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PREPARATORY NOTE
FOR
QUIZ, TEST & EXAMINATION
PASS WITHOUT TEAR
...
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 CIRCUIT
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
...
Note:
A synchronous machine is one of the important type of electric
machine
...
It provides constant speed industrial (drives with)
...
It has a driving possibility of power factor correction
...
They are generally constructed in larger sizes
...
Small size alternators are not economical
...
TYPE OF SYNCHRONOUS MACHINE
The synchronous machine consists of two parts namely below:
1
...
The field magnet(ic) system (or rotor)
...
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)
...
USE OF SLOT IN ARMATURE (STATOR)
a
...
b
...
c
...
- Note:
General the number of slots per pole per phase is three to
four for small machine and more than five for large
machine
...
2
...
c machine which is
supplied with direct current
...
c generator is installing for the purpose of making the
alternator self – contained and independent of other sources of
supply
...
Exciter is coupled to the
engine driving the alternator
...
- Note:
The resistance of the exciter load is constant for the successful
operation of alternator
...
The exciting current is supplied to the rotor through two slip – rings and
brushes
...
North (N)
b
...
ii
...
5 to 1%
...
- 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
...
c machine
...
OPERATING PRINCIPLE OF SYNCHRONOUS MOTOR
The action of a synchronous motor is the same to that of a three –
phase, two – pole synchronous machines
...
The rotor rotate in clockwise direction when the S – pole attract
the N – pole
...
But the
armature winding is house in slots in the concave periphery of
the stator
...
The polarity of stator pole is reversed while
b
...
- Note:
At this instant the rotor S – pole is repelled by the stator, S –
pole being similar nature
...
- EXCITATION METHOD: In a d
...
c supply mains
...
Alternator the armature winding is connected to a three – phase a
...
c excitation may be provided either from an exciting plant d
...
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
...
In many applications optimum performance and
efficiency are the main concern
...
- Note:
Energy savings is another big advantage of variable speed
drives
...
Thyratrons: (Ignitrons, mercury): These are rectifiers magnetic
amplifiers, motor generator sets have all been replaced by solid
state circuit employing semiconductor diodes and thyristors
...
c and a
...
- Note:
In 1960 a
...
c power for direct
control of drive
...
Initially saturable reactors were employed in conjunction with
high power silicon rectifier for d
...
Nowadays thyristors are extensively used for a
...
c
conversion
...
The response of the thyristor control device is faster
- Note:
As it eliminate the time lag introduced by the inductances of
the generator field and the armature
...
It has high efficiency of the control system due to low voltage drop
across thyristor
3
...
4
...
Simple and reliable operation
...
- Note:
In practice energy is a quantity that provides the capacity to
perform work
...
Energy is transferable to a different location or object but it
cannot be created or destroy
...
It may be used in natural processes
b
...
Heating refrigeration
ii
...
It may used for performing mechanical work to operate machines
...
ELECTROMECHANICAL ENERGY CONVERSION:
It means either the conversion of electric energy into mechanical or vice
versa for, an example
...
Electric generator: it transforms mechanical energy to electric
energy
...
REVERSIBLE: it means the energy can be transferred back and
forth between the electrical and the mechanical system
...
ENERGY CONSERVATION PRINCIPLE
a
...
Energy balance equation = function (energy input, energy/
output, energy stored + total energy dissipated)
c
...
d
...
ENERGY STORAGE: This is the captures of energy produced at
one time uses at a later time
...
a
...
c
...
e
...
g
...
i
...
Some technology provide short – term energy storage which
other endure for much longer
...
- Note:
Common examples of energy storage are listed below:
a
...
b
...
C storage tank
...
I C E STORAGE TANK: It store ice frozen by cheaper energy at
night to meet peak day time demand for cooling
...
Buried over
time and were then converted into these fuels food which is
made by the same process as fossil fuels
...
- Note:
It may also be used for energy per unit mass
Energy per unit volume has the same physical units as pressure
and in many circumstances is a synonym
...
Change in volume determines the difference between internal
gas pressure and external gas pressure
...
TYPE OF ENERGY STORED
There are many different type of energy stored in materials and it takes
a particular type of reaction to release each type of energy
...
b
...
d
...
Both of which derive energy from the building energy of
nuclei
Chemical reaction: this used by animal to derive energy from
food and by automobile to derive energy from gasoline
...
CHAPTER THREE
CONSTANT CURRENT
A constant current also know as steady current, time –
independent current, and stationary current
...
c) that does not
change its intensity with time
...
