EE 2251 ELECTRICAL MACHINES – I
AIMTo expose the students to the basic principles of Electro mechanical Energy Conversion in
Electrical Apparatus and the operation of Transformers and DC Machines.
OBJECTIVESi. To familiarize the constructional details, the principle of operation, prediction of performance,
the methods of testing the transformers and three phase transformer connections.
ii. To introduce the principles of electromechanical energy conversion in singly and multiply
iii. To study the working principles of electrical machines using the concepts of electromechanical
energy conversion principles and derive expressions for generated voltage and torque
developed in all Electrical Machines.
iv. To study the working principles of DC machines as Generator and Motor, types, determination
of their no-load/load characteristics, starting and methods of speed control of motors.
v. To estimate the various losses taking place in D.C. machines and to study the different testing
methods to arrive at their performance.
UNIT I INTRODUCTION 6Electrical machine types – Magnetic circuits – Inductance – Statically and Dynamically induced EMF
- Torque – Hysteresis- Core losses - AC operation of magnetic circuits.
UNIT II TRANSFORMERS 10Construction – principle of operation – equivalent circuit – losses – testing – efficiency and voltage
regulation – auto transformer – three phase connections – parallel operation of transformers – tap
UNIT III ELECTROMECHANICAL ENERGY CONVERSION 9Energy in magnetic systems – field energy, coenergy and mechanical force – singly and multiply
UNIT IV BASIC CONCEPTS IN ROTATING MACHINES 9Generated voltages in ac and dc machines, mmf of distributed windings – magnetic fields in rotating
machines – rotating mmf waves – torque in ac and dc machines.
UNIT V DC MACHINES 11Construction – EMF and torque – circuit model – armature reaction – commutation – methods of
excitation – characteristics of generators – characteristics of motors – starting and speed control –
testing and efficiency – parallel operation.
L = 45 T = 15 TOTAL = 60 PERIODS
TEXT BOOKS:1. Nagrath I. J and Kothari D. P. ‘Electric Machines’, Tata McGraw Hill Publishing Company Ltd,
2. P.S. Bimbhra, ‘Electrical Machinery’, Khanna Publishers, 2003.
REFERENCES:1. Fitzgerald.A.E., Charles Kingsely Jr, Stephen D.Umans, ‘Electric Machinery’, McGraw Hill Books
2. P. C. Sen., ‘Principles of Electrical Machines and Power Electronics’, John Wiley&Sons, 1997.
3. K. Murugesh Kumar, ‘Electric Machines’, Vikas publishing house Pvt Ltd, 2002.