ABSTRACT
Uninterruptible
power supplies (UPS) are used to provide power when regular utility power is
unavailable. Although they are commonly used for providing power in
remote locations or emergencies, this is not because they are the same as
auxiliary power units, emergency power units or standby generators.
Unlike the aforementioned power sources, UPS provides an immediate and
continuous supply of power to a device, hence protecting it from power
interruption and allowing time for auxiliary or emergency powers, to kick in
equipment to be safely shut down or utility power restored.
The major aim of this was to design a system
which will be able to convert battery voltage(12v) to 220v, which is equivalent
to wall outlet and secondly able to charge the battery.
The chapter one of this work, gives the
over-view of UPS, it’s importance, uses, and application and some of its
special features like its ability to correct frequency instability and many
more.
Secondly, this work dealt with all components
used in the construction of the device, there working condition and uses. Some
basic abstract phenomenon were also treated like wave forms and electronic
switching.
The chapter three, basically dealt on all
electrical measuring instrument used in and on the device, how they are used,
why and where.
The fourth chapter explains how the components
where assembled into section and the sectional connection used to form the
device.
The last chapter is a simple conclusion with
honest recommendation.
TABLE OF CONTENT
CERTIFICATION - - - - - - - - i
DEDICATION - - - - - - - - ii
ACKNOWLEDGEMENT - - - - - - iii
ABSTRACT - - - - - - - - iv
TABLE OF CONTENT - - - - - - - v
CHAPTER ONE
1.1 INTRODUCTION - - - - - - 1
1.1 AIMS AND
OBJECTIVES - - - - - 8
1.2 SCOPE OF THIS
PROJECT - - - - - 8
1.3 AVAILABILITY OF
DESIGN MATERIALS - - 8
CHAPTER TWO
2.1 LITERATURE
REVIEW - - - - - 9
2.1 WHAT IS A UPS? - - - - - - 9
2.2 WAVEFORMS - - - - - - - 9
2.2.1 SQUAREWAVE - - - - - - - 9
2.2.2 MODIFIED SINE WAVE - - - - - 10
2.2.4 TRUE SNE WAVE - - - - - - 10
2.3 RESISTORS - - - - - - - 11
2.4 CAPACITORS - - - - - - - 12
1.4.1 CAPACITANCE - - - - - - - 13
2.4.2 ELECTROLYTIC CAPACITOR - - - - 14
2.4.3 PLASTIC FILM,
CERAMIC NAD MONOLITHIC
CAPACTOR - - - - - - - - 14
2.5 DIODE - - - - - - - - 16
2.5.1 MOUNTING A DIODE - - - - - - 18
2.5.2 CHARACTERISTICS CURVES OF A DIODE - - 18
2.5.3 IDEAL DIODE - - - - - - - 19
2.5.4 LIGHT EMITTING DIODE - - - - - 19
2.5.5 DIODES AS RECTIFIERS - - - - - 21
2.5.5.1 HALF-WAVE RECTIFIER - - - - - 22
2.5.5.2 FULL-WAVE,
CENTER-TAP RECTIFIE - - 23
2.5.6 FILTERS - - - - - - - - 24
2.6 TRANSISTORS - - - - - - - 26
2.6.1 TRANSISTOR AS A SWIRCH - - - - 26
2.6.2 MOSFETS - - - - - - - - 28
2.6.2.1 SUPER-HIGH INPUT IMPEDANCE - - - - 29
2.6.2.2. SETBACKS IN MOSFETS - - - - - 29
2.6.2.3 ITS FLEXIBILITY - - - - - - 30
2.7 OPTO-COUPLER - - - - 30
2.7.1 OPTO-COUPLER
CHARACTERISTICS - - 31
2.7.2 ITS INPUT - - - - - - - - 32
2.7.3 ITS OUTPUT - - - - - - - 32
2.7.4 ITS OPERATING
MODE - - - - - 33
2.8 THE SG3524
INTEGRATED CIRCUIT - - - 33
2.8.1 OPERATING
PRINCIPLE OF SG3524 - - - 34
CHAPTER THREE
3.0 METHODOLOGY - - - - - - 36
3.1 ELECTRONIC
WORKBENCH - - - - 37
3.2 GALVANOMETER - - - - - - 37
3.3 OSCILLOSCOPE - - - - - - - 38
3.4 VOLTMETER - - - - - - - 39
3.5 AMPMETER - - - - - - - 41
3.6 WATTMETER - - - - - - - 43
3.7 MULTIMETERS - - - - - - - 44
CHAPTER FOUR
4.0 DESIGN AND
CONSTRUCTION METHODS - - 46
4.1 COMPLETE CIRCUIT
DIAGRAM OF A UPS - - 47
4.2 STAGE BY STAGE
DESIGN - - - - - 47
4.2.1 OSCILLATOR
SECTION - - - - - 50
4.2.2 DRIVER/SWITCHING
SECTION - - - - 51
4.2.3 THE OUTPUT
SECTION - - - - - 52
4.2.4 THE CHANGEOVER
SECTION - - - - 53
4.2.5 THE LOW BATTERY CUT-OFF SECTION - - 54
4.3 COMPONENT
JUSTIFICATION - - - - 55
4.3.1 MOSFETS - - - - - - - - 55
4.3.2 SG3524 OSCILLATOR - - - - - - 55
4.3.3 OPTO-COUPLER - - - - - - - 56
