CHAPTER ONE
1.0 INTRODUCTION
The
idea behind a UPS (Uninterruptible
Power Supply) is pretty obvious from the name, in addition to filtering,
enhancing or modifying the unity power, special circuit and batteries are used
to prevent electrical machines from losing power during a disruption (blackout
or voltage sag brownout). The units are all called different names depending on
the next design, but all fit into general category of backup power.
Before delving into details of how an
uninterruptible power supply works, let’s take a quick look of the basic of the
type of equipment. An electrical device plugged into the wall or into a surge
suppressor has only one source of power. If there is a blackout, the
electricity is out an the device obviously goes off immediately. A UPS changes this equation by providing its
equipment two source of power.
UPS
are designed so that there is one source of power normally used called the
primary power source and another source that kicks in if the primary is
disrupted called the secondary power source. The power from the wall is always
one of those sources and the battery contains within the UPS is the other. A switch is used to control each
of these powers and the equipment of any given time. The switch changes from
the primary of the secondary when it detects the primary has gone out. It
switches back from the secondary power the primary power, source has returned.
Contrary to what you might think, the
wall A.C power is not always the primary power source and the battery the
secondary source. Which source is primary and which is secondary depends on the
type of UPS. Therefore, circuit is
provided with this UPS to convert
AC power to DC to change the battery. A device called an invert is also
provided to change the battery stone DC electricity to AC to run your
equipment.
Furthermore, those components of the
uninterruptible power supply and other one discussed in details in the section
covering the various parts of the UPS.
The size of the UPS is primary
dictated by the size of the time your equipment can run on battery power
switching down, higher units not only can power equipment for more time they
can also handle a large total demand for power.
1.1 BACKGROUND
In
this section we will take a brief look of the various parts that are made up of
typical UPS. Focus is on small
units more commonly used for home and smaller business.
INVERTER
PART: That is inversion circuit, all UPS
include cone circuit that manipulates electricity converting it from AC power
produced by your utility company to DC power stored in the battery and back
again for use by your equipment. The inverter section converts a DC voltage
into an AC voltage with the help of an oscillator. This section also consists
of two stages of switching circuits which comprises of a power transistor
connected i in the common emitter configuration.
Since
the oscillator has two outputs each of the switching circuits is coupled to the
two outputs of the oscillator respectively. The two outputs one explained in
detail in subsequent chapter. The exact type, netune size and quality of the
circuit depend on the type of UPS
and more specifically the model you have chosen. As with all things the better
the unit, the high the quality of the components and as with all thins quality
is often corrected to price but not always.
Voltage
conversion and inversion, the process of changing AC to DC is called conversion
(actually, this is an imprecise term because conversion refers to changing our
DC voltage to another and other thing as well, but it will do for our purpose
device that perform this process are called converters, but are also sometimes
called adapter, and if being used for changing batteries they are often just
called charger. Charging DC into AC is the opposite process and is called
inversion. A device that does this is of cause called an inverter.
The
Automatic control unit, this unit provides all the required control needed to
meet up the aim of the entire system. Controls like automatically
"ON" of the system into NEPA and hence obtaining a NEPA line jamming
is encountered by properly carrying out the exchange system.
Meanwhile,
in bringing background information it is important to have a look of the block
diagram of a complete UPS. A very
basic block diagram of a UPS,
showing basic design of to power sources, controlled by a switch is drawn
above.
1.2 AIMS
The
general objective of the system is to provide efficiency in the use of power
suppliances by ensuring continuous availability of power supply in the absence
of NEPA. Uninterruptability of the system made it possible to eliminate all
suspense arising from NEPA outage during the execution of an important and
urgent assignment requiring
The use of power especially with
computer PC system. The fundamentals purpose of a UPS
is to provide an interrupted source of power for the equipment it protects.
For
better production of the system it is advisable to operate the system of a
fully charged condition of the battery. Also the problem due to excessive
heating could be eliminated by the use of a hat sink with a thick and a large
surface area for sufficient absorption of heat. This project is rated 200W of
220V and 50H2. It is expected at all condition favourable to carry load of
higher power factor of the approximation of the power stated. Loads of low
power factor are always not helpful overloading is not potent to provide zero
changeover time and has audio helper which indicates mains fail and battery
discharge. It provides 100% protection against live noise, swages all radio
frequency interference.
1.3 SCOPE
A UPS makes it possible to provide a clean reliable
supply of alternating current free of says or surges in the line voltage
frequency variation, spikes and transient. UPS
systems achieves this by rectifying the standard mean supply, using the direct
current to charge the standby battery and to produce clean alternating current
by passing through an inverter and filter system. It has zero change over time
and has audio beeper which indicates mains foil and battery discharge. It
provides 100% protection against line noise spikes surges and audio frequency
interference.
1.4 DEFINITION
(i) Inverter Unit: This unit converts a DC voltage into an AC
voltage with the help of a oscillator.
(ii) Automatic Control Unit: This provides all the required control
needed to meet up the objectives of the whole system.
(iii) Battery
Unit: This is a secondary cell
unit capable of storing enough DC voltage of which is later converted to AC
voltage.
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