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Electrical Machine 2
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TABLE OF CONTENT
TITLE PAGE
TABLE OF CONTENT
CHAPTER ONE
DEFINITION OF SYNCHRONOUS MACHINE
IMPORTANT OF SYNCHRONOUS MACHINE/MOTOR
ADVANTAGE OF SYNCHRONOUS MACHINE/MOTOR
TYPE OF SYNCHRONOUS MACHINE
OPERATING PRINCIPLE OF SYNCHRONOUS GENERATOR
OPERATING PRINCIPLE OF SYNCHRONOUS MOTOR
DIFFERENCE BETWEEN STATOR & ROTOR
EXCITATION METHOD
DIRECT CONNECTED EXCITERS
CONTROL & PROTECTION OF ELECTRIC MOTORS
VARIABLE SPEED DRIVE SYSTEM
THYRISTOR
THYRATRON(IGNITRONS MERCURY)
THYRISTOR CONTROLLED DRIVE
NEED FOR CIRCUIT PROTECTION ADVANTAGE OF
THYRISTOR
CHAPTER TWO
ENERGY CONVERSION
USE OF ENERGY
ELECTROMECHANICAL ENERGY CONVERSION
ELECTROMECHANICAL ENERGY CONVERSION PRINCIPLE
ENERGY CONVERSION PRINCIPLE
ENERGY STORAGE
ACCUMULATOR (BATTERY)
ENERGY DENSITY
TYPE OF ENERGY STORED
CHAPTER THREE
CONSTANT CURRENT
IMPORTANT OF CONSTANT CURRENT
DIFFERENTIAL FORM (DIFFERENT INDUCTION MACHINE)
FARADAY LENZ LAW
MAXWELL STRESS
CHAPTER FOUR
TRANSFORMER
FUNCTION OF TRANSFORMER
TYPE OF TRANSFORMER CORES AND WINDING
TYPE OF TRANSFORMER
COMPARISON BETWEEN THE CORE TYPE & SHELL TYPE
TRANSFORMER
EQUIVALENT CCT OF A TRANSFORMER
ELECTROMAGNETIC
LIMITATION OF THE EQUIVALENT CIRCUIT &
APPROXIMATE
CONNECT 3 SINGLE PHASE TRANSFORMER FOR 3PHASE
OPERATION
STAR/STAR CONNECTION
ADVANTAGE OF STAR CONNECTION
DISADVANTAGE
STAR/DELTA CONNECTION
DIFFERENCE BETWEEN POWER & DISTRIBUTION
TRANSFORMER
IMPORTANCE OF POWER TRANSFORMER
FUNCTION OF POWER TRANSFORMER
DISTRIBUTION TRANSFORMER
FUNCTION OF DISTRIBUTION TRANSFORMER
EFFECT OF TEMPERATURE RISE ON TRANSFORMER
FUNCTION OF TRANSFORMER
METHOD OF COOLING TRANSFORMER
DISADVANTAGE OF COOLING METHOD
COOLING METHOD FOR OIL IMMERSED TYPE
TRANSFORMER
ADVANTAGE OF METHOD OF COOLING
ESSENTIAL FACTORS FOR NOISE PRODUCTION IN
TRANSFORMER
CHAPTER FIVE
NOISE EMISSION
CONSTRUCTIONAL FEATURES (NOISE EMISSION)
TAP CHANGING IN VOLTAGE CONTROL
VOLTAGE VARIATION IN POWER SYSTEM
PRINCIPLE OF REGULATING VOLTAGE
REASON FOR PROVIDING TAPPING
CAUSES OF HARMONICS IN TRANSFORMER
MAGNITUDE & FREQUENCY HARMONIC
OVER CURRENT & OVER CURRENT PROTECTIVE DEVICES
TYPE OF CURRENT FLOW IN AN ELECTRICAL CIRCUI
FUSE
CIRCUIT BREAKER
RELAY
TYPE OF ELECTROMECHANICAL RELAY
SELECTOR SWITCHES
INDICATOR LIGHT
LED INDICATOR
NON FLASHING LED INDICATOR LIGHT
PUSH BUTTON
TERM FOR THE PUSHING OF A BUTTON
CONTACTOR
ENERGY BALANCE
SYNCHRONOUS MACHINE CONSTITUTE OF BOTH
GENERATOR & MOTOR
CHAPTER ONE
ELECTRICAL MACHINE II
(EEC233
SYNCHRONOUS MACHINE (SYNCHRONOUS MOTOR)
DEFINITION:
A Synchronous machine is an a.c machine in which the rotor moves at a
speed which bears a constant relationship to the frequency of the
current in armature winding.
