is

measured in farads. This is the ratio of the electric charge on each conductor to the potential

difference between them. In practice, the dielectric between the plates passes a small amount

of leakage current. The conductors and leads introduce an equivalent series resistance and the

dielectric has an electric field strength limit resulting in a breakdown voltage.

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CAPACITOR

Capacitors store electric charge. They are used with resistors in timing circuits

because it takes time for a capacitor to fill with charge. They are used to smooth varying DC

supplies by acting as a reservoir of charge. They are also used in filter circuits because

capacitors easily pass AC (changing) signals but they block DC (constant) signals.

Electrolytic Capacitors:

Electrolytic capacitors are polarised and they must be connected the correct way

round, at least one of their leads will be marked + or -. They are not damaged by heat when

soldering. There are two designs of electrolytic capacitors; axial where the leads are attached

to each end (220µF in picture) and radial where both leads are at the same end (10µF in

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picture). Radial capacitors tend to be a little smaller and they stand upright on the circuit

board.

4.9 RESISTOR

FIG 2.8.1 RESISTORS

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A resistor is a two-terminal

terminals that is proportional

Ohm's law:

Resistors are elements of

in most electronic equipment. Practical resistors can be made of various compounds and

films, as well as resistance wire

nickel/chrome).

The primary characteristics of a resistor are the

working voltage and the power

noise, and inductance. Less well

dissipation limits the maximum permitted current flow, and above which the limit is applied

voltage. Critical resistance is determined by the design, materials and dimensions of the

resistor.

4.9.1 Fixed and Variable Resistors

There are two kinds of resistors, FIXED and VARIABLE. The fixed resistor will

have one value and will never change (other than through temperature, age, etc.). The

resistors shown in A and B of figure 1

illustrated in B has several fixed taps and makes more than one resistance value available.

The sliding contact resistor shown in C has an adjustable collar that can be moved to tap off

any resistance within the ohmic value range of the resistor.


terminal electronic component that produces a

proportional to the electric current passing through it in accordanc

V = IR

Resistors are elements of electrical networks and electronic circuits and are ubiquitous


resistance wire (wire made of a high-resistivity alloy, such as

The primary characteristics of a resistor are the resistance, the tolerance

power rating. Other characteristics include temperature coefficient

. Less well-known is critical resistance, the value below which power



Fixed and Variable Resistors:



resistors shown in A and B of figure 1-29are classed as fixed resistors. The tapped r



any resistance within the ohmic value range of the resistor.

FIG 2.8.2 VARIABLE RESISTORS

29

that produces a voltage across its

passing through it in accordance with

and electronic circuits and are ubiquitous


resistivity alloy, such as

tolerance, maximum

temperature coefficient,

the value below which power





29are classed as fixed resistors. The tapped resistor



FIG 2.8.2 VARIABLE RESISTORS

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A high current-handling capability. The potentiometer has a wide range of values, but

it usually has a limited current-handling capability. Potentiometers are always connected as

voltage dividers.

4.10 TRANSFORMER

A transformer is a device that transfers electrical energy from one circuit to another through

inductively coupled conductors—the transformer's coils. A varying current in the first or

primary winding creates a varying magnetic flux in the transformer's core, and thus a varying

magnetic field through the secondary winding. This varying magnetic field induces a varying

electromotive force (EMF) or "voltage" in the secondary winding. This effect is called mutual

induction.

If a load is connected to the secondary, an electric current will flow in the secondary

winding and electrical energy will be transferred from the primary circuit through the

transformer to the load. In an ideal transformer, the induced voltage in the secondary winding

(VS) is in proportion to the primary voltage (VP), and is given by the ratio of the number of

turns in the secondary (NS) to the number of turns in the primary (NP) as follows:

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Models of an ideal transformer typically assume a core of negligible

two windings of zero resistance

current flows, driving flux around the

field induces an electromotive force

which states that the induction of EMF would always be such that it will oppose development

of any such change in magnetic field.


TRANSFORMER

Models of an ideal transformer typically assume a core of negligible

resistance. When a voltage is applied to the primary winding, a small

around the magnetic circuit of the core. The changing magnetic

electromotive force (EMF) across each winding. ". This is due to


of any such change in magnetic field.

31

Models of an ideal transformer typically assume a core of negligible reluctance with

the primary winding, a small

. The changing magnetic

(EMF) across each winding. ". This is due to Lenz's law


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CHAPTER 5

OPTOCOUPLER IC

Working principle Optocoupler IC:-

Optocoupler is a component that serves to regulate the feedback that goes into STR /

Transistor / IC power on the power supply. Optocoupler is typically used on TV not too long

ago produced. Optocoupler is also instrumental in the start-up TV, and also serves as a

stabilizer output voltage switching power supply.

Optocoupler is a device that consists of two parts: transmitter and receiver, which is between

the light with the light source detection separately. Optocoupler is usually used as an

electrical switch, which works automatically. Optocoupler is a component connector

(coupling), which works based on optical light trigger. Optocoupler consists of two parts: At

the transmitter is built from an infrared LED. When compared to using regular LED, infrared

LED has better resistance to the signal appears. Light emitted by the LED infrared invisible

to the naked eye. At the receiver is built with the basic components of Photodiode.

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Photodiode is a power transistor that is sensitive to light. A light source produces heat energy,

as well as the infrared spectrum. Because it has the effect of thermal infra spectrum greater

than visible light, then Photodiode more susceptible to capture radiation of infrared rays.

Judging from its use, the physical form of the optocoupler can vary. When only be used to

isolate the voltage levels or data on the transmitter and receiver side, the optocoupler is

usually made in solid form (no space between the LED and Photodiode). So that the electrical

signal at the input and output there will be isolated. In other words optocoupler is used as an

optoisolator IC type. The working principle of the optocoupler is: If between Photodiode and

LED Photodiode blocked it off so it will be output from the collector logic high. Conversely,

if the Photodiode and LED are not blocked so that its output will be logic low.

