i

VOLTAGE SOURCE INVERTER

BASED ON MOSFET

A Project Report Submitted to the

POWER ELECTRONICS ENGINEERING

DEPARTMENT

AS TERM WORK FOR THE SUBJECT

PROJECT - i

OF SEMESTER VII

OF

B.E. (Power Electronics)

GUIDE: PREPARED BY: MR.M.V.MAKWANA

MR.M.H.AYALANI

MR. A.M.HAQUE

MR.P.J.MUNJANI

MR. S.H.TRIVEDI

VAIBHAV K.MEHTA

GAURAV D.KUKARVADIYA

DHARMENDRA J.KANJARIA

RAVI T. CHAVADA

POWER ELECTRONICS ENGINEERING

DEPARTMENT

L. E. COLLEGE, MORBI

SAURASHTRA UNIVERSITY, RAJKOT

YEAR 2010

ii

POWER ELECTRONICS ENGINEERING

DEPARTMENT

L. E. COLLEGE, MORBI

LUKHDHIRJI ENGINEERING COLLEGE MORBI -363642

CERTIFICATE

This is to certify that the project work titled “VOLTAGE SOURCE

INVERTER” is being submitted by

Mr. RAVI T CHAVADA 09 EXAM NO:

Mr. DHARMENDRA J KANJARIA 17 EXAM NO:

Mr. GAURAV D KUKARVADIYA 20 EXAM NO:

Mr. VAIBHAV K MEHTA 21 EXAM NO:

For fulfillment of partial requirements of Semester VII

of the degree Bachelor of Engineering (Power

Electronics) of Saurashtra University for the academic

year 2010.

GUIDED BY:

HEAD OF THE DEPARTMENT

MR. M.H. AYALANI

MR. P.J.MUNJANI

MR. A.M.HAQUE

MR. S.H.TRIVEDI

POWER ELECTRONICS

ENGINEERING DEPT.

PROF. M.V. MAKVANA

POWER ELECTRONICS

ENGG. DEPTT.

L. E. COLLEGE

Place: MORBI-2

DATE:

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ACKNOWLEDGEMENT

We express our deep and sincere thanks to our guide MR.M.V.MAKVANA Head of the

Power Electronics Engineering Department, L. E. College, Morbi. Initially he helped us in

selecting this project and then guided us throughout the project. He also helped us by taking a lot

of pain and sacrificing his personal valuable time in completion of this practical project as well as

the project report.

Next, we would like to express our deep gratitude towards Prof.M.H.AYALANI,

Mr.A.M.HAQUE, Mr.P.J.MUNJANI, Mr.S.H.TRIVEDI, Mr.V.J.RUPAPARA Lecturer in Power

electronics Engineering Department who motivated us at one or another stage of the project work.

We are also thankful to Mr.B.K.DEY, Instructor and Mr.A.K.PARMAR, Laboratory

Assistant of Power Electronics Engineering Department who helped permitted us every time

when we needed support.

We express our gratitude to the staff members of Power Electronics Engineering

Department, who directly or indirectly helped us.

MEHTA VAIBHAV

KUKARVADIYA GAURAV

KANJARIA DHARMENDRA

CHAVDA RAVI

Place: MORBI

Date: / /

iv

ABSTRACT

The aim of development of this project is towards providing efficient and compact

inverter rated of 300-VA.

The input of inverter may be battery or fuel cell of 12 volt, dc Two batteries of 12 volt

are connected in series and 24 volt is obtained and output is 230 volt ac and frequency of 50

Hz.

This inverter can be used in uninterruptible power supply, induction heating and

melting furnace etc.

This inverter can also be used in where speed control of induction motor is needed very

precisely and in variable-speed ac motor drives and other industrial applications.

By means of inverter design, driver circuit of power switches is made of operational amplifier.

With the help of op-amp pulse-width is obtained and this pulse is given to J-K flip-flop and two

pulses are taken from Q and Q.

In the design of gate drive circuit preset resistors are used so; frequency of gate signal can be

varied up to 1 kHz.

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GLOSSARY OF TERMS

AC - Alternating Current

CRO - Cathode Ray Oscilloscope

DC - Direct Current

IC - Integrated Circuit

MOSFET - Metal Oxide Semiconductor Field Effect Transistor

OP-AMP - Operational amplifier

TABLE OF CONTENTS

ACKNOWLEDGMENT……………………………………………………..III

ABSTRECT…………………………………………………………………..IV

GLOSSARY OF TERMS……………………………………………….…...V

1. INTRODUCTION…………………………………………………...1

GOAL…………………………………………………………….……...……….….…….2

Inverter circuit description……………………………………...….…………….…...…...2

Inverter circuit configuration…………………………………….………………………..3

Basic inverter designs………………………………………………………………….….3

Inverter application………………………………………………..............................……5

2. OBJECTIVE………………………………………………….…..…7

Goal……………………………………………………………………………..….……..8

Target specification………………………………………………………………….........8

3. THEORY OF PROJECT…………………………………..…….....9

Goal………………………………………………………………………..…….……….10

Power MOSFET…………………………………………………………………………10

Battery…………………………………………………….……….……………....……..17

Transformer……………………………………………………………………..….…….19

Instrument transformer……………………………………………………………...…...25

Pulse transformer…………………………………………………………...…….…......27

RF transformer………………………………………………………………...…….…..28

Use of transformer…………………………………………………………....…….…...28

Operational amplifier………………………………………………………….…...…....29

Flip-flop section……………………………………………………………….…….…..33

4. WORKING OF INVERTER………………………………..…..…36

Goal………………………………………………………………..….………………….37

Basic block diagram of inverter………………………………..….…………….……….37

Description of the block diagram……………………………………….…….…..……..37

Flip-flop …………………………………………………………………………………42

Working of a inverter……………………………………………………………………49

5. DESIGN DETAILS OF INVERTER………………………..........51 Goal…………………………………………………………………...………...…….....52

Design calculation…………………………………………………....………...………..52

Design of Control circuit…………………………………....…………………...…..…..52

Design of power circuit…………………………………...………………...…….……..53

Design of 300 VA inverter transformer with given specification……………………….55

Circuit diagram of inverter……………………………………………………………....59

6. TESTING & CALIBRATION…………………………………....60

Goal……………………………………………………………...……………………….61

Testing procedure and calibration………………………………………………………..61

7. RESULTS……………………………………………………......…63

Goal………………………………………………………………………………………64

Power circuit………………………………………………………...…………...………64

Base drive circuit specification……………………………………..….………………...64

8. TIME & COST ANALYSIS………………………………………65

Goal……………………………………………………………………………………...66

Time Analysis…………………………………………………………………………...66

Cost Analysis……………………………………………………………………………67

9. CONCLUSION……………………………………………………..68

Goal………………………………………………………………....……………………69

Conclusion………………………………………………………………………………..69

10. FUTURE MODIFICATION………………………..…......…….. 70

Goal………………………………………………………………….………….….......71

As a AC drives/ AC voltage controller…………………..……….………...………...71

APPENDIX…………………………………………………………………... 72 IC 555………………...……………………………………………………………….73

IC 741…………...………………………………………………………………..….. 83

IC 74LS73A…………………………………………………………………………..87

BIBLIOGRAPHY……………………………………………………………90

1.

INTRODUCTION

1. 1

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1. INTRODUCTION

1.1 GOAL

“To explain theme of the project

1.2 INVERTER CIRCUIT DISCRIPTION

A device that converts DC power to AC power at desired output voltage and frequency is

called an INVERTER. Some industrial applications of inverters are for adjustable speed ac

drives, induction heating, stand by air craft power supplies, UPS (Uninterruptible power

supplies) for computers, HVDC transmission lines etc. phase controlled converters , when

operated in inverter mode, are called line commuted inverter. But line commuted inverters

require at the output terminals an existing ac supply which is used for the commutation. This

means that line-commuted inverters can’t function as isolated ac voltage sources or as

variable frequency generators with dc power at the input. Therefore, voltage level, frequency

and waveform on the ac side of line commuted inverters can not be changed. On the other

hand, forced commutated inverters provide an independent ac output voltage of adjustable

voltage and adjustable frequency and have therefore much wider applications.

The dc power input to the inverter is obtained from an existing power supply

network or from a rotating alternator through a rectifier or a battery, fuel cell, photovoltaic

array or magneto hydrodynamic (MHD) generator. The configuration of ac to dc converter

and dc to ac converter is called dc link converters.

Inverters can be broadly classified into two types;

a. Voltage source inverter.

b. Current source inverter.

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In voltage source inverter are made up of using GTOs, power transistor, power mosfet or

IGBTs, self commutation with base or gate drives signals is employed for their controlled

turn on and turn off.

