Output equation of Induction motor; Main dimensions; Separation of D and L; Choice of Average flux density; length of air gap; Design of Stator core; Rules for selecting rotor slots of squirrel cage machines; Design of rotor bars and slots; Design of end rings; Design of wound rotor; Magnetic leakage calculations; Leakage reactance of polyphase machines; Magnetizing current; Short circuit current; Operating characteristics; Losses and Efficiency.
The document discusses the design considerations for a synchronous generator with a round rotor. It covers topics such as:
- The maximum allowable rotor peripheral speed is typically 250 m/s for modern steel alloys.
- Formulas are provided for calculating copper resistivity based on temperature, as well as the number of turns and conductor size for the generator armature winding.
- Other factors discussed include the number of armature slots based on the number of phases, length/diameter ratio, air gap size selection, and rotor slot design considerations such as the number of poles and slots.
Design of stator & rotor for Wound Induction MotorParth Patel
The document provides details on the design of stator and rotor slots for a 3-phase wound-rotor induction motor. It discusses the construction of the motor including the stator core and winding, wound rotor with slip rings, and end shields. For stator design, it describes slot types, selection of number of slots, conductor cross-section, slot area and size, length of mean turn and resistance calculation. For rotor design, it discusses air gap length, number of rotor slots selection to avoid crawling and cogging, end ring current, design of wound rotor including number of turns and rotor current calculation. It provides an example design problem for a 30kW squirrel cage induction motor and asks to design a suitable rotor
An alternator is an electrical generator that converts mechanical energy to electrical energy in the form of alternating current. For reasons of cost and simplicity, most alternators use a rotating magnetic field with a stationary armature.
The document summarizes key aspects of alternator construction and operation. It describes:
1) The main components of an alternator including the stationary stator with 3-phase winding and rotating rotor with DC field winding. Two common rotor types are salient pole and smooth cylindrical.
2) Armature and field windings, including single vs. double layer windings and full vs. short pitch windings.
3) Synchronizing and parallel operation which allows multiple alternators to run in unison by matching voltage, frequency, and phase sequence.
4) Synchronizing current, power, and torque which occur during the matching process prior to paralleling alternators.
The document discusses synchronous generators and provides details about:
1. The types of synchronous generators based on the arrangement of field and armature windings.
2. The construction and components of a synchronous generator including the stationary armature and rotating field.
3. The different tests conducted on synchronous generators like open circuit, short circuit, and zero power factor tests to determine parameters like synchronous reactance.
4. Methods to calculate the voltage regulation of a synchronous generator like the EMF method, MMF method, and zero power factor method.
The document discusses synchronous generators. It begins by listing various topics related to synchronous generators including constructional details, types of rotors, the EMF equation, synchronous reactance, armature reaction, voltage regulation methods, synchronization, and operating characteristics. It then provides more details on synchronous generators, describing their construction, types including salient pole and cylindrical rotors, EMF equation derivation, armature windings, and causes of voltage drops. Finally, it discusses various methods for determining voltage regulation including the direct loading method, synchronous impedance method, MMF method, zero power factor method, and two reaction theory.
The document discusses direct current (DC) generators, including:
1. DC generators operate by converting mechanical energy to electrical energy as conductors move through a magnetic field, inducing an electromotive force (EMF) based on Faraday's law of induction.
2. The construction of DC generators includes a yoke, rotor, stator, field electromagnets, pole cores, brushes, shaft, armature coils, commutator, and bearings. The commutator is needed to produce steady DC output from the pulsating current induced in the armature coils.
3. There are different types of DC generators including separately excited, self-excited (shunt-wound,
Output equation of Induction motor; Main dimensions; Separation of D and L; Choice of Average flux density; length of air gap; Design of Stator core; Rules for selecting rotor slots of squirrel cage machines; Design of rotor bars and slots; Design of end rings; Design of wound rotor; Magnetic leakage calculations; Leakage reactance of polyphase machines; Magnetizing current; Short circuit current; Operating characteristics; Losses and Efficiency.
The document discusses the design considerations for a synchronous generator with a round rotor. It covers topics such as:
- The maximum allowable rotor peripheral speed is typically 250 m/s for modern steel alloys.
- Formulas are provided for calculating copper resistivity based on temperature, as well as the number of turns and conductor size for the generator armature winding.
- Other factors discussed include the number of armature slots based on the number of phases, length/diameter ratio, air gap size selection, and rotor slot design considerations such as the number of poles and slots.
Design of stator & rotor for Wound Induction MotorParth Patel
The document provides details on the design of stator and rotor slots for a 3-phase wound-rotor induction motor. It discusses the construction of the motor including the stator core and winding, wound rotor with slip rings, and end shields. For stator design, it describes slot types, selection of number of slots, conductor cross-section, slot area and size, length of mean turn and resistance calculation. For rotor design, it discusses air gap length, number of rotor slots selection to avoid crawling and cogging, end ring current, design of wound rotor including number of turns and rotor current calculation. It provides an example design problem for a 30kW squirrel cage induction motor and asks to design a suitable rotor
An alternator is an electrical generator that converts mechanical energy to electrical energy in the form of alternating current. For reasons of cost and simplicity, most alternators use a rotating magnetic field with a stationary armature.
