2 kVA Inverter Project

ABSTRACTAn inverter is an µelectronic circuit§ for converting µdirect current§ (DC) to µalternating current§ (AC). Inverters are used in a wide range of applications, from small µswitched power supplies§ for a computer to large µelectric utility§ applications to transport bulk power. This report contains details of the design and construction of a modern 3000W dc to ac inverter. The system consists of the main inverter stage, the charging unit and the overload protector. These units are further subdivided into different stages. The main inverter performs the basic operation of converting the input DC signal from the battery into an AC signal. It then amplifiers the AC signal by the use of transistor MOSFET drivers and then step-up the signal to the require power (3000W) by the use of step-up transformer. The charging unit contains an automatic switch that transfers the battery from supply to charge when it senses supply from mains. Lastly, the overload protector is a thermal detector that determines the heat generated by the step-up transformer. This heat is directly proportional to the current drown from the transformer and thus to the load. . Chapter one contains an introduction to inverters, chapter two contains a review of related literature, chapter three contains the circuit design analysis, chapter four contains the contraction details ,and five contains the summery.

CHAPTER ONE

INTRODUCTION

1.1 PREAMBIE

Due to toady’s total dependence on electricity and because of frequent

Power outage, back up power is becoming a necessity. Emergency back up

power system can provide electrical power to critical loads or the whole

house during power outages.

Emergency power systems are types of systems, which may include lighting

generator and other apparatus, to provide back up resources in a crisis or

when regular systems fail.

They find uses in a wide variety of setting from residential homes to

hospitals scientific laboratories and computerized systems. Emergency

power system can rely on generators or uninterruptible power supplies.

All type of electronic devices requires power supply from electric power for

their operation. This source can be either generator or a battery. In our

society today, the need for power supply can not be over emphasize, because

the provision of good and services could be completely cut off without

power supply. For one to fully enjoy the betterment of living in this new

dispensation there should be an adequate stable source of power supply.

Over the years electricity has been generated through energy conversion

from one place to another. Some of these energy sources are,

. Solar

. Thermal

.Wind

. Electric generators.

They have proved to be quite reliable and efficient but over the years due to

inadequate sources of energy to run the engines or a fault in the system its

self poor maintenance, they fail the users at one time or the other. As such

the need for standby power supply is essential which brought into existence

an alternative means called. INVERTER. An inverter is simply an electronic

source of power supply, that work on the principle or save and spend, thus it

has a storage unit and a processor with the Dc battery serving as

the``backup``for storage, while the electronic circuit could basically be seen

as the inverter. An inverter is an electronic circuit for converting direct

current (DC) to alternating current (AC). Inverters are used in a wide range

of application from small-switched power supply for a computer to large

electric utility applications to transport bulk power. It allows the 12 or

24volt (battery) Dc power available in an automobile or from solar panels to

supply (AC) power to operate equipment that is normally supplied from a

power source.

1.2 STATEMENT OF THE PROBLEM

Inverters generally are made to give an AC output. However, most inverters

in the market today use oscillators that produce square pulse or rough sine

wave. This result in noise in the output, which calls for an inverter with an

output that is an approximate sine wave thereby reducing the noise.

1.3 AIMS AND OBJECTIVE

The aim of this project is to design and construct a 3KW inverter with little

or no noise. This is to be realized by achieving the following specification

objectives;

-Design and construction of a CD4047 based oscillator circuit.

-Implementation of a fine slow charging unit to recharge the battery

-Implementation of an automatic switch unit from charge to supply

1.4 METHODOLOGY

To achieve the aim of this work, research was undertaking on the net and

other source to ascertain the basic operating principle of inverters in general.

The block was then developed which reflects the basic units of the desire

system. The units are; main inverter is an oscillator, which converts dc to ac,

a signal amplifier whose function is to amplify the oscillator output, the

driver stage, which further amplifies the signal to drive the primary winding

of the step-up transformer. The transformer step the output AC power to the

require 3000watt output. The charging and switching units are also included.

CHAPTER TWO

LITERATURE REVIEW

2.1 INTRODUCTION

Technological advancement brought us into new era

where by the whole world is now a global village,

electronic component and appliance are not left behind.

So as the need for generating electricity through

“inverter” increase, there are various designs, which

have been carried out in the past to achieve this aim.

But one thing that needs to be stressed here is that the

previous designs have some shortcoming that led to

design of this project whose aim is to eliminate these

shortcomings. The past (previous) designs will be

review and their shortcoming will be clearly explained

in this chapter.

2.2 INVERTER USING 555 TIMER

DC to AC inverter using 555 IC timer is one of the

previous designs. In this project it product a square

wave, but its shortcoming here is, it does not have

battery charging system incorporated in the design.

The square wave produced by this system set the

system to be unsuitable for inductive loads. As seen in

the figure below transistors are used for the switching

aspect.

While the 555 IC timer produces the oscillation pulse

Fig. 2.1: Current diagram of an inverter with 555 timer

In the output of the visible multivibrator, it’s added to

be stable at 50HZ; signal is uttered by transistor TR and

TR4 which are arranged as emitter followers to provide

current gain at most unity voltage gain. D and D2

protect the circuit against induced high voltage strikes.

The butters output drives high gain power darlington

devices TR5 and TR6 with this transistor, they are

concerned with heat sink. With this also the system is

found to be functioning as desired except, the

shortcoming there are some little variation in the

output signal due to temperature rise, which could

change the operation point of the transistors. Also the

darlington transistor used for switching CJa not

withstand high output current. The design of the

diagram is as show in Fig. 2.2.

Fig. 2.2: Circuit diagram of an inverter-using

transistor.

2.4 INVERTER USING CD 4047 AND CD 4049

In the project is it the CD 4047 with provide the

oscillation stage. It produces an oscillating voltage that

has rectangular waveforms. The desired output

frequency of inverter in 50HZ,but the oscillator is

generating a frequency of 3.27 to 68HZ therefore CD

4049, which is a frequency division stages is employed

to obtain 50HZ at the output. It shortcoming have is,

the complexity of the circuit and the wave produce by

the circuit makes it unstable, below the circuit diagram.