If the load is constant, a steady, current can be obtained
through a constant voltage source
...
If the load is varying, a steady current can be obtained
through a constant current supply source
...
IMPORTANT OF CONSTANT CURRENT
a
...
A high series resistance is sufficient to light an LED
- Note:
Sometime the design needs to guard against high current (or
risk burning at the LED)
c
...
d
...
DIFFERENTIAL FORM (DIFFERENTIAL INDUCTION MACHINE)
Differential induction machine is a special type of induction machine
having two shaft protected from the two ends of a single stator
...
1st law: emf is directly proportional to the change in flux ∆ᵠ
2nd law: emf is greatest when the change in time ∆t is smallest – that
is, emf is inversely proportional to ∆t
...
The unit being in volt
The minus sign in faraday law of induction is very important
...
- Note:
(The direction given by the minus sign) of the emf is so
important that it is called Lenz law (1809 + _ 1865)
Faraday was well aware of the direction but Lenz stated it so
clearly that he is credited for its discovery
MAXWELL STRESS: This is symmetric second order tensor used
in classical electromagnetism to represent the interaction between
electromagnetic forces and mechanical momentum
...
- Note:
Transformer can raise or lower the voltage in a circuit but with
a corresponding decrease or increase in current
...
TYPE OF COILS
a
...
Magnetically coil
- Note:
A transformer is a device that transfer electric power from one
circuit to another it does so without change of frequency
FUNCTION OF TRANSFORMER
1
...
3
...
It
It
It
It
transfer electric power from one circuit to another
does so without change of frequency
accomplishes this, by electromagnetic induction
link two electric circuit by mutual inductor
...
of turns in primary
N2 = no
...
c input in Hz
- Note:
From the fig the core flux increase from its zero value to
maximum value ᵠm in one quarter of the cycle is in ¼
Average rate of change of flux
=ᵠm/1/4f =4fᵠmwb/s
...
If flux ᵠ varies sinusoid ally then rms value of induced emf
is obtained by multiplying the average value with form
factors
...
11
Therefore rms value of emf/turn = 1
...
44fᵠmvolts
...
44fᵠm volt
...
44fN2ᵠm = 4
...
Estimate the number of turns in each winding,
if the maximum flux is 0
...
Solution:
Using the transformer emf equation we get
E1= 4
...
44 * 50 * N1* 0
...
44 * 50 * N2 * 0
...
TYPE CLASSIFICATION
a
...
Shell type
Another recent development is spiral core or wound core type or spiral
core transformer
...
1
...
Distribution transformer
...
- Note:
Each limb carries one half of the primary winding and one half
of the secondary winding so as to reduce the leakage reactance
to the minimum possible
...
HV WINDING: The Hv winding is wound over the Lv winding
away from the core in order to reduce the amount of insulation
material required
...
- Note:
In shell type construction the coils are wound are the central
limb of a three limb core
...
It gives better support against
electromagnetic forces between
current carrying conductors
...
The shell type construction is
commonly
used
for
small
transformer where a square or
rectangular core cross - section
suitable
for
economic
consideration
...
- Note:
The later offers an additional advantage of permitting
visual inspection of coil in the case of fault and ease of
repair at substation site
...
EQUIVALENT CCT OF A TRANSFORMER:
This is a device that helps in determining the behavior of various
operating condition of transformer
...
- Note:
The induced emf in primary winding E1 is applied (primary
voltage V1 less primary voltage drop)
...
After
transferring the secondary voltage current and impedance
to primary side equivalent circuit is reduced to that of
show below
...
LIMITATION OF THE EQUIVALENT CIRCUIT AND
APPROXIMATE
Equivalent circuit of the transformer:
CONNECT THREE SINGLE PHASE TRANSFORMER FOR
THREE PHASE OPERATION (I
...
STAR/ STAR (ϒעO OR ϒУ6 ) CONNECTION: This type of
transformer is most economical for small current and high
voltage transformer
...
The amount of insulation and no of turn per phase is minimum
because phase voltage = 1/√3 of line voltage
...
There is no phase displacement between the primary and
secondary
c
...
DISADVANTAGE
a
...
b
...
STAR/ DELTA (ϒɖ or עɗii) CONNECTION: This type of
transformer connection is used principally where the voltage to be
stepped down as for example at the end of a transmission line
...
7% of the line voltage and therefore is some saving in the
cost of insulation
...
- Note:
They may be single phase or 3 – phase, 3wire delta/delta or
delta/star connected and of voltage rating 220/11KV or in high
voltage range
...
