MACHAKOS UNIVERSITY
SYLLABUS
DC MACHINES AND TRANSFORMERS
19A02303T DC MACHINES & TRANSFORMERS
UNIT-I
Magnetic Material Properties and Applications:
Introduction, Magnetic materials and their properties, magnetically induced emf and force, AC operation
of magnetic circuits, hysteresis and eddy current losses, permanent magnets, and applications of permanent
magnet materials.
Principles of electromechanical energy conversion:
Energy in magnetic system, field energy and mechanical force, multiply-excited magnetic field systems,
forces/torques in systems with permanent magnets, energy conversion via electric field, dynamical
equations of electro mechanical systems
Unit Outcomes:
Able to understand the electromechanical energy conversion system To
understand about various magnetic materials, properties and Applications
UNIT-II
DC Generators
Constructional details of DC machine, principle of operation of DC generator, armature windings and its
types, emf equation, armature reaction, effect of brush lead, demagnetizing and cross magnetizing ampere
turns, compensating windings, commutation, emf induced in a coil undergoing commutation, methods of
improving commutation, OCC and load characteristics of different types of generators.
Parallel operation of DC Generators: DC shunt and series generators in parallel, equalizing connections
, Unit Outcomes:
Able to understand the construction, operation and armature windings of a DC generator
Able to analyze the characteristics of DC generators
UNIT-III
DC Motors
Force on conductor carrying current, back emf, Torque and power developed by armature, speed control of
DC motors(Armature control and Flux control methods), Necessity of starters, constructional details of 3-
point and 4-point starters, characteristics of DC motors, Losses in DC machines, condition for maximum
efficiency
Testing of DC machines: Brake test, Swinburne’s test, Hopkinson's test, Fields test, Retardation
test.
Unit Outcomes:
• Able to analyze speed control of DC motors, testing methods and parallel operation of DC
machines
• Analyze the characteristics of DC motors
UNIT-IV
Single Phase Transformers
Principle, construction and operation of single-phase transformers, equivalent circuit, phasor
diagrams(no load and on load), Magnetizing current, effect of nonlinear B-H curve of magnetic core
material, harmonics in magnetization current, losses and efficiency Testing - open circuit and short circuit
tests, voltage regulation,Sumpner’s test, separation of hysteresis and eddy current losses. Parallel
operation of single-phase transformers, Autotransformers - construction, principle, applications and
comparison with two winding transformer.
Unit Outcomes:
• Able to understand the construction, operation and parallel operation of transformer
• To predetermine the efficiency and regulation of a transformer
UNIT-V
Three Phase Transformers
Three-phase transformer – construction, types of connection and their comparative features, Phase
conversion - Scott connection, Tap-changing transformers - No-load and on-load tap- changing of
transformers, Three-winding transformers- Cooling of transformers.
, Unit Outcomes:
• Able to understand and analyze the phase conversions
• Analyze the tap changing of transformers
Course Outcomes:
At the end of this course, students will demonstrate the ability to
Understand the concepts of magnetic circuits.
• Understand the operation of DC machines.
• Analyse the differences in operation of different DC machine configurations.
Analyse single phase and three phase transformers circuits.
Text Books:
1. P. S. Bimbhra, “Electrical Machinery”, Khanna Publishers, 2011. 2. I. J. Nagrath and
D. P. Kothari, “Electric Machines”, McGraw Hill Education,2010.
References:
1. A. E. Fitzgerald and C. Kingsley, "Electric Machinery”, New York, McGraw Hill
Education, 2013.
2. A. E. Clayton and N. N. Hancock, “Performance and design of DC machines”, CBS
Publishers, 2004. 3. M. G. Say, “Performance and design of AC machines”, CBS
Publishers, 2002.
UNIT – I
ELECTROMECHANICAL ENERGY CONVERSION
1.1 Electromechanical-Energy-Conversion Principles
The electromechanical-energy-conversion process takes place through the medium of the electric or
magnetic field of the conversion device of which the structures depend on their respective functions.
• Transducers: microphone, pickup, sensor, loudspeaker
• Force producing devices: solenoid, relay, and electromagnet
3|Page
, • Continuous energy conversion equipment: motor, generator
1.2 Forces and Torques in Magnetic Field Systems
The Lorentz Force Law gives the force F on a particle of charge q in the presence of electric and
magnetic fields.
F= q(E+v×B)
Where, F : newtons, q: coulombs, E: volts/meter, B : telsas, v: meters/second
• In a pure electric-field system,
F = qE
• In pure magnetic-field systems,
F = q(v×B)
Figure : Right hand rule
• For situations where large numbers of charged particles are in motion,
Fv = ρ(E+v×B)
J = ρv
Fv =J×B
ρ (charge density): coulombs/m3, Fv (force density): newtons/m3, J = ρv (current density):
amperes/m2.
Most electromechanical-energy-conversion devices contain magnetic material.
• Forces act directly on the magnetic material of these devices which are constructed of rigid,
non-deforming structures.
• The performance of these devices is typically determined by the net force, or torque, acting
on the moving component. It is rarely necessary to calculate the details of the internal force
distribution.