Fig 2.3 circuit diagram of an inverter using CD4047 IC and CD4049

INVERTER USING SG 3524

With an improve diagram, which involve the used of SG

3524 and CMOS CD 4049 which are also special

integrated circuit. IC SG 3524, which is design for the

purpose of frequency generation while buffer IC CD

4049, stabilizes the frequency. The design is

incorporated with battery charger-section and also over

load protection section. More also the oscillation

produce by this system is a quasi wave.

With this, the system is said to be stable, but when the

load is introduced that is inductive load, the voltage

reduces which nature changes the quasi wave to a

square wave making the system to be unstable and

unreliable. Also with the in corporation of the battery

charger section it makes the system to be complex.

Below is the diagram.

Fig. 2.4: Circuit diagram of an inverter using SG 3524.

Apart from the PPC, the MOSFET is also involved in this

project. The metal oxide semiconductor field effect

transistor (MOSFET) is a switching device. The MOSFET

circuit consumes negligible power, its gate terminal is

insulated from the chidunel by a layer of silicon dioxide.

The layer of silicon dioxide increase the input

impedance of the FCT to an extremely high value is

maintained from all valves and polarities of gate.

Source voltage, since the impedance does not depend

up on a reverse biased p-n junction. MOSFETS have

facts switching and can switch very high currents in a

few billionth of a second, and also the drain current of a

MOSFET decreases with increase in temperature and

the risk of terminal instability is reduced.

MOSFETS can function as voltage controlled variable

resistor; the gate voltage controls channel resistance.

The pic based inverter produced pure sine wave

however it has the limitation of circuit. Complexity and

overall cost. It also poses one general problem

associated was been programmed in the pic, which

controls the overload protection section (battery under

voltage protection) battery charger section (over

voltage protection) and also controls the drive section

of the inverter; as shown in fig 2.5 below. Pin RBO of

the PIC 16F84A the under voltage protection, when the

battery is at ion, it signal the pilot short, it OH. Pin RBO

also controls the over voltages protection at 14v it

signal the PJC and at RBT the signal is pass to a relay

through (via) a resistor and transistor, which short off

the system. R. A. 2 and RA3 leds to the MOSFETs. The

pic along does all the work, which makes it easier, more

reliable and reduces the complexity. The pic provides a

quasi wave at a frequency at 50H3. The introduction of

inductive leads the wave does not change at all, the

still maintain the same wave.

Other design with poor storage system charging and

supplying timing.

THE INVERTER WITH AUTOMATIC SWITCHING OF

BATTERY

This is an inverter with two battery and automatic

switching between them. The block diagram of the

system is presented below.

µ§

Fig 2.5 Inverter with automatic battery switching

The system consists of three basic stages. The main

inverter stage, the switching unit and the timer. These

units are further subdivided into different stages. The

Battery1

Battery2

main inverter performs the basic operation of

converting the input DC signal from the battery into an

AC signal. It then amplifiers the AC signal by the use of

transistor / MOSFET drivers and then step-up the signal

to the require power (1000W) by the use of step-up

transformer. The timer unit generates electrical pulse to

produce an up counting sequence which is displayed by

a 7 – segment LED display. This timer sequence

determines the supply and charging time of the

batteries. The switching unit performs automatic

switching between the batteries at ensures that each

battery supply the inverter for batteries. The switching

unit performs automatic switching between the

batteries it ensures that each battery supply the

inverter for approximately 90 minutes and switch over

for 90 min charge to replace it lost energy. The

switching operation is been controlled by the signal

from the timer unit via the logic unit. This, every 90

minutes switching over operation from charging to

supply and vise vase in performed.

2.5 INVERTER USING PIC 16f84a

This project produce a pure sine wave output signal

unlike all the others explained above. The inverter use the

PIC 16F84A as its basic component. PIC which is peripheral.

Interface controller, it is different from integrated circuit (IC)

which are used in the previous design. PIC 16+84A which

belongs to micro controller devices. PIC 1684A is an 18 pin

14 bit embedded micro featuring electronically erasable

programmable read only memory (EEPROM). This program

can be erased using ultraviolet light.

Fig 2.6

Simple inverter circuit with an electromechanical switch and

with a transistor switch.

2.6 BASIC INVERTER DESIGNS: In one simple inverter

circuit, DC powers connected to a transformer through

the centre 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 alternate

current (AC) in the secondary circuit.

2.7 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 switching rapidly back

and forth.

This type of electromechanical inverter switch called a

vibrator or a buzzer was once used in vacuum tube

automobile radios (refine). A similar mechanism has

been used in door bells, buzzers and tattoo guns. As

they have become available, transistors and various

other types of semiconductor switches have been

incorporated into inverter circuit designs.

2.7 INVERTER OUTPUT WAVEFORM

The switch in the simplest inverter described above

produces a square voltage waveforms as opposed to

the sinusoidal waveform that is the usual waveform of

an AC power supply that is the usual waveform of an AC

power supply. Using Fourier analysis, periodic

waveforms are represented as the sum of an infinite

series of sine waves. The sine wave that has the same

frequency as the original waveform is called the

fundamental component.

The other sine waves called harmonies, that are

included in the series have frequencies that are integral

multiples of the fundamental frequency.

The quality of the inverter output waveform can be

expressed by using the Fourier analysis data to

calculate the total harmonic distortion (THD). The total

harmonic distortion is the square root of the sum of the

squares of the harmonic voltages divided by the

fundamental voltage.

THD = V22 + v3

2 + V42 + + Vn

2 ……….. (1)

The quality of the output waveform that is needed from

asn inverter depends on the characteristic of the

connected load (Ref) some loads media nearly perfect

sine wave voltage supply in order to work properly.

Other loads may work quite well with a square wave

voltage.