1.3 INVERTER CIRCUIT CONFIGURATION:

5.2 Inverter

Simple power inverter circuit using mosfet and battery

1.4 BASIC INVERTER DESIGNS:

1..1 Basic

In one simple inverter circuit, DC power is connected to a transformer through the center tap

of the primary winding. A switch is rapidly switched back and forth to allow current to flow

back to the DC source following two alternate paths through one end of the primary winding

and then the other. The alternation of the direction of current in the primary winding of the

transformer produces alternating current (AC) in the secondary circuit.

The electromechanical version of the switching device includes two stationary contacts and a

spring supported moving contact. The spring holds the movable contact against one of the

stationary contacts and an electromagnet pulls the movable contact to the opposite stationary

contact. The current in the electromagnet is interrupted by the action of the switch so that the

switch continually switches rapidly back and forth. This type of electromechanical inverter

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switch, called a vibrator or buzzer, was once used in vacuum tubes automobile radios. A

similar mechanism has been used in door bells, buzzers and tattoo guns.

These electromechanical inverters explain the source of the term "inverter". Early AC to DC

converters combined a synchronous AC motor with a commutator so that the commutator

reversed its connections to the AC line exactly twice per cycle. This results in AC-in, DC-out.

If you invert the connections to a converter you put DC in and get AC out. Hence an inverter

is an inverted converter.

As they became available, transistors and various other types of semiconductor switches have

been incorporated into inverter circuit designs.

1.4.1 MORE ADVANCED DESIGN:

1..2 More 1

In more advanced inverter designs various techniques are used to improve the quality of the

sine wave at the transformer input, rather than relying on the transformer to smooth it.

Capacitors and inductors (but not freewheel diode as it is AC) can be used to filter the

waveform at the primary of the transformer. Also, it is possible to produce a more sinusoidal

wave by having split-rail direct current inputs at two voltages, or positive and negative inputs

with a central ground. By connecting the transformer input terminals in sequence between the

positive rail and ground, the positive rail and the negative rail, the ground rail and the

negative rail, then both to the ground rail, a stepped sinusoid is generated at the transformer

input and the current drain on the direct current supply is less choppy. These methods result

in an output that is called a "modified-sine wave". Modified-sine inverters may cause some

loads, such as motors, to operate less efficiently.

More expensive power inverters use Pulse Width Modulation (PWM) with a high frequency

carrier to more closely approximate a sine function. The quality of an inverter is described by

its pulse-rating: a 3-pulse is a very simple arrangement, utilising only 3 transistors, whereas a

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more complex 12-pulse system will give an almost exact sine wave. In remote areas where a

utility generated power is subject to significant external, distorting influences such as

inductive loads or semiconductor-rectifier loads, a 12-pulse inverter may even offer a better,

"cleaner" output than the utility-supplied power grid, and are thus often used in these areas.

Inverters with greater pulse ratings do exist.

Simple inverters generate harmonics which affect the quality of power obtained using them.

But PWM inverters eliminate this by means of a sine wave cancellation using the properties

of Fourier series.

1.5 INVERTER APPLICATION:

5.2 Inverter app

The following are examples of inverter applications.

DC power source utilization

Inverter designed to provide 115 VAC from the 12 VDC source provided in an automobile

An inverter allows the 12 volt DC power available in an automobile to supply AC power to

operate equipment that is normally supplied from a mains power source.

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or just inverters Inverters are also used to provide a source of AC power from solar cell and

fuel cell power supplies.

1.5.1 UNINTEREPTABLE POWER SUPPLIES:

1..1 Uninterrupti

One type of uninterruptible power supply uses batteries to store power and an inverter to

supply AC power from the batteries when mains power is not available. When mains power

is restored, a rectifier is used to supply DC power to recharge the batteries.

1.5.2 INDUCTION HEATING:

1..2 Induction

Inverters are used to convert low frequency mains AC power to a higher frequency for use in

induction heating. To do this, AC power is first rectified to provide DC power. The inverter

then changes the DC power to high frequency AC power.

1.5.3 HIGH VOLTAGE DIRECT CURRENT:

With HVDC power transmission, AC power is rectified and high voltage DC power is

transmitted to another location. At the receiving location, an inverter in a static inverter plant

converts the power back to AC.

1..3 Variable

A variable frequency drive controls the operating speed of an AC motor by controlling the

frequency and voltage of the power supplied to the motor. An inverter provides the controlled

power. In most cases, the variable frequency drive includes a rectifier so that DC power for

the inverter can be provided from mains AC power.

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2.

OBJECTIVE

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2. OBJECTIVE

2.1 GOAL

“To set target specifications and objectives of the project”

2.2 TARGET SPECIFICATIONS

The target specifications set for this power supply are as under.

Input Source : 12 V dc

Output : 230VA

Efficiency : > 80%

Switching Frequency : 50Hz

VPP(RIPPLE) : < 5% of VO

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3.

THEORY OF PROJECT

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3. THEORY OF PROJECT COMPONENT

3.1 GOAL

“To explain the working of POWER MOSFET as switch and describe the detail

of battery”

3.2 POWER MOSFET

Discrete power MOSFETs employ semiconductor processing techniques that are

similar to those of today's VLSI circuits, although the device geometry, voltage and current

levels are significantly different from the design used in VLSI devices. The metal oxide

semiconductor field effect transistor (MOSFET) is based on the original field-effect transistor

introduced in the 70s. Figure 3.1 shows the device schematic, transfer characteristics and

device symbol for a MOSFET. The invention of the power MOSFET was partly driven by the

limitations of bipolar power junction transistors (BJTs) which, until recently, were the device

of choice in power electronics applications.

Figure 0-1 POWER MOSFET (A) SCHEMATIC (B) TRANSFER

CHARACTERISTICS (C) SYMBOL

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Although it is not possible to define absolutely the operating boundaries of a power

device, we will loosely refer to the power device as any device that can switch at least 1A.

The bipolar power transistor is a current controlled device. A large base drive current as high

as one-fifth of the collector current is required to keep the device in the ON state.

Also, higher reverse base drive currents are required to obtain fast turn-off. Despite

the very advanced state of manufacturability and lower costs of BJTs, these limitations have

made the base drive circuit design more complicated and hence more expensive than the

power MOSFET.

Another BJT limitation is that both electrons and holes contribute to conduction.

Presence of holes with their higher carrier lifetime causes the switching speed to be several

orders of magnitude slower than for a power MOSFET of similar size and voltage rating.

Also, BJTs suffer from thermal runaway. Their forward voltage drop decreases with

increasing temperature causing diversion of current to a single device when several devices

are paralleled. Power MOSFETs, on the other hand, are majority carrier devices with no

minority carrier injection. They are superior to the BJTs in high frequency applications where

switching power losses are important. Plus, they can withstand simultaneous application of

high current and voltage without undergoing destructive failure due to second breakdown.

Power MOSFETs can also be paralleled easily because the forward voltage drop increases

with increasing temperature, ensuring an even distribution of current among all components.

Figure 0-2 CURRENT -VOLTAGE LIMITATIONS OF MOSFET AND BJT

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However, at high breakdown voltages (>200V) the on-state voltage drop of the power

MOSFET becomes higher than that of a similar size bipolar device with similar voltage

rating. This makes it more attractive to use the bipolar power transistor at the expense of

worse high frequency performance. Figure 3.2 shows the present current-voltage limitations

of power MOSFETs and BJTs. Over time, new materials, structures and processing

techniques are expected to raise these limits.

Figure 3.3 shows schematic diagram and Figure 3.4 shows the physical origin of the

parasitic components in an n-channel power MOSFET. The parasitic JFET appearing

between the two body implants restricts current flow when the depletion widths of the two

adjacent body diodes extend into the drift region with increasing drain voltage. The parasitic

BJT can make the device susceptible to unwanted device turn-on and premature breakdown.

The base resistance RB must be minimized through careful design of the doping and distance

under the source region. There are several parasitic capacitances associated with the power

MOSFET as shown in Figure 3.3.

Figure 0-3 SCHEMATIC DIAGRAM OF THE n- CHANNEL POWER MOSFET AND

THE DEVICE SYMBOL

CGS is the capacitance due to the overlap of the source and the channel regions by the

poly silicon gate and is independent of applied voltage. CGD consists of two parts, the first is

the capacitance associated with the overlap of the poly silicon gate and the silicon underneath

in the JFET region. The second part is the capacitance associated with the depletion region

immediately under the gate. CGD is a nonlinear function of voltage. Finally, CDS, the

capacitance associated with the body-drift diode, varies inversely with the square root of the

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drain-source bias. There are currently two designs of power MOSFETs, usually referred to as

the planar and the trench designs. The planar design has already been introduced in the

schematic of Figure 3.3. Two variations of the trench power MOSFET are shown Figure 3.5.

