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ELECTRICAL MACHINE &
CONTROL
ECT0313
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Chapter 1
Introduction
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Type of electrical machine
Static Machine
>Transformer
Step down voltage
Revolving Machine
> Motor
> Generator
Electrical to mechanical
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Magnetic Field
NS
S N
NS
Magnetic field flow fromNorth to South
Sample of Magnetic field
Magnetic field shown by
iron filling on paper
http://upload.wikimedia.org/wikipedia/en/a/a6/Solenoid.svghttp://upload.wikimedia.org/wikipedia/en/a/a6/Solenoid.svghttp://upload.wikimedia.org/wikipedia/en/a/a6/Solenoid.svghttp://en.wikipedia.org/wiki/Image:Magnet0873.pnghttp://en.wikipedia.org/wiki/Image:Magnet0873.pnghttp://upload.wikimedia.org/wikipedia/en/a/a6/Solenoid.svghttp://en.wikipedia.org/wiki/Image:Magnet0873.pnghttp://upload.wikimedia.org/wikipedia/en/a/a6/Solenoid.svg7/28/2019 Electrical Machine & Control
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Type of Magnet
Permanent Magnet
A permanent magnet retains its magnetism without anexternal magnetic field Inducing magnetism in steelresults in a permanent magnet but iron loses its
magnetism when the inducing field is withdrawn.
Electro Magnet
Electrical moving through a wire, the resulting field is
directed according to the "right hand rule." the reverse ofthe direction of actual movement of electrons, then themagnetic field will wrap around the wire in the directionindicated by the fingers of the right hand.
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Principles Involved
Solenoid Magnet
C
u
r
r
e
n
t
Bar MagnetM
a
g
ne
t
i
c
Fi
e
l
d
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Magnetic Flux Density
AB
B = Density
= FluxA= Area
N N
S S
Low DensityHigh Density
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Electromagnetism
Flux line of winding
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Corkscrew Principle
The rule predicts the direction of themagnetic field around a straight, current-carrying conductor.
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Imagine that you are using a right-handed
corkscrew, so that it moves forward in the
direction of the current flow. Then, thedirection of rotation of the handle is the
direction of the magnetic field lines around
the conductor.
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Corkscrew Principle
Anti clock
wise
Clock wise
Into
conductor
Out
conductor
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Corkscrew Principle
Denotes current flowing in
Denotes current flowing out
*I = Current
Conductor
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Hand Rule
Right hand rule
for GENERATOR
Left hand rule for
MOTOR
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Induction-Induced Voltage
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Lenzs Law
An induced current flows in a direction to create a magneticfield which will counteract the change in magnetic flux.
or An induced electromagnetic force generates a current that
induces a counter magnetic field that opposes the
magnetic field generating the current.
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Flemings Left Hand Rule
Also known as Fleming's Left Hand Motor Rule.
If you point your left forefinger in the direction of themagnetic field, and your second finger in the direction ofthe current flow, then your thumb will point naturally in thedirection of the resulting force.
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Right Hand Rule
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Torque , M
F = Force
r = RadiusN= Speed in r.p.m
r
r
FShaft
Pulley
N r.p.m
The turning or twisting moment of a force about an axis is called Torque
Torque, M = F x r newton-metres (N-m)
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Mechanical Power (Pmech)
Power = The ability to do work
60
2 NrFPP outmech
t
SFWork
rNS 2
F = ForceS = Distancet= Time (Second)
Whereby:M=Fr
60
2 NM
PP outmech
watt
And input power, Pin
Pin=I x V watt
Efficiency of machine@motor:
100
in
out
P
P
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Motors Rating Plate
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Chapter 2
DC Motors
Series, Shunt and Compound
Motors
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Construction of DC Machine
Frame orYoke
Terminal Box
Armature Core
Commutator
Field Pole
Field Winding
Armature Winding
Brushes
Shaft
DC M t R t ti
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DC Motor Rotation
A simple DC electric motor.
When the coil is powered,
a magnetic field is
generated around thearmature. The left side of
the armature is pushed
away from the left magnet
and drawn toward the right,causing rotation.
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DC Motor Rotation
The armature
continues to rotate.
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DC Motor Rotation
When the armature
becomes horizontally
aligned, the
commutator reversesthe direction of
current through the
coil, reversing the
magnetic field. Theprocess then repeats.
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