DESIGN AND CONSTRUCTION OF A 5KVA POWER INVERTERS
ABSTRACT
This project titled “design and construction of a DC to AC inverter system” is
designed to meet up with the power demand in the offices and in homes in the
absence of power supply from the national grid, NEPA. In order words, the
device serves as a substitute for the national grid.
It is designed in such a way that it will take up 12V DC from battery and inverts
it to an output of 230V, 50Hz AC. It makes no noise during operation and no
hazardous carbon monoxide is generated in the surrounding.
This feature makes it safe to use anywhere when compared to generator. Also,
the circuit is capable of charging the battery (i.e. 12V source) when the power
from the supply authority is ON.
TABLE OF CONTENTS
TITLE PAGE
APPROVAL PAGE
DEDICATION
ACKNOWLEDGEMENT
ABSTRACT
TABLE OF CONTENT
CHAPTER ONE
1.0
INTRODUCTION
1.1
OBJECTIVE OF THE PROJECT
1.2
SIGNIFICANCE OF THE PROJECT
1.3 APPLICATION OF THE PROJECT
1.4
SCOPE OF THE PROJECT
1.5
LIMITATION OF THE PROJECT
1.6
PURPOSE OF THE PROJECT
1.7
PROJECT ORGANISATION
CHAPTER TWO
2.0
LITERATURE REVIEW
2.1
REVIEW OF HISTORY OF AN INVERTER
2.2 REVIEW OF HOW TO CHOOSING THE RIGHT INVERTER
2.3
REVIEW OF THE DIFFERENCE BETWEEN SINE WAVE AND MODIFIED SINE
WAVE INVERTER.
2.4
REVIEW OF INVERTER CAPACITY
2.5
SAFETY OF INVERTER
2.6
INVERTER RATING
2.7
WHY CHOOSE A MODIFIED SINE WAVE INVERTER?
2.8
TYPES OF INVERTER
CHAPTER THREE
3.0
CONSTRUCTION
3.1
BASIC DESIGNS OF AN INVERTER
3.2
BLOCK DIAGRAM OF THE SYSTEM
3.3
SYSTEM OPERATION
3.4
CIRCUIT DIAGRAM
3.5
CIRCUIT DESCRIPTION
3.6
DESCRIPTION OF COMPONENTS USED
3.7
HOW TO CHOOSE A RIGHT INVERTER AND BATTERY
3.8
HOW TO CHOOSE THE BEST INVERTER BATTERY
CHAPTER FOUR
RESULT ANALYSIS
4.0
CONSTRUCTION PROCEDURE AND TESTING
4.1
CASING AND PACKAGING
4.2
ASSEMBLING OF SECTIONS
4.3
TESTING OF SYSTEM OPERATION
4.4
COST ANALYSIS
CHAPTER FIVE
5.1
CONCLUSION
5.2
RECOMMENDATION
5.4
REFERENCES
CHAPTER ONE
INTRODUCTION
1.1 Historical background
A power inverter converts DC power (also known as direct current), to standard
AC power (alternating current). Inverters are used to operate electrical
equipment from the power produced by a car or boat battery or renewable
energy sources, like solar panels or wind turbines. DC power is what batteries
store, while AC power is what most electrical appliances need to run so an
inverter is necessary to convert the power into a usable form. For example,
when a cell phone is plugged into a car cigarette lighter to recharge, it supplies
DC power; this must be converted to the required AC power by a power inverter
to charge the phone.
In modified sine wave, The waveform in commercially available modified-sinewave inverters is a square wave with a pause before the polarity transition,
which only needs to cycle through a three-position switch that outputs forward,
off, and reverse output at the pre-determined frequency. The peak voltage to
RMS voltage does not maintain the same relationship as for a sine wave. The
DC bus voltage may be actively regulated or the "on" and "off" times can be
modified to maintain the same RMS value output up to the DC bus voltage to
compensate for DC bus voltage variation[1] [2].
The ratio of on to off time can be adjusted to vary the RMS voltage while
maintaining a constant frequency with a technique called PWM. Harmonic
spectrum in the output depends on the width of the pulses and the modulation
frequency. When operating induction motors, voltage harmonics is not of great
concern, however harmonic distortion in the current waveform introduces
additional heating, and can produce pulsating torques.
Most AC motors will run on MSW inverters with an efficiency reduction of
about 20% due to the harmonic content [1]. Please use API referencing style.
1.1
OBJECTIVE OF THE PROJECT
The objective of this project is to design and construct a 5kva modified sine
wave inverter which can be powered from the source of 12V battery to produce
an output of 230vac. This inverter is capable of operating a wide variety of
loads; electronic and household items including but not limited to TV, VCR,
and satellite receiver, computers, and printers.
1.2
PURPOSE OF THE PROJECT
The purpose of this work is to design an electronic device or circuitry that
changes direct current (DC) to alternating current (AC). The input voltage
(12vdc), output voltage (230vac) and frequency (50hz), and overall power
handling depend on the design of the specific device or circuitry. The inverter
does not produce any power; the power is provided by the DC source.
A typical power inverter device or circuit requires a relatively stable DC power
source capable of supplying enough current for the intended power demands of
the system. The input voltage depends on the design and purpose of the inverter.
Examples include: 12 VDC, for smaller consumer and commercial inverters that
typically run from a rechargeable 12 V lead acid battery[3].
The waveform of this work is modified sine wave. The modified sine wave
output of such an inverter is the sum of two square waves one of which is
phase shifted 90 degrees relative to the other. The result is three level
waveform with equal intervals of zero volts; peak positive volts; zero volts;
peak negative volts and then zero volts. This sequence is repeated. The
resultant wave very roughly resembles the shape of a sine wave[3].
1.3
SIGNIFICANCE OF THE PROJECT
In the recent years, power inverter has become a major power source due to
its environmental and economic benefits and proven reliability. Since the solar
power system does not have moving parts, virtually it does not require any
kind of maintenance once installed.
Power inverter is produced by connecting the device on the 12VDC battery as
the input to produce 230VAC as the required output. It can also be connected
to solar panel.
Second, the whole energy conversion process is environmentally friendly. It
produces no noise, harmful emissions or polluting gases. The burning of
natural resources for energy can create smoke, cause acid rain and pollute
water and air. Carbon dioxide, CO2, a leading greenhouse gas, is also produced
in the case of burning fuels. Power inverter uses only the power of the battery
as its fuel. It creates no harmful by-product and contributes actively to the
reduction of global warming[5] [7].
1.4
SCOPE OF THE PROJECT
A power inverter is a power conversion device. It converts fixed direct current
(DC) voltage to frequency sinusoidal alternating current (AC) voltage output.
Power inverters are used to power and control the speed, torque, acceleration,
deceleration, and direction of the motor. The use of inverter has become
prevalent in wide range of industrial applications; from motion control
applications to ventilation systems, waste water processing facilities to
machining areas, and many others. Though power inverters offer lower
operating costs and higher efficiency, they are not without their problems[7].
1.5
LIMITATION OF THE PROJECT

Expensive when compared to traditional generators

There are no large capacity inverter in the markets[8]