The trench technology has the advantage of higher cell density but is more difficult to

manufacture than the planar device.

Figure 0-4 POWER MOSFET PARASYTIC COMPONENTS

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Figure 0-5 TRENCH MOSFET (A) CURRENT CROWDING IN V-GROOVE

TRENCH MOSFET, (B) TRUNCATED V-GROOVE MOSFET

Break Down Voltage (BVDSS)

Breakdown voltage, BVDSS, is the voltage at which the reverse-biased body-

drift diode breaks down and significant current starts to flow between the source and

drain by the avalanche multiplication process, while the gate and source are shorted

together. The breakdown characteristics are shown in fig. below.

Figure POWER MOSFET BREAKDOWN CHARACTERISTICS

3.2.1 ON State Resistance (RDS(ON))

The on-state resistance of a power MOSFET is made up of several components as

shown in Figure 3.7:

RwcmlRsubRRRRchRsourceR DJAONDS Equation - 0-1

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Where:

Rsource = Source diffusion resistance, Rch = Channel resistance,

RA = Accumulation resistance, RD = Drift region resistance,

Rsub = Substrate resistance,

RJ = "JFET" component-resistance of the region between the two body regions

Figure 0-6 INTERNAL RESISTANCE IN A POWER MOSFET

3.2.2 POWER DISSIPATION

The maximum allowable power dissipation that will raise the die temperature to the

maximum allowable when the case temperature is held at 250C is important. It is give by Pd

where:

JCthR

25maxTjPd

Equation - 0-2

Tjmax= Maximum allowable temperature of the p-n junction in the device (normally

1500C or 175

0C) RthJC = Junction-to-case thermal impedance of the device.

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3.2.3 DYNAMIC CHARACTERISTICS

When the MOSFET is used as a switch, its basic function is to control the drain

current by the gate voltage. Figure 3.8(a) shows the transfer characteristics and Figure 3.8(b)

is an equivalent circuit model often used for the analysis of MOSFET switching performance.

The switching performance of a device is determined by the time required to establish

voltage changes across capacitances. RG is the distributed resistance of the gate and is

approximately inversely proportional to active area. LS and LD are source and drain lead

inductances and are around a few tens of NH. Typical values of input (CISS), output (COSS)

and reverse transfer (CRSS) capacitances given in the data sheets are used by circuit designers

as a starting point in determining circuit component values. The data sheet capacitances are

defined in terms of the equivalent circuit capacitances as:

CISS = CGS + CGD, CDS shorted, CRSS = CGD, and COSS = CDS + CGD

Figure 0-7 POWER MOSFET (a) TRANSFER CHARACTERISTICS (b)

EQUIVALENT CIRCUIT SHOWING COMPONENTS

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3.3 BATTERY

Basically there are two types of batteries available in the market. Comparisons for this

are as under:

PRIMARY CELLS SECONDARY CELLS

1. This can not be recharged. 1. It can be recharged.

2. One may change the parts of the

cell.

2. Plates cannot be changed they are to

be thrown out.

3. High internal resistance. 3. Low internal resistance.

4. Light in weight. 4. Heavy in weight.

5. Lesser life. 5. Long life.

6. It can be used for low energy

requirements.

6. It can be used for high energy

requirements.

Table 0-1 COMPARISON BETWEEN PRIMARY & SECONDARY CELLS

3.3.1 EFFICIENCY OF BATTERY

The efficiency of battery is given by the following equation:

Efficiency =Output in amp – hr.

Input in amp – hr.Equation 3-3

If percentage efficiency is required then this quantity should be multiplied by 100.

3.3.2 PRECAUTIONS TO BE TAKEN AT THE TIME OF BATTERY

CHARGING

The charging voltage and charging current should be set to correct value.

The polarities should be connected in proper and correct manner.

The temperature should be maintained constant.

The time for charging should carefully noted.

The level of electrolyte should be maintained constant.

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3.3.3 FEATURE OF LEAD ACID CELL

FEATURE LEAD ACID CELL

1. Open circuit e.m.f. when fully

charged. 1. 2.2 Volt.

2. Voltage at discharge condition. 2. 1.8 Volt

3. Package 3. Bulky and heavy

4. Life 4. Limited, if left unused it gets

discharged.

5. Maintenance 5. Require periodical maintenance.

6. Discharge rate 6. If discharge at high rate the cell gets

damaged.

7. Charging time 7. The charging rate is limited so it

takes long time to charge.

8. Low temperature operation. 8. Can not be used below -20° C.

9. Efficiency 9. Limited.

10. Cost per Ah. 10. Higher.

Table 4-1 FEATURE OF LEAD - ACID CELL

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3.4 TRANSFORMER:

Three-phase pole-mounted step-down transformer.

A transformer is an electrical device that transfers energy from one circuit to another by

magnetic coupling with no moving parts. A transformer comprises two or more coupled

windings, or a single tapped winding and, in most cases, a magnetic core to concentrate

magnetic flux. An alternating current in one winding creates a time-varying magnetic flux in

the core, which induces a voltage in the other windings. Transformers are used to convert

between high and low voltages, to change impedance, and to provide electrical isolation

between circuits.

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3.4.1 Basic principles

3.4.1.1 Coupling by mutual induction

A simple transformer consists of two electrical conductors called the primary winding and

the secondary winding. Energy is coupled between the windings by the time-varying

magnetic flux that passes through (links) both primary and secondary windings. When the

current in a coil is switched on or off or changed, a voltage is induced in a neighboring coil.

The effect, called mutual inductance, is an example of electromagnetic induction.

3.4.1.2 Elementary analysis

Practical transformer showing magnetizing flux in the core

If a time-varying voltage is applied to the primary winding of turns, a current will

flow in it producing a magneto motive force (MMF). Just as an electromotive force (EMF)

drives current around an electric circuit, so MMF tries to drive magnetic flux through a

magnetic circuit. The primary MMF produces a varying magnetic flux in the core, and,

with an open circuit secondary winding, induces a back electromotive force (EMF) in

opposition to . In accordance with Faraday's law of induction, the voltage induced across

the primary winding is proportional to the rate of change of flux:

And

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Where

vP and vS are the voltages across the primary winding and secondary winding,

NP and NS are the numbers of turns in the primary winding and secondary winding,

dΦP / dt and dΦS / dt are the derivatives of the flux with respect to time of the primary

and secondary windings.

Saying that the primary and secondary windings are perfectly coupled is equivalent to saying

that . Substituting and solving for the voltages shows that:

Where

vp and vs are voltages across primary and secondary,

Np and Ns are the numbers of turns in the primary and secondary, respectively.

Hence in an ideal transformer, the ratio of the primary and secondary voltages is equal to the

ratio of the number of turns in their windings, or alternatively, the voltage per turn is the

same for both windings. The ratio of the currents in the primary and secondary circuits is

inversely proportional to the turn’s ratio. This leads to the most common use of the

Transformer: to convert electrical energy at one voltage to energy at a different voltage by

means of windings with different numbers of turns. In a practical transformer, the higher-

voltage winding will have more turns, of smaller conductor cross-section, than the lower-

voltage windings.

The EMF in the secondary winding, if connected to an electrical circuit, will cause current to

flow in the secondary circuit. The MMF produced by current in the secondary opposes the

MMF of the primary and so tends to cancel the flux in the core. Since the reduced flux

reduces the EMF induced in the primary winding, increased current flows in the primary

circuit. The resulting increase in MMF due to the primary current offsets the effect of the

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opposing secondary M delivered to the secondary winding. Also because of this, the flux

density will always stay the same as long as the primary voltage is steady.

For example, suppose a power of 50 watts is supplied to a resistive load from a transformer

with a turn’s ratio of 25:2.

P = EI (power = electromotive force × current)

50 W = 2 V × 25 A in the primary circuit if the load is a resistive load. (See note 1)

Now with transformer change:

50 W = 25 V × 2 A in the secondary circuit.

.

3.4.2 Classifications

Transformers are adapted to numerous engineering applications and may be classified in

many ways:

By power level (from fraction of a volt-ampere(VA) to over a thousand MVA),

By application (power supply, impedance matching, circuit isolation),

By frequency range (power, audio, radio frequency(RF))

By voltage class (a few volts to about 750 kilovolts)

By cooling type (air cooled, oil filled, fan cooled, water cooled, etc.)

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By purpose (distribution, rectifier, arc furnace, amplifier output, etc.).