Circuit Diagram

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OPERATION

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In three phase supply, first R phase with neutral is connected to primary winding of

the step-down transformer X1. This step-down transformer X1 reduces the 240V AC to 12V

AC. We get 12V AC at secondary winding of step-down transformer X1. An isolation

rectifier circuit is connected to the secondary winding of step-down transformer X1.

This rectifier circuit rectifies the 12V AC to 12V DC. A LED is connected to rectifier

circuit in series with resistor to indicate the presents of R phase. And a freewheeling diode is

connected to rectifier circuit. The output of this circuit is connected to coil of 12V operational

relay RL1. The NO of operational relay RL1 is connected to Y phase. The pole of operational

relay RL1 is connected to primary winding of step-down transformer X2.

This step-down transformer X2 reduces the 240V AC to 12V AC. We get 12V AC at

secondary winding of step-down transformer X2. An isolation rectifier circuit is connected to

the secondary winding of step-down transformer X2.


circuit in series with resistor to indicate the presents of Y phase. And a freewheeling diode is

connected to rectifier circuit.

The output of this circuit is connected to coil side of 12V operational relay RL2. The

NO of operational relay RL2 is connected to B phase. The pole of operational relay RL2 is

connected to primary winding of step-down transformer X3.

This step-down transformer X3 reduces the 240V AC to 12V AC. We get 12V AC at

secondary winding of step-down transformer X3. An isolation rectifier circuit is connected to

the secondary winding of step-down transformer X3.


circuit in series with resistor to indicate the presents of B phase.

For this rectifier circuit 555 timers is connected to produce the certain time delay in

order to avoid surges and momentary fluctuations. Variable resistor is used to 555 timer to set

the time delay. In 555 timers at pin 3 we get the output.

This output is connected to the transistor base. Transistor emitter is connected to the

ground and collector is connected to the anode of freewheeling diode. Across the

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freewheeling diode operational relay RL3 is connected. The NO of operational relay RL3 is

connected to B phase. The pole of operational relay RL3 is connected to coil of 4 pole

contactor RL4.

For input side of 4 pole contactor RL4, three phase supply is connected. And for

output side, load is connected. This contactor RL4 acts as switch depending up on the

presents of all the 3 phases.

As we give three phase supply to the circuit:

R phase passes through the step-down transformer X1. This step-down transformer reduces

the voltage to 12V AC. Rectifier circuit rectifies the 12V AC to 12V DC. As the output

appear at rectifier circuit 1 then LED glows. Rectifier circuit 1 gives the 12V DC to coil of

relay RL1. When coil of relay RL1 gets triggered its pole connects to the NO. Then phase Y

given to pole of relay RL1 passes to transformer X2 through NO.

Then Y phase passes from the step-down transformer X2. This step-down transformer

reduces the voltage to 12V AC. Rectifier circuit rectifies the 12V AC to 12V DC. As the

output appear at rectifier circuit 2 then LED glows. Rectifier circuit 2 gives the 12V DC to

coil of relay RL2. When coil of relay RL2 gets triggered its pole connects to the NO. Then

phase B given to pole of relay RL2 passes to transformer X3 through NO.

Then B phase passes through the step-down transformer X3. This step-down transformer

reduces the voltage to 12V AC. Rectifier circuit rectifies the 12V AC to 12V DC. As the

output appear at rectifier circuit 3 then LED glows. Rectifier circuit 3 gives the 12V DC to

555 timer.

This 555 timer produces the delay to produce the output at pin 3 in order to avoid surges and

momentary fluctuations. The time delay can be adjusted by the variable resistor connected at

pin 6.

The output at pin3 is given to the base of transistor. Then this output is given to coil of relay

RL3 through collector of transistor. When coil of relay RL3 gets triggered its pole connects to

the NO. Then phase B given to pole of relay 3 passes to coil of 4pole contactor RL4 through

NO.When coil of contactor gets triggered it connects the three-phase supply to the load.

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When any one or two phase gets failure in three phase supply then this circuit fails in above

operation. As the circuit fails in operation 4-Pole contactor RL4 automatically disconnects

the three-phase supply to load.

CONCLUSION

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The test system considered in the project is worked out for the best protection for the

3- phase appliance in absence of any of the phase. The main objective of this prospective

protector is to maintain the efficiency of the appliance which we use with the 3- phase

supply.

The 4-pole contactor locking assures the presence of all the 3-phases. Remaining three relays

placed for all the three phases show there working with a hissing sound and glowing LED’S.

Due to any erratic action taking place there will be absence of any o the phase results in the

un-locking of the 4- pole contactor with an rapid fast off sound.

The 555 timer which we used in the destination tip of the circuit provides the time delay for

each phase which would be around 4sec as the timer working in astable mode.

For review time delay from the 555 timer we need to connect an variable resistor due to that

time delay can subjected and maximum is upto 4 sec.

A transistor is placed in need of a switch which is used for getting the output in the third

phase.

Using this protector scheme would be useful to protector the appliance and at the same time

it would reduce the frequent money lending in fault occurrence or failure of the appliance.

REFERENCES

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1 Electrical And Electronics

S. K. Bishnoi

MAHENDRA BHADU

M. L. Meena

2 www.circuittoday.com

3 http://www.deekshith.in/search/label/Projects

4 Electrical Power System – C. L. Wadhwa

5 Power Electronics – P. S. Bimbra

6 http://www.deekshith.in/search/label/Projects/Paper R.G. Thiagaraj Kumar P. Kasi Rajan

Engineering

Report on minor project