CONSTRUCTION OF SINGLE PHASE INDUCTIVE LOAD
AMALA JULIET MOKWUGWO
julietmokwugwo5@gmail.com
DEPARTMENT OF COMPUTER ENGINEERING
SCHOOL OF ENGINEERING TECHNOLOGY
FEDERAL POLYTECHNIC OKO
ABSTRACT
This project is titled construction of single phase inductive load.
Load affects the performance of circuits with respect to output
voltages or currents, such as in sensors, voltage sources, and
amplifiers. An inductive load converts current into a magnetic field.
Inductive reactance resists the change to current, causing the
circuit current to lag voltage. Examples of devices producing
reactive/inductive loads include motors, transformers and chokes.
The single-phase motors are more preferred over a three-phase
induction motor for domestic, commercial applications because
form utility, only single-phase supply is available. A single phase
induction motor is similar to the three phase squirrel cage
induction motor except there is single phase two windings (instead
of one three phase winding in 3-phase motors) mounted on the
stator and the cage winding rotor is placed inside the stator which
freely rotates with the help of mounted bearings on the motor shaft.
The construction of a single-phase induction motor is similar to the
construction of a three-phase induction motor.
Keywords: Inductive motor, Single Phase, squirrel cage induction
motor, Load, Power factor
CHAPTER 1
1.1 Introduction/Background of Project
Load describes the amount of power (amps) consumed by an
electrical circuit or device. Load affects the performance of circuits
with respect to output voltages or currents, such as in sensors,
voltage sources, and amplifiers (Karady, 2013). In electricity, the
phase refers to the distribution of a load. Single-phase power is a
two-wire alternating current (ac) power circuit. Mains power outlets
provide an easy example: they supply power at constant voltage,
with electrical appliances connected to the power circuit collectively
making up the load. When a high-power appliance switches on, it
dramatically reduces the load impedance. An inductive load
converts current into a magnetic field. Inductive reactance resists
the change to current, causing the circuit current to lag voltage.
Examples of devices producing reactive/inductive loads include
motors, transformers and chokes. According to Kundur (2003),
Inductive loads are more complex loads where the current and
voltage are out of phase, and therefore there is a secondary voltage
created that moves in opposition to the supply voltage. Because of
this, they tend to create power surges when turned on or off. They
include motor loads (horsepower loads) and magnetic (coils,
electromagnetic) loads.
Basically inductive loads are those loads which consume reactive
power (Q). In laymen’s language all the loads which have rotating
part are inductive loads like fans, motors, etc. As the current lags
the voltage the inductive load is present. There for more the
inductive load more will be power consumed. No load is pure
inductive as every inductive load consists of some part of resistor.
The single-phase motors are more preferred over a three-phase
induction motor for domestic, commercial applications because
form utility, only single-phase supply is available.
A single phase induction motor is similar to the three phase squirrel
cage induction motor except there is single phase two windings
(instead of one three phase winding in 3-phase motors) mounted on
the stator and the cage winding rotor is placed inside the stator
which freely rotates with the help of mounted bearings on the motor
shaft. The construction of a single-phase induction motor is similar
to the construction of a three-phase induction motor. While 3-phase
induction motors are mainly used in commercial and industrial
applications, there are cases where the use of a 3-phase power
supply is not possible and subsequently single-phase induction
motors (SPIM)s are adopted. The application field range of SPIMs is
impressive; they are extensively used in numerous industrial,
agricultural,
and
residential
applications
such
as
washing
machines, compressors, refrigerating and kitchen appliances, heatcirculating pumps, power tools, fans, sewing machines, vacuum
cleaners, grain dryers, etc. In general, there is a strong demand for
SPIMs, and it can be said without exaggeration that literally
millions of them are produced every year.1
The main feature of SPIMs is that if they are put into operation by
means of a rotating magnetic field, then their rotor will continue to
rotate even if the coils are supplied with single-phase current,
which does not create a rotating magnetic field.2 A SPIM that is
equipped with a permanent capacitor (capacitor-run type) and that
is usually designed for power outputs of 0.25 HP up to 1.5 HP
presents the following characteristics and/or advantages over other
types (thus, it will be the subject of study in this work): (1) it is less
expensive and more reliable as it does not need any centrifugal
switch, (2) it has a low starting to rated torque ratio, (3) it needs
less starting current than any other design of SPIM and withstands
a large load cycle, (4) it works silently while serving its load, (5) it
enables adjusting its speed by changing the voltage of the power
supply, (6) it is easily reversible (can stop and change rotation
direction) because of the low torque, (7) it has a relatively high
efficiency and high-power factor.3
As the power requirements of single load systems are usually small,
all our homes, offices are supplied with a single–phase A.C. supply
only. To get proper working conditions using this single-phase
supply, compatible motors have to be used. Besides being
compatible, the motors have to be economical, reliable and easy to
repair. One can find all of these characteristics in a single phase
induction motor readily.