By ratio of the number of turns in the coils

Step-up

The secondary has more turns than the primary.

Step-down

The secondary has fewer turns than the primary.

Isolating

Intended to transform from one voltage to the same voltage. The two coils have

approximately equal numbers of turns, although often there is a slight difference in

the number of turns, in order to compensate for losses (otherwise the output voltage

would be a little less than, rather than the same as, the input voltage).

3.4.3 Circuit symbols

Standard symbols

Transformer with two windings and iron core.

Transformer with three windings. The dots show the relative winding

configuration of the windings.

Step-down or step-up transformer.The symbol shows which winding

has more turns,but does not usually show the exact ratio.

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Transformer with electrostatic screen, which prevents capacitive

coupling between the windings.

3.4.4 Losses

An ideal transformer would have no losses, and would therefore be 100% efficient. In

practice, energy is dissipated due both to the resistance of the windings known as copper loss

or I2 R loss, and to magnetic effects primarily attributable to the core (known as iron loss

measured in watts per pound). Transformers are, in general, highly efficient. Large power

transformers (over 50 MVA) may attain efficiency as high as 99.75%. Small transformers,

such as a plug-in "power brick" used to power small consumer electronics, may be less than

85% efficient.

Transformer losses arise from:

Winding resistance

Current flowing through the windings causes resistive heating of the conductors (I2 R loss).

At higher frequencies, skin effect and proximity effect create additional winding resistance

and losses.

Eddy currents

Induced eddy currents circulate within the core, causing resistive heating. Silicon is added to

the steel to help in controlling eddy currents. Adding silicon also has the advantage of

stopping aging of the electrical steel that was a problem years ago.

Hysteresis losses

Each time the magnetic field is reversed, a small amount of energy is lost to hysteresis within

the magnetic core. The amount of hysteresis is a function of the particular core material.

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Magnetostriction

Magnetic flux in the core causes it to physically expand and contract slightly with the

alternating magnetic field, an effect known as magnetostriction. This in turn causes losses

due to frictional heating in susceptible ferromagnetic cores.

Mechanical losses

In addition to magnetostriction, the alternating magnetic field causes fluctuating

electromagnetic forces between the primary and secondary windings. These incite vibrations

within nearby metalwork, creating a familiar humming or buzzing noise, and consuming a

small amount of power.MF. In this way, the electrical energy fed into the primary winding is

Stray losses

Not all the magnetic field produced by the primary is intercepted by the secondary. A portion

of the leakage flux may induce eddy currents within nearby conductive objects, such as the

transformer's support structure, and be converted to heat.

3.5 Instrument transformers

3.5.1 Current transformers

Current transformers used in metering equipment for three-phase 400 ampere electricity

supply

26

A current transformer is a type of "instrument transformer" that is designed to provide a

current in its secondary which is accurately proportional to the current flowing in its

primary.

Current transformers are commonly used in metering and protective relaying to facilitate the

measurement of large currents and isolation of high voltage systems which would be difficult

to measure more directly. Current transformers are often constructed by passing a single

primary turn (either an insulated cable or an uninsulated conductor (copper or aluminum are

typical in electric utility applications) through a well-insulated toroidal core wrapped with

many turns of wire. Current transformers (CTs) are used extensively in the electrical power

industry for monitoring of the power grid. The CT is described by its current ratio from

primary to secondary. Common secondary’s are 1 or 5 amperes. The secondary winding can

be single ratio or multi ratio, with five taps being common for multi ratio CTs. Typically, the

secondary connection points are labeled as X1, X2 and so on. The multi ratio CTs are

typically used for current matching in current differential protective relaying applications.

Often, multiple CTs will be installed as a "stack" for various uses (for example, protection

devices and revenue metering may use separate CTs). For a three-stacked CT application, the

secondary winding connection points are typically labeled Xn, Yn, Zn.Specially constructed

wideband current transformers are also used (usually with an oscilloscope) to measure

waveforms of high frequency or pulsed currents. One type of specially constructed wideband

transformer provides a voltage output that is proportional to the measured current. Another

type (called a Rogowski coil) requires an external integrator in order to provide a voltage

output that is proportional to the measured current. Care must be taken that the secondary of a

current transformer is not disconnected from its load while current is flowing in the primary,

as this will produce a dangerously high voltage across the open secondary.

3.5.2 Voltage transformers

Voltage transformers (or potential transformers) are another type of instrument

transformer, used for metering and protection in high-voltage circuits. They are designed to

present negligible load to the supply being measured and to have a precise voltage ratio to

accurately step down high voltages so that metering and protective relay equipment can be

operated at a lower potential. Typically the secondary of a voltage transformer is rated for 69

or 120 Volts at rated primary voltage, to match the input ratings of protection relays.

27

The transformer winding high-voltage connection points are typically labelled as H1, H2

(sometimes H0 if it is internally grounded) and X1, X2, and sometimes an X3 tap may be

present. Sometimes a second isolated winding (Y1, Y2, Y3) may also be available on the

same voltage transformer. The high side (primary) may be connected phase to ground or

phase to phase. The low side (secondary) is usually phase to ground.

The terminal identifications (H1, X1, Y1, etc.) are often referred to as polarity. This

applies to current transformers as well. At any instant terminals with the same suffix numeral

have the same polarity and phase. Correct identification of terminals and wiring is important

for proper operation of metering and protection relays.

3.6 Pulse transformers

A pulse transformer is a transformer that is optimized for transmitting rectangular electrical

pulses (that is, pulses with fast rise and fall times and a constant amplitude). Small versions

called signal types are used in digital logic and telecommunications circuits, often for

matching logic drivers to transmission lines. Medium-sized power versions are used in

power-control circuits such as camera flash controllers. Larger power versions are used in the

electrical power distribution industry to interface low-voltage control circuitry to the high-

voltage gates of power semiconductors. Special high voltage pulse transformers are also used

to generate high power pulses for radar, particle accelerators, or other pulsed power

applications.

To minimize distortion of the pulse shape, a pulse transformer needs to have low

values of leakage inductance and distributed capacitance, and a high open-circuit inductance.

In power-type pulse transformers, a low coupling capacitance (between the primary and

secondary) is important to protect the circuitry on the primary side from high-powered

transients created by the load. For the same reason, high insulation resistance and high

breakdown voltage are required. A good transient response is necessary to maintain the

rectangular pulse shape at the secondary, because a pulse with slow edges would create

switching losses in the power semiconductors.

The product of the peak pulse voltage and the duration of the pulse (or more accurately,

the voltage-time integral) is often used to characterized pulse transformers. Generally

speaking, the larger this product, the larger and more expensive the transformer.

28

3.7 RF transformers (transmission line transformers)

For radio frequency use, transformers are sometimes made from configurations of

transmission line, sometimes bifilar or coaxial cable, wound around ferrite or other types of

core. This style of transformer gives an extremely wide bandwidth but only a limited number

of ratios (such as 1:9, 1:4 or 1:2) can be achieved with this technique. The core

material increases the inductance dramatically, thereby raising its Q factor. The cores of such

transformers help improve performance at the lower frequency end of the band. RF

transformers sometimes used a third coil (called a tickler winding) to inject feedback into an

earlier (detector) stage in antique regenerative radio receivers.

3.7.1 Baluns

Baluns are transformers designed specifically to connect between balanced and

unbalanced circuits. These are sometimes made from configurations of transmission line and

sometimes bifilar or coaxial cable and are similar to transmission line transformers in

construction and operation.

3.8 Uses of transformers

For supplying power from an alternating current power grid to equipment which uses

a different voltage.

Electric power transmission over long distances.

Large, specially constructed power transformers are used for electric arc furnaces

used in steelmaking.

Rotating transformers are designed so that one winding turns while the other remains

stationary. A common use was the video head system as used in VHS and Beta video

tape players. These can pass power or radio signals from a stationary mounting to a

rotating mechanism, or radar antenna.

Sliding transformers can pass power or signals from a stationary mounting to a

moving part such as a machine tool head.

A transformer-like device is used for position measurement. See linear variable

differential transformer.

29

Some rotary transformers are used to couple signals between two parts which rotate in

relation to each other.

Other rotary transformers are precisely constructed in order to measure distances or

angles. Usually they have a single primary and two or more secondaries, and

electronic circuits measure the different amplitudes of the currents in the secondaries.

See synchro and revolver.

Small transformers are often used internally to couple different stages of radio

receivers and audio amplifiers.

Transformers may be used as external accessories for impedance matching; for

example to match a microphone to an amplifier.

Balanced-to-unbalanced conversion. A special type of transformer called a balun is

used in radio and audio circuits to convert between balanced line circuits and

unbalanced transmission lines such as antenna down leads.