The inverter can power a few appliances for a short period

The input is limited to 12VDC, output to 230VAC and the frequency to
50Hz

1.6
The power rating of the work is 5kva
APPLICATION OF THE PROJECT
The applications and uses of a power inverter which are as follows:
DC power source utilization
Inverter designed to provide 230 VAC from the 12 VDC source provided in an
automobile. The unit shown provides more than 20 amperes of alternating
current, or enough to power more than 3KW load.
An inverter converts the DC electricity from sources such as batteries, solar
panels, or fuel cells to AC electricity. The electricity can be at any required
voltage; in particular it can operate AC equipment designed for mains operation,
or rectified to produce DC at any desired voltage[4].
Uninterruptible power supplies
An uninterruptible power supply (UPS) uses batteries and an inverter to supply
AC power when main power is not available. [5]When main power is restored, a
rectifier supplies DC power to recharge the batteries.
Induction heating
Modified Sine wave Inverters convert low frequency main AC power to 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.
HVDC power transmission
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. The inverter must be
synchronized with grid frequency and phase and minimize harmonic
generation[6].
Variable-frequency drives
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
main AC power. Since an inverter is the key component, variable-frequency
drives are sometimes called inverter drives or just inverters.
VFDs that operate directly from an AC source without first converting it to DC
are called cyclo-converters. They are now commonly used on large ships to
drive the propulsion motors.
Electric vehicle drives
Adjustable speed motor control inverters are currently used to power the
traction motors in some electric and diesel-electric rail vehicles as well as some
battery electric vehicles and hybrid electric highway vehicles[5].
Air conditioning
An inverter air conditioner uses a variable-frequency drive to control the speed
of the motor and thus the compressor[5].
Electroshock weapons
Electroshock weapons and tasters have a DC/AC inverter to generate several
tens of thousands of V AC out of a small 12 V DC battery. First the 12VDC is
converted to 400–2000V AC with a compact high frequency transformer, which
is then rectified and temporarily stored in a high voltage capacitor until a pre-set
threshold voltage is reached. When the threshold (set by way of an air gap or
TRIAC) is reached, the capacitor dumps its entire load into a pulse transformer
which then steps it up to its final output voltage of 20–60 kV. A variant of the
principle is also used in electronic flash and bug zappers, though they rely on a
capacitor-based voltage multiplier to achieve their high voltage[5].
1.7
PROJECT WORK ORGANISATION
The various stages involved in the development of this project have been
properly put into five chapters to enhance comprehensive and concise reading.
In this project thesis, the project is organized sequentially as follows:
Chapter one of this work is on the introduction to a power inverter. In this
chapter, the background, significance, objective limitation and problem of a
power inverter were discussed.
Chapter two is on literature review of a power inverter. In this chapter, all the
literature pertaining to this work was reviewed.
Chapter three is on design methodology. In this chapter all the method
involved during the design and construction were discussed.
Chapter four is on testing analysis. All testing that result accurate functionality
was analyzed.
Chapter five is on conclusion, recommendation and references.
REFERENCES
1. The Authoritative Dictionary of IEEE Standards Terms, Seventh Edition, IEEE
Press, 2000,ISBN 0-7381-2601-2, page 588
2. http://www.solar-electric.com/lib/wind-sun/Pump-Inverter.pdf
Choose an Inverter for an Independent Energy System
3. http://www.wpi.edu/Pubs/E-project/Available/E-project-042507092653/unrestricted/MQP_D_1_2.pdf
How
to
4. Taylor-Moon, Jonathan (2013). "Alabama Engineering University, Invertors,
Prof.dr.Eng. Jonathan Taylor - Moon | Power Inverter | Photovoltaic
System". Scribd. 7 (Convertor and invertor technologies).
5. Barnes, Malcolm (2003). Practical variable speed drives and power
electronics. Oxford: Newnes. p. 97. ISBN 0080473911.
6. Tripp Lite: Power Inverter FAQ, http://www.tripplite.com/support/inverterfaq
7. "New and Cool: Variable Refrigerant Flow Systems". AIArchitect. American
Institute of Architects. 2009-04-10. Retrieved 2013-08-06.
8. Du, Ruoyang; Robertson, Paul (2017). "Cost Effective Grid-Connected
Inverter for a Micro Combined Heat and Power System". IEEE Transactions
on Industrial Electronics. ISSN 0278-0046.
9. James, Hahn. "Modifi ed Sine-Wave Inverter Enhanced" (PDF). Power
Electronics.
CHAPTER TWO
2.0
LITERATURE REVIEW
2.1
HISTORICAL BACKGROUND OF AN INVERTER
Early inverters
From the late nineteenth century through the middle of the twentieth century,
DC-to-AC power conversion was accomplished using rotary converters or
motor-generator sets (M-G sets). In the early twentieth century, vacuum tubes
and gas filled tubes began to be used as switches in inverter circuits. The most
widely used type of tube was the thyratron.
The origins of electromechanical inverters explain the source of the term
inverter. Early AC-to-DC converters used an induction or synchronous AC
motor direct-connected to a generator (dynamo) so that the generator's
commutator reversed its connections at exactly the right moments to produce
DC. A later development is the synchronous converter, in which the motor and
generator windings are combined into one armature, with slip rings at one end
and a commutator at the other and only one field frame. The result with either is
AC-in, DC-out. With an M-G set, the DC can be considered to be separately
generated from the AC; with a synchronous converter, in a certain sense it can
be considered to be "mechanically rectified AC". [1] [3] Given the right
auxiliary and control equipment, an M-G set or rotary converter can be "run
backwards", converting DC to AC. Hence an inverter is an inverted converter.
Controlled rectifier inverters
Since early transistors were not available with sufficient voltage and current
ratings for most inverter applications, it was the 1957 introduction of the
thyristor or silicon-controlled rectifier (SCR) that initiated the transition to solid
state inverter circuits.
The commutation requirements of SCRs are a key consideration in SCR circuit
designs. SCRs do not turn off or commutate automatically when the gate control
signal is shut off. They only turn off when the forward current is reduced to
below the minimum holding current, which varies with each kind of SCR,
through some external process. For SCRs connected to an AC power source,
commutation occurs naturally every time the polarity of the source voltage
reverses. SCRs connected to a DC power source usually require a means of
forced commutation that forces the current to zero when commutation is
required. The least complicated SCR circuits employ natural commutation
rather than forced commutation. With the addition of forced commutation
circuits, SCRs have been used in the types of inverter circuits described above
[3].
In applications where inverters transfer power from a DC power source to an
AC power source, it is possible to use AC-to-DC controlled rectifier circuits
operating in the inversion mode. In the inversion mode, a controlled rectifier
circuit operates as a line commutated inverter. This type of operation can be
used in HVDC power transmission systems and in regenerative braking
operation of motor control systems.
Another type of SCR inverter circuit is the current source input (CSI) inverter.
A CSI inverter is the dual of a six-step voltage source inverter. With a current
source inverter, the DC power supply is configured as a current source rather
than a voltage source. The inverter SCRs is switched in a six-step sequence to
direct the current to a three-phase AC load as a stepped current waveform. CSI
inverter commutation methods include load commutation and parallel capacitor
commutation. With both methods, the input current regulation assists the
commutation. With load commutation, the load is a synchronous motor operated
at a leading power factor.
As they have become available in higher voltage and current ratings,
semiconductors such as transistors or IGBTs that can be turned off by means of
control signals have become the preferred switching components for use in
inverter circuits [2].
Rectifier and inverter pulse numbers
Rectifier circuits are often classified by the number of current pulses that flow
to the DC side of the rectifier per cycle of AC input voltage. A single-phase
half-wave rectifier is a one-pulse circuit and a single-phase full-wave rectifier is
a two-pulse circuit. A three-phase half-wave rectifier is a three-pulse circuit and
a three-phase full-wave rectifier is a six-pulse circuit.
With three-phase rectifiers, two or more rectifiers are sometimes connected in
series or parallel to obtain higher voltage or current ratings. The rectifier inputs
are supplied from special transformers that provide phase shifted outputs. This
has the effect of phase multiplication. Six phases are obtained from two
transformers, twelve phases from three transformers and so on. The associated
rectifier circuits are 12-pulse rectifiers, 18-pulse rectifiers and so on