2.8 MORE ADVANCE INVERTER DESIGNS

Introduce what you want to discuss

Fig. 2.8: H-bridge inverter circuit with transformer

switches and anti parallel diodes.

There are many different power circuit topologies and

control strategies used in inverter designs. Different

design approaches are used to address various issues

that may be more or less important depending on the

way that the inverter is intended to be used.

The issue of waveform quality can be addressed on

many ways. Capacitors and inductors can be used to

filter the waveform. If the design include the

transformer, filtering can be applied to the primary or

secondary side of the transformer or to both sides. Low

pass filters are applied to allow the fundamental

component of the waveform to pass to the output while

limiting the passage of the harmonic components. If the

inverter is designed to provide power at a fixed

frequency, a resonant filter can be used. For an

adjustable frequency inverter, the filter must be turned

to a frequency that is above the maximum fundamental

frequency.

Since most loads contain inductance, feedback rectifier

a parallel diodes are often connected across each

semiconductor switch to provide a path to the peak

inductive load current when the semiconductor is

turned off. The antiparallel diodes are somewhat similar

to the free wheeling diodes used in AC/DC converter

circuits.

Fourier analysis reveals that a waveform, like a square

wave that is antisymetrical about the 180 degree point

contain only odd harmonics, the 3rd, 5th, 7th etc.

Waveforms that have steps of certain widths and

heights eliminate or “cancel” additional harmonics. For

example, by inserting a zero voltage step between the

positive and negative sections of the square wave, all of

the harmonics that are divisible by three can be

eliminated.

That leaves only the 5th, 7th, 11th, 13th etc. the required

width of the steps is one third of the period for each of

the positive and negative voltage steps and one switch

of the period for each of the zero voltage steps.

Changing the square wave as described above is an

example of pulse width modulation (PWM). Modulating

or regulating the width of a square wave pulse is often

used as a method of regulating or adjusting inverters

output voltage. When voltage control is not required, a

fixed pulse width can be selected to reduce or eliminate

selected harmonics. Harmonic elimination techniques

are generally applied to the lowest harmonics filtering

is more effective at high frequencies than at how

frequencies. Multiple pulse width or carrier based

(PWM) control scheme’s produce waveforms that are

composed of many narrow pulses. The frequency

represented by the number of narrow pulses per

second is called the switching frequency or carrier

frequency. These control scheme’s are often used in

variable frequency motor control inverters because

they allow a wide range of output voltage and

frequency adjustment while also improving the quality

of the waveform.

Multilevel inverters provide another approach to

harmonic cancellation. Multilevel inverters provide an

output waveform that exhibits multiple steps at several

voltage levels. For example 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 inverter

output terminals in sequence between the positive rail

and ground, the positive rail and negative rail, the

ground rail and the negative, then both to the ground

rail, a stepped waveform is generated at the inverter

output. This is an example of three level inverter; the

two voltages are ground.

Fig. 2.9: 3 PHASE IVNERTER WITH WYE CONNECTED

LOAD

Three phase inverter are used for variable frequency

drive applications and for high power applications such

as HVDC power transmission. A basic three phase

inverter as show in Fig 2.4 consists of three single

phase inverter switches each connected to one of the

three load terminals. For the most basic control

scheme, the operation of the three witches is

coordinated so that one switch operates at each 60

degree point f the fundamental output waveform. This

creates a line to line output wave form that has size

steps. The six step waveform has a zero voltage step

between the positive and negative sections of the

square wave such that the harmonics that are multiples

of three are eliminated as described above. When

carrier based PWM techniques are applied to six step

waveforms, the basic overall shape, or envelope, of the

waveform is retained so that the third harmonic and its

multiples are cancelled.

3.3 CIRCUIT DESIGN ANALYSIS

3.3.1 DESIGN SPECIFICATION

Output power = 3000W

Frequency = 50Hz

Input voltage = 12Vdc

Output voltage = 220Vac

3.3.2 POWER SUPPLY / CHARGERThe switching unit, timer, thermal sensor/indicator, and the charging unit, require a well-filtered and regulated DC power to drive their individual components. The power supply is made up of step down transformer, which steps the input 220Vac down to 15Vac. The bridge rectifier converts the AC signal to DC of the same voltage

level. The rectifier consists of diodes D1-D4. The circuit arrangement is such that at any point in time, two diodes are conducting while the other two are at cut-off.The filter capacity removes the AC ripples from the DC voltage. The IC regulator regulates the DC signal to give a steady, well-regulated dc output voltage.

Fig. 3.2 power supply circuit

Transformer Rating Required output voltage (V2) =15VInput voltage (V1) =220vPrimary turns (N1) =300Secondary turns (N2) =x

N2 =N1V2/V1

=300(15) 220 =20 turns.Transformer output current = 2VOutput power = 15V x 2A = 30W

Rectifierµ §Fig.3.3 Rectifier circuitAs explained earlier, The Bridge rectifier is a circuit, which converts an ac voltage to dc voltage using both half cycles of the input ac voltage. The Bridge rectifier circuit is shown in the figure. The circuit has four diodes connected to form a bridge. The ac input voltage is applied to the diagonally opposite ends of the bridge. The load resistance is connected between the other two ends of the bridge.For the positive half cycle of the input ac voltage, diodes D1 and D3 conduct, whereas diodes D2 and D4 remain in the OFF state. The conducting diodes will be in series with the load resistance RL and hence the load current flows through RL. For the negative half cycle of the input ac voltage, diodes D2 and D4 conduct whereas, D1 and D3 remain OFF. The conducting diodes D2 and D4 will be in series with the load resistance RL and hence the current flows through RL in the same direction as in the previous half cycle. Thus a bi-directional wave is converted into a unidirectional wave.Peak Inverse VoltagePeak inverse voltage represents the maximum voltage that the non- conducting diode must withstand. At the instance the secondary voltage reaches its positive peak value, Vm the diodes D1 and D3 are conducting, where as D2 and D4 are reverse biased and are non-conducting. The conducting diodes D1 and D3 have almost zero resistance. Thus the entire voltage Vm appears across the load resistor RL. The reverse voltage across the non-

conducting diodes D2 (D4) is also Vm. Thus for a Bridge rectifier the peak inverse voltage is given by µ § Since transformer output voltage = 15V VM = 15V Diode current rating = 2 x transformer current = 2 x 2A = 4A

Rectifier diode to match this rating = IN4007 (Obtained from diode transistor specification book).

The output from the rectifier is given as –

Without capacitor. With capacitor.

VAC = 1.1x (VDC = 2) VAC = 0.8 (VDC +2)

= 1.1 X (12X2) = 0.8 (14)

1.1 X 14 = 11.2v

= 15.4v

This shows the need of the capacitor. Hence output current

IDC = 1.8 X IDV

= 1.8XO.5A

0.9A

Power output after fliter stage = 0.9 x 11.2

= 10.0w

= 10w

Calculating for the capacitor

C = (Il x t )/Vrip) x106

When Il = 0.9

T = 1/2x60

= 0.008333 (for 60H Z SUPPLY)

Vrip = Vrms x Ripple Vp-p

= 0.325v+ 2.828v

= 0.92

C (uf) (0.9 x 0.00833/0.92) x 106

=0.00814891 x 106

= 1000 uf (standard value)

Capacitor voltage rating should be at least

1.5 x VDA

= 1.5X11.2

= 16.8V

=16V (standard value)

C = 1000uf 16V.

Ripple FactorThe ripple factor for the Full Wave Rectifier is given byµ §The average voltage or the dc voltage available across the load resistance isµ §µ § µ §RMS value of the voltage at the load resistance isµ §µ §Efficiency Efficiency, is the ratio of the dc output power to ac input power µ §µ §The maximum efficiency of a Full Wave Rectifier is 81.2%.

THERMAL SENSING AND INDICATION UNIT

This unit converts the electrical signal from the heat sensor (thermistor) into an electrical

signal. The basic component of the circuit is LM 741 operational amplifier configured in

the comparator mode.

Figure 3.2 Operational Amplifier

Where V+ is non-inverting input pin 3

V- is inverting input pin 2

Vout is output pin 6

Vst is positive power supply pin 7

Vs- is negative power supply pin 4

The general operational amplifier has two inputs and one output, the output voltage is a multiple of the difference between the two inputs (one can be made floating).

Figure 3.3. unit of comparator circuit.

R1 sets the reference (non-inverting) voltage

Vout = t (Vin – Vref),

Where (t is the open-loop gain of the operational amplifier.

In this comparator mode, Vout is HIIGH if the incoming voltage is equal to

or above Vref. Otherwise, the output is LOW.

Since R1 is variable in other to set different reference voltage levels, its

value is not critical. Thus picking a 50K ohms resistor, R1 could be seen as

consisting of two fixed resistors and at 5o% variation, Ra=25K and

Rb=25K.

V = supply voltage x Ra/Ra+Rb

V= 9v x 25000/  25000+25000

v = 9v x (25000/50000 ohms)

V = 9v x 0.5 ohms

V = 4.5v

µ §

Vin is determine by the resistance of the thermistor. It varies with the

magnitude of heat from the transformer. The resistance can vary from

approximately 200Kohms to about 10 Ohms. In between, different voltages

are produce as a result of the variation in resistance. The output from the op-

amp is then fed to the transistor which drives the buzzer.

THE STEP-UP TRANSFORMER DESIGN

Determination of number of turns is calculated using 3000W

In order to achieve a good number of turns flux density of 1.531tesla was assume and the

following calculation was made

A = (√P/5.58

Where A = Area in square meter (M2), P = power in watts (W) = 3000W and 5.58

is a constant

A = √3000/5.58 = 9.8158CM2 = 9.8158 x 10-4M2

E = 4.44 F ΦmN and

Φm = BmxA

Where E = emf of transformer in volt (V), F = frequency in Hertz (HZ) = 50Hz,

Φm = flux in Weber (w), Bm = flux density in tesla = 1.531tesla, A = Area in

square meter (M2) = 9.8158 x 10-4M2 and N = number of turns

Φm = 1.531 x 9.8158 x 10-4 = 1.5028 x 10-3w = 1.5028mw

Determination of number of turns on primary side, emf per turn E1.

E1 = 4.44 x F x Φm = 4.44 x 50 x 1.5028 x 10-3 = 0.3336 V/turn

Primary turn N1

N1 = V1/E1 = 12/0.3336 = 35.9689turns ≈ 36turns

Secondary turns N2

(N1/N2) = (V1/V2)

N2 = (N1 x V2)/V1 = ( 36 x 220) / 12 = 660turns

Determination of wire diameter

A = I/D and d = √((A x 4)/Π)

Where A = cross-sectional area in square millimeters (mm2), D = current density

= constant = 3.08A/mm2, I = current in Amperes (A), d = diameter in millimeters

(mm) and Π = 3.142

Primary current I1

I1 = 3000/12 = 250A

A1 = I1/D = 250/3.08 = 81.1688mm2

d1 = √((81.1688 x 4) / 3.142) = 10.1653 mm

Secondary current I2

I2 = 3000/220 = 13.6364A

A2 = I2/D = 13.6364/3.08 = 4.4274mm2

d2 = √((4.4274 x 4) / 3.142) = 2.3741mm

3.3 CIRCUIT DIAGRAM OF THE SYSTEM

CIRCUIT A CIRCUIT DIAGRAM OF A MORDEN 3000W DC-AC INVERTER

CIRCUIT DIAGRAM OF A 3KW INVERTER

3.4 COMPONENT REVIEWThis unit reviews some of the components used in this circuit design.3.4.1 INTEGRATED CIRCUITA monolithic integrated circuit (also known as IC, microcircuit, microchip, silicon chip, or chip) is a miniaturized µelectronic circuit§ (consisting mainly of µsemiconductor devices§, as well as µpassive components§) that has been manufactured in the surface of a thin substrate of µsemiconductor§ material.A µhybrid integrated circuit§ is a miniaturized electronic circuit constructed of individual semiconductor devices, as well as passive components, bonded to a substrate or circuit board.Integrated circuits were made possible by experimental discoveries which showed that µsemiconductor devices§ could perform the functions of µvacuum tubes§, and by mid-20th-century technology advancements in µsemiconductor device fabrication§. The integration of large numbers of