3.9 OPERATIONAL AMPLIFIER

3.9.1 THEORY

An Op-amp is a direct coupled high gain amplifier usually consisting of one or more

differential amplifier and usually followed by level translator and output stage. The output

stage is generally push-pull pair.

The op-amp is a versatile device that can be used to amplify dc as well as input signals

and was originally designed for computing such mathematical function as addition,

subtraction, and multiplication and intigaration.thus name op-amp stamps from its original

use for mathematical operations and is abbreviated to op-amp. With the addition of suitable

external feedback components, the modern day op-amp can be used for a Varity of

application such as ac and dc amplifications, active filters, oscillators, comparators and

others.

3.9.2 BASIC BLOCK DIAGRAM OF TYPICAL OP-AMP

30

The input stage is the dual input, balanced output differential amplifier. This stage

generally provides most of the voltage gain of the amplifier and also establishes the input

resistance of the op-amp. The intermediate stage is usually another differential amplifier,

which is given by output of the first stage, in most amplifiers the intermediate stage is dual

input, unbalanced output. Because direct coupling is used, the dc voltage at the output of

the intermediate stage is well above ground potential. Therefore, generally, the level

translator circuit is used after the intermediate stage to shift the dc level at the output of

intermediate stage downward to zero volts with respect to ground. The final stage is usually

the push-pull compliment amplifier output stage. The output stage increases the output

voltage swing and raises and the current supplying capability of the op-amp. A well design

op-amp also provides low output resisters.

3.9.3 SQUAREWAVE GENERATOR:

In contrast to sine wave oscillators, squqre wave outputs are generated when the op-

amp is forced to operate in the saturated region. That is output of op-amp is forced to swing

repetively between positive saturation +Vsat and negative saturation –Ve, resulting in

square wave output. One such circuit is shown in fig (a.).This square wave generator is also

called a free-running or astable multivibartor, depended on whether the differential voltage

Vid is negative or positive respectively.

3.9.4 TRIANGULAR WAVE GENERATOR: The output waveform of the integrator is triangular if its input is a square wave. This

means that a triangular wave generator can be formed by simply connecting an integrator to

31

the square wave generator of fig (a.)The circuit is shown in fig (b.).This circuit requires a

dual op-amp, two capacitor, and at least five resistors. The frequencies of square and

triangular wave are the same. for fixed resistors R1, R2 and c values, the frequency of the

square wave and triangular wave depends on resistance R.as R is increased or decreased,

frequency of the triangular wave will decrease or increase, respectively. Although the

amplitude of the square wave is constant; the amplitude of the triangular wave decreases with

an increase I its frequency, and vice-versa.

3.9.5 COMPARATOR: Fig shows an op-amp as a comparator. A fixed reference voltage Vref of 1 volt is applied

to (-) input. Because of this arrangement, the circuit is called the non-inverting comparator.

When Vm is less than Vref, the output Vo is at input. On the other hand, when Vm is greater

than Vref, the (+) input becomes positive with respect to (-) input, and Vo goes to + Vsat.

Thus Vo changes from one saturation level to another whenever Vin =Vref, as shown in

fig(c.).In short, the comparator is a type of analog to digital converter. At any time the Vo

waveform shows whether Vin is greater or less than Vref.the comparator is some time also

called voltage-level detector because, for a desired value of Vref, the voltage of the Vin can

be detected. The diodes D1 and D2 protect the op-amp from the damage due to excessive

input voltage Vin.

3.9.6 ADDER:

Whenever we are needed to add two different voltages, it can be obtained by the adder

circuit. This adder circuit is also called summing amplifier. In this configuration op-amp can

be used in both configurations as inverting and non inverting. One terminal is grounded as

shown in fig (d.).Different inputs are in given to another terminal. If input voltage sources

and resistors are connected to the no inverting terminal as shown in fig (d.), here formula

given below is used calculate the addition of the voltage.

Vo= (Va+Vb+Vc)/3

32

3.9.7 Operational amplifier implementation:

Today Schmitt triggers are typically built around operational amplifiers, connected to

have positive feedback instead of the usual negative feedback. The reference voltage levels

can be adjusted by controlling the resistances of R1 and R2:

Figure 0-8 OP-AMP AS COMPARATOR

An op-amp comparator simply gives out the highest voltage it can, +VS when the positive

input is at a higher voltage than the negative, and then switches to the lowest output voltage it

can, −VS, when the positive input drops below the negative.For instance, if the Schmitt

Trigger is currently in the high state, the output will be at the positive power supply rail

(+VS). V+ is then a voltage divider between Vin and +VS. The comparator is comparing V+ to

ground. VinR2 must be equal to −VSR1 for V+ to equal zero, so Vin must drop below

−(R1/R2)VS to get the output to switch. At this 0point, the output becomes −VS, and the

threshold becomes +(R1/R2)VS to switch back to high.

33

So this circuit creates a switching band centered around zero, with trigger levels ±(R1/R2)VS.

The input voltage must rise above the top of the band, and then below the bottom of the band,

for the output to switch on and then back off. If R1 is zero or R2 is infinity (an open circuit),

the band collapses to zero width, and it behaves as a standard comparator. The output

characteristic is shown in the picture on the right. The value of the threshold T is given by

(R1/R2)VS and the maximum value of the output M is the power supply rail.

3.10 FLIP-FLOP SECTION

Sequential circuits are made of combinational circuits and memory elements. The most

important memory element is the flip-flop, which is made of an assembly of logic gates. Even

though logic gate by itself no storage capability, several logic gates can be connected together

in ways that permit information to be stored. There are several different gate arrangements’

are use to construct flip-flop in a wide variety of ways.

A flip-flop, known more formally as a bistable multivibrator, has two stable states. it can

remain in either of the states indefinately.its states can be changed by applying the proper

triggering signal.

Flip-flop has two outputs; labelled Q and Q.we can used any of this output. But generally

Q is used. There is a different type of flip-flop as given below.

34

S-R flip-flop

D-flip-flop

J-K flip-flop

T flip-flop

Here we are described below about J-K flip-flop. The J-K flip-flop is a very

versatile and also the most widely used. The J and K designation for the synchronous control

inputs have no known significance. The functioning of the J-K flip-flop is identical to that of

the S-R flip-flop, except that it has no invalid state like that of the S-R flip-flop. The logic

symbol and truth table for a positive edge-triggered J-K flip-flop are shown in fig.

Logic symbol

J K Q comments

0 0 Qo No change

0 1 0 Reset

1 0 1 Set

1 1 Qo Toggle

Positive edge triggered J-K flip-flop (truth table)

When J=0, K=0, no change of state takes place even if a clock pulse is applied.

When J=0,K=1,the flip-flop resets at the positive-going edge of the clock pulse

When J=1, K=0, the flip-flop sets at the positive-going edge of the clock pulse.

When J=1, K=1, the flip-flop toggels, i.e.goes to the opposite state.

35

A T flip-flop has a single control input, labelled T for toggle. When T is HIGH, the flip-

flop toggles on every new clock-pulse, When T is LOW, the flip-flop remains in whatever

state it was before. Although T flip-flop are not widely available commercially, it is easy to

convert a J-K flip-flop to the functional equivalent of a T flip-flop by just connecting J and K

together and labeling the common connection as T.Thus ,when T=0,we have J=K=0,and there

is no change. The logic symbol and truth table of a T flip-flop are shown in below fig.

Logic symbol

T Q

0 Qo

1 Qo

Truth table

We are using this flip-flop in this project to make half frequency of main source

frequency from adder in control circuit.so,by this flip-flop we get 50Hz frequency pulse from

the output and also we get two toggle pulse from Q and Q.To use this configuration of flip-

flop we are using IC7473 in this project. Our square wave pulse we are given as clock pulse

and 5V given to T, and by the Q and Q we are getting square pulse.

36

4.

WORKING OF INVERTER

37

4. WORKING OF SINGLE PHASE INVERTER

4.1 GOAL

“To explain the operation of single phase inverter”.

4.2 BASIC BLOCK DIAGRAM OF INVERTER:

4.3 DESCRIPTION OF THE BLOCK DIAGRAM:

4.3.1 REGULATOR SECTION:-

The positive voltage regulator IC7805 has only three terminals as showen in figure.Its

output voltage is +5V constant.

BATTERY DIVIDER

CIRCUIT

OSCILLATOR REGULATOR OUTPUT

TRANSFORMER POWER

AMPLIFIER

L.E.D LOW

BATTERY

INDICATOR

38

4.3.2 OSCILLATOR SECTION (IC 555):-

If we rearrange the circuit slightly so that what the trigger and threshold input are controlled

by the capacitor voltage, We can cause the IC555 to trigger it self repeatedly. In this case, we

need two resistor in the capacitor charging path so that one of them can also be in the

capacitor discharge path. This gives us the circuit shown as a below.