When controlled rectifier circuits are operated in the inversion mode, they
would be classified by pulse number also. Rectifier circuits that have a higher
pulse number have reduced harmonic content in the AC input current and
reduced ripple in the DC output voltage. In the inversion mode, circuits that
have a higher pulse number have lower harmonic content in the AC output
voltage waveform.
Modified Sine-Wave Inverter Enhanced
Altering the waveform produced by a modified sine-wave inverter reduces
distortion products, while still permitting use of efficient switching techniques.
Aug. 1, 2006 James H. Hahn, Associate Professor Emeritus, University of
Missouri-Rolla Engineering Education Center, St. Louis | Power Electronics
With the increasing popularity of alternate power sources, such as solar and
wind, the need for static inverters to convert dc energy stored in batteries to
conventional ac form has increased substantially. Most use the same basic
concept: a dc source of relatively low voltage and reasonably good stability is
converted by a high-frequency oscillator and step up transformer to a dc voltage
with magnitude corresponding to the peak of the desired ac voltage. A power
stage at the output then generates an ac voltage from the higher-voltage dc [5]
[6].
Implementation
As demonstrated here, the modified-sine-wave inverter can be modified further
to produce a much closer approximation to a sine wave, at a relatively small
increase in manufacturing costs, simply by incorporating another level into the
waveform. The design still uses switching technology in the power stage,
assuring high efficiency.
The switching stage could be implemented with a combination of bridge and
half-bridge components commonly used in power switching applications. To
produce the proposed multiple-level waveform, several implementations are
possible. In general, they all involve connecting the output lead to a specific
voltage level with switches such as power MOSFETs capable of handling
substantial current.
Appropriate digital logic and timing circuits will be used to activate each switch
at the correct time to achieve the α and β pulse widths. A table can be developed
to indicate which switches must be closed for each section of the output
waveform.
Unlike conventional PWM-inverter designs, which switch at high frequencies,
the proposed inverter design switches at just three times the line frequency. As a
consequence, the proposed inverter design will reduce switching losses from
that of the PWM-controlled inverter and will save power regardless of the
output power level [3].
2.2 REVIEW OF HOW TO CHOOSING THE RIGHT INVERTER
Depending on how you use them, pure sign wave inverters have distinct
advantages over modified sign wave inverters. There are, however, some
instances when the latter are just as effective as the former, if not more so. For
example, if you need to power equipment that requires a single induction load,
or a resistive load, modified sine wave inverters are an ideal choice for two
reasons: they often cost less than pure sine wave inverters, and they use DC
power quite efficiently[4] [6].
Choosing a DC to AC inverter is an important decision concerning the type of
equipment that will be powered; the amount of energy consumed by the
inverter, and the inverter’s cost.
2.3
REVIEW OF THE DIFFERENCE BETWEEN SINE WAVE AND
MODIFIED SINE WAVE INVERTER
As their names would suggest, the primary difference between pure sine wave
and modified sine wave inverters lies in the type of sign wave they exhibit. A
modified sign wave is similar to a square wave, which looks like a succession of
evenly spaced squares when it is expressed as a waveform. However, unlike a
square wave, a modified sine wave’s output rests at zero volts for a short time
before switching positive or negative.
Far from looking like a succession of blocks when viewed as a waveform, a
pure sine wave looks like a series of smooth, evenly spaced hills and valleys.
Due to its nearly perfect sine wave output, a pure sine wave inverter is
compatible with all types of electronics, even sensitive, specialized equipment
such as laser printers and audio equipment. A modified sine wave inverter, on
the other hand, is not compatible with these electronic devices. It can power
most types of standard electrical, but cannot be used for equipment whose
performance requires refined sine wave input.
Another difference between pure signs wave inverters and modified sine wave
inverters is the latter offer less energy efficiency than the former. For example,
while an AC motor will run off a modified sine wave, its operational efficiency
is nearly twenty percent less than it would be if a pure sine wave were present.
For companies whose green initiatives include energy efficiency, using an AC
to DC inverter that delivers a pure sine wave is typically the best choice. Using
a transformerless inverter will also boost efficiency[4] [6].
2.5
REVIEW OF INVERTER CAPACITY
Different models of power inverters vary in how many watts of power they can
supply. The capacity of an inverter should equal the total number of watts
required by each device, plus at least a 50% addition to account for peaks or
spikes in the power draw. For example, if a DVD player draws 100 watts and a
small TV another 100 watts, a minimum 300-watt inverter is recommended.
Getting an inverter with more capacity than what is immediately needed is a
good idea for many people, as it means that different or new devices can be
added without the need for a new power inverter[7] [9].
2.6
SAFETY OF INVERTER
When using a power inverter continuously inside a vehicle that is not turned on,
the engine should be started at least once an hour for 10 to 15 minutes to keep
the battery from running down. A vehicle should never be started in a closed
garage, as the carbon monoxide in the exhaust is fatal.
Power inverters should only be used with batteries that are in good condition
and fully charged. A weak battery will be drained easily if demand is too high.
If used in a car, this could leave a driver stranded, so the battery's condition
should be checked before using an inverter in a stationary vehicle. If the inverter
is being used while the vehicle is running, as in the case of a road trip, there
should be no problem with the extra draw as long as the battery is in good
condition.
Working with large batteries can be dangerous, and when not done properly,
can result in serious injury. Improper use of a power inverter can even lead to
electrocution. For safety reasons, someone attempting to hook an inverter
directly to a battery should be sure to read and follow any and all safety
precautions listed in the inverter's instruction booklet.
It is important for people to always use a power inverter that is rated high
enough for the device that needs to be run. If a heavy-duty power saw is
plugged into a cigarette lighter, for example, the lightweight inverter might
overheat and cause a fire in the dashboard. Adapters that allow more outlets
than the unit is designed to accommodate should be avoided, and proper
ventilation around the inverter is required to prevent overheating[6].
2.7
INVERTER RATINGS
The ratings that you should look at when buying an inverter (depending on the
type) are:
1. Continuous Rating: This is the amount of power you could expect to use
continuously without the inverter overheating and shutting down.
2. Half Hour Rating: This is handy as the continuous rating may be too low to
run a high energy consumption power tool or appliance, however if the
appliance was only to be used occasionally then the half hour rating may
well suffice.
3. Surge Rating: A high surge is required to start some appliances and once
running they may need considerably less power to keep functioning. The
inverter must be able to hold its surge rating for at least 5 seconds. TVs and
refrigerators are examples of items that require only relatively low power
once
running,
but
require
a
high
surge
to
start.
4. IP rating - defines the ability of the inverter seals to prevent water and dust
ingress. Although some inverter manufacturers claim high IP ratings suitable
for outdoor installation, the quality and location of the seals and ventilation
will greatly affect the ability of the inverter to outlast the many years solar
installations are expected to work.
5. Peak efficiency - represents the highest efficiency that the inverter can
achieve.
2.8
WHY CHOOSE A MODIFIED SINE WAVE INVERTER?
For running typical resistive loads like lights and appliances, a modified sine
wave inverter is a reliable, cost-effective choice. Though modified sine wave
inverters do not produce a perfect replica of AC true sine wave power, they do
provide an affordable option that for many mobile power applications is
perfectly adequate. Some devices, however, may not recognize the modified
sine wave and may run poorly or not at all[5].
Some of our most popular modified sine wave inverters are from our HeavyDuty line up. These are excellent solutions for fleet, utility trucks and vans
looking for a powerful and economical alternative to a pure sine wave product.
2.8
TYPES OF INVERTER
There are different types of inverters for home and industries available which
can suit your various electricity needs. Following are the two basic types of
inverters.
1. Modified Sine Wave Inverters
This type of home inverter obtains power from a battery of 12 volts and must be
recharged using a generator or a solar panel. Appliances like microwave ovens,
light bulbs, etc. can be run using these types of inverter[7].

