Electrical Machine & Control

7/28/2019 Electrical Machine & Control

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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
http://en.wikipedia.org/wiki/Image:PoleMountTransformer02.jpg


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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.svg


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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magnetism when the inducing field is withdrawn.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.
http://en.wikipedia.org/wiki/Image:Electric_motor_cycle_1.png


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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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http://en.wikipedia.org/wiki/Image:3phase-rmf-320x240-180fc.gif

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Electrical Machine & Control