4.3.4 RESISTORS - - - - - - - 56
4.4 TEST AND ANALYSIS - - - - - - 56
4.4.1 TESTING AND
SETTING THE INVERTER - - 57
4.5 BILL OF
ENGINEERING CONSTRUCTION - - 60
CHAPTER FIVE
5.0 CONCLUSION - - - - - - - 62
5.1 RECOMMENDATION - - - - - - 62
REFERENCES - - - - - - - 63
LIST
OF FIGURES
Fig 1. Offline/ standby diagram - - - 5
Fig 2. A capacitor - - - - - 12
Fig 3. Capacitors - - - - - - 15
Fig 4. Circuit Symbol of a diode - - - - 17
Fig 5. A Led - - - - - - 20
Fig 6. Half-wave rectifier - - - - 21
Fig 7. Half wave Rectifier - - - - 22
Fig 8. A full-wave centre tap rectifier - - 24
Fig 9. A Simple filter - - - - - 25
Fig 10. Transistor as a Switch - - - - 27
Fig 11. A Transistor as a Switch - - - 27
Fig 12. A Mosfet - - - - - - 28
Fig 13 Opto-Coupler’s Input - - - - 32
Fig 14. Inputs and output circuit of an opto-coupler - 32
Fig 15. A Digram of a Voltmeter - - - 41
Fig 16. Diagram of Amp meter - - - - 42
Fig 17 Diagram of a Wattmeter arrangement - 43
Fig 18 Oscillator Circuit - - - - - 49
Fig 19 Pre-Driver Section - - - - 51
Fig 20 Change over circuit of the UPS - - 53
Fig 21 Low battery cut-off circuit - - - 54CHARACTERISTICS CURVES OF A DIODE CITORS
CHAPTER ONE
1.10 INTRODUCTION
As
blackouts roll through power-starved communities, the threat to you and your
computer is not the lack of electricity, but the change in power. When the
lights are off and you are about to start any industrial or computer-based
projects, all your efforts will be
wasted. Even when your system acts as a server, a sudden shutdown could disrupt
the processing of many others. You can make your work immune to the intransigence
of rolling blackouts and protect against many other types of unexpected power
disturbances. Your secret weapon is the uninterruptible power supply or
uninterruptible power source. Commonly called the UPS, this devices is
a cleaver threefold package-a set of battery, an inverter that transforms the
low-voltage direct current of the batteries into the standard alternating
current equivalent to your wall outlet, and a battery changer that assures that
reserve power storage system (the batteries) with interfaces to mach it to
utility power and your computer system. A
UPS differs from an auxiliary emergency power system or standby generator in that it will provide instantaneous
or near-instantaneous protection from input power interruptions by means of one
or more attached batteries and associated electronic circuitry for low power
users, and or by means of diesel generators and flywheels for high power users. While
not limited to protecting any particular type of equipment, a UPS is typically
used to protect computers, data centers, telecommunication equipment or other
electrical equipment where an unexpected power disruption could cause injuries,
fatalities, serious business disruption and/or data loss. UPS units range in
size from units designed to protect a single computer without a video monitor (around
200 VA rating) to large units powering entire data centers, buildings, or even
cities. The
UPS is designed to project against changes, specifically a temporary loss of
electrical supply.
This
project focuses on conversion of AC to DC and from DC to AC power inverters,
which aim to efficiently transform a DC power source to a high voltage AC
source, similar to power that would be available at an electrical wall outlet.
Inverters are used for many applications, as in situations where low voltage DC
sources such as batteries, solar panels or fuel cell must be converting
electrical power from a car battery to run a laptop, TV or cell phone.
DC and AC Current
In the world today there are currently two
forms of electrical transmission, Direct Current (DC) and Alternating Current
(AC), each with its own advantages and disadvantages. DC power is simply the application
of a steady constant voltage across a circuit resulting in a constant current.
A battery is the most common source of DC transmission as current flows from
one end of a circuit to the other. Most digital circuitry today is run off of
DC power as it carries the ability to provide either a constant high or constant
low voltage, enabling digital logic to process code executions. Historically, electricity
was first commecially transmitted by Thomas Edison, and was a DC power line.
However, this electricity was low voltage, due to the inability to step up DC
voltage at the time, and thus it was not capable of transmitting power over
long distances.
V =IR
P=IV
= I2R
As can be seen in the equations above, power
loss can be derived from the electrical current squared and the resistance of a
transmission line. When the voltage is increased, the current decreases and
concurrently the power loss decreases exponentially; therefore high voltage
transmission reduces power loss. For this reasoning electricity was generated
at power stations and delivered to homes and businesses through AC power.
Alternating current, unlike DC, oscillates between two voltage values at a specified
frequency, and it’s ever changing current and voltage makes it easy to step up
or down the voltage. For high voltage and long distance transmission situations,
all that is needed to step up or down the voltage of the transformer. Developed
in 1886 by William Stanley Jr., the transformer made long distance electrical
transmission using AC power possible.
Electrical
transmission has therefore been mainly based upon AC power, supplying most
Nigerian homes with a 220 volt AC source. It should be noted that since 1954
there have been many high voltage DC transmission systems implemented around
the globe with the advent of DC/DC converters, allowing the easy stepping up
and down of DC voltages. Like DC power, there exist many devices such as power
tools, radios and TV’s that run off of AC power.
It is therefore
crucial that both forms of electricity transmission exist; the world cannot be powered
with one simple form. It then becomes a vital matter for there to exist easy
ways to transform DC to AC power and vice versa in an efficient manner. Without
this ability people will be restricted to what electronic devices they use
depending on the electricity source available. Electrical AC/DC converters and
DC/AC inverters allow people this freedom in transferring electrical power
between the two.
Offline / standby
Inverters and Applications
Power inverters are devices which can convert
electrical energy of DC form into that of AC. They come in all shapes and
sizes, from low power functions such as powering a car radio to that of backing
up a building in case of power outage. Inverters can come in many different
varieties, differing in price, power, efficiency and purpose. The purpose of a
DC/AC power inverter is typically to take DC power
supplied by a battery, such as a 12 volt car
battery, and transform it into a 220 volt AC power source operating at 50Hz,
emulating the power available at an ordinary household electrical outlet. Power
inverters are used today for many tasks like powering appliances in a car such
as cell phones, radios and televisions. They also come in handy for consumers
who own camping vehicles, boats and at construction sites where an electric
grid may not be as accessible to hook into. Inverters allow the user to provide
AC power in areas where only batteries can be made available, allowing
portability and freeing the user of long power cords. However, most UPS units are also capable in varying
degrees of correcting common utility power problems like:
1.
Power
failure: defined as a total loss of input voltage.
2.
Surge:
defined as a momentary or sustained increase in the mains voltage.
3.
Sag:
defined as a momentary or sustained reduction in input voltage.
4.
Spikes,
defined as a brief high voltage excursion.
5.
Noise,
defined as a high frequency transient or oscillation, usually injected into the
line by nearby equipment.
6.
Frequency
instability: defined as temporary changes in the mains frequency.
7.
Harmonic
sinusoidal waveform distortion: defined as a departure from the ideal expected
on the line
Factors
to consider when designing an inverter is
·
The input voltage
·
The output voltage
·
The frequency of the oscillators
·
The rating of the load to be powered by the inverter
·
The ampere range of the charging unit
·
The cost of the construction
·
The relative importance of the inverter
·
The ampere ranger of the charging unit
·
The cost of the construction
·
The relative importance of the inverter at
that time specification
·
D.C input voltage (12V-24V)
·
A.C output voltage (220v-240v)
·
Output frequency (50Hz-60Hz)
·
Output power (450-550)
·
Maximum power (550)
·
Continuous output power (500)
·
Overload shutdown
·
Low voltage shutdown
1.11 AIMS AND OBJECTIVES
The objective
of this project may be summarized as listed below
·
To give a brief introduction on what UPS.
·
To highlight the basic components used in the
construction of a UPS and their functions .
·
To describe the way in which there are designed
and
·
Finally to highlight its application and relevance
in the society
1.12 SCOPE
OF THIS PROJECT
This project
research encompasses the features of the variety of the components used in the construction
of a UPS, their limitations and favourable working conditions, and the application
of inverter in different field.
1.13 AVAILABILITY
OF DESIGN MATERIALS
Materials
used in the construction of this UPS are readily available in electronic stores
across the country and are also very affordable depending on the rating of the
UPS to be constructed.
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