They can be rightly held as the best inverters for homes as they are efficient
enough to provide power to the normal home requirement.

They are the home inverters that are most affordable too.

You can run the daily used home appliances using the modified sine wave
home inverters.

The electric appliances that involve motor speed controls or timers are not to
be run using these types of home inverters.
The wave form of a modified sine wave inverter is as below:
2. True sine wave inverters
This is one of the better types of inverters as they provide better power as
compared to the modified sine wave inverters for homes. These types of home
inverter are also run using a battery of a larger capacity[7].

Technically speaking, the sine waves they produce are purer, thus the
efficiency.

They are best inverters employed for the power sensitive appliances like
refrigerators, televisions, air conditioners, washing machines, etc.

These types of inverters are extremely reliable. The only drawback is that
they are a bit expensive and cannot be afforded by the common man.

There are various models available based on the electricity requirement of
the house [7].
The wave form of a sine wave inverter is as below:
3. Square wave inverter
This is the simplest form of output wave available in the cheapest form of
inverters. They can run simple appliances without problem but much else.
Square wave voltage can be easily generated using a simple oscillator. With the
help of a transformer, the generated square wave voltage can be transformed
into a value of 240VAC or higher [7].
The wave form of a square wave inverter is a below:
2.8
DIFFERENCE BETWEEN CONVENTIONAL GENERATOR AND INVERTER
CONVENTIONAL GENERATOR
DC/AC INVERTER
Conventional generators have been Dc/ac Inverter are a relatively recent
around for quite a while, and the basic development,
concept behind them has remained advanced
made
electronic
possible
by
circuitry.
It
essentially unchanged. They consist of inverter draws power from a fixed DC
an energy source, usually a fossil fuel source (typically a comparatively fixed
such as diesel, propane or gasoline, source like a car battery or a solar
which powers a motor attached to an panel), and uses electronic circuitry to
alternator that produces electricity. “invert” the DC power into the AC
The motor must run at a constant power. The converted AC can be at
speed (usually 3600 rpm) to produce any required voltage and frequency
the
standard
current
that
most with
the
use
of
appropriate
household uses require (in Nigeria, equipment, but for consumer-level
typically 220 Volts AC @ 50 Hertz). If applications in Nigeria, the most
the engine’s rpm fluctuates, so will the common combination is probably
frequency (Hertz) of electrical output.
taking the 12V DC power from car,
boat or RV batteries and making it
into the 230V AC power required for
most everyday uses[6].
Conventional
generators
always The compact size, relatively light
bigger and heavier than inverter
weight and resulting portability of
inverter generators make them the
clear winner in this category.
Conventional generators always noisy
Dc/ac Inverters are often designed
from
the
ground
up
to
be
comparatively quiet
Conventional generators are often Dc/ac Inverter draws power from DC
designed simply to get a certain source, either from battery or solar
amount of power where it is needed, panel.
and to keep the power on. Factors like
the size of the unit have not been a
major consideration. This has meant
that conventional designs can often
accommodate sizeable fuel tanks, with
the obvious result being relatively long
run times. This means that it uses fuel
for it to operate [6].
Conventional generators emit smoke
Inverter produces no smoke
smoke which causes pollution
A conventional generator is nothing With an inverter generator, a rectifier
more than an engine connected to an is used to convert the AC power to DC
alternator and run at a speed that and capacitors are used to smooth it
produces the desired AC frequency, out to a certain degree. The DC power
regardless of the load on it (as the is then “inverted” back into clean AC
load increases the engine throttles up power of the desired frequency and
to keep the engine speed the same). voltage
The output of the alternator is
connected
directly
to
the
load,
without any processing [6].
Many inverters can be paired with Conventional units simply can’t offer
another identical unit to double your this feature. Note that you will need a
power capacity. This type of parallel special
cable
to
connect
your
capability means you can use two generators, which is generally not
smaller, lighter generators to provide
the same wattage and amperage of
one much larger generator – without
sacrificing all the benefits of the
smaller,
lighter,
quieter,
more
portable inverter units [6].
REFERENCES
1. Rodriguez, Jose; et al. (August 2002). "Multilevel Inverters: A Survey of
Topologies, Controls, and Applications". IEEE Transactions on Industrial
Electronics. IEEE. 49 (4): 724–738.
2.
"Archived copy". Archived from the original on 2014-07-23. Retrieved
2014-07-23.
3. Owen, Edward L. (January–February 1996). "Origins of the Inverter". IEEE
Industry Applications Magazine: History Department. IEEE. 2 (1): 64–66.
4. D. R. Grafham and J. C. Hey, editors, ed. (1972). SCR Manual (Fifth ed.).
Syracuse, N.Y. USA: General Electric. pp. 236–239.
5.
http://web.eecs.utk.edu/~tolbert/publications/ecce_2011_bailu.pdf
6. http://www05.abb.com/global/scot/scot271.nsf/veritydisplay/369669d5dd6
e8e6ec1257ba500293166/$file/70-78%202m315_EN_72dpi.pdf
7.
New electric vehicle technology packs more punch in smaller
package, Phys.org, 14 October 2014
CHAPTER THREE
3.0
3.1
CONSTRUCTION
BASIC DESIGNS OF AN INVERTER
In an inverter circuit, DC power is 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 alternating
current (AC) in the secondary circuit.
3.2 BLOCK DIAGRAM
The block diagram of a modified sine wave inverter is as below:
Pulse generator: this is the signal processing and control circuit that generates
the logic level control signals used to turn the power switch (semiconductor)
ON and OFF. There are many different circuits that one can adopt and use a
pulse generator or oscillator, in fact many ICs that need few external
components to be connected are available in the market for use. Such IC is
SG3524. The output of this circuit is either sent to the power switch (transistor)
directly the or via the driver circuit for amplification before it is sent to the
power switch as the case may be. Of course the choice depends on the designs
and / or transistor used as power switch[2].
Driver circuits : this circuits amplifies the signal from pulse generator to levels
required by the power switch and provides electrical isolation when required
between the power switch and the logic level signal processing circuit (pulse
generator).
Power switch: MOSFET is also known as switch. They are used here as the
switching devices. They should stand to withstand the high current of the
primary winding (low voltage side) of the transformer.
Transformer: transformer also belongs to output device. Transformers are of
various types: step up, step down, auto-transformer etc. They comprises of
primary and secondary windings which may not be isolated from each other.
The winding are electrically interlinked by a common magnetic circuit and
operate based on the principle of electromagnetic induction. The number of
turns of the primary and secondary winding is related to their voltages and
current with the following equation:
The size of the transformer is proportional to its power. For an ideal
transformer, the input power equals the output power; but in practice, there is no
loseless transformer [2].
3.3 MODIFIED SINE WAVE INVERTER CIRCUIT USING IC 3525,
WITH REGULATED OUTPUT AND LOW BATTERY PROTECTION
The post explains a simple modified sine wave inverter circuit using a single IC
SG 3525. The circuit is equipped with a low battery detection and cut off
feature,
and
an
automatic
output
voltage
regulation
feature[1].
THE DESIGN
From the circuit diagram above, the ICSG3525 is rigged in its standard PWM