The document summarizes key aspects of alternator construction and operation. It describes:
1) The main components of an alternator including the stationary stator with 3-phase winding and rotating rotor with DC field winding. Two common rotor types are salient pole and smooth cylindrical.
2) Armature and field windings, including single vs. double layer windings and full vs. short pitch windings.
3) Synchronizing and parallel operation which allows multiple alternators to run in unison by matching voltage, frequency, and phase sequence.
4) Synchronizing current, power, and torque which occur during the matching process prior to paralleling alternators.
The document discusses synchronous generators and provides details about:
1. The types of synchronous generators based on the arrangement of field and armature windings.
2. The construction and components of a synchronous generator including the stationary armature and rotating field.
3. The different tests conducted on synchronous generators like open circuit, short circuit, and zero power factor tests to determine parameters like synchronous reactance.
4. Methods to calculate the voltage regulation of a synchronous generator like the EMF method, MMF method, and zero power factor method.
The document discusses synchronous generators. It begins by listing various topics related to synchronous generators including constructional details, types of rotors, the EMF equation, synchronous reactance, armature reaction, voltage regulation methods, synchronization, and operating characteristics. It then provides more details on synchronous generators, describing their construction, types including salient pole and cylindrical rotors, EMF equation derivation, armature windings, and causes of voltage drops. Finally, it discusses various methods for determining voltage regulation including the direct loading method, synchronous impedance method, MMF method, zero power factor method, and two reaction theory.
The document discusses direct current (DC) generators, including:
1. DC generators operate by converting mechanical energy to electrical energy as conductors move through a magnetic field, inducing an electromotive force (EMF) based on Faraday's law of induction.
2. The construction of DC generators includes a yoke, rotor, stator, field electromagnets, pole cores, brushes, shaft, armature coils, commutator, and bearings. The commutator is needed to produce steady DC output from the pulsating current induced in the armature coils.
3. There are different types of DC generators including separately excited, self-excited (shunt-wound,
Code of Practice for Power Installations, materials required for power circuit wiring and
their specifications, Prepare the layout diagram of machines showing clearances as per IS
standards, draw wiring plan of the Power circuit for workshops, Decide the type of wiring system, load calculations, determine the size of conductors, main switch, Isolators, sub
switches and protective devices, Draw the SLD of Power Distribution Scheme showing
grading/discrimination of ratings of protective devices, Prepare the schedule of materials with
specifications for workshops and their estimates, Determine the rating of motor for IP set and
the concept (only)of pump house wiring.
This document discusses the design of core type and shell type transformers. It begins by classifying transformers based on their construction as either core type or shell type. It then compares the two types and outlines their relative advantages and disadvantages. Core type transformers are simpler to construct but have poorer mechanical strength, while shell type transformers can better withstand short circuits. The document also provides the output equations for single phase and three phase transformers of both core type and shell type construction. It discusses design considerations such as core and winding dimensions, current density, and resistance and reactance calculations.
The document provides details of OHE assets along the Mansarovar to Sindhi Camp and yard section of JMRC metro rail. It includes track length, contact and messenger wires, mast types, cantilevers, section insulators, and other OHE components. It then summarizes the ROCS system used in tunnels, details of masts, steady arms, encumbrance, wire sizes and tensions. The document also discusses regulating equipment, section insulators, neutral section design, earthing and bonding systems, return conductors, OHE parameters and sectioning. Finally, it outlines the maintenance and inspection schedules and vehicles used to maintain the overhead line equipment.
This document contains design calculations for a single-phase distribution transformer. It specifies design parameters such as a rated output of 50 kVA, primary voltage of 13800V, secondary voltage of 460/230V, and an efficiency of at least 0.96 at full load. The document then shows calculations for transformer components like winding dimensions and currents, core size, flux density, losses, and temperature rise. Design goals are to have losses lower than specified guarantees and a temperature rise under 55°C at full load.
Alternators operate using the same principles of electromagnetic induction as DC generators but produce an AC output. They have a stationary armature winding (stator) and rotating field windings (rotor). As the rotor spins, the magnetic field cuts the stator conductors, inducing an alternating voltage. This voltage alternates in magnitude and direction as the north and south poles of the rotor pass by. Alternators can have either a rotating field and stationary armature or vice versa. Rotating field designs are commonly used as they allow for simpler construction, higher speeds of operation, and easier insulation of the high voltage stator windings.
The document describes the design of an axial flux permanent magnet generator. It includes specifications for electrical and mechanical components. Key points:
1) An axial flux design was selected for its simplicity and efficiency over a radial design. It uses a stationary stator and rotating rotor with magnets.