In this mode, initial pulse when power is first applied is a bit longer than the other, having a

duration of

t1= 1.1(Ra+Rb)*C

However, from then on the capacitor alternately charges and diacharges between the

two comparator threshold voltage. When charging C starts at (1/3)Vcc and charges towards

Vcc. However it is interrupted exactly halfway there, at (2/3)Vcc. Therefore the charging time,

t2 = 0.693(Ra+Rb)*C

39

When the capacitor voltage reaches (2/3)vcc, the discharge transistor is enabled (pin.7)

And this point in the circuit becomes grounded. Capacitor C now discharges through Rb

alone. Starting at (2/3)Vcc, it discharge towards ground, but again is interrupted halfway

there, at (1/3)Vcc the discharging time.

t2 = 0.693Rb*C

The total period of the pulse train is

t1 + t2 = 0.693 (Ra+Rb)*C

The output frequency of this circuit is the inverse of the period,

Note that the duty cycle of IC 555 timer circuit in astable mode cannot reach 50% ,

On time must always be longer than Off time , because Ra must have a resistance value

greater than zero to prevent the discharge transistor from directly shorting Vcc to ground.

Such an action would immediately destroy the 555 IC.

One interesting and very useful feature of the 555 timer in either mode is that the

timing interval for either charge or discharge is independent of the supply voltage Vcc, This is

because the same Vcc is used both as the charging voltage and as the basic of the reference

voltage for the two comperators insige the IC 555. Thus, the timing equations above depend

only on the values for R and C in either operating mode.

4.3.2.1 SQUARE WAVE:-

Here we are using a 12V DC as an input source, which is given to the square wave

generator. In this generator op-amp based square wave generator is used. Output of this stage

is square wave. Its frequency is set on 100Hz by the varying the feedback resistor of op-amp.

This output is given to the next stage of triangular wave generator.

40

4.3.2.2 TRIANGULAR WAVE :

Output of previous stage is square wave and by this triangular wave generator,

square is converted to triangular wave. In this stage op-amp is used. And it works as an

integrator in the generator Frequency of this triangular wave is also same means 100Hz.this

triangular wave is given to the next stage means comparator.

4.3.3 COMPARATOR:

41

This stage is compare the triangular wave of 100Hz with +12V and -12V DC and then

it will gives square wave in pulse position Frequency of this stage wave also being same of

100Hz.here we can see that triangular wave is converted to pulsed square wave. And it is

given to the next stage means adder circuit.

4.3.4 ADDER:

Pulsed square wave is given to the adder circuit. It will add the DC level whatever we

add with it. Here we are add 12V DC with square wave and so, it will be pulsating DC, which

is present on above the 0 reference line. So output of this stage is given to the flip-flop.

42

4.4 FLIP-FLOP:

Basically switching circuit may be combinational switching circuit or sequential

switching circuits. The switching circuits considered so far have been combinational

switching circuits. Combinational switching circuits are those whose output levels at any

instant of time are dependent only on the level present at that time. Any prior input level

conditions have no effect on the present output because combinational logic circuit have no

memory. On the other hand, sequential switching circuits are those whose output levels at any

instant of time are dependent not only levels present at the at that time, but also on the prior

level input level conditions. It means that sequential switching circuits have memory.

Sequential circuits are thus made of combinational circuit in memory elements.

The most important memory element is the flip-flop, which is made up of an

assembly of logic gates. Even though a logic gates is itself has no storage capability, several

logic can be connected together in ways that permit information to be stored. There are

several different gate arrangement that are used to construct flip-flop in wide variety of ways.

Each type of flip-flop has special features or characteristics necessary for particular

application

NORMAL OUTPUT

INPUT

INVERTED OUTPUT

Q

FF

Q

43

The flip-flop has two output labeled Q and Q . Actually any letter can be used to

represent the output. But Q is the most often used. The Q output is the normal output of the

flip-flop and Q is the inverted output. The state of flip-flop is always refers to the state of the

normal output Q.

4.4.1. EDGE TRIGGERED FLIP-FLOP:-

There are the basic three types of edge triggered flip-flops:

(1) S-R FLIP-FLOP

(2) J-K FLIP-FLOP

(3) D FLIP-FLOP

4.4.1.1 J-K FLIP-FLOP:-

Here we are described below about J-K flip-flop. The J-K flip-flop is a very

versatile and also the most widely used. The J and K designation for the synchronous control

inputs have no known significance. The functioning of the J-K flip-flop is identical to that of

the S-R flip-flop, except that it has no invalid state like that of the S-R flip-flop. The logic

symbol and truth table for a positive edge-triggered J-K flip-flop are shown in fig.

Logic symbol

J K Q comments

0 0 Qo No change

44

0 1 0 Reset

1 0 1 Set

1 1 Qo Toggle

Positive edge triggered J-K flip-flop (truth table)

When J=0, K=0, no change of state takes place even if a clock pulse is applied.

When J=0,K=1,the flip-flop resets at the positive-going edge of the clock pulse

When J=1, K=0, the flip-flop sets at the positive-going edge of the clock pulse.

When J=1, K=1, the flip-flop toggels, i.e.goes to the opposite state.

A T flip-flop has a single control input, labelled T for toggle. When T is HIGH, the flip-

flop toggles on every new clock-pulse, When T is LOW, the flip-flop remains in whatever

state it was before. Although T flip-flop are not widely available commercially, it is easy to

convert a J-K flip-flop to the functional equivalent of a T flip-flop by just connecting J and K

together and labeling the common connection as T.Thus ,when T=0,we have J=K=0,and there

is no change. The logic symbol and truth table of a T flip-flop are shown in below fig.

Logic symbol

T Q

0 Qo

1 Qo

Truth table

45

We are using this flip-flop in this project to make half frequency of main source

frequency from adder in control circuit.so,by this flip-flop we get 50Hz frequency pulse from

the output and also we get two toggle pulse from Q and Q.To use this configuration of flip-

flop we are using IC7473 in this project. Our square wave pulse we are given as clock pulse

and 5V given to T, and by the Q and Q we are getting square pulse.

4.4.2. FLIP-FLOP OPERATING CHARACTERISTICS:-

Flip-flop operating characteristics are as below:-

(1) PROPOGATIONAL DELAY:-

The output of a flip-flop will not changed state immediately after the

application of the clock signal or asynchronous inputs. The time interval between the time of

application of the triggering edge or asynchronous Inputs and the time at which the output

actually makes a transition is called the propagation delay time of the flip-flop.

(2) SET-UP TIME :-

The setup time is the minimum time for which two control levels need to bemention

constant on the input terminal of the input terminal of the flip-flop, prior to the arrival of the

triggering edge of the clock pulse, in order to unable the flip-flop to respond reliably.

(3) Hold time:-

The hold time (th) is the minimum time for which the control signal needs to be

maintained constant at the input terminals of the flip-flop, after the arrival of the triggering

edge of the clock pulse, in order to unable the flip-flop to respond reliably.

(4) MAXIMUM CLOCK FREQUENCY:-

The maximum clock frequency (fmax) is the highest frequency at which a flip-flop can

be reliably triggered. If the clock frequency is above this maximum, the flip-flop will be

46

unable to response quickly enough and its operation will be unreliable. The fmax limit will

vary from one flip to another.

(5) PULSE WIDTHS:-

The manufacture usually specified the minimum pulse width for the clock and

asynchronous inputs. For the clock signals, the minimum high time tw(H) and the minimum

low time tw(L) are specified and for asynchronous inputs, i.r PRESETS and CLEAR, the

minimum active state time is specified.

(6) CLOCK TRANSITION TIMES:-

For reliable triggering, the clock waveform transition time (rise and fall times) should

be kept very short. If the clock signal takes too long to make the transition from one level to

the other, the flip-flop may either erratically or not trigger at all.

(7) POWER DISSIPATION:-

The power dissipation of the flip-flop is the total power consumption of the device. It

is equal to the product of the supply voltage (Vcc) and the current (Icc) drawn from the supply

by it.

P = Vcc×Icc

The power dissipation of the flip-flop is usually in mW.

If a digital system has N flip-flop and if each flip-flop dissipates P mW of

power, the total power requirement Ptot is

Ptot = N×VCC×ICC = (N×P)mW

(8) CLOCK SKEW AND TIME RACE:-

The clock signal which is applied simultaneous to all flip-flops in synchronous system

may undergo varying degrees of delay caused by wiring between components, and arrive the

CLK inputs of different flip-flop at different times. This delay is called clock skew.