generator/oscillator mode where the frequency of oscillation is determined by
C1, R2 and P1.
P1 can be adjusted for acquiring accurate frequencies as per the required specs
of the application.
The range of P1 is from 50Hz to 100Hz, here we are interested in the 50 Hz
value which ultimately provides a 50Hz across the two outputs at pin#11 and
Pin#14.
The above two outputs oscillate alternately in a push pull manner (totem pole),
driving the connected MOSFETS into saturation at the fixed frequency - 50 Hz.
The MOSFETS in response "push and Pull the battery voltage/current across the
two winding of the transformer which in turn generates the required mains AC
at the output winding of the transformer [1].
The peak voltage generated at the output would be anywhere around 300 Volts
which must adjusted to around 230V RMS using a good quality RMS meter and
by adjusting P2. [1]
P2 actually adjusts the width of the pulses at pin#11/#14, which helps to provide
the required RMS at the output.
This feature facilitates a PWM controlled modified sine waveform at the output.
AUTOMATIC OUTPUT VOLTAGE REGULATION FEATURE
Since the IC facilitates a PWM control pin-out this pin-out can be exploited for
enabling
an
automatic
output
regulation
of
the
system.
Pin#2 is the sensing input of the internal built in error Op-amp, normally the
voltage at this pin (non inv.) should not increase above the 5.1V mark by
default,
because
the
inv
pin#1
is
fixed
at
5.1V
internally.
As long as pin#2 is within the specified voltage limit, the PWM correction
feature stays inactive, however the moment the voltage at pin#2 tends to rise
above 5.1V the output pulses are subsequently narrowed down in an attempt to
correct and balance the output voltage accordingly.
A small sensing transformer TR2 is used here for acquiring a sample voltage of
the output, this voltage is appropriately rectified and fed to pin#2 of the IC1.
P3 is set such that the fed voltage stays well below the 5.1V limit when the
output voltage RMS is around 220V. This sets up the auto regulation feature of
the circuit. Now if due to any reason the output voltage tends to rise above the
set value, the PWM correction feature activates and the voltage gets reduced.
Ideally P3 should be set such that the output voltage RMS is fixed at 250V.
So if the above voltage drops below 250V, the PWM correction will try to pull
it upward, and vice versa, this will help to acquire a two way regulation of the
output,
A careful investigation will show that the inclusion of R3, R4, P2 are
meaningless, these may be removed from the circuit. P3 may be solely used for
getting
the
intended
PWM
LOW BATTERY CUT-OF FEATURE
control
at
the
output.
The other handy feature of this circuit is the low battery cut off ability.
Again this introduction becomes possible due to the in built shut down feature
of the IC SG3525.
Pin#10 of the IC will respond to a positive signal and will shut down the output
until the signal is inhibited.
A
741
opamp
here
functions
as
the
low
voltage
detector.
P5 should be set such that the output of 741 remains at logic low as long as the
battery voltage is above the low voltage threshold, this may be 11.5V. 11V or
10.5 as preferred by the user, ideally it shouldn't be less than 11V.
Once this is set, if the battery voltage tends to go below the low voltage mark,
the output of the IC instantly becomes high, activating the shut down feature of
IC1, inhibiting any further loss of battery voltage.
The feedback resistor R9 and P4 makes sure the position stays latched even if
the battery voltage tends to rise back to some higher levels after the shut down
operation is activated.
3.4
PARTS LIST
All resistors are 1/4 watt 1% MFR. unless otherwise stated.
R1, R7 = 22 Ohms
R2, R4, R8, R10 = 1K
R3 = 4K7
R5, R6 = 100 Ohms
R9 = 100K C1 = 1uF/50V MKT
C2, C3, C4, C5 = 100nF
C6, C7 = 4.7uF/25V
P1---P5 = 10 presets
T1, T2 = IRF540N
D1----D6 = 1N4007
IC1 = SG 3525
IC2 = LM741
TR1 = 8-0-8V.....current as per requirement
TR2 = 0-9V/100mA
Battery = 12V/25 to 100 AH
3.5
DESCRIPTION OF COMPONENTS USED
Components used in this work are described as below:
RECTIFYING DIODE
A rectifier is an electrical device that converts alternating current (AC), which
periodically reverses direction, to direct current (DC), which flows in only one
direction. The process is known as rectification. Physically, rectifiers take a
number of forms, including vacuum tube diodes, mercury-arc valves, copper
and selenium oxide rectifiers, semiconductor diodes, silicon-controlled rectifiers
and other silicon-based semiconductor switches. Historically, even synchronous
electromechanical switches and motors have been used. Early radio receivers,
called crystal radios, used a "cat's whisker" of fine wire pressing on a crystal of
galena (lead sulphide) to serve as a point-contact rectifier or "crystal detector".
Rectifiers have many uses, but are often found serving as components of DC
power supplies and high-voltage direct current power transmission systems.
Rectification may serve in roles other than to generate direct current for use as a
source of power. As noted, detectors of radio signals serve as rectifiers. In gas
heating systems flame rectification is used to detect presence of flame.
Because of the alternating nature of the input AC sine wave, the process of
rectification alone produces a DC current which, although unidirectional,
consists of pulses of current. Many applications of rectifiers, such as power
supplies for radio, television and computer equipment, require a steady constant
DC current (as would by produced by a battery). In these applications the output
of the rectifier is smoothed by an electronic filter to produce a steady current.
BATTERY
An electric battery is a device consisting of one or more electrochemical cells
that convert stored chemical energy into electrical energy. Each battery consists
of a negative electrode (anode) that holds charged ions, a positive electrode
(cathode) that holds discharged ions, an electrolyte that allows ions to move
from anode to cathode during discharge (and return during recharge) and
terminals that allow current to flow out of the battery to perform work.
Batteries are either primary (single-use or "disposable") that are used once and
discarded or secondary (rechargeable batteries) that are discharged and
recharged multiple times.
A battery, which is actually an electric cell, is a device that produces electricity
from a chemical reaction. Strictly speaking, a battery consists of two or more
cells connected in series or parallel, but the term is generally used for a single
cell. A cell consists of a negative electrode; an electrolyte, which conducts ions;
a separator, also an ion conductor; and a positive electrode. The electrolyte may
be aqueous (composed of water) or non-aqueous (not composed of water), in
liquid, paste, or solid form. When the cell is connected to an external load, or
device to be powered, the negative electrode supplies a current of electrons that
flow through the load and are accepted by the positive electrode. When the
external load is removed the reaction ceases.
A primary battery is one that can convert its chemicals into electricity only once
and then must be discarded. A secondary battery has electrodes that can be
reconstituted by passing electricity back through it; also called a storage or
rechargeable battery, it can be reused many times.
Batteries are made from many materials including various metals, carbon,
polymers and even air. The most common are lead-acid batteries used in
vehicles and lithium ion batteries used for portable electronics. Batteries come
in many shapes and sizes, from miniature cells used to power hearing aids and
wristwatches to battery banks the size of rooms that provide standby power for
telephone exchanges and computer centres.
LIGHT-EMITTING DIODE (LED)
A light-emitting diode (LED) is a semiconductor light source. LEDs are used as
indicator lamps in many devices and are increasingly used for general lighting.
Appearing as practical electronic components in 1962, early LEDs emitted lowintensity red light, but modern versions are available across the visible,
ultraviolet, and infrared wavelengths, with very high brightness.