2) Electrical specifications include selecting neodymium magnets, 9 coils in a star configuration to produce 3-phase power, and calculations to achieve a 60V 3-phase output at 750 RPM.
3) Mechanically, aluminum, steel, and plastics are used. Alignment is critical and achieved via a casing connecting the upper and lower rotors with male-female features and bolts. Total mass is estimated at
The document discusses various methods to determine the voltage regulation of a synchronous generator or alternator. It describes the synchronous impedance method, MMF (ampere-turns) method, and zero power factor (Potier) method. The synchronous impedance method calculates regulation using synchronous reactance Xs obtained from open-circuit and short-circuit tests. The MMF method considers the field mmf required for open-circuit voltage and to cancel armature reaction mmf. The zero power factor method separates armature leakage reactance from armature reaction effects using open-circuit and zero power factor tests.
The document discusses direct current (DC) machines and their operation. It provides details on:
1) The basic components and construction of a DC machine including its armature winding, commutator, and field poles.
2) How an alternating current induced in the armature coils is converted to direct current via the commutator and brush assembly.
3) Different types of armature windings including lap and wave windings.
4) Factors that affect the performance of DC machines such as armature reaction and how it can be mitigated through techniques like using interpoles.
5) Equations for calculating the generated electromotive force (EMF) in a DC generator.
This document discusses DC motors, including their construction, working principle, types, and applications. It describes the key components of a DC motor such as the yoke, poles, field windings, armature, commutator, and brushes. It explains how DC motors work by converting electrical energy from direct current into mechanical energy. It also covers the different types of DC motors like series, shunt, and compound wound motors along with their characteristics. Common applications of DC motors mentioned include use in vehicles, industrial machinery, and household appliances.
Manfacturing of turbo generators at BHELPrabhu Raj
This document discusses the components, operation, and testing of a 200MW turbo generator manufactured by BHEL Hyderabad. It describes the main components of the generator including the stator frame, core, and windings as well as the rotor, cooling system, and testing procedures. Key specifications of the 200MW generator are provided such as a rated output of 200MW, rated voltage of 15.75kV, and efficiency of 98.5%.
This document provides reading material for electrical and electronics engineering students studying electrical machines II at RGPV affiliated colleges. It covers the syllabus for the unit on DC machines, including the basic construction of DC machines, types of excitation, armature and field windings, EMF equations, armature reaction and methods to limit it, commutation processes, performance of DC generators, and different types of DC motors like metadyne, amplidyne, permanent magnet, and brushless motors. The topics are explained over several pages with diagrams and examples. Key concepts covered are the magnetic circuits, armature and commutator construction, separately excited and self-excited machines, wave and lap windings, EMF equations, ar
RBL paper _Design_of_MIGFET_based_junctionless_transistorHema N
1) The document describes the design and analysis of a junctionless transistor using TCAD simulation tools. A MIGFET-based junctionless transistor structure with two independent gates is modeled.
2) ID-VG characteristics are obtained by varying one gate voltage while keeping the other fixed. The mixer output of the MIGFET junctionless transistor is also analyzed and found to have higher but distorted amplitude compared to a conventional MIGFET.
3) In conclusion, the MIGFET junctionless transistor structure is not suitable for mixer applications due to distortion in the output, though it has higher amplitude. The junctionless transistor design and simulation is performed using Sentaurus TCAD tools.
Output equations; Main Dimensions; kVA output for 1 & 3 phase transformers; Window space factor; Design of core and winding; Overall dimensions; Operating characteristics; No-load current; Temperature rise in Transformers; Design of Tank; Methods of cooling of Transformers.
IRJET- Design and Fabrication of a Single-Phase 1KVA Transformer with Aut...IRJET Journal
1) The document describes the design and fabrication of a 1KVA, single-phase shell type transformer with an automatic cooling system. It discusses the core and winding designs based on specifications like voltage and power ratings.
2) A temperature sensor circuit with a thermistor is used to sense the temperature. When the temperature increases above a preset level, a DC fan is automatically switched on to cool the transformer. It is switched off once the temperature decreases.
3) The transformer is designed to output two voltages - 115V and 120V from an input of 230V, without any tapping. This is achieved through appropriate winding designs based on design calculations.
diseño y conocimineto sobre los transformadores electricosdibujante32
This document discusses the design of transformers. It begins by classifying transformers based on their construction type, either core type or shell type. It then compares the two types and discusses their relative mechanical strengths, leakage reactances, ease of repairs, and cooling capabilities. The document goes on to discuss the construction of transformers including their core, windings, insulation, tank, bushings, and other components. It provides equations for calculating transformer output and discusses factors involved in the optimal design of transformers such as minimizing total volume, weight, cost, or losses. The design of components like the core, insulation, yoke, and tank are described. The document concludes by discussing heat dissipation from the tank and the use of cooling tubes.
The document provides information about permanent magnet DC motors and brushless DC motors. It discusses the construction, working principle, and applications of permanent magnet DC motors. It then describes the construction of brushless DC motors including the stator, rotor, position sensors. It explains the working of trapezoidal and sinusoidal brushless DC motors. Trapezoidal BLDC motors have trapezoidal back-EMF and current waveforms for smooth torque production, while sinusoidal BLDC motors have sinusoidal waveforms.
This document contains questions for an exam on electrical machine design. It includes multiple questions related to topics like heating time constants, armature mmf calculations, cooling methods for transformers, transformer core and yoke dimensions, factors affecting sizes of rotating machines, airgap choices for induction motors, and limits on electrical machine design. The document provides information to assist students in answering questions on their exam over electrical machine design.
This document contains questions for an exam on electrical machine design. It includes questions related to factors that limit electrical machine design, calculating mmf for a DC machine, requirements of conducting materials, transformer core construction, flux densities, eddy current loss, ventilation and cooling methods, heat transfer calculations, machine classifications, transformer cooling methods, mmf calculations, stacking factor, field winding design, transformer output equations, designing transformer core and yoke dimensions, calculating flux and no-load current, designing a transformer tank, alternator field coil design, factors affecting machine size, and brush friction loss factors.
Code of Practice for Power Installations, materials required for power circuit wiring and
their specifications, Prepare the layout diagram of machines showing clearances as per IS
standards, draw wiring plan of the Power circuit for workshops, Decide the type of wiring system, load calculations, determine the size of conductors, main switch, Isolators, sub
switches and protective devices, Draw the SLD of Power Distribution Scheme showing
grading/discrimination of ratings of protective devices, Prepare the schedule of materials with
specifications for workshops and their estimates, Determine the rating of motor for IP set and
the concept (only)of pump house wiring.
This document discusses the design of core type and shell type transformers. It begins by classifying transformers based on their construction as either core type or shell type. It then compares the two types and outlines their relative advantages and disadvantages. Core type transformers are simpler to construct but have poorer mechanical strength, while shell type transformers can better withstand short circuits. The document also provides the output equations for single phase and three phase transformers of both core type and shell type construction. It discusses design considerations such as core and winding dimensions, current density, and resistance and reactance calculations.
The document provides details of OHE assets along the Mansarovar to Sindhi Camp and yard section of JMRC metro rail. It includes track length, contact and messenger wires, mast types, cantilevers, section insulators, and other OHE components. It then summarizes the ROCS system used in tunnels, details of masts, steady arms, encumbrance, wire sizes and tensions. The document also discusses regulating equipment, section insulators, neutral section design, earthing and bonding systems, return conductors, OHE parameters and sectioning. Finally, it outlines the maintenance and inspection schedules and vehicles used to maintain the overhead line equipment.
This document contains design calculations for a single-phase distribution transformer. It specifies design parameters such as a rated output of 50 kVA, primary voltage of 13800V, secondary voltage of 460/230V, and an efficiency of at least 0.96 at full load. The document then shows calculations for transformer components like winding dimensions and currents, core size, flux density, losses, and temperature rise. Design goals are to have losses lower than specified guarantees and a temperature rise under 55°C at full load.
Alternators operate using the same principles of electromagnetic induction as DC generators but produce an AC output. They have a stationary armature winding (stator) and rotating field windings (rotor). As the rotor spins, the magnetic field cuts the stator conductors, inducing an alternating voltage. This voltage alternates in magnitude and direction as the north and south poles of the rotor pass by. Alternators can have either a rotating field and stationary armature or vice versa. Rotating field designs are commonly used as they allow for simpler construction, higher speeds of operation, and easier insulation of the high voltage stator windings.
The document describes the design of an axial flux permanent magnet generator. It includes specifications for electrical and mechanical components. Key points:
1) An axial flux design was selected for its simplicity and efficiency over a radial design. It uses a stationary stator and rotating rotor with magnets.
2) Electrical specifications include selecting neodymium magnets, 9 coils in a star configuration to produce 3-phase power, and calculations to achieve a 60V 3-phase output at 750 RPM.
3) Mechanically, aluminum, steel, and plastics are used. Alignment is critical and achieved via a casing connecting the upper and lower rotors with male-female features and bolts. Total mass is estimated at
The document discusses various methods to determine the voltage regulation of a synchronous generator or alternator. It describes the synchronous impedance method, MMF (ampere-turns) method, and zero power factor (Potier) method. The synchronous impedance method calculates regulation using synchronous reactance Xs obtained from open-circuit and short-circuit tests. The MMF method considers the field mmf required for open-circuit voltage and to cancel armature reaction mmf. The zero power factor method separates armature leakage reactance from armature reaction effects using open-circuit and zero power factor tests.
The document discusses direct current (DC) machines and their operation. It provides details on:
1) The basic components and construction of a DC machine including its armature winding, commutator, and field poles.
2) How an alternating current induced in the armature coils is converted to direct current via the commutator and brush assembly.
3) Different types of armature windings including lap and wave windings.
4) Factors that affect the performance of DC machines such as armature reaction and how it can be mitigated through techniques like using interpoles.
5) Equations for calculating the generated electromotive force (EMF) in a DC generator.
This document discusses DC motors, including their construction, working principle, types, and applications. It describes the key components of a DC motor such as the yoke, poles, field windings, armature, commutator, and brushes. It explains how DC motors work by converting electrical energy from direct current into mechanical energy. It also covers the different types of DC motors like series, shunt, and compound wound motors along with their characteristics. Common applications of DC motors mentioned include use in vehicles, industrial machinery, and household appliances.
Manfacturing of turbo generators at BHELPrabhu Raj
This document discusses the components, operation, and testing of a 200MW turbo generator manufactured by BHEL Hyderabad. It describes the main components of the generator including the stator frame, core, and windings as well as the rotor, cooling system, and testing procedures. Key specifications of the 200MW generator are provided such as a rated output of 200MW, rated voltage of 15.75kV, and efficiency of 98.5%.
This document provides reading material for electrical and electronics engineering students studying electrical machines II at RGPV affiliated colleges. It covers the syllabus for the unit on DC machines, including the basic construction of DC machines, types of excitation, armature and field windings, EMF equations, armature reaction and methods to limit it, commutation processes, performance of DC generators, and different types of DC motors like metadyne, amplidyne, permanent magnet, and brushless motors. The topics are explained over several pages with diagrams and examples. Key concepts covered are the magnetic circuits, armature and commutator construction, separately excited and self-excited machines, wave and lap windings, EMF equations, ar
RBL paper _Design_of_MIGFET_based_junctionless_transistorHema N
1) The document describes the design and analysis of a junctionless transistor using TCAD simulation tools. A MIGFET-based junctionless transistor structure with two independent gates is modeled.
2) ID-VG characteristics are obtained by varying one gate voltage while keeping the other fixed. The mixer output of the MIGFET junctionless transistor is also analyzed and found to have higher but distorted amplitude compared to a conventional MIGFET.
3) In conclusion, the MIGFET junctionless transistor structure is not suitable for mixer applications due to distortion in the output, though it has higher amplitude. The junctionless transistor design and simulation is performed using Sentaurus TCAD tools.
Output equations; Main Dimensions; kVA output for 1 & 3 phase transformers; Window space factor; Design of core and winding; Overall dimensions; Operating characteristics; No-load current; Temperature rise in Transformers; Design of Tank; Methods of cooling of Transformers.
IRJET- Design and Fabrication of a Single-Phase 1KVA Transformer with Aut...IRJET Journal
1) The document describes the design and fabrication of a 1KVA, single-phase shell type transformer with an automatic cooling system. It discusses the core and winding designs based on specifications like voltage and power ratings.
2) A temperature sensor circuit with a thermistor is used to sense the temperature. When the temperature increases above a preset level, a DC fan is automatically switched on to cool the transformer. It is switched off once the temperature decreases.
3) The transformer is designed to output two voltages - 115V and 120V from an input of 230V, without any tapping. This is achieved through appropriate winding designs based on design calculations.
diseño y conocimineto sobre los transformadores electricosdibujante32
This document discusses the design of transformers. It begins by classifying transformers based on their construction type, either core type or shell type. It then compares the two types and discusses their relative mechanical strengths, leakage reactances, ease of repairs, and cooling capabilities. The document goes on to discuss the construction of transformers including their core, windings, insulation, tank, bushings, and other components. It provides equations for calculating transformer output and discusses factors involved in the optimal design of transformers such as minimizing total volume, weight, cost, or losses. The design of components like the core, insulation, yoke, and tank are described. The document concludes by discussing heat dissipation from the tank and the use of cooling tubes.
The document provides information about permanent magnet DC motors and brushless DC motors. It discusses the construction, working principle, and applications of permanent magnet DC motors. It then describes the construction of brushless DC motors including the stator, rotor, position sensors. It explains the working of trapezoidal and sinusoidal brushless DC motors. Trapezoidal BLDC motors have trapezoidal back-EMF and current waveforms for smooth torque production, while sinusoidal BLDC motors have sinusoidal waveforms.
This document contains questions for an exam on electrical machine design. It includes multiple questions related to topics like heating time constants, armature mmf calculations, cooling methods for transformers, transformer core and yoke dimensions, factors affecting sizes of rotating machines, airgap choices for induction motors, and limits on electrical machine design. The document provides information to assist students in answering questions on their exam over electrical machine design.
This document contains questions for an exam on electrical machine design. It includes questions related to factors that limit electrical machine design, calculating mmf for a DC machine, requirements of conducting materials, transformer core construction, flux densities, eddy current loss, ventilation and cooling methods, heat transfer calculations, machine classifications, transformer cooling methods, mmf calculations, stacking factor, field winding design, transformer output equations, designing transformer core and yoke dimensions, calculating flux and no-load current, designing a transformer tank, alternator field coil design, factors affecting machine size, and brush friction loss factors.
Similar to Induction Motors design procedure and construction (20)
Better Builder Magazine brings together premium product manufactures and leading builders to create better differentiated homes and buildings that use less energy, save water and reduce our impact on the environment. The magazine is published four times a year.
Online train ticket booking system project.pdfKamal Acharya
Rail transport is one of the important modes of transport in India. Now a days we
see that there are railways that are present for the long as well as short distance
travelling which makes the life of the people easier. When compared to other
means of transport, a railway is the cheapest means of transport. The maintenance
of the railway database also plays a major role in the smooth running of this
system. The Online Train Ticket Management System will help in reserving the
tickets of the railways to travel from a particular source to the destination.
2. Introduction
A poly phase induction motor consists of two major parts,
the stator and rotor
When stator is excited with a.c voltage, rotating field is set
up
This field produces an EMF in the rotor winding by mutual
induction principle, which in turn circulates current when
the rotor is short circuited
This current interacts with the field produced by the stator
winding, thereby producing torque which is responsible for
the rotation of rotor.
2
3. Construction
Stator :
Consists of core and winding .
It is of cylindrical in structure , made of laminated sheet metal,
build up of laminations.
Laminations are of thickness 0.35mm to 0.5mm
Stator core internal diameter and length are the main
dimensions of induction motor
Rotor:
Types: Squirrel Cage and Wound Rotor
Squirrel cage rotors, consists of uninsulated bars of
aluminium or copper that are joined together at both ends by
rings of similar conducting material
Rotor core is made up of laminated sheet of steel with
thickness of 0.5 mm
3
4. Construction
Aluminium bars and endrings are cased directly over the
rotor core
When copper bars are employed , rotor bar are inserted on
the slots from the end of the rotor and end rings are joined to
them by bracing
Wound rotor – consists of core, winding, sliprings and
brushes.
Rotor core is made of laminations and it carries a three phase
winding
One end of each phase are connected to form a star point
Other end of each phase are connected to three slip rings
4
5. Slip rings are mounted on the rotor shaft and they
are insulated from the rotor and from each other
Carbon brushes are mounted over the slip rings ,
facilitate the connection from rotor winding to the
external resistances
Construction
5
15. Advantages of Squirrel Cage Rotor over Wound
Rotors
i. No slip rings, brushes, short circuiting devices are
required
ii. Higher efficiency
iii. Cheaper and rugged in construction
iv. Has better space factor, shorter over hang, smaller
copper loss
v. Has bare end rings, larger space for fans, thus cooling is
better
vi. Better power factor, pull out torque and overload
capacity
15
16. OUTPUT EQUATION
Out put equation for A.C machines is,
The rating of induction motor is given in Horse Power
16
cosφ
η.
kW
Q
X10
.ac
.B
K
1.1
C
where,
n
L
D
.
C
Q
kVA,
Input
3
-
av
w
o
2
o
η.cosφ
0.746
X
HP
Q
17. CHOICE OF SPECIFIC MAGNETIC LOADING
i. Power Factor: with higher values of Bav in the gap ,
results in large magnetizing current , giving low power
factor. However in I.M Bg should be such that there is no
saturation in any part of the magnetic circuit
ii. Iron loss: an increased in Bav result in increased in iron
loss an decreased in efficiency
iii. Over load capcacity : with increase in Bav, flux per pole
is large. Turns per phase and no of tursn becomes less.
Reduction in leakage reactance. Thereby gives maximum
output for same voltage. So machines has larger over load
capcity
17
18. CHOICE OF SPECIFIC ELECTRIC LOADING
i. Copper loss and temp rise: large value of ac , needs
greater amount of copper , results in higher copper losses
and large temperature rise
ii. Voltage: for high voltage machines , less value of ac should
be chosen, because it needs large space for insulation .
iii. Overload capacity: larger value of ac , results in large
number of turns per phase. Which in turn increase the
leakage reactance of the machine, reduces the overload
capacity of the machine.
18
19. SPECIFIC MAGNETIC & ELECTRIC LOADING:
Bav Specific magnetic loading:
Depends on power factor , iron loss and overload capacity.
For 50Hz machine, Bav – 0.3 to 0.6T.
For machines used in cranes, rolling mills tec., need large
overload capacity Bav- 0.65T
ac :Specific electric loading:
Depends on copper loss, temp rise, voltage rating and
overload capacity.
Varies between 5000 to 45000 ac/m.
19
20. MAIN DIMENSIONS
Separation of D and L depends on the ratio of L/τ ( length
of core to pole pitch)
L/τ = 1.5 to 2 for minimum cost
L/τ = 1.0 to 1.25 for good power factor
L/τ = 1.5 for good efficiency
L/τ = 1 for over all design
Generally L/τ – 0.6 to 2; τ = √0.18L
Diameter of the stator bore and hence diameter of rotor is
also limited by Va.
Va up to 60m/s can be employed
Stator - provided ventilating ducts (L ≥ 125mm) of 10mm
width
20
21. STATOR WINDING
In general double layer lap type winding with diamond
shaped coils is generally used for stators
Small motors with a small no of slots and having large
no of turns per phase may use single layer mush
windings
Three phase of the winding may be connected in either
star or delta depending upon starting methods
employed.