4.4.3 APPLICATIONS OF FLIP-FLOPS:-

There are large number of application of flip-flops. Some of basic application are

as below:

47

1. Parallel data storage

2. Serial data storage

3. Transfer of data

4. Serial to parallel conversion

5. Parallel to serial conversion

6. Counting

7. Frequency division

4.4.4 FREQUENCY DIVISION:-

Output of square wave is given to this stage and it will generate 0 levels and 1 level

pulse. But it will make frequency half of the source frequency means it will generate 50Hz

frequency pulse. Here output of flip-flop is Q and Q.So, it will give two toggle output pulses.

And in this configuration T flip-flop is generally used. Though T flip-flop is not present in

the market, there is a J-K flip-flop is used with sorted the both the input. Pulse of the previous

stage is given as clock pulse and as an input of T is 5V DC is given. And then it will generate

50Hz pulse. This type of both the pulse is given to the delay circuit.

48

4.4.5 OUTPUT OF INVERTER CIRCUIT:

Pulse with proper delay is given to the inverter circuit. in this part mosfet is used with

its snubber circuit. MOSFET is a switching device, which converted delayed pulse into AC

waveform. through it will not pure but it will be square type sinewave.snubber circuit is used

for the over current protection. It will save the circuit from the dangerous ara.output of this

stage is AC waveform but it will be low voltage output so, it is required to step-up the

voltage, to run the home appliances load. And also current will be decrease, but power output

we will make by drain-source voltage.so, this output given to the transformer.

4.4.6 TRANSFORMER:

Low voltage output is coming from the inverter circuit is step-up by the step-up

transformer. so, required voltage and current (power) is getting by the transformer. Which

gives 50Hz frequency.

49

4.5 WORKING OF INVERTER :

Every inverter works on the same basic principle. When we switch ON the inverter, DC

supply of battery is applied to the PCB of inverter. From PCB to pulses having 180 phase

shift are generated, which reaches 12-0-12 volt winding of inverter transformer. By

transformer action in secondary winding 230volt ac supply is generated and which is supplied

to O/P circuit.

There are many method of producing series of pulse with 180 phase shift. One of the

easiest circuit is describe as under.

4.5.1 WORKING OF CHANGE OVER CIRCUIT:-

In this inverter relay is on (when current flows in relay coil) when AC mains supplies

is ON and inverter is OFF. In this circuit, 5 pole relay and 12-0-12 volt transformer are used.

Phase of main supply is connected to NO2 terminal of relay and 12-0-12 volt transformer

primary. Neutral of main supply is connected with 2nd

terminal of primary winding of 12-0-

12 volt transformer which is connected to N terminal of the output circuit and common

terminal of inverter/charger transformer. P2 and P3 terminal of relay are connected with

phase of o/p circuit.

4.5.2 FOLLOWING FUNCTIONS ARE CARRIED OUT WHEN ac

SUPPLY IS GIVEN TO MAIN LEAD OF INVERTER:-

(1) Main supply 220/(12-0-12) volt reaches primary of transformer and in secondary

generates 12-0-12 volt AC. Full wave rectifier and filter capacitor converts this supply into

12 volt DC supply which flows current in a relay coil. With this all pole gets attached to NO

terminal. 220/(12-0-12) volt transformer is used only to give current to the relay coil.

(2)The relation of NC1, NC2 and NC3 does not reach to the dc supply inverter switch

because of the breaking of poles, due to this inverter does not work and AC supply not reach

on NC3.

(3) The phase present on NO2 of AC main supply reaches at two places.

50

(a) From P2 ,o/p reaches circuit with which the bulbs,etc connected with circuit

works on mains Ac supply.

(b) From P2 to P3, then P3 to NO3 and from NO3 the phase of AC main supply

reaches winding of loss (low) volt of inverter transformer wih which the current starts

flowing in the primary coil and 12-0-12 volt AC is generated in the secondary

winding.

(4) With the help of diodes on the secondary winding battery gets charged.

4.5.3 WHEN AC MAINS SUPPLY IS OFF (GONE), THEN THE

FOLLOWING FUNCTIONS TAKES PLACE AS UNDER:-

1) Primary of 220/12 volt transformer does not get AC supply. With this 12 volt relay

coil does not get DC supply and relay will gets OFF.

2) The relation of poles of relay gets connected with the NC terminal.

3) DC supply of battery passing from P1 connected with NC1 reaches the inverter switch

and when inverter switch becomes on, at that time inverter reached PCB.

4) The pulses generated from inverter circuit on reaching 12-0-12 volt winding of

inverter transformer continuously produces direction charging current in it, with

which 230 volt AC is obtained on tapping ,joined with NC3.

5) Due to the connection of P3 with NC3, the AC supply generated from inverter reaches

o/p circuit and when mains AC supply is OFF (gone) at that time also fan, bulb, etc

are working.

6) Due to the opening of NC2, the supply of inverter reaching on P2 has no effect.

7) Due to the opening of NO1, the switch made of NC1 and P1 works as pole1 way

switch. When mains supply is gone (OFF) at that time this switch gets ON.

8) Due to the opening of NC2, the switch made of P2 and NO2 also works as 1 pole 1

way switch. When mains supply comes at that time, this switch gets ON.

9) The switch made NC3-P3-NO3 works as 1 pole 2 way switch. The output circuit

connected with P3 either gets the mains AC supply or the AC supply generated from

inverter.

51

5.

DESIGN DETAILS OF

INVERTER

52

5. DESIGN DETAILS OF INVERTER

5.1 GOAL “To compute and decide various component values.”

5.2 DESIGN CALCULATIONS Design calculations have been divided into following sections

1) Design of control circuit

2) Design of power circuit

3) Transformer

5.3 DESIGN OF CONTROL CIRCUIT:-

BATTERY

C4

RB

C3

LM555C

5264

37CON

TRIGTHRESRST

OUTDIS

RA

CALCULATION FOR FREQUENCY:-

F = 1/T Hz

= *103

= 100 Hz

Ra = 10KΩ

53

F = 100 Hz

C = 0.1 µF

F =

100 =

Hence, Rb = 67.5 KΩ

TIME DELAY SECTION:-

T = R * C

= 1k * 0.1 uf

= 0.1 ms

CALCULATION FOR LOAD RESISTANCE:-

Vo= Io * RL

230 = 1.3 * RL

RL = 177Ω

5.4 DESIGN OF POWER CIRCUIT:-

54

R11

50Hz

R5

RESISTOR

R13

C7

M1

IRFZ44N

C7 OUTPUT

R14

230V AC

R12

M4

IRFZ44N

Q1

T1

TRANSFORMER

M6

IRFZ44N

Q2

M5

IRFZ44N

R5

RESISTOR

M2

IRFZ44N

M3

IRFZ44N

We Know that for Transformer Efficiency is 80%, So

η =

80 = 300/ V*I

I = 300/24*0.8

I = 15.62A

Imax = 22.22A

Imin = 12.22A

Now, P =V*I

P = 15.62*12

P = 187.5 VA

Now, Vds = 12 V

Vdsmin = 12-5 = 7V

Vdsmax = 12+5 = 17V

Ig =

Ig =

55

= 0.07mA

We are using IRFZ44N MOSFET for our power circuit which operates

at 55V & 49A of current and it has resistant of 0.22Ω .

Design of a snubber circuit :-

Cs = 0.1 μF

Rs = 1/ 3fCs

= 66 KΩ

5.5 DESIGN OF 300 VA INVERTER TRANSFORMER

WITH GIVEN SPECIFICATION

PRIMARY : 10.8 – 0 – 10.8 V, 46.30A, 50 Hz

SECONDARY: 0 – 230 - 270 V, 1.3A, 50Hz

5.5.1 DESIGNING PROCEDURE

The procedure for designing a transformer is as follows:

STEP – 1:

Firstly the total output power is calculated by using the following relation:

P0 = V0 * I0

= 230 * 1.3

= 300

= 300 watt

Where,

Po is total output power of the transformer in watts.

56

Vo is the total output voltage in volts.

Io is the output current in amperes.

STEP – 2:

Now considering the efficiency of the transformer be 95%, we have to

calculate the total input power by using the following relation,

N = Po/Pi

Pi = Po / 95%

= 500 / 95%

= 52.6%

Where,

N is the efficiency of the transformer.

P0 is the output power of the transformer.

Pi is the input power of the transformer.

STEP – 3:

Now the third step is to calculate the area of cross section of the core. The

area of cross section of the core is calculated by using the relation.