When a light-emitting diode is switched on, electrons are able to recombine
with holes within the device, releasing energy in the form of photons. This
effect is called electroluminescence, and the color of the light (corresponding to
the energy of the photon) is determined by the energy band gap of the
semiconductor. An LED is often small in area (less than 1 mm2), and integrated
optical components may be used to shape its radiation pattern. LEDs have many
advantages
over
incandescent
light
sources
including
lower
energy
consumption, longer lifetime, improved physical robustness, smaller size, and
faster switching. However, LEDs powerful enough for room lighting are
relatively expensive, and require more precise current and heat management
than compact fluorescent lamp sources of comparable output.
Light-emitting diodes are used in applications as diverse as aviation lighting,
automotive lighting, advertising, general lighting, and traffic signals. LEDs
have allowed new text, video displays, and sensors to be developed, while their
high switching rates are also useful in advanced communications technology.
Infrared LEDs are also used in the remote control units of many commercial
products including televisions, DVD players and other domestic appliances.
LEDs are also used in seven-segment display [3].
CAPACITORS
A capacitor essentially consists of two conducting surfaces separate by a layer
of a insulating medium called dielectric. The purpose of a capacitor is to store
electric energy or electrostatic stress in the dielectric.
A parallel palate capacitor as drawn below, are plate is connected to the positive
of the power supply and the other is connected to the negative of the power
supply. It sis experimentally found that in the presence of an earthed plate B,
pate A is capable of withholding more charge than when B is not here.
When such capacitor is put across a battery there is a momentary flow of
electrons from A to B. As negatively charged electrons are withdrawn from A,
A becomes positively charge and as negatively charged electrons are withdrawn
from B, becomes negative.
Hence a potential difference is established between A and B the transient flow
of electrons gives rise to charging current. The charging current is maximum
when two plates are uncharged but it decreases and finally leases when potential
difference across the plate, slowly equals and is opposite to eh battery emf.
Symbolic representation of ceramic capacitor
General representation
MOSFET
MOSFET (metal-oxide semiconductor field-effect transistor, pronounced
MAWS-feht ) is a special type of field-effect transistor ( FET ) that works by
electronically varying the width of a channel along which charge carriers (
electron s or hole s) flow. The wider the channel, the better the device conducts.
The charge carriers enter the channel at the source , and exit via the drain . The
width of the channel is controlled by the voltage on an electrode called the gate
, which is located physically between the source and the drain and is insulated
from the channel by an extremely thin layer of metal oxide.
There are two ways in which a MOSFET can function. The first is known as
depletion mode . When there is no voltage on the gate, the channel exhibits its
maximum conductance . As the voltage on the gate increases (either positively
or negatively, depending on whether the channel is made of P-type or N-type
semiconductor material), the channel conductivity decreases. The second way in
which a MOSFET can operate is called enhancement mode . When there is no
voltage on the gate, there is in effect no channel, and the device does not
conduct. A channel is produced by the application of a voltage to the gate. The
greater the gate voltage, the better the device conducts.
The MOSFET has certain advantages over the conventional junction FET, or
JFET. Because the gate is insulated electrically from the channel, no current
flows between the gate and the channel, no matter what the gate voltage (as
long as it does not become so great that it causes physical breakdown of the
metallic oxide layer). Thus, the MOSFET has practically infinite impedance .
This makes MOSFETs useful for power amplifiers. The devices are also well
suited to high-speed switching applications. Some integrated circuits ( IC s)
contain tiny MOSFETs and are used in computers.
Because the oxide layer is so thin, the MOSFET is susceptible to permanent
damage by electrostatic charges. Even a small electrostatic buildup can destroy
a MOSFET permanently. In weak-signal radio-frequency ( RF ) work,
MOSFET devices do not generally perform as well as other types of FET[4].
Circuit symbols
A variety of symbols are used for the MOSFET. The basic design is generally a
line for the channel with the source and drain leaving it at right angles and then
bending back at right angles into the same direction as the channel. Sometimes
three line segments are used for enhancement mode and a solid line for
depletion mode.
The bulk connection, if shown, is shown connected to the back of the channel
with an arrow indicating PMOS or NMOS. Arrows always point from P to N, so
an NMOS (N-channel in P-well or P-substrate) has the arrow pointing in (from
the bulk to the channel). If the bulk is connected to the source (as is generally
the case with discrete devices) it is sometimes angled to meet up with the source
leaving the transistor. If the bulk is not shown (as is often the case in IC design
as they are generally common bulk) an inversion symbol is sometimes used to
indicate PMOS, alternatively an arrow on the source may be used in the same
way as for bipolar transistors (out for nMOS, in for pMOS).
Comparison of enhancement-mode and depletion-mode MOSFET symbols,
along with JFET symbols (drawn with source and drain ordered such that higher
voltages appear higher on the page than lower voltages):[4][5][6]
Pchannel
Nchannel
MOSFET
JFET
MOSFET
MOSFET enh (no bulk)
enh
dep
For the symbols in which the bulk, or body, terminal is shown, it is here shown
internally connected to the source. This is a typical configuration, but by no
means the only important configuration. In general, the MOSFET is a fourterminal device, and in integrated circuits many of the MOSFETs share a body
connection, not necessarily connected to the source terminals of all the
transistors.
CENTRE TAP TRANFORMER
In electronics, a centre tap is a contact made to a point halfway along a winding
of a transformer or inductor, or along the element of a resistor or a
potentiometer. Taps are sometimes used on inductors for the coupling of
signals, and may not necessarily be at the half-way point, but rather, closer to
one end. A common application of this is in the Hartley oscillator. Inductors
with taps also permit the transformation of the amplitude of alternating current
(AC) voltages for the purpose of power conversion, in which case, they are
referred to as autotransformers, since there is only one winding. An example of
an autotransformer is an automobile ignition coil. Potentiometer tapping
provides one or more connections along the device's element, along with the
usual connections at each of the two ends of the element, and the slider
connection. Potentiometer taps allow for circuit functions that would otherwise
not be available with the usual construction of just the two end connections and
one slider connection.
Volts centre tapped (VCT) describes the voltage output of a centre tapped
transformer. For example: A 24 VCT transformer will measure 24 VAC across
the outer two taps (winding as a whole), and 12 VAC from each outer tap to the
centre-tap (half winding). These two 12 VAC supplies are 180 degrees out of
phase with each other, thus making it easy to derive positive and negative 12
volt DC power supplies from them. The circuit symbol of a centre tap
transformer is as below:
INTEGRATED CIRCUITS
The integrated circuits used in these work are as follow:
SG3525 IC : the pin out functions of the IC SG3525 which is a regulating pulse
width modulator IC. Let's understand in details:
The main features of the IC SG3525 may be understood with the following
points:

Operating voltage = 8 to 35V

Error amp reference voltage internally regulated to 5.1V

Oscillator frequency is variable through an external resistor within the
range of 50Hz to 500 kHz.

Facilitates a separate oscillator sync pin out.

Dead time control is also variable as per intended specs.

Has an internal soft start feature

Shut down facility features a pulse by pulse shutdown enhancement.

Input under voltage shut down feature also is included.

PWM pulses are controlled through latching for inhibiting multiple pulse
outputs or generation.

Output supports a dual totem pole driver configuration.
SG3525 PIN-OUT DESCRIPTION
A practical implementation of the following pin-out data may be understood
through this INVERTER CIRCUIT
The IC SG3525 is a single package multi function PWM generator IC, the main
operations of the respective pin outs are explained with the following points:
Pin#1 and #2 (EA inputs): These are inputs of the built-in error amplifier of the
IC. Pin#1 is the inverting input while pin#2 is the complementary non-inverting
input.
It's a simple opamp arrangement inside the IC whose output controls the PWM
of the output. Thus these pin outs can be effectively used for correcting the
output voltage of a converter.
It may be done by applying a sample voltage from the output through a voltage
divider network to the non-inverting input of the opamp (pin#1). The fed
voltage should be adjusted to be just below the internal reference voltage value
when the output is normal.....now if the output voltage increases, the sample
voltage would also increase and at some point exceed the reference limit,
prompting the IC to take necessary corrective measures so that the voltage is
restricted to the normal level.
Pin#3 (Sync): This pin can be used for synchronizing the IC with an external
oscillator frequency. This is generally done when more than a single IC is used
and requires to be controlled with a common oscillator frequency.
Pin#4 (Osc. Out): It's the oscillator output of the IC, the frequency of the IC
may be confirmed at this pin out.
Pin#5 and #6(Ct, Rt): These are termed Ct, Rt respectively. Basically these pin
outs are connected with external resistors and capacitors for setting up
the frequency of the inbuilt oscillator stage or circuit. Ct must be attached with a
relevant capacitor while the Rt pin with a resistor for optimizing the frequency
of the IC.
Pin#7 (discharge): This pin out can be used for determining the dead time of the
IC, meaning the time gap between the switching of the two outputs of the IC (A
and B). A resistor connected across this pin and ground fixes the dead time of
the IC.
Pin#8 (Soft Start): This pin out as the name suggests is used for initiating the
operations of the IC in a soft manner instead of a sudden or abrupt jerk. The
capacitor connected across this pin and ground decides the level of soft
initialization of the output of the IC.
Pin#9 (Comp): This pin out is not so important, just needs to be connected with
the INV input of the error amplifier in order to keep the EA operations smooth
and without hiccups.
Pin#10 (Shutdown): As the name suggest this pin out may be used for shutting
down the outputs of the IC in an event of a circuit malfunction or some drastic
conditions. Logic high at this pin out will instantly narrow down te PWM pulses
to the maximum possible level making the output device's current go down to
minimal levels. However if the logic high persists for longer period of time, the
IC prompts the slow start capacitor to discharge, initiating a slow turn ON and
release. This pin out should not be kept unconnected for avoiding stray signal
pick ups [1].
Pin#11 and #14 (output A and output B): These are the two outputs of the IC
which operate in a totem pole configuration or simply in a flip flop or push pull
manner. External devices which are intended for controlling the converter
transformers are integrated with these pin outs for implementing the final
operations.
Pin#12 (ground): It's the ground pin of the IV or the Vss.
Pin#13(Vc): The output to A and B are switched via the supply applied to
pin#13. This is normally done via a resistor connected to the main DC supply.
Thus this resistor decides the magnitude of trigger current to the output devices.
Pin#15 (Vi): It's the Vcc of the IC, that is the supply input pin.
Pin#16: It provides the internal 5.1V reference for optional use. This pint must
be terminated with a low value capacitor to ground.
LM 741 : another IC used in this work is LM741, an op-amp which has two
inputs and one output which also called a comparator was used because of its
ability to compare two input voltages to give out one output voltage. The type
of an op-amp used in this circuit is LM741. The schematic diagram of a typical
IC is as below:
RESISTORS
A resistor in its definition is an electrical and electronic component that offers
opposition to the flow of electrical current. It also acts as a pre-load on the
voltage supplies to a system i.e. causes an initial voltage drop across it this is a
pre-load component. It is often called a bleeder resistor because it provides the
following advantages.
1.
It improves voltage regulation of he supply by acting as a pre-load on the
supply, thereby causing a initial voltage drop. In this way difference
between no-load and full-load is reduced hence improving the regulation
of the system.
2.
It improves filtering action
3.
It also provides safety to the technician handling the equipment when
power supply is switched off by providing a path for the filtering
capacitor to discharge through it, and that is why it is called bleeder
resistor. Without the resistor, the capacitor will retain its charges for quite
a very long time even when the power supply is switched off. This high
voltage is always a problem to electrical electronic engineers working on
equipments [3].
TYPES OF RESISTOR
 variable resistor
 rheostat resistor
 potentiometer resistor
 fixed resistor
Table 1.0: A table showing the resistor colour code
COLOUR
FIRST
SECOND
THIRD
BAND
BAND
BAND
TOLERANCE
BLACK
_
0
X10
BROWN
1
0
±1%
RED
2
00
±2%
ORANGE
3
000
YELLOW
4
0000
GREEN
5
00000
BLUE
6
000000
VIOLET
7
0000000
GREY
8
00000000
WHITE
9
000000000
GOLD
_
_
X0.1
±5%
SILIVER
_
_
X0.01
±10%
The symbol is as below:
3.4 HOW TO CHOOSE A RIGHT INVERTER AND BATTERY
Inverter is a type of electronic power generator which convert low voltage direct
current (DC) from a battery to a high voltage alternating current(AC).Power
failures can be really very frustrating at times, especially during the night time.
Inverters will help you to cope up with the blackout and do away with your
problems. Choosing a right inverter and battery is not very easy.
Load Calculation: First of all calculate your Power Consumption. This can be
done by adding up the Watts (W) of all loads(CFLs,TV..), to be powered by the
inverter. For example one 20W CFL + one 60W TV =20+60 =80W.
Inverter Capacity: Never select the Volt-Ampere (VA) rating of Inverter.
VA=Watts x Power Factor. Power factor value varies from 0.6 to 0.8.Note that
a 600VA rated inverter (with power factor 0.8) delivers approximately 480
Watts only!
Inverter Type: Square wave, Quasi- Sine wave and Pure Sine wave inverters
are now available. In practice, sine wave is the correct waveform on which all
electronic equipment, including televisions and computers are designed to run.
Battery Selection: Battery is the back bone of any inverter. Usually 12V
battery is used with home inverters. Tubular type storage batteries are
recommended for inverters because they are capable of long hours of
guaranteed backup time. Backup time is simply the number of hours for which
an inverter will be able to run the output electric load during power failure.
Batteries are available in different voltage and Ampere-Hour (Ah) ratings. Back
up time is mainly determined by this Ah rating of the battery. Tubular batteries
have higher capacity-to-size ratio. These types can be recharged faster and are
energised to deliver increased power and higher efficiency.
Backup Time: Formula to Calculate the backup time of Inverter is Ahx12V x
PFx0.9/Load VA hours. Where Ah is the ampere-hour capacity of the battery,
PF stands for the power factor of the inverter and load is the sum of VA ratings
of the electrical loads connected to the inverter [2].
3.5
HOW TO CHOOSE THE BEST INVERTER BATTERY
Every inverter has a battery. There are 2 types of inverter batteries