Squirrel cage induction motors - star delta starters
21
22. 22
Stator turns per phase:
Flux /pole Фm = Bav τ L = Bav πDL/P
Stator voltage / phase = Es = 4.44 Kws . f. Фm.Ts
Therefore stator turns / phase
Ts= Es /( 4.44 Kws . f. Фm)
Stator conductors:
X-sectional area of stator conductors can be estimated from the
knowledge of current density, kVA rating and stator phase voltage.
δs – 3 to 5 A/mm2 : Is = Q/(3Es x 10-3)
as = Is/ δs and
Round conductors are used for smaller diameter.
If diameter is more than 2mm, use bar and strip conductors for better
space factor for slots
a
4
d s
s
23. STATOR CORE
Made of laminations of thickness of 0.5mm
Design of stator core involves shape of slots, no. of slots ,
dimensions of teeth and depth of slot
Shape of slot :
Open and Semi-closed slots may be used
When open slots are used, winding coils can be formed and
insulated completely before they are inserted in the slots.
Easy for repair. Avoids excessive slot leakage
Semi-closed slots are usually preferred of I.M because Kg will
be less, results in less magnetizing current, also results in
low tooth pulsation loss and less noise operation
Tapered coils are used in semi closed slots
23
24. 24
In small motors round conductors are used
In large and medium size motors strip conductors are
preferred
In both case tapered slot with parallel sided tooth
arrangement is preferred, because it gives maximum slot
area for particular flux density.
Number of slots :
Depends on tooth pulsation loss, leakage reactance ,
ventilation, magnetizing current , iron loss and cost.
In general no. of slots should be chosen as an integral
For open type slots, slot pitch at the gap – 15 to 25mm
For semi closed slots, the slot pitch may be less than 15mm
STATOR CORE
25. 25
Yss= Gap surface/Total no of slots = π D/Ss
Then Ss=π D /Yss
winding
layer
double
for
Even
–
Z
S
6T
Z
Slot
per
Conductors
slots
stator
of
No.
Condcutors
Stator
Total
Z
Slot
per
Conductors
6T
2T
x
3
conductors
stator
of
no.
Total
phase
per
Conductors
x
phases
No.of
conductors
stator
of
no.
Total
SS
S
S
SS
SS
S
S
STATOR CORE
26. 26
Area of stator slots :
Once no. of conductors per slot has been obtained,
approximate area of the slot can be calculated
Area of the slot = (Copper area/slot)/Space factor
= ZssX ag/Space factor
Space factor - 0.25 to 0.4
High voltage machines have lower space factors
owing to large thickness of insulation.
After obtaining the area of the slot, the dimensions of
the slot should be adjusted
Tooth width and the slot width at gap surface should
be approx equal
STATOR CORE
27. 27
The width of the slot should e so adjusted such that
Bt – 1.3 to 1.7 T.
In general ratio of slot depth / slot pitch- 3 to 6
Length of mean turn
Lmts = 2L + 2.3τ + 0.24
Stator teeth:
The dimensions of the slot determines the value of Bt.
High value of Bt is not desirable, as it leads to a higher iron
loss and greater magnetizing MMF.
Bt should not exceed 1.7 T.
STATOR CORE
28. 28
The minimum width of stator teeth is near the air gap surface or
1/3rd of height of the slots
A check for minimum tooth width using the above equation
should be applied before finally deciding the dimensions of
stator slot
i
S
m
min
ts
ts
i
S
m
L
P
S
1.7
φ
W
.W
L
P
S
/pole
area
Total
tooth
of
Width
length
iron
Net
pole
per
slots
of
No.
/pole
area
Total
1.7
φ
area/pole
tooth
Minimum
STATOR CORE
29. 29
Depth of the stator core :
Depends on flux density in the core,
BCS - 1.2 to 1.5 T
Flux passing through the stator core is
half of the flux per pole.
)
d
2(d
D
D
core,
stator
of
diameter
Outside
L
.
2B
φ
d
core,
of
Depth
(2)
and
(1)
Equating
(2)
d
X
L
core
stator
the
of
Area
also,
(1)
2B
φ
core
stator
in
density
Flux
Core
through
Flux
core
stator
the
of
Area
2
φ
φ
core,
stator
the
in
Flux
Therefore,
cs
ss
o
i
CS
m
CS
CS
i
CS
m
m
c
STATOR CORE
D
dss
Do
dcs
Cross Section of Stator Core
30. LENGTH OF THE AIR GAP
30
lg - decided by considering the following factors:
Power factor
Overload capacity
Pulsation loss
Unbalanced magnetic pull
Cooling
Noise
Power factor:
MMF required to send the flux through the air gap is
proportional to the product of B and lg
Even with small B, MMF required for air gap is much more than
that for the rest of the magnetic circuit.
lg – determines the magnetizing current drawn by the machine.