tiny µtransistors§ into a small chip was an enormous improvement over the manual assembly of circuits using discrete µelectronic components§. The integrated circuit's µmass production§ capability, reliability, and building-block approach to circuit design ensured the rapid adoption of standardized ICs in place of designs using discrete transistors.There are two main advantages of ICs over discrete circuits: cost and performance. Cost is low because the chips, with all their components, are printed as a unit by µphotolithography§ and not constructed a transistor at a time. Performance is high since the components switch quickly and consume little power, because the components are small and close together. As of 2006, chip areas range from a few square µmm§ to around 350 µmm§2, with up to 1 million µtransistors§ per µmm§2.Advances in integrated circuitsAmong the most advanced integrated circuits are the µmicroprocessors§ or "cores", which control everything from µcomputers§ to µcellular phones§ to digital µmicrowave ovens§. Digital µmemory chips§ and µASICs§ are examples of other families of integrated circuits that are important to the modern µinformation society§. While cost of designing and developing a complex integrated circuit is quite high, when spread across typically millions of production units the individual IC cost is minimized. The performance of ICs is high because the small size allows short traces which in turn allows low µpower§ logic (such as µCMOS§) to be used at fast switching speeds.ICs have consistently migrated to smaller feature sizes over the years, allowing more circuitry to be packed on each chip. This increased capacity per unit area can be used to decrease cost and/or increase functionality—see µMoore's law§ which, in its modern interpretation, states that the number of transistors in an integrated circuit doubles every two years. In general, as the feature size shrinks, almost everything improves—the cost per unit and the switching power consumption go down, and the speed goes up. However, ICs with µnanometer§-scale devices are not without their problems, principal among which is leakage current (see µsubthreshold leakage§ and µMOSFET§ for a discussion of this), although these problems are not insurmountable and will likely be solved or at least ameliorated by the introduction of µhigh-k dielectrics§. Since these speed and power consumption gains are apparent to the end user, there is fierce competition among the manufacturers to use finer geometries. This process, and the expected progress over the next few years, is well described by the µInternational Technology Roadmap for Semiconductors§ (ITRS).Classification

Integrated circuits can be classified into µanalog§, µdigital§ and µmixed signal§ (both analog and digital on the same chip).Digital integrated circuits can contain anything from a few thousand to millions of µlogic gates§, µflip-flops§, µmultiplexers§, and other circuits in a few square millimeters. The small size of these circuits allows high speed, low power dissipation, and reduced manufacturing cost compared with board-level integration. These digital ICs, typically µmicroprocessors§, µDSPs§, and micro controllers work using binary mathematics to process "one" and "zero" signals.Analog ICs, such as sensors, power management circuits, and µoperational amplifiers§, work by processing continuous signals. They perform functions like µamplification§, µactive filtering§, µdemodulation§, µmixing§, etc. Analog ICs ease the burden on circuit designers by having expertly designed analog circuits available instead of designing a difficult analog circuit from scratch.ICs can also combine analog and digital circuits on a single chip to create functions such as µA/D converters§ and µD/A converters§. Such circuits offer smaller size and lower cost, but must carefully account for signal interference (see µsignal integrity§).PackagingThe earliest integrated circuits were packaged in ceramic flat packs, which continued to be used by the military for their reliability and small size for many years. Commercial circuit packaging quickly moved to the µdual in-line package§ (DIP), first in ceramic and later in plastic. In the 1980s pin counts of VLSI circuits exceeded the practical limit for DIP packaging, leading to µpin grid array§ (PGA) and µleadless chip carrier§ (LCC) packages. µSurface mount§ packaging appeared in the early 1980s and became popular in the late 1980s, using finer lead pitch with leads formed as either gull-wing or J-lead, as exemplified by µSmall-Outline Integrated Circuit§. A carrier which occupies an area about 30 – 50% less than an equivalent µDIP§, with a typical thickness that is 70% less. This package has "gull wing" leads protruding from the two long sides and a lead spacing of 0.050 inches.µSmall-Outline Integrated Circuit§ (SOIC) and µPLCC§ packages. In the late 1990s, µPQFP§ and µTSOP§ packages became the most common for high pin count devices, though PGA packages are still often used for high-end µmicroprocessors§. Intel and AMD are currently transitioning from PGA packages on high-end microprocessors to µland grid array§ (LGA) packages.

µBall grid array§ (BGA) packages have existed since the 1970s. µFlip-chip Ball Grid Array§ packages, which allow for much higher pin count than other package types, were developed in the 1990s. In an FCBGA package the die is mounted upside-down (flipped) and connects to the package balls via a package substrate that is similar to a printed-circuit board rather than by wires. FCBGA packages allow an array of input-output signals (called Area-I/O) to be distributed over the entire die rather than being confined to the die periphery.Traces out of the die, through the package, and into the µprinted circuit board§ have very different electrical properties, compared to on-chip signals. They require special design techniques and need much more electric power than signals confined to the chip itself.When multiple dies are put in one package, it is called SiP, for µSystem In Package§. When multiple dies are combined on a small substrate, often ceramic, it's called a MCM, or µMulti-Chip Module§. The boundary between a big MCM and a small printed circuit board is sometimes fuzzy.3.4.2 DIODEIn µelectronics§, a diode is a µcomponent§ that restricts the direction of flow of µcharge carriers§. Essentially, it allows an µelectric current§ to flow in one direction, but blocks it in the opposite direction. Thus, the diode can be thought of as an electronic version of a µcheck valve§. Circuits that require current flow in only one direction typically include one or more diodes in the circuit design.Early diodes included µ"cat's whisker" crystals§ and µvacuum tube§ devices (called µthermionic valves§ in µBritish English§ µDialect§). Today the most common diodes are made from µsemiconductor§ materials such as µsilicon§ or µgermanium§.Semiconductor diodesµµ §§µµ §§Diode schematic symbol. Conventional current can flow from the anode to the cathode, but not the other way around.Most modern diodes are based on µsemiconductor§ µp-n junctions§. In a p-n diode, µconventional current§ can flow from the p-type side (the µanode§) to the n-type side (the µcathode§), but cannot flow in the opposite direction. Another type of semiconductor diode, the µSchottky diode§, is formed from the contact between a metal and a semiconductor rather than by a p-n junction.A semiconductor diode's µcurrent-voltage, or I-V, characteristic§ curve is ascribed to the behavior of the so-called µdepletion layer§ or µdepletion

