DC Machines and Transformers

EE25402:

DC Machines and Transformers

Course objective:

To educate the students about the concept of electromechanical energy conversion system , construction and different types of DC generator and its characteristics. To impart knowledge on the principle of operation, starting and speed control methods of DC motor. To facilitate the students regarding the working principle of single phase Transformers and various tests involved . To make the students to understand the working of auto transformer and three phase transformers.

Electro Mechanical Energy Conversion: Principle of Energy conversion – Review of magnetic circuit–Faraday's law of induced EMF - Hysteresis and Eddy Current losses – AC operation of magnetic circuits - Singly and Doubly Excited magnetic field systems – Torque production in rotating machines

DC Generators: Principle of operation, constructional details, armature windings and its types, EMF equation, armature reaction, demagnetizing and cross magnetizing Ampere turns, compensating winding, commutation, methods of improving commutation, interpoles, OCC and load characteristics of different types of DC Generators.ParalleloperationofDCGenerators,equalizingconnections-

applications of DC Generators.

DC Motors: Principle of operation, significance of back emf, torque equations and power developed by armature, speed control of DC motors, starting methods of DC motors, load characