Antony Evodius Malauri 21
Antony Evodius Malauri 21
Antony Evodius Malauri 21
SENIOR PROJECT I
Project Title: DESIGN OF OVER AND UNDER VOLTAGE
PROTECTION SYSTEM FOR MILLING MACHINE AT
KAGERA SUGAR CO.LTD
Project Type: PROBLEM SOLVING
January,2019
DECLARATION
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ABSTRACT
When grinding mills at camp number seven in Kagera sugar company limited,
there some different problems that normally occur on the motor which is used to
run such milling machine. The motor is operated in a manner that leads different
breakdowns, and theses breakdowns leads to cut services to workers, wasting
time and results to unnecessary maintenance cost of machine. The purpose of this
project is to provide the protection system that will avoid or permanently stop
those motor breakdowns. The method used to accomplish this project is through
collecting relevant data, designing the required circuit, selecting proper
components for the circuit, building the required circuit, testing the required
circuit. The objective of the project is met. The project can be further advanced
to ensure system reliability being more automated.
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ACKNOWLEDGEMENT
iv
TABLE OF CONTENTS
DECLARATION..................................................................................................................... II
ACKNOWLEDGEMENT .................................................................................................... IV
INTRODUCTION ................................................................................................................ 1
METHODOLOGY .................................................................................................................. 4
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3.2 PROPOSED SYSTEM ...................................................................................................... 7
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LIST OF SYMBOLS
vii
LIST OF TABLES
viii
LIST OF FIGURES
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INTRODUCTION
Now -a-days, greater demands have been placed on the transmission network,
and these demands will continue to rise because of increasing number of
nonutility generators and great competition among utilities themselves. Increased
demand on transmission, absence of long term planning, and the need to provide
open access to generating companies and customers have resulted in less security
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and reduced quality of supply. Several types of power enhancement devices have
been developed over the years to protect equipment from power disturbances, but
these devices can also fail or malfunction sometimes. Thus the need for more
security is always wanted and that’s why I decided to come with this idea, that
will generally provide the security of milling machine that control motor from
being damaged again.
Due to the fact that, the voltage fluctuations from substation around this area and
voltage surges due to the lightning and switching impulses tends to cause these
voltage abnormalities (over voltage and under voltage). Therefore this comes the
big problem since it cuts services to workers, wasting time and results to
unnecessary maintenance cost of machine.
1.3 Objectives
The objectives of this project is divided into two categories
i. Main objective
ii. Specific objectives
2
Now the general or main objective of my project is to provide protection system
for milling machine that will avoid motor breakdowns.
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METHODOLOGY
2.0 Introduction
This chapter gives explanations of various procedures which were taken in order
to fulfill the expected objectives of the project. The following are explanations of
some approaches, on performing my project the following are methodologies that
I will use to accomplish my project
i. Literature review
ii. Data collection
iii. Data analysis
iv. System design
v. Circuit simulation
vi. Design implementation and testing.
vii. Report writing
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2.4 Data Analysis
This process will involve evaluation of data collected, with the aim of obtaining
useful information which will help in drawing conclusion on what to be used in
system design. Data analysis will aid in deciding the type of software and
hardware to be used.
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3.0 Literature review
Through doing the literature review, the following aspects should be considered
This case discusses about the existing system and the proposed system whereby
it discusses the previous relevant works, also comprises the expiations and
definitions of the devices, different techniques involved in the project completion
and the explanations of other people(authors) whom are aware to the device
concern.
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This is shown to the block diagram of the existing system in (figure. 1)
AC MOROR FOR
SWITCHING
VOLTAGE MILLING
MECHANISM
SUPPLY MACHINE
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POWER LOAD SWITCHING
SUPPLY (MOTOR) MECHANISM
POWER REGULATING
CONVERSION
DEVICE
PRESETING COMPARATING
UNIT UNIT
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The transformer actually steps down and converts 230-volt power to 30 volts or
less. Sometimes transformers have more than one voltage connection point,
called a multi-tap transformer. Transformers are constructed of two tightly wound
coils encased in a metal cover. Since the two coils are placed closely together in
the case, current flows through the primary winding (the 120-volt side) and as it
does this, it produces a magnetic flow. This flow produces current in the second
coil winding (secondary winding) that produces the low voltage output. The
primary coil has more windings than the secondary coil. Because of the reduced
number of windings in the secondary coil, the voltage output is much less.
Secondary windings usually produce voltages between 8 and 24 volts. An
electronic low voltage transformer also contains an electronic device, called an
inverter, which allows the size of the low voltage transformer to be substantially
smaller. An inverter and a small transformer make up the main components of
what we normally call an electronic low voltage transformer (Mohammad Shah
Alamgir and Sumit Dev, “Design and Implementation of an Automatic Voltage
Regulator with a Great Precision and Proper Hysteresis”, Vol.75, year 2015)
b. Bridge Rectifier:
A diode bridge is a device that changes Alternating Current (AC) to Direct
Current(DC). A diode bridge is an arrangement of four (or more) diodes in a
bridge configuration that provides the same polarity of output for either
polarity of input. When used in its most common application, for conversion
of an alternating current (AC) input into direct current a (DC) output, it is
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known as a bridge rectifier. A bridge rectifier provides full-wave rectification
from a two wire AC input, resulting in lower cost and weight as compared to
a rectifier with a 3-wire input from a transformer with a center-tapped
secondary winding. The essential feature of a diode bridge is that the polarity
of the output is the same regardless of the polarity at the input.
c. Voltage Regulator
A voltage regulator is an electrical regulator designed to automatically
maintain a constant voltage level. A voltage regulator is an example of a
negative feedback control loop. It may use an electromechanical mechanism,
or electronic components. Depending on the design, it may be used to regulate
one or more AC or DC voltages. Electronic voltage regulators operate by
comparing the actual output voltage to some internal fixed reference voltage.
Any difference is amplified and used to control the regulation element in such
a way as to reduce the voltage error. This forms a negative feedback control
loop; increasing the open-loop gain tends to increase regulation accuracy but
reduce stability (avoidance of oscillation, or ringing during step changes).
There will also be a trade-off between stability and the speed of the response
to changes.
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If the output voltage is too low (perhaps due to input voltage reducing or load
current increasing), the regulation element is commanded, up to a point, to
produce a higher output voltage - by dropping less of the input voltage (for
linear series regulators and buck switching regulators), or to draw input
current for longer periods (boost-type switching regulators); if the output
voltage is too high, the regulation element will normally be commanded to
produce a lower voltage.
However, many regulators have over-current protection, so that they will
entirely stop sourcing current (or limit the current in some way) if the output
current is too high, and some regulators may also shut down if the input
voltage is outside a given range.
d. zener diode
A Zener diode is a type of diode that permits current not only in the forward
direction like a normal diode, but also in the reverse direction if the voltage is
larger than the breakdown voltage known as "Zener knee voltage" or "Zener
voltage".A conventional solid-state diode will not allow significant current if
it is reverse-biased below its reverse breakdown voltage. When the reverse
bias breakdown voltage is exceeded, a conventional diode is subject to high
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current due to avalanche breakdown. Unless this current is limited by circuitry,
the diode will be permanently damaged. In case of large forward bias (current
in the direction of the arrow), the diode exhibits a voltage drop due to its
junction built
in voltage and internal resistance. The amount of the voltage drop depends on
the semiconductor material and the doping concentrations. (Silicon institute
of technology, “Power quality problem identification and protection scheme
for low voltage system”, Orissa, November 2010.)
e. comparator
Is the device that compares two voltages or currents and outputs a digital
signal indicating which is large. It has two analogy input terminals and one
binary output and output is usually ideal.
The comparator consists of four independent, high gains; internally frequency
compensated operational amplifiers which were designed specifically to
operate from a single power supply over a wide range of voltages. Operation
from split power supplies is also possible and the low power supply current
drain is independent of the magnitude of the power supply voltage.
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f. Relay
A relay is an electrically operated switch. Many relays use an electromagnet
to
operate a switching mechanism mechanically, but other operating principles
are also used. Relays are used where it is necessary to control a circuit by a
low-power signal (with complete electrical isolation between control and
controlled circuits), or where several circuits must be controlled by one signal
A simple electromagnetic relay consists of a coil of wire surrounding a soft
iron core, an iron yoke which provides a low reluctance path for magnetic flux,
a movable iron armature, and one or more sets of contacts (there are two in
the relay pictured). The armature is hinged to the yoke and mechanically
linked to one or more sets of moving contacts. It is held in place by a spring
so that when the relay is de-energized there is an air gap in the magnetic
circuit. In this condition, one of the two sets of contacts in the relay pictured
is closed, and the other set is open. Other relays may have more or fewer sets
of contacts depending on their function.
The relay in the picture also has a wire connecting the armature to the yoke
When the coil is energized with direct current, a diode is often placed across
the coil
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to dissipate the energy from the collapsing magnetic field at deactivation,
which would otherwise generate a voltage spike dangerous to semiconductor
circuit components. Some automotive relays include a diode inside the relay
case. Alternatively, a contact protection network consisting of a capacitor and
resistor in series may absorb the surge. If the coil is designed to be energized
with alternating current (AC), a small copper "shading ring" can be crimped
to the end of the solenoid, creating a small out-of-phase current which
increases the minimum pull on the armature during the AC cycle.
(http://www.allaboutcircuits.com/vol_2/chpt_9/6.html)
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DATA COLLECTION
4.0 DATA COLLECTION
The data were collected from source of problem by considering the number of
workers living in the area of camp number seven at Kagera sugar company
limited.
The workers’ residence of that area are arranged systematically as there are 18
barracks and every barrack has at least 48 rooms, then the maximum workers
living that place are about 864.All these people depends on the milling machine
for grinding their mill for food purpose. On collecting data, I basically dialed with
specifications and how motor for milling purpose can be rated on protecting its
breakdowns so as to save the large number of people against the temporary
hunger and other catastrophe.
ITEMS SPECIFICATIONS UNITS
AC VOLTAGE SUPPLY THREE PHASE
(400-415)/50Hz
MOTOR FOR VOLTAGE 415V
MILLING MACHINE POWER RATED 22.5KW/22.9HP
CURRENT 38A
AMBIENT
TEMPERATURE 40˚C
OVERVOLTAGEAND
UNDERVOLTAGE ON THREE PHASE 400<V<415
MILLING MACHINE
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OVERVOLTAGE AND
UNDERVOLTAGE THREE PHASE 400V +_6%
TOLERANCE OF
MAINS (TANESCO)
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