1.2 Statement of the Problem
At the same time and although the design and the use of SPIMs has
evolved throughout the decades, there are still some factors related
to optimization and efficiency, which have remained critical to
engineers. A review in the relevant technical literature shows that
there are several research efforts concerning the broad aspect of
SPIM performance improvement, eg, previous studies.
There is a need not only for a simple, reliable, and cost-effective
single phase inductive load design procedure but also for a
“multifeature” selection approach that can be easily followed to any
application at the early stage of the design. Thus, the aim of this
project tend to construct a single phase inductive load effective, and
multicriteria approach as a decision aid tool, dealing with the
appropriate design and selection of a certain SPIM topology among
others, which meets the basic industrial standards regarding the
motor’s frame sizes on one hand and satisfies certain specification
criteria on the other.
1.3 Method of Solution
The proposed approach begins with a preliminary design phase
described that is based mainly on classical motors output
coefficient concept while the diameter and length of the motor are
modified according to the corresponding standards frame size. A
systematic evaluation of (1) stator/rotor slots combination and (2)
the rotors bars and rings material is performed. After an
appropriate design is reached, a simple but effective selection
strategy is also proposed, and a parametric analysis of the required
permanent capacitor to be installed is investigated, to validate the
appropriateness of the selected SPIM topology.
1.4 Aims and Objectives
The aim of this project is to construct a single phase inductive load.
The objectives include:
1. To understand the basic principles of operation of a single
phase inductive load.
2. To provide efficiency, steadiness in the use of electrical
appliances or devices.
3. To determine the starting methods of single-phase induction
motors
4. To analyze capacitor split-phase motors (or) Capacitor start
motors.
1.5 Justification
This project construction of single phase inductive load is of great
important because of its efficiency to power electronic appliances at
residences. Power factor correction (PFC) is common in commercial
and industrial applications. A need to extend the application of PFC
will increased with the dwindling natural resources used for power
generation and also exceeding energy demand, hence more efficient
power usage and motor system are required at the forefront of
utility's demand side management system.
1.6 Report Layout
This project is arranged in five different chapters. Chapter one
focused on the introduction, background, statement of problem,
and scope of the project. Chapter two is on literature review; it
reviewed related works. Chapter three is the methodology which
focused on systematic and theoretical analysis of the methods
applied in the project. Chapter four is the results and discussion
while chapter five is the summary and conclusion of the project
report.
CHAPTER 2
LITERATURE REVIEW
According to Fuchs (2009), protection apparatus prevent damage to
the most vulnerable part of the motor, the insulation on the stator
windings. For low-power motors, a temperature-sensitive device is
often mounted inside the motor and used to switch off the electric
supply if the temperature reaches its limiting safe value. With larger
motors, temperature-sensitive detectors may be imbedded at one or
more locations in the stator windings.
An induction motor or asynchronous motor is an AC electric motor
in which the electric current in the rotor needed to produce torque
is obtained by electromagnetic induction from the magnetic field of
the stator winding. An induction motor can therefore be made
without electrical connections to the rotor. An induction motor's
rotor can be either wound type or squirrel-cage type.