Magnetizing current inversely proportional to power factor
31. 31
Overload capacity:
lg affects the value of zig-zag leakage reactance which
forms a large part of total leakage reactance .
If lg is larger, then zig-zag leakage flux will be less and so
leakage reactance will be less, results in increase in
overload capacity
Pulsation loss:
With larger length of air gap, the variation of reluctance due
to slotting is small.
The tooth pulsation loss, which is produced due to
variation in reluctance of air gap, is reduced accordingly.
Therefore, the pulsation loss is less with large air gaps.
LENGTH OF THE AIR GAP
32. 32
Unbalanced magnetic pull
If the lg is small, then even for small deflection or eccentricity of the
shaft would produce large irregularity in lg .
It is responsible for the production of UMP, which has the tendency to
bend the shaft still more at a place where it is already bent resulting in
fouling of rotor with stator.
If lg is large, a small eccentricity would not able to produce noticeable
UMP.
Cooling:
If lg is large, cylindrical surfaces of rotor and stator are separated by a
large distance.
This would afford better facilities for cooling at the gap surfaces
especially when a fan is fitted for circulation of air
Noise:
The principle cause of noise in I.M is the variation of reluctance of the
path of the zig-zag leakage as small as possible, can be done by
increasing lg.
LENGTH OF THE AIR GAP
33. Relations for length of air gap
33
i. For small I.M , lg = 0.2 + 2√DL mm
ii. Alternate formula for small Induction Motors,
lg = (0.125 + 0.35 D + L + 0.015Va ) mm
iii. For general use, lg = (0.2 + D) mm
iv. For machines with journal bearings
lg = 1.6 √D – 0.25 mm
D,L and Va are in meters
D in mm lg in mm
0.15 0.35
0.20 0.50
0.25 0.60
0.30 0.70
0.45 1.30
0.55 1.80
0.65 2.50
0.80 4.00
34. DESIGN OF SQUIRREL CAGE INDUCTION ROTOR
34
The squirrel cage rotor consists of laminated core, rotor
bars and end rings
The rotor bars and end rings are made of Al or Cu
lr is same as that of stator
Diameter of the rotor is slightly lesser than the stator to
avoid mechanical friction between the stationary stator and
rotating rotor
Rotor diameter Dr = Stator Bore(D) – 2lg
35. DESIGN OF ROTOR BARS AND SLOTS
35
For a three phase machine , the rotor bar current is given
by the equation,
Rotor bar current Ib =(6Ts.Is)Kws cosФ/Sr
o.85(6Ts.Is)/Sr
Performance of an induction motor is greatly influenced by
the resistance of the rotor
Higher rotor resistance has higher starting torque but
lesser efficiency
Rotor resistance is the sum of resistance of the bars and
the endrings
The cross section of the rotor bars and end rings are
selected to meet both requirements of Tst as well as
efficiency
36. 36
Current density of the rotor bar,δb - 4 to 7 A/mm2
Area of each rotor bar, ab = Ib/ δb mm2
In case of squirrel cage motor the X-sectional area of bars will
take the shape of the slot and insulation is not used between bars
and rotor core.
The rotor slots for squirrel cage rotor may be either closed or
semi closed types.
Advantages of closed slots:
Low reluctance
Less magnetizing current
Quieter operation
Large leakage reactance and so starting current is limited
Disadvantage of closed slots:
Reduced overload capacity
DESIGN OF ROTOR BARS AND SLOTS
37. 37
Rules for Selecting Rotor Slots:
i. No. of stator slots should never be equal to rotor slots.
Sr is 15% less than Ss
ii. The difference (Ss-Sr) should not be equal to ± P, ±2P or ±
5P to avoid synchronous steps
iii. The difference (Ss-Sr) should not be equal to ±3 P to
avoid magnetic locking
iv. The difference (Ss-Sr) should not be equal to ± 1, ±2 ,± (p
± 1) or ,± (p ± 2) to avoid noise and vibrations
DESIGN OF ROTOR BARS AND SLOTS
38. DESIGN OF END RINGS
38
The distribution of current in the bars and end rings of a
squirrel cage motor is complicated
It can be shown that if flux distribution is sinusoidal then the
bar current and end ring current will also be sinusoidal
Max. value of end ring current
However , current is not maximum in all the bars under one pole
at the same time but varies according to sine law
Hence the max. value of the current in the end ring is the
average of the current of half the bars under one pole
b(max)
r
e(max)
I
2p
S
Bar
per
Current
X
2
Pole
per
Bars
I
39. 39
Maximum value of end ring current,
Current density of the end ring δe - 4 to 7 A/mm2
Ae= Ie/ δe mm2
also Ae = Depth of end ring X Thickness of end rings = de X te
πp
S
I
2
I
2
π
2
2p
S
I
π
2
2p
S
I
2
pole
per
Bars
I
r
b
b
r
b(max)
r
b(ave)
e(max)
DESIGN OF END RINGS