• Just as a compass needle tries to align with the earth’s magnetic field, the two sets of fields
associated with the rotor and the stator of rotating machinery attempt to align, and torque is
4|Page
SYLLABUS
DC MACHINES AND TRANSFORMERS
19A02303T DC MACHINES & TRANSFORMERS
UNIT-I
Magnetic Material Properties and Applications:
Introduction, Magnetic materials and their properties, magnetically induced emf and force, AC operation
of magnetic circuits, hysteresis and eddy current losses, permanent magnets, and applications of permanent
magnet materials.
Principles of electromechanical energy conversion:
Energy in magnetic system, field energy and mechanical force, multiply-excited magnetic field systems,
forces/torques in systems with permanent magnets, energy conversion via electric field, dynamical
equations of electro mechanical systems
Unit Outcomes:
Able to understand the electromechanical energy conversion system To
understand about various magnetic materials, properties and Applications
UNIT-II
DC Generators
Constructional details of DC machine, principle of operation of DC generator, armature windings and its
types, emf equation, armature reaction, effect of brush lead, demagnetizing and cross magnetizing ampere
turns, compensating windings, commutation, emf induced in a coil undergoing commutation, methods of
improving commutation, OCC and load characteristics of different types of generators.
Parallel operation of DC Generators: DC shunt and series generators in parallel, equalizing connections
, Unit Outcomes:
Able to understand the construction, operation and armature windings of a DC generator
Able to analyze the characteristics of DC generators
UNIT-III
DC Motors
Force on conductor carrying current, back emf, Torque and power developed by armature, speed control of
DC motors(Armature control and Flux control methods), Necessity of starters, constructional details of 3-
point and 4-point starters, characteristics of DC motors, Losses in DC machines, condition for maximum
efficiency
Testing of DC machines: Brake test, Swinburne’s test, Hopkinson's test, Fields test, Retardation
test.
Unit Outcomes:
• Able to analyze speed control of DC motors, testing methods and parallel operation of DC
machines
• Analyze the characteristics of DC motors
UNIT-IV
Single Phase Transformers
Principle, construction and operation of single-phase transformers, equivalent circuit, phasor
diagrams(no load and on load), Magnetizing current, effect of nonlinear B-H curve of magnetic core
material, harmonics in magnetization current, losses and efficiency Testing - open circuit and short circuit
tests, voltage regulation,Sumpner’s test, separation of hysteresis and eddy current losses. Parallel
operation of single-phase transformers, Autotransformers - construction, principle, applications and
comparison with two winding transformer.
Unit Outcomes:
• Able to understand the construction, operation and parallel operation of transformer
• To predetermine the efficiency and regulation of a transformer
UNIT-V
Three Phase Transformers
Three-phase transformer – construction, types of connection and their comparative features, Phase
conversion - Scott connection, Tap-changing transformers - No-load and on-load tap- changing of
transformers, Three-winding transformers- Cooling of transformers.
, Unit Outcomes:
• Able to understand and analyze the phase conversions
• Analyze the tap changing of transformers
Course Outcomes:
At the end of this course, students will demonstrate the ability to
Understand the concepts of magnetic circuits.
• Understand the operation of DC machines.
• Analyse the differences in operation of different DC machine configurations.
Analyse single phase and three phase transformers circuits.
Text Books:
1. P. S. Bimbhra, “Electrical Machinery”, Khanna Publishers, 2011. 2. I. J. Nagrath and
D. P. Kothari, “Electric Machines”, McGraw Hill Education,2010.
References:
1. A. E. Fitzgerald and C. Kingsley, "Electric Machinery”, New York, McGraw Hill
Education, 2013.
2. A. E. Clayton and N. N. Hancock, “Performance and design of DC machines”, CBS
Publishers, 2004. 3. M. G. Say, “Performance and design of AC machines”, CBS
Publishers, 2002.
UNIT – I
ELECTROMECHANICAL ENERGY CONVERSION
1.1 Electromechanical-Energy-Conversion Principles
The electromechanical-energy-conversion process takes place through the medium of the electric or
magnetic field of the conversion device of which the structures depend on their respective functions.
• Transducers: microphone, pickup, sensor, loudspeaker
• Force producing devices: solenoid, relay, and electromagnet
3|Page
, • Continuous energy conversion equipment: motor, generator
1.2 Forces and Torques in Magnetic Field Systems
The Lorentz Force Law gives the force F on a particle of charge q in the presence of electric and
magnetic fields.
F= q(E+v×B)
Where, F : newtons, q: coulombs, E: volts/meter, B : telsas, v: meters/second
• In a pure electric-field system,
F = qE
• In pure magnetic-field systems,
F = q(v×B)
Figure : Right hand rule
• For situations where large numbers of charged particles are in motion,
Fv = ρ(E+v×B)
J = ρv
Fv =J×B
ρ (charge density): coulombs/m3, Fv (force density): newtons/m3, J = ρv (current density):
amperes/m2.
Most electromechanical-energy-conversion devices contain magnetic material.
• Forces act directly on the magnetic material of these devices which are constructed of rigid,
non-deforming structures.
• The performance of these devices is typically determined by the net force, or torque, acting
on the moving component. It is rarely necessary to calculate the details of the internal force
distribution.
• Just as a compass needle tries to align with the earth’s magnetic field, the two sets of fields
associated with the rotor and the stator of rotating machinery attempt to align, and torque is
4|Page