Single-phase induction motors are used extensively for smaller
loads,
such
as
household
appliances
like
fans.
Although
traditionally used in fixed-speed service, induction motors are
increasingly being used with variable-frequency drives (VFD) in
variable-speed service. VFDs offer especially important energy
savings opportunities for existing and prospective induction motors
in variable-torque centrifugal fan, pump and compressor load
applications. Squirrel-cage induction motors are very widely used in
both fixed-speed and variable-frequency drive applications.
2.1 Induction motor
Induction machines are the most frequently-used type of motor
used in residential, commercial, and industrial settings so far. In an
induction motor, the electric current in the rotor needed to produce
torque is obtained via electromagnetic induction from the rotating
magnetic field of the stator winding.
An induction motor has 2 main parts; the Stator and Rotor. The
Stator is the stationary part and the rotor is the rotating part. The
Rotor sits inside the Stator. There will be a small gap between rotor
and stator, known as air-gap. The value of the radial air-gap may
vary from 0.5 to 2 mm. An induction motor therefore does not
require
mechanical
commutation,
separate-excitation
or
self-
excitation for all or part of the energy transferred from stator to
rotor, as in universal, DC and large synchronous motors. An
induction motor’s rotor can be either wound type or squirrel-cage
type.
The two types of induction motor is Single phase induction motor
and three phase induction motor.
Single phase induction motor
The single-phase induction motor does not self-start. The main
winding carries a sporadic current when the motor is attached to a
single-phase power supply. It is quite logical that the cheapest,
most reduced upkeep sort engine ought to be used most regularly.
Based on their way of starting, these machines are categorized
differently. Those types are shaded pole, split phase, and capacitor
motors. Also, capacitor motors are started with capacitor, run with
capacitor and have permanent capacitor motors.
In these single-phase types of motors the start winding can have a
series capacitor and a centrifugal switch. When the supply voltage
is applied, current in the main winding holdups the supply voltage
because of the main winding impedance. And current in the start
winding leads/lags, the supply voltage depending on the starting
mechanism impedance. The angle between the two windings is
sufficient phase difference to provide a rotating magnitude field to
produce a starting torque. The point when the motor reaches 70%
to 80% of synchronous speed, a centrifugal switch on the motor
shaft opens and disconnects the starting winding.
Applications of Single-phase Induction Motors
The
single-phase
induction motors are used in low power
applications. These motors are widely used in domestic and
industrial applications. Some of the applications are mentioned
below:
 Pumps
 Compressors
 Small fans
 Mixers
 Toys
 High speed vacuum cleaners
 Electric shavers
 Drilling machines
Three-Phase Induction Motor:
Being self-starting, the three-phase induction motors use no start
winding, centrifugal switch, capacitor, or other starting device.
Three-phase AC induction motors have various uses in commercial
and industrial applications. The two types of three-phase induction
motors are- squirrel cage and slip ring motors. The features which
make the squirrel cage motors widely applicable are mainly their
simple design and rugged construction. With external resistors, the
slip ring motors can have high starting torque.
Three-phase induction motors are used extensively in domestic and
industrial appliances because these are rugged in construction
requiring little to no maintenance, comparatively cheaper, and
require supply only to the stator.
Applications of Three Phase Induction Motor
 Lifts
 Cranes
 Hoists
 Large capacity exhaust fans
 Driving lathe machines
 Crushers
 Oil extracting mills
 Textile and etc.
Principles of operation
 In both induction and synchronous motors, the AC power
supplied to the motor’s stator creates a magnetic field that
rotates
in
time
with
the
AC
oscillations.
Whereas
a
synchronous motor’s rotor turns at the same rate as the stator
field, an induction motor’s rotor rotates at a slower speed than
the stator field. The induction motor stator’s magnetic field is
therefore changing or rotating relative to the rotor.
