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

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