They are put in operation during load hours i
...
b
...
They are arranged in bank and can be drawn in parallel with other
unit or disconnected at will
...
They are designed to have maximum efficiency at or near full load
b
...
It usually make used of flux density of 1
...
7 T having percent
impedance ranging from 6 – 18% and regulation of 6 – 10%
...
They may be self oil cooled, forced air/ water cooled
...
- Note:
They are kept in operation all the 24hours a day whether they
are carry by any load or not
...
FUNCTION OF DISTRIBUTION TRANSFORMER
a
...
b
...
c
...
d
...
e
...
- Note:
Such transformers have percentage impedance of 4 – 5% and
voltage regulation of 4 – 8%
...
7T
...
- Note:
The term temperature is caused by power loss which is
converted into heat
...
Losses due to resistance of the winding while passing current
through winding (proportional to square of current X resistance)
...
Hysteresis losses in the core are due to reversed in magnetic field
leaving some remnant of magnetism
...
c
...
- Note:
This lead to heat generation in the core and winding of the
transformer leading to temperature rise in the transformer
FUNCTION OF TRANSFORMER
1
...
temperature 120oC assuming normal
temperature as 40oC)
...
ENERGY TRANSFORMER: Play a crucial role in the power
distribution system
...
The Secondary winding
b
...
The core
...
2
...
b
...
They transform electric current down the line
...
- Note:
Distribution transformer are used for distribution purpose
While
Power transformers are employed within the power distribution
industry
...
S/NO
1
2
3
4
5
6
7
POWER TRANSFORMER
The step-down application of
power transformer is composed
of 400KV, 200KV, 110KV,
66KV and 33KV
...
They are bigger as compared to
distribution
transformers;
installation process is very
complicated and challenging
...
It is at the rate of times
free of value and disturbance
...
It incurs irons and copper losses
within the day due to continuous
passage of large current within
the transformer
...
They are utilized in transmission
network of high voltage
...
DISTRIBUTION TRANSFORMER
They are utilized for lower voltage
distribution network as a means of
end user connectivity
...
3KV, 6
...
They are much smaller and higher
when
compared
to
power
transformer installation process is
simple
...
Irons losses only take place within
24hours
...
It operate 75% of full load, they
are time dependent unlike the
power transformer
...
It very low
...
It jobs is to bring down and
lessen the mass core
...
The flux density is somewhat low
It might have one primary and one
divided
...
They are connected in the This is customarily used in 3 –
substation
end
of
the phase step – down purpose the
transmission line in star – delta connection here is in delta star
...
Its performance is usually It performance is judged from all
judged by commercial efficiency day to day efficiency
...
up with one input and output
pin
...
They have higher criterions
...
It have no voltage fluctuation, Distribution
transformers
are
they provide continuous power intended for residential supply most
supply free of disturbance and of the time they can have consistent
values
...
smooth with least fluctuate
...
AIR NATURAL (AN) COOLING: For small output (5 – 10KVA)
the external surface is sufficient to dissipate the heat produced by
losses
...
Instrument transformers except for those for the highest
voltage are ordinarily of dry type
...
2
...
- Note:
In this method of cooling heat dissipation is improved by a
continuous blast of air forced through the core and winding
...
[
USES
a
...
- Note:
Usually transformers are placed over an air chamber in which
the air is maintained under pressure by blowers
...
a
...
- Note:
A filter to remove the dust from the cooling air thus preventing
it deposits in the transformer ducts it desirable
...
The cooling methods used for oil immersed type transformer are:
a
...
- Note:
Here the assembly of core and winding is immersed in an
insulating oil contained in an iron tank
...
Oil in contact with heating parts rises and its
placed is taken by cool oil from the bottom
...
Freedom from dust
2
...
Easy extraction of heat from inner most parts as oil is better
conductor of heat
...
Good amount of natural convection current since oil has high
efficiency of value expansion
...
Oil natural air force (or) cooling: in this case also the assembly of
core and winding is immersed in an insulating oil
...
The air is force over external surface such as the case tubes and
radiators usually by means of fans mounted external to the
transformer
...
c
...
- Note:
The heated water is cooled in a spray pond or cooling tower
...
d
...
- Note:
This method proves very useful when the coolers have to be
well removed from the transformer
...
OIL FORCED AIR FORCED (OFB) COOLING: This method of
cooling the oil is cooled in external heat exchanger using air blast
produced by fans
...
f
...