 This induces an opposing current in the induction motor’s
rotor, in effect the motor’s secondary winding, when the latter
is short-circuited or closed through an external impedance.
The rotating magnetic flux induces currents in the windings of
the rotor, in a manner similar to currents induced in a
transformer’s secondary winding(s).
 The currents in the rotor windings in turn create magnetic
fields in the rotor that react against the stator field. Due to
Lenz’s Law, the direction of the magnetic field created will be
such as to oppose the change in current through the rotor
windings.
 The cause of induced current in the rotor windings is the
rotating stator magnetic field, so to oppose the change in
rotor-winding currents the rotor will start to rotate in the
direction of the rotating stator magnetic field.
 The rotor accelerates until the magnitude of induced rotor
current and torque balances the applied load. Since rotation at
synchronous speed would result in no induced rotor current,
an induction motor always operates slower than synchronous
speed.
 For rotor currents to be induced, the speed of the physical
rotor must be lower than that of the stator’s rotating magnetic
field ( ); otherwise the magnetic field would not be moving
relative to the rotor conductors and no currents would be
induced.
 Synchronous speed
An AC motor’s synchronous speed, , is the rotation rate of the
stator’s magnetic field, which is expressed in revolutions per minute
as (RPM), Where is the motor supply’s frequency in hertz and is the
number of magnetic poles. That is, for a six-pole three-phase motor
with three pole-pairs set 120° apart, equals 6 and equals 1,000
RPM and 1,200 RPM respectively for 50 Hz and 60 Hz supply
systems.
2.2 Working Principle of Single Phase Induction Motor
The Single-phase induction motor’s main winding is supplied with a
single-phase AC. This produces fluctuating magnetic flux around
the rotor. This means as the direction of the AC changes, the
direction of the generated magnetic field changes. This is not
enough condition to cause rotation of the rotor. Here the principle
of double-revolving field theory is applied.
According to the double-revolving field theory, a single alternating
field is due to the combination of two fields of equal magnitude but
revolving in the opposite direction. The magnitude of these two
fields is equal to half the magnitude of the alternating field. This
means that when AC is applied, two half-magnitude fields are
produced
with
equal
magnitudes
but
revolving
in
opposite
directions.
So, now there is a current flowing in the stator and magnetic field
revolving on the rotor, thus Faraday’s law of electromagnetic
induction acts on the rotor. According to this law, the revolving
magnetic fields produce electricity in the rotor which generates the
force that can rotate the rotor.
2.3 Starting Methods of Single Phase Induction Motor
Single -phase induction motor doesn’t have starting torque, so
external circuitry is needed to provide this starting torque. The
stator of these motors contains Auxiliary winding for this purpose.
The Auxiliary winding is connected in parallel to a capacitor. When
the capacitor is turned on, similar to main winding, revolving two
magnetic fields of the same magnitude but opposite direction are
observed on Auxiliary winding.
From these two magnetic fields of Auxiliary winding, one cancel
outs one of the magnetic fields of main winding whereas the other
adds up with another magnetic field of main winding. Thus,
resulting in a single revolving magnetic field with high magnitude.
This produces force in one direction, hence rotating the rotor. Once
the rotor starts rotating it rotates even if the capacitor is turned off.
There are different stating methods of single-phase induction
motors. Usually, these motors are chosen based on their starting
methods. These methods can be classified as;
 Split-phase starting.
 Shaded-pole starting.
 Repulsion motor starting
 Reluctance starting.
In the split -phase starts, the stator has two types of windings –
main winding and Auxiliary winding, connected in parallel. Motors
with this type of starting methods are;
 Resistor split -phase motors.
 Capacitor split -phase motors.
 Capacitors start and run motors.
 Capacitor-run motor.
2.3 Power factor of an induction motor
The power factor of induction motors varies with load, typically from
around 0.85 or 0.90 at full load to as low as about 0.20 at no-load,
due to stator and rotor leakage and magnetizing reactances. Power
factor can be improved by connecting capacitors either on an
individual motor basis or, by preference, on a common bus covering
several motors. For economic and other considerations, power
systems are rarely power factor corrected to unity power factor
(Jordan, 2004). Power capacitor application with harmonic currents
requires power system analysis to avoid harmonic resonance
between capacitors and transformer and circuit reactances (Fink,
2008). Common bus power factor correction is recommended to
minimize resonant risk and to simplify power system analysis. The
only possible source of excitation in an induction machine is the
stator input. The induction motor therefore must be operate at a
lagging power factor. The power factor is very low at no load and
increases to about 85 to 90 percent at full load in an induction
motor. The improvement being caused by the increased real-power
requirements with increasing load. The presence of air-gap between
the stator and rotor will greatly increases the reluctance of the
magnetic circuit of an induction motor (Liang, 2011). Also an
induction motor draws a large magnetizing current (Im) to produce
the required flux in the air-gap.
i.
At no load condition, an induction motor draws a large
magnetizing current and a small active component to meet the
no-load losses. Thus, the induction motor takes a high no-load
current lagging the applied voltage by a large angle. Hence the
power factor of an induction motor on no load is very low, it
may about 0.1 lagging.
ii.
When an induction motor is at loaded condition, the active
component of current will increases while the magnetizing
component remains about the same. Also the power factor of
the motor is increased. Because of the large value of
magnetizing current, which is present regardless of load, the
power factor of an induction motor even at full load exceeds
0.9 lagging.
Induction machine may become self-excited when a sufficiently
heavy capacitive load is present in their stator circuits. Then the
capacitive current furnishes the excitation and cause serious
overvoltage or excessive transient torques.
Current components of an induction motor
The magnetizing current is the current that establishes the flux in
the iron and it becomes very necessary if the motor is going to
operate. The magnetizing current does not contribute to the actual
work output of the motor. The magnetizing current and the leakage
reactance can be considered as the passenger components of
current that will not affect the power drawn by the motor. But it will
contribute to the power dissipated in the supply and distribution
system.
Current components after adding capacitor current
In reducing the losses in the distribution system, power factor
correction is added to neutralize a portion of the magnetizing
current of the motor. The corrected power factor will be 0.92 - 0.95
some power retailers offer incentives for operating with a power
factor of better than 0.9, while others penalize consumers with a
poor power factor. The net result is that in order to reduce wasted
energy in the distribution system. Thus the consumer will be
encouraged to apply power factor correction methods.
2.4 Construction of Single Phase Induction Motor
Single phase induction motor is very simple and robust in
construction. The stator carries a distributed winding in the slots
cut around the inner periphery. The stator conductors have low
resistance and they are winding called Starting winding is also
mounted on the stator. This winding has high resistance and its
embedded deep inside the stator slots. The rotor is invariably of the
squirrel cage type. The auxiliary winding has a centrifugal switch in
series with it. The function of the switch is to cut off the starting
winding, when the rotor has accelerated to about 75% of its rated
speed. In capacitor-start motors, an electrolytic capacitor of suitable
capacitance value is also incorporated in the starting winding
circuit.
The main stator winding and auxiliary (or starting) winding are
joined in parallel, and the polarity of only the starting winding can
be reversed. This is necessary for changing the direction of rotation
of the rotor.
A 1-phase induction motor is similar to a 3-phase squirrel cage
induction motor in physical appearance. The rotor is same as that
employed in 3-phase squirrel cage induction motor. There is
uniform air gap between stator and rotor but no electrical
connection between them. Although single phase induction motor is
more simple in construction and is cheaper than a 3-phase
induction motor of the same frame size, it is less efficient and it
operates at lower power factor.
CHAPTER 3
3.1 Introduction
This chapter focuses on the method and processes applied in
actualizing this project work, the materials used and the detailed
report of the system. It also relates to the principle, methods or set
of arrangement of used to actualize the project.
3.2 Methodology
This involves the tools or steps taken to conduct this research
which includes survey, and analytical. Survey method was based on
attaining the cost price of the materials used while the analytical
method analyzed the system so as to achieve the objectives of the
project
3.3 Single-phase induction motors
The development of a rotating field in an induction machine
requires a set of currents displaced in phase (as shown in the
figure) flowing in a set of stator windings that are displaced around
the stator periphery (Mera, 2012). While this is straightforward
where a three-phase supply is available, most commercial and
domestic supplies are only of a single phase, typically with a voltage
of 120 or 240 volts. There are several ways in which the necessary
revolving field can be produced from this single-phase supply.
A single phase induction motor consists of a single phase winding
on the stator and a cage winding on the rotor. When a 1 phase
supply is connected to the stator winding, a pulsating magnetic
field is produced. In the pulsating field, the rotor does not rotate
due to inertia. Therefore a single phase induction motor is not selfstarting and requires some particular starting means. Two theories
have been suggested to find the performance of a single phase
induction motor.
To produce a rotating field, consider two winding 'A' and 'B' so
displaced that they produce magnetic field 90° apart in space. The
resultant of these two fields is a rotating magnetic field of constant
magnitudeϕm. Non-Uniform magnetic field produces a non-uniform
torque which makes the operation of the motor noisy, affect starting
torque.
Production of the uniform magnetic field
Single-phase inductive load equivalent circuits:
a – accounting for copper loss; b, c – accounting for both copper
and eddy current iron
3.4 Efficiency
Full-load motor efficiency is around 85–97%, related motor losses
being broken down roughly as follows:

Friction and windage, 5–15%

Iron or core losses, 15–25%

Stator losses, 25–40%

Rotor losses, 15–25%

Stray load losses, 10–20%.
For an electric motor, the efficiency, represented by the Greek letter
Eta, is defined as the quotient of the output mechanical power and
the input electric power, and calculated using this formula:
Various regulatory authorities in many countries have introduced
and implemented legislation to encourage the manufacture and use
of
higher
efficiency
electric
motors.
There
is
existing
and
forthcoming legislation regarding the future mandatory use of
premium-efficiency induction-type motors in defined equipment.
3.5 Equivalent Circuit
The equivalent circuit of a single phase induction motor can be
developed on the basis of two revolving field theory. To develop the
equivalent circuit it is necessary to consider standstill or blocked
rotor conditions.
The motor with a blocked rotor merely acts like a transformer with
its secondary short circuited and its equivalent circuit will be as
shown in figure below, (a) Em being e.m.f. induced in the stator.
Equivalent Circuit of a Single Phase Induction Motor
The motor may now be viewed from the point of view of the two
revolving field theory. The two flux components induce e.m.f. Emf
and Emb in the respective stator winding. Since at standstill the
two oppositely rotating fields are of same strength, the magnetizing
and rotor impedances are divided into two equals halves connected
in series as shown in figure above.
Equivalent Circuit of Single Phase Induction Motor at Standstill
on the basis of Two Revolving Field Theory
When the rotor runs at speed N with respect to forward field, the
slip is S w.r.t. forward field and (2-S) w.r.t. backward field and the
equivalent circuit is as shown in below.
Equivalent Circuit of a Single Phase Induction Motor Under
Normal Operating Conditions
If the core losses are neglected the equivalent circuit is modified as
shown in fig:1.6(d). The core losses, here, are handled as rotational
losses and subtracted from the power converted into mechanical
power; the amount of error thus introduced is relatively small.
Approximate Equivalent Circuit of a Single Phase Induction
Motor Under Normal Operating Conditions
CHAPTER 4
TESTING AND RESULTS
4.1 Testing of single phase induction motor
The need for estimating the performance of the machine can be
done by two methods namely; 1. Direct method (for smaller rated
machine) and 2. Indirect method (higher rated machine).