zone§ which exists at the µp-n junction§ between the differing semiconductors. When a p-n junction is first created, conduction band (mobile) electrons from the N-doped region diffuse into the P-doped region where there is a large population of holes (places for electrons in which no electron is present) with which the electrons "recombine". When a mobile electron recombines with a hole, the hole vanishes and the electron is no longer mobile. Thus, two charge carriers have vanished. The region around the p-n junction becomes depleted of µcharge carriers§ and thus behaves as an µinsulator§.However, the µdepletion width§ cannot grow without limit. For each electron-hole pair that recombines, a positively-charged dopant ion is left behind in the N-doped region, and a negatively charged dopant ion is left behind in the P-doped region. As recombination proceeds and more ions are created, an increasing electric field develops through the depletion zone which acts to slow and then finally stop recombination. At this point, there is a 'built-in' potential across the depletion zone.If an external voltage is placed across the diode with the same polarity as the built-in potential, the depletion zone continues to act as an insulator preventing a significant electric current. This is the µreverse bias§ phenomenon. However, if the polarity of the external voltage opposes the built-in potential, recombination can once again proceed resulting in substantial electric current through the p-n junction. For silicon diodes, the built-in potential is approximately 0.6 V. Thus, if an external current is passed through the diode, about 0.6 V will be developed across the diode such that the P-doped region is positive with respect to the N-doped region and the diode is said to be 'turned on' as it has a µforward bias§.µµ §§I-V characteristics of a P-N junction diode (not to scale).A diode's I-V characteristic can be approximated by two regions of operation. Below a certain difference in potential between the two leads, the depletion layer has significant width, and the diode can be thought of as an open (non-conductive) circuit. As the potential difference is increased, at some stage the diode will become conductive and allow charges to flow, at which point it can be thought of as a connection with zero (or at least very low) resistance. More precisely, the µtransfer function§ is µlogarithmic§, but so sharp that it looks like a corner on a zoomed-out graph (see also µsignal processing§).In a normal silicon diode at rated currents, the voltage drop across a conducting diode is approximately 0.6 to 0.7 µvolts§. The value is different for other diode types - µSchottky diodes§ can be as low as 0.2 V and µlight-

emitting diodes§ (LEDs) can be 1.4 V or more (Blue LEDs can be up to 4.0 V).Referring to the I-V characteristics image, in the reverse bias region for a normal P-N rectifier diode, the current through the device is very low (in the µA range) for all reverse voltages up to a point called the peak-inverse-voltage (PIV). Beyond this point a process called reverse µbreakdown§ occurs which causes the device to be damaged along with a large increase in current. For special purpose diodes like the µavalanche§ or µzener diodes§, the concept of PIV is not applicable since they have a deliberate breakdown beyond a known reverse current such that the reverse voltage is "clamped" to a known value (called the zener voltage or µbreakdown voltage§). These devices however have a maximum limit to the current and power in the zener or avalanche region.Types of semiconductor diodeµµ §§µµ §§µµ §§µµ §§DiodeµZenerDiode§µSchottkyDiode§µTunnelDiode§µµ §§µµ §§µµ §§µµ §§µLight-emittingdiode§µPhotodiode§µVaricap§µSCR§Some diode symbols

3.4.3 RESISTOR

A resistor is a two-terminal µelectrical§ or µelectronic§ component that resists an µelectric current§ by producing a voltage drop between its terminals in accordance with µOhm's law§: µ §The µelectrical resistance§ is equal to the µvoltage§ drop across the resistor divided by the current through the resistor. Resistors are used as part of µelectrical networks§ and electronic circuits.Calculations Ohm's lawThe relationship between voltage, current, and resistance through a metal wire, and some other materials, is given by a simple equation called µOhm's Law§:µ §where V (or U in some languages) is the voltage (or potential difference) across the wire in µvolts§, I is the current through the wire in µamperes§, and R, in µohms§, is a constant called the resistance—in fact this is only a simplification of the original Ohm's law (see the article on that law for further details). Materials that obey this law over a certain voltage or current

range are said to be ohmic over that range. An ideal resistor obeys the law across all frequencies and amplitudes of voltage or current.µSuperconducting§ materials at very low temperatures have zero resistance. Insulators (such as µair§, µdiamond§, or other non-conducting materials) may have extremely high (but not infinite) resistance, but break down and admit a larger flow of current under sufficiently high voltage. Power dissipationThe power dissipated by a resistor is the voltage across the resistor multiplied by the current through the resistor:µ §All three equations are equivalent. The first is derived from µJoule's law§, and other two are derived from that by Ohm's Law.The total amount of heat energy released is the integral of the power over time:µ §If the average power dissipated exceeds the power rating of the resistor, then the resistor will first depart from its nominal resistance, and will then be destroyed by overheating. Series and parallel circuitsResistors in a µparallel§ configuration each have the same potential difference (voltage). To find their total equivalent resistance (Req):µµ §§µ §The parallel property can be represented in equations by two vertical lines "||" (as in geometry) to simplify equations. For two resistors,µ §The current through resistors in µseries§ stays the same, but the voltage across each resistor can be different. The sum of the potential differences (voltage) is equal to the total voltage. To find their total resistance:µµ §§µ §A resistor network that is a combination of parallel and series can sometimes be broken up into smaller parts that are either one or the other. For instance,µµ §§µ §