SOURCES OF VIBRATION AND NOISE INSIDE TRANSFORMER
Under not load condition the hum( noise) caused by energized power
transformers originates in the core
...
ESSENTIAL FACTORS FOR NOISE PRODUCTION IN
TRANSFORMER
1
...
Mechanical vibration caused by the laminations depending up on
the tightness of clamping size gauge, associated structural part
etc
...
Mechanical vibration of tank wells
4
...
CONSTRUCTION FEATURES (NOISE EMISSION)
Such as clamping bolts, proportions and dimension of the step in plate,
width, tightness of damping and uniformity of plates
1
...
2
...
3
...
VOLTAGE VARIATION IN POWER SYSTEM: In a normal
phenomenon owing to the rapid growth in industries and
distribution network
...
- Note:
The transformer output voltage and so the consumer terminal
voltage may be controlled by providing tapping on the
transformer windings
...
e
Example:
1
...
2
...
REASON FOR PROVIDING TAPPING
Tapping are usually provided on the high winding (voltage) due to the
following reason
...
The no of turns in the Hv winding is large and it allows fine and
smooth control of the output voltage
...
Tap is not possible except an integral number of turn and may
cause difficulty with HV winding
- Note:
260V phase winding with 13V per turn cannot be tapped closer
than 5%
c
...
d
...
CAUSES OF HARMONICS IN TRANSFORMERS
The effects of harmonics current in transformer
a
...
b
...
Magnetic interference with communication circuit and protective
gears
...
Increased dielectric stress
b
...
Resonance between the inductance of the transformer winding
and the capacitance of feeder to which these are connected
...
OVER CURRENT AND OVER CURRENT PROTECTIVE DEVICES
...
- Note:
Unconnected over current can cause serious safety hazards and
easily damage to electrical equipment and property
...
Fuse and typical circuit breakers respond and open for both low
and high values of over current flow
...
TYPE OF CURRENT FLOW IN AN ELECTRICAL CIRCUIT
There are three (3) basic type of current flow in an electrical circuit
1
...
Abnormal over current flow with a value of up to 10time the
normal current flow
...
Abnormal over current flow with a value more than 10 time the
normal current flow is know as short current or taut current flow
...
FUSES: This contain an element that act like a conductor for the
normal current flow
...
When the over load or fault
condition that caused the fuse to open is connected a proper
replacement fuse restores the original dependable protection
...
CIRCUIT BREAKER: This contain resettable latch which act like
an on – off switch for the normal flow
...
Once the over current problem has been corrected the indicator
level can be reset into the ON position, which automatically/
simultaneously resets the latch inside the circuit breaker
3
...
- Note:
Electromechanical relay: contact are opened or closed by a
magnetic force
...
TYPE OF ELECTROMECHANICAL RELAY
There are three (3) types of electromechanical relays
...
GENERAL PURPOSE RELAY: These are electromechanical
switches, usually operated by a magnetic coil
...
c or d
...
These relay are economical easy to replace and allow a wide
range of switch configuration
...
MACHINE CONTROL RELAY: This is also operated by a
magnetic coil
...
3
...
SELECTOR SWITCHES: This is a control device that is operated
by turning knob instead of pushing a button d
INDICATOR LIGHT: Indicator lights are highly useful for
automotive marine and industrial panels
- Note:
LED indicator: are available in
a) Red
b) Green or
c) Amber option in both styles
Non Flashing Led Indicator Light:
They are also available in blue
...
PUSH BUTTON: This is a sample switch mechanism for
controlling some aspect of a machine or a process
...
TERM FOR THE PUSHING OF A BUTTON
a)
b)
c)
d)
e)
Pressing
Depressing
Mashing
Slapping
Hitting and
f) Punching
- Note:
Push button has been utilized in calculators, push button
telephones, kitchen appliance and various other mechanical
and electronic device home and commercial
...
ENERGY BALANCE: The principle of conservation of energy
states that energy is neither created nor destroyed
...
Synchronous motor as well as synchronous generators
...
c system
has some advantage over a d
...
Example
No = 120f/1 or F = PNS/120
Where:
Ns= synchronous speed (in rpm)
F = supply frequency
P = No of poles of the machines
...
Law of electromagnetic induction and
b
...
THE END
This note is prepared by Henry precious which
is the own of it, for student all over the world,
who is determined to do exploit in academic
(quiz’s, tests and exams) despised the challenge
to come out from school with good grade
...
Success is sure in using this material I assure
you of that
...
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material is a summary of lecture note, note
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