Direct method (LOAD TEST)
PROCEDURE:
The connections are made, as per the circuit diagram. With no
mechanical loading on the motor, it is started by using the starter
provided. The motor will be running with a small slip, very near to
the synchronous speed. The readings of the ammeter IL, line voltage
applied VL, speed "N" in r.p.m., and power drawn from supply WL
are noted. The belt is slowly tightened against the brake drum. Now
the readings of the spring balances, S1 and S2 in kg, are noted, in
addition to the readings mentioned earlier. The loading is increased
in convenient steps until 110% of rated current is reached. The
readings taken for each loading are tabulated. Gradually decrease
the load and after removing the entire load, stop the motor. The
effective radius “R” of the brake drum is measured.
CALCULATION:
Frequency = F = 50Hz
Synchronous speed = Ns = -------------- rpm
Speed at the load = N =-------------rpm
Per unit slip = S = (Ns - N) / Ns
Radius of the brake drum = r =--------------meter
Thickness of the belt = t = -----------meter
Mechanical Power output = Po = 2 NT / 60 Watts.
Torque Output of Motor = T = (S1 - S2) x (Reff) x 9.81 NM
Effective radius of the brake drum = Reff = r + t/2 = --------------meter
Electrical Power input to motor = Pi = WL = ---------------wat
Indirect Method of Testing
In indirect method, two special tests were conducted, based on the
test result, equivalent circuit was constructed and performance of
motor was analysed.
Blocked Rotor Test
 Connections are given as per circuit diagram.
 The motor should not be allowed to run by tightening the belt
around the break drum.
 Now using auto transformer apply single phase A.C supply is
applied, until the ammeter shows the rated current.
No Load Test
 Connections are given as per circuit diagram.
 Dpst switch is closed and 1phase A.C supply is applied to the
motor, through the variac rated voltage is applied
 Note down the meter reading and tabulate it
4.2 Result
A single phase induction motor consists of a single phase winding
on the stator and a cage winding on the rotor. When a phase supply
is connected to the stator winding, a pulsating magnetic field is
produced. In the pulsating field, the rotor does not rotate due to
inertia. Therefore a single phase induction motor is not self-starting
and requires some particular starting means.
Single phase induction motor is very simple and robust in
construction. The stator carries a distributed winding in the slots
cut around the inner periphery. The stator conductors have low
resistance and they are winding called Starting winding is also
mounted on the stator. This winding has high resistance and its
embedded deep inside the stator slots. The rotor is invariably of the
squirrel cage type. The auxiliary winding has a centrifugal switch in
series with it. The function of the switch is to cut off the starting
winding, when the rotor has accelerated to about 75% of its rated
speed. In capacitor-start motors, an electrolytic capacitor of suitable
capacitance value is also incorporated in the starting winding
circuit.
The main stator winding and auxiliary (or starting) winding are
joined in parallel, and the polarity of only the starting winding can
be reversed. This is necessary for changing the direction of rotation
of the rotor.
CHAPTER 5
CONCLUSION AND RECOMMENDATION
5.1 Conclusion
The project presented a design and analysis approach for singlephase induction load mainly from a construction perspective.
Single-phase a.c supply is commonly used for lighting purpose in
shops, offices, houses, schools etc..Hence instead of d.c motors, the
motors which work on single-phase a.c. supply are popularly used.
These a.c motors are called single-phase induction motors. A large
no. of domestic applications use single-phase induction motors.
The values of the power factor gotten are close to the standard
power factor of the load. However, due to human errors the
accuracy might be affected.
Standard industrial frame sizes were taken into account, and also,
some
strict
constraints
were
set
to
meet
higher
efficiency
applications. Several combinations for stator/rotor slots were
investigated. Different types of testing were carried out so as to
achieve desired output.
5.2 Recommendation
Through this project, it is recommended that;
1. The Numerical Machine Complex initiates the process of
designing and constructing local made single phase induction
loads.
2. Companies
should
invest
in
assembling
the
necessary
machines for the construction process.
3. Also, companies
personnel
for
should
the
equally
purpose
invest
in
training
of cementing
a
her
better
understanding of the construction process, and to ensure
high quality products.
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