3.4.4 TRANSISTOR

A transistor is a µsemiconductor device§, commonly used as an amplifier or an electrically controlled switch. The transistor is the fundamental building block of the µcircuitry§ that governs the operation of µcomputers§, µcellular phones§, and all other modern µelectronics§.Because of its fast response and accuracy, the transistor may be used in a wide variety of µdigital§ and µanalog§ functions, including µamplification§, µswitching§, µvoltage regulation§, signal µmodulation§, and µoscillators§. Transistors may be packaged individually or as part of an µintegrated circuit§ chip, which may hold millions of transistors in a very small area.Modern transistors are divided into two main categories: µbipolar junction transistors§ (BJTs) and µfield effect transistors§ (FETs). Application of current in BJTs and voltage in FETs between the input and common terminals increases the µconductivity§ between the common and output terminals, thereby controlling current flow between them. The transistor characteristics depend on their type. See µTransistor models§.The term "transistor" originally referred to the µpoint contact§ type, but these only saw very limited commercial application, being replaced by the much more practical µbipolar junction§ types in the early 1950s. Ironically both the term "transistor" itself and the µschematic symbol§ most widely used for it today are the ones that specifically referred to these long-obsolete devices.µ[1]§ For a short time in the early 1960s, some manufacturers and publishers of electronics magazines started to replace these with symbols that more accurately depicted the different construction of the bipolar transistor, but this idea was soon abandoned.In µanalog circuits§, transistors are used in µamplifiers§, (direct current amplifiers, audio amplifiers, radio frequency amplifiers), and linear µregulated power supplies§. Transistors are also used in µdigital circuits§ where they function as electronic switches, but rarely as discrete devices, almost always being incorporated in monolithic µIntegrated Circuits§. Digital circuits include µlogic gates§, µrandom access memory§ (RAM), µmicroprocessors§, and µdigital signal processors§ (DSPs).Advantages of transistors over vacuum tubesBefore the development of transistors, µvacuum tubes§ (or in the UK thermionic valves or just valves) were the main active components in electronic equipment. The key advantages that have allowed transistors to replace their vacuum tube predecessors in most applications are:

Smaller size and lighter (despite continuing miniaturization of vacuum tubes)

Highly automated manufacture Lower cost (in volume production)

Lower possible operating voltages (but vacuum tubes can operate at higher voltages)

No warm-up period (most vacuum tubes need 10 to 60 seconds to function correctly)

Lower power dissipation (no heater power, very low saturation voltage)

Higher reliability and greater physical ruggedness (although vacuum tubes are electrically more rugged, and are much more resistant to µnuclear electromagnetic pulses§ and µelectrostatic discharge§)

Much longer life (vacuum tube cathodes are eventually exhausted and the vacuum can become contaminated)

Complementary devices available (allowing circuits with complementary-symmetry: vacuum tubes with a polarity equivalent to PNP BJTs or P type FETs are not available)

Ability to control large currents (power transistors are available to control hundreds of amperes, vacuum tubes to control even one ampere are large and costly)

Much less µmicrophonic§ (vibration can modulate vacuum tube characteristics, though this may contribute to the sound of µguitar amplifiers§)

Typesµµ §§PNPµµ §§P-channelµµ §§NPNµµ §§N-channelBJTJFETBJT and JFET symbolsTransistors are categorized by:

Semiconductor material: germanium, silicon, gallium arsenide, silicon carbide

Structure: µBJT§, µJFET§, IGFET (µMOSFET§), µIGBT§, "other types"

Polarity: µNPN§, µPNP§ (BJTs); N-channel, P-channel (FETs) Maximum power rating: low, medium, high Maximum operating frequency: low, medium, high, µradio

frequency§ (RF), µmicrowave§ (The maximum effective frequency of a transistor is denoted by the term fT, an abbreviation for "frequency of transition". The frequency of transition is the frequency at which the transistor yields unity gain).

Application: switch, general purpose, audio, high voltage, super-beta, matched pair

Physical packaging: µthrough hole§ metal, through hole plastic, µsurface mount§, ball grid array, power modules

Thus, a particular transistor may be described as: silicon, surface mount, BJT, NPN, low power, high frequency switch.UsageIn the early days of transistor circuit design, the µbipolar junction transistor§, or BJT, was the most commonly used transistor. Even after MOSFETs became available, the BJT remained the transistor of choice for digital and analog circuits because of their ease of manufacture and speed. However, desirable properties of MOSFETs, such as their utility in low-power devices, have made them the ubiquitous choice for use in digital circuits and a very common choice for use in analog circuits.

CHAPTER FOUR

4.0 CONSTRUCTION

This chapter contains the construction work details. It also contains the list

of tools used in the construction work and the testing and result analysis.

4.1 CIRCUIT CONSTRUTION

The circuit board consists of the vero board and all other components

mounted on it. In its construction, the vero board was cleaned with an iron

brush to remove dirt from its surface which might affect soldering quality.

Subsequently, following the circuit diagram, the components were mounted

on the board one after the other and soldered. The IC was not directly

soldered to the board but was mounted on an IC socket. This is to prevent

heat damage and for ease of replacement. Units like the power switch,

display etc were connected to the board via flexible wires.

In the soldering process, care was taken to ensure that the soldered joints

have good mechanical and electrical contact. Also great care was taken to

ensure that the components were not damage from excess heat from the

soldering iron. The following procedures were followed in the soldering

process.

- A 40W pencil type soldering iron was used.

- A good quality rosin-core solder was used.