Sealed Maintenance-Free Battery (SMF)

Lead- Acid Battery
THE DOWNSIDE OF LEAD-ACID BATTERIES

Emit lead fumes which pollute the environment.

Breathing this polluted air affects the health drastically.

When charged, the lead-acid battery emits harmful fumes.

The inverter battery consists of lead plates that react with water and acid
while storing electricity. This charging process results in the heating of
the battery in turn resulting in the emission of the fumes.

The lead-acid inverter battery is more harmful in a closed or an airconditioned space as there is no fresh air to dilute the lead fumes. This
results in the recirculation of the dangerous fumes in the air.
PREFERENCE OF SEALED MAINTENANCE-FREE BATTERY

Completely sealed inverter battery.

This kind of battery is preferred for inverters.

They are safe to handle and lesser maintenance is required.

Since these inverter batteries are fully sealed, there is no emission of
fumes.

No water topping is required.

The charging time of the SMF battery is much lesser in comparison to the
lead-acid battery.
REFERENCES
1. http://circuitdiagramcentre.blogspot.com/2013/01/modified-sine-waveinverter-circuit.html
2. Dr. Ulrich Nicolai, Dr. Tobias Reimann, Prof. Jürgen Petzoldt, Josef Lutz:
Application Manual IGBT and MOSFET Power Modules, 1. Edition, ISLE
Verlag, 1998, ISBN 3-932633-24-5 PDF-Version
3. Yuhua Cheng, Chenming Hu (1999). " MOSFET classification and operation".
MOSFET modeling & BSIM3 user's guide. Springer. p. 13. ISBN 0-7923-85756.
4. U.A.Bakshi, A.P.Godse (2007). " The depletion mode MOSFET". Electronic
Circuits. Technical Publications. pp. 8–2. ISBN 978-81-8431-284-3.
CHAPTER FOUR
RESULT ANALYSIS
4.0
CONSTRUCTION PROCEDURE AND TESTING
In building this project, the following procedures were properly considered,
I.
Purposing of the entire materials / Components needed
ii.
Resistance check of the components bought with the help of ohmmeter
before making the necessary connection with the components
iii.
Drafting out a schematic diagram or how to arrange the materials /
components.
iv.
Testing the completed system to see if the design works and
v.
Finally, implementation of design of the project.
Having procured all the materials, I processed into the arrangement of the
components into the Vero board but we could not place the MOSFETs on the
bread board because the heat it emit when we load it, proper soldering of the
components then followed. The components were all soldered into the board
after which it was correctly confirmed done.
4.1
CASING AND PACKAGING
All the components were soldered onto the Vero Board. Then after that, a case
was gotten where the entire circuit was mounted follow by other external
components such as indicators, battery contacts and switch.
4.2
ASSEMBLING OF SECTIONS
Having provided the casing and having finished the construction of the sections
of this system, the assembling into the casing followed. The sections were
properly laid out and assembled into the casing where the general coupling and
linkages into the peripheral devices took place.
Finally; the indicator was brought out to indicate when the system is powered.
Switch was brought out for powering the system and battery contact was also
brought out where batteries are been connected.
4.3
TESTING OF SYSTEM OPERATION
In this stage, the system was due for testing and operation. The system
operation was tested where all its required performance was maintained.
First; batteries were connected and the system was powered through the
switch the LED displayed indicating ON. Then after we powered the system,
load of up to 1KW was loaded on the system with a which was allowed to
stay on the system for more than 20mins in other to monitor the amount of
heat MOSFETs will emit and to see whether the system will be able to carry
such load.
4.4
COST ANALYSIS
The expenditure made in purchasing all the components / materials and quantity
used in building this project is tabulated as show below:
MATERIAL
COMPONENTS
DESCRIPTION
QTY
UNITY
TOTAL
PRICE (N)
PRICE (N)
CHAPTER FIVE
5.1
CONCLUSION
In the context of renewable energy, a solar inverter is a device that will convert
DC battery/solar panel voltage into mains type AC power; suitable for use in
your home or business.
Without this conversion from DC to AC, special appliances or adapters often
need to be purchased - and DC appliances are often more expensive than their
AC counterparts.
The above two types of batteries are popular inverter batteries. Before buying
the inverter and the battery, ask your dealer which suits your requirement better.
5.2
RECOMMENDATION
This project is designed to be used in our homes, offices and industries where
the need for 24hrs supply is needed. And should be used and maintain by a
qualified personnel.
5.3
REFERENCES
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