Note:
A synchronous machine is one of the important type of electric
machine.
IMPORTANT OF SYNCHRONOUS MACHINE/ MOTOR
a. It provides constant speed industrial (drives with)
b. It has a driving possibility of power factor correction.
ADVANTAGE OF SYNCHRONOUS MACHINES/ MOTOR
a. They are generally constructed in larger sizes.
b. Small size alternators are not economical. The best is to build alternators of very large sizes capable of generating 500MVA or
more.
TYPE OF SYNCHRONOUS MACHINE
The synchronous machine consists of two parts namely below:
1. The armature ( or stator) and,
2. The field magnet(ic) system (or rotor)
1. Armature (Stator): Is an iron ring, formed of lamination of
special magnetic iron or steel alloy having slots on it periphery to
accommodate armature conductor (stator).
- Note:
The whole structure is held in a frame which may be cast iron
or welded steel plate.
USE OF SLOT IN ARMATURE (STATOR)
a. The open slots are more commonly used because the coils can be
form – wound and insulated, before being placed in the slots
giving least expenditure and more satisfactory winding method.
b. The slots facilitate the removal and replacement of effective coils.
c. Number of slots per pole per phase should be large to give
sinusoidal generated emf.
- Note:
General the number of slots per pole per phase is three to
four for small machine and more than five for large
machine.
SMALL MACHINE: Using three to four slot per pole per phase
LARGE MACHINE: Using more than five slots per pole phase.
2. FIELD MAGNET SYSTEM (ROTOR): It provide the generation of
alternating voltage similar to those of a d.c machine which is
supplied with direct current.
- Note:
A small d.c generator is installing for the purpose of making the
alternator self – contained and independent of other sources of
supply.
Generator: It is called the exciter. Exciter is coupled to the
engine driving the alternator.
Exciter armature: Is completed directly to the alternator field
winding, usually without any kind of controlling resistance.
- Note:
The resistance of the exciter load is constant for the successful
operation of alternator.
The field magnet system of the alternator is rotated with in the
armature ring and is known as rotor.
The exciting current is supplied to the rotor through two slip – rings and
brushes. There a polarity of the field produced is alternately:
a. North (N)
b. South (S)
USE OF EXCITER IN FIELD MAGNET SYSTEM (ROTOR)
i. Both exciter and synchronous generator have the same power
rating of 0.5 to 1%.
ii. Its voltage rating is usually between 125 to 250volt.
- Note:
In case of large synchronous machine of the power rating of
few hundred 19w, the excitation need become very large and
the problem of supplying such amount of power through high
speed sliding contacts become acute.
OPERATING PRINCIPLE OF SYNCHRONOUS GENERATOR
The operating principle of a synchronous machine/ generator is
fundamentally the same as that of d.c machine.
- Note:
But unlike the latter, in the synchronous machine, there is no
need to rectify the time varying emf, which is induced in the
armature winding.
OPERATING PRINCIPLE OF SYNCHRONOUS MOTOR
The action of a synchronous motor is the same to that of a three –
phase, two – pole synchronous machines.
- Note:
The rotor has two poles and the stator has two poles per phase.
The rotor rotate in clockwise direction when the S – pole attract
the N – pole.
In practice it is usual to have salient pole on the rotor. But the
armature winding is house in slots in the concave periphery of
the stator.
DIFFERENT BETWEEN STATOR AND ROTOR
a. The polarity of stator pole is reversed while
b. Rotor: the polarity of rotor pole remained the same.
- Note:
At this instant the rotor S – pole is repelled by the stator, S
pole being similar nature.
Question: How does repelling occur between the rotor S – pole and
stator S – pole.
- EXCITATION METHOD: In a d.c motor, the field and armature
both are supplied from d.c supply mains.
Synchronous motor the field structure is to be energized by direct
current.
Alternator the armature winding is connected to a three – phase a.c
supply mains
- Note:
D.c excitation may be provided either from an exciting plant d.c
system or if no direct current is available.
DIRECT CONNECTED EXCITERS
Are frequently found on high speed motors (high loaded vehicle)
CONTROL AND PROTECTION OF ELECTRIC MOTOR:
Electric motors are employed in a very large power range from a few
watts to thousand kilowatts.
- Note:
Many applications require very precise position adjustment (as
in robotics). In many applications optimum performance and
efficiency are the main concern.
VARIABLE SPEED DRIVE SYSTEM: This help in optimization of
process so as to reduce investment cost, operational cost and
maintenance costs.
- Note:
Energy savings is another big advantage of variable speed
drives.
Thyristors: This is capable of handling large currents has
revolutionalized the field of electric power control.
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