- For the iron to properly conduct heat, the soldering tip was well tinned

(coated with a tin layer of solder). To keep the tip clean, it was wiped

from time to time on a damp spurge or cloth.

- All component lead and copper fort pads were cleaned and free of

oxidation at the time of soldering by lightly brushing them with steel

wool.

- While soldering and unsoldering, a safety glass was used to avoid eye

injury due to flying particle of hot solder.

- The top of the soldering iron was firmly was placed against the wire lead

and copper pad to heat the connection to be soldered.

Before soldering semiconductor components such as transistors, diode etc.

the lead near semi conductor was held with needle nose pliers or tweezers to

prevent the heat from the soldering iron from getting to into the component.

- Soldering flux is applied to the connection as it is been heated. Care was

taken not to apply solder directly onto the top of the iron.

- Enough solder was applied to form a tin, smooth coating in all metal part

in the connection.

- The heat was allowed on the connection for an INSTANT after

application of the solder has been stopped. This is to aid the flow of

solder and insure against ‘Poor’ or ‘cooled’ solder connections.

- Care was taken not tot move the soldered connection until the solder has

cooled (solidified), thus reducing the possibilities of improper soldering.

- Excess lead length were cut as close as possible to the soldering

connections.

4.2 ENCLOSURE CONSTRUCTION

The enclosure was practically made from a sheet of thin metal. Using a

meter rule and pencil, the require shape and size for the enclosure was

marked. The parts were then joined together with special plastic glue to

form the shape shown below.

Paste picture here…………

Fig. 4.2 Enclosure

Using a hand drill with tiny drilling bit, screw holes and other relevant

ventilation holes were performed.

Factors that were considered before choosing a specific shape and size

include, a large enough space inside the enclosure to prevent over

compression of the circuit board.

4.3 ASSEMBLING

Havng constructed the circuit board and the enclosure and being satisfied

with the functionality of the constructed circuit, the project was assembled.

Assembling was simply fixing the circuit board firmly in the enclosure and

screwing that there was no conducting object like lead ball, nail etc inside

the enclosure and also that enclosure was not to small for the circuit board

since this might cause compression which might result to breakage or the

Vero board track.

Proper connections were made between the units. This was a beat

complicated and demand great care and attention since the use of a lot of

connecting wires were involved.

4.3 TESTING AND RESULT

Testing of the project proved satisfactorily. The power cord was connected

to the mains and the power switch toggled on. Using a multimeter, the

voltage levels at various points were taking to ensure that the correct amount

of power was reaching all the unit. Expected voltages were,

Vcc of all Ics…………………9V

GND of all Ics………………..0V etc.

The power supply output waveform observed with an oscilloscope is shown below.

µ §

Next, resistance test was carried out. This was to ensure the there was no

open or close circuit within the board strips or the connecting wires.

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The test shows that the system functionality corresponds to design intention.

.

4.4.1 LIST OF TOOLS USED IN CONSTRUCTION

1- Soldering iron

2- Pair of pliers

3- Side cutter

4- Nails

5- Tweezers

CHAPTER FIVE

5.0 CONCLUSION AND RECOMMENDATION

This chapter consists of the conclusion and recommendation, and reference.

5.1 CONCLUSION

write this

5.2 RECOMMENDATION

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References1. µ ^§ (2000) "µPower Electronics: Energy Manager for Hybrid Electric

Vehicles§". Oak Ridge National Laboratory Review 33 (3). Retrieved on µ2006§-µ11-08§. 

2. µ ^§ Rodriguez, Jose; et al. (August 2002). "Multilevel Inverters: A Survey of Topologies, Controls, and Applications". IEEE Transactions on Industrial Electronics 49 (4): 724-738. 

3. B.L Theraja and A.K Theraja (1995) A TEXT BOOK OF

ELECTRICAL TCHNOLOGY publish by publication division of

Nrja construction company CP/LTD pp 1457-1468

4. Allel CL Atwood K.W (John Authur II) (1973) ELECTRONIC

ENGINEERING third edition, John willy and sons INC.

5. JC Moris (1989), ELECTRONICS; PRACTICAL APPLICATION

AND DESIGN, pub. Edward Arnold, pp 130.

6. R.J Maddock and D.M Calcult (1987), ELECTRONIC; A COURSE

FOR ENGINEERING, pub. Longman group LTD, ELBS Edition, pp

601.

7. µ www.wikipedia.com/machine§

8. µ 400 Hz Electrical Systems§. Aerospaceweb.org. Retrieved on µ2007§-µ05-21§. 9. Allan, D.J. (1991), "Power transformers – the second century", Power Engineering

Journal, IEE .  10.11. Dixon, Lloyd, µ"Eddy Current Losses in Transformer Windings and Circuit Wiring"§ 12. Flanagan, William (1993). Handbook of Transformer Design and Applications. McGraw-

Hill. µISBN 0-0702-1291-0§.  13. Harlow, James (2004). Electric Power Transformer Engineering. CRC Press. µISBN 0-

8493-1704-5§.  14. Hindmarsh, John (1977). Electrical Machines and their Applications, 4th edition. Exeter:

Pergammon. µISBN 0-08-030573-3§.  15. µ International Electrotechnical Commission§. µOtto Blathy, Miksa Déri, Károly

Zipernowsky§. IEC History. Retrieved on µ2007§-µ05-17§. 16. Kubo, T.; H. Sachs & S. Nadel (2001), µOpportunities for new appliance and equipment

efficiency standards§, American Council for an Energy-Efficient Economy, at p39 17. McLaren, Peter (1984). Elementary Electric Power and Machines. Ellis Horwood.

µISBN 0-4702-0057-X§.  18. McLyman, Colonel William (2004). Transformer and Inductor Design Handbook. CRC.

µISBN 0-8247-5393-3§. 

Chargingunit

SwitchingCircuit

Dc-AcInverter Driver

Step-upTransform-er

ThermalMonitorAnd indicator

Logicgate

Pulse Generator

Counter Decoder

7-segmantdisplay

Motor