A = Fm/Bm

= 0.00232/1

= 2.32*10^-3mm^2

Where

Fm=core flux and Bm = magnetic flux density.

Here we have to add 10% of the core area in calculated core area for safety margin of

bobbin.

57

STEP – 4:

After calculating the area of core we have to find out an appropriate size of

former (bobbin) for the core by looking in the Table – 2. The Table – 2 consists of the sizes

of former available in the market.

The former to be used is 7 no. 2” inches i.e. the area is [2” * 5/2”].

STEP – 5:

Now the wire gauge is selected for the primary and the secondary windings of

the transformer. As we know the input and output current so by using the Table-1 we can find

the appropriate wire gauge for the primary and the secondary.

STEP – 6:

Now the number of turns for the two windings is being calculated. For this,

first we have to find ratio of turns/volts for 300VA transformer. So, turn/volt for 300VA

transformer is 2.0.Magnetic flux density for primary winding is assumed 1.0Wb/m^2 and for

secondary winding it is assumed 2.03Wb/m^2.

STEP – 7:

For primary winding use bifilar winding because it is more efficient than the random

winding. For this take two 13 gauge wire and 21 turns of these wires on bobbin parallel.

The turns required for 230 volt tapping

Ts = 1.05*Vs*2

= 1.05*230*2

58

= 483 turns

So, turns required for secondary is 483.

Turns required for primary

Tp = Vp*Te

= 10.8*2

=21.8

~22

So, turns required for primary is22.

Where Tp and Ts are the total number of turns for the primary and the secondary

windings respectively and Vi, Vo is the input and output voltages of the transformer. Also we

have to add 10% of the primary and secondary turns in the calculated primary and secondary

turns for the primary and secondary voltage regulation respectively.

So, we have

Primary has total 22 turns bifilar winding with 13 SWG and secondary has total 483

turns with 22 SWG. The bobbin used is 7 no. 2” inches.

Thus the complete design for a given ratings of transformer is worked-out by using

the above procedure. After the designing of the transformer the winding is done on bobbin by

a hard grinder setup machine or BNC machine. Between primary and secondary winding an

insulated paper is kept for proper insulation. After the winding of the coils the laminations are

fitted in alternate order and finally the clamp is fitted and the transformer is dipped in the

liquid varnish and then it is allowed to dry for about 12 hours and thus the transformer is

manufactured.

59

CIRCUIT DIAGRAM OF INVERTER:-

R1 RESI

STOR

C8

M5

IRFZ

44N

C1

R3T1 TR

ANSF

ORME

R

M3

IRFZ

44N

RB

BATT

ERY

R5

OUTPUT

74LS

7314 1 3

12 13

2

J CLK

K

Q Q

CL

C6 CAPA

CITO

R NO

N-PO

L

50Hz

Q2

D4

1 2

R2

LM78

051

3

2VI

N

GND

VOUT

C2

M2

IRFZ

44N

230V AC

R4R5

C3

R6

R6

M1

IRFZ

44N

LM55

5C

5 2 6 4

3 7CO

NTR

IGTH

RES

RST

OUT

DIS

C4

C5RA

M4

IRFZ

44N

Q1

M6

IRFZ

44N

D5

1 2

C7

0

60

6

TESTING &

CALIBRATION

61

6 .TESTING & CALIBRATION

6.1 GOAL

“To give details of testing procedure”

6.2 TESTING PROCEDURE AND CALIBRATION

As in any technical project, it is necessary to test the work carried out. Here also we

carried out various tests on our project. Testing needed to test performance of the power

supply was carried out during assembling of the circuit. We assembled the circuit in section-

by-section manner, tested the individual section and if required the section component values

were modified depending upon requirements. The overall testing and calibration was divided

into various steps.

1) Testing of Regulator section.

2) Testing of Oscillator section.

3) Testing of J-K flip flop.

4) Testing of Time delay section.

1) TESTING OF REGULATOR SECTION:

Apply 12 v dc at pin no. 1 and get output on pin no. 3 5 v dc.

ON Apply +12 v dc at pin no 7 And -12 v dc at pin no.4.Get output on pin no. 6 of 12dc at

100 Hz frequency.

2) TESTING OF OSCILLATOR SECTION:

Apply 5 v dc at pin no. 8 and get output on pin no. 3 3 v dc at 100 Hz

frequency.

62

3) TESTING OF J-K FLIP FLOP:

Apply 5V, 100 Hz frequency signal at pin no. 4 and get output on pin no. 12

and 13 at 50 Hz frequency with 180 degree phase shift.

4) TESTING OF TIME DELAY SECTION:

Apply 50 Hz frequency signal on delay circuit and the delay between two

circuits is obtained.

63

7.

RESULTS

64

7. RESULTS

7.1 GOAL

“To give obtained results of the project”

7.2 POWER CIRCUIT:-

Table 2 POWER CIRCUIT

Input voltage (battery voltage) 24 volt

Input current

Output voltage 230 v a.c

Output current

Output frequency 50Hz

Output power 300watt

7.3 BASE DRIVE CIRCUIT SPECIFICATION

Table 3 BASE DRIVE SECTION SPECIFICATION

Input voltage 12 v dc

Output voltage 4 v,50Hz

65

8.

TIME & COST

ANALYSIS

66

8. TIME & COST ANALYSIS

8.1 GOAL

“To give time and cost analysis of the project”

8.2 TIME ANALYSIS

TABLE 0-1 TIME ANALYSIS

SR.

NO.

TASK TIME

REQUIRED

(IN WEEKS)

1 Study of various options for project 1

2 Selection of project 1

3 Study of fundamental theory 1

4 Selection of topology 1

5 Preparation of basic schematic according to the control IC 741,

IC 74LS73,IC 7805

1

8 Design of overall circuitry and component selection 1

9 Purchasing components 1

10 Testing of individual sections (on Bread Board) and making

necessary modifications

1

11 Integrated testing of the project (on Bread Board) and making

necessary modifications

1

12 Designing of PCB 1

13 Making of PCB 1

14 Assembling and testing of the project on final PCB 1

15 Writing Project report 1

16 Computerization of the report ( including figures) 1

Total Time Required in Weeks 16

67

8.3 COST ANALYSIS

TABLE 0-2 COST ANALYSIS

SR.

NO.

WORK / COMPONENT

COST

Rs.

1 POWER MOSFET IRF Z44N, 180

2 POWER TRANSFORMER CORE, WINDING WIRE AND

LABOUR CHARGES FOR WINDING

1200

3 DIODES & LEDS 20

4 RESISTORS 0.5 WATT,OTHER,PRESET RESISTOR 35

5 BATTERY 300

6 CONTROL IC 741, IC74LS73, IC 7805, 50

7 CAPACITORS 25

8 GENERAL PURPOSE PRINTED CIRCUIT BOARD 200

9 POWER TRANSISTOR BD139 & 2N2222 45

10 RELAY 75

11 PROJECT REPORT DATA ENTRY, PRINTING , XEROXING

AND BINDING CHARGES

500

TOTAL COST OF THE PROJECT 2630

68

9.

CONCLUSION

69

9. CONCLUSION

9.1 GOAL

“To conclude the work carried out.”

9.2 CONCLUSION

From the project work, following points can be concluded.

1. The INVERTER works successfully under operating voltage range 0 V AC to 230V AC

at full load.

2. It fulfils all the requirements for its application.

3. The output ripple voltage on each output measured is 0.5 V which is less than desired

0.6V.

4. Through such SINGLE PHASE INVERTER, we can get output of desired frequency.

70

10.

FUTURE

MODIFICATIONS

71

10. FUTURE MODIFICATIONS

10.1 GOAL

This inverter is a general purpose module, which can be modified in many ways for

different applications to get desired output. This modification may be functional or physical.

Some of the modifications, which can be made in existing module for different application,

are discussed here.

10.2 AS A.C DRIVES / A.C VOLTAGE CONTROLLER:-

A.C Voltage controllers are the devices which are used to control the speed of

the a.c motor by controlling supply voltage, supply frequency or both the supply voltage and

frequency. In our module we can control the frequency of the output by simply controlling

the frequency of the firing pulses.

72

APPENDIX

73

74

75

76

77

78

79

80

81

82

83

84

85

86

87

88

89

90

BIBLIOGRAPHY

91

POWER ELECTRONICS - M.H.RASHID

- P.S.BHIMRA

- NED MOHAN

LINEAR INTEGRATED CIRCUITS - GAIKWAD

SEMICONDUCTOR DATA-BOOK - INTERNET

LOGIC DATA-BOOK - NATIONAL

SEMICONDUCTOR

ANALOG AND DIGITAL - ANAND KUMAR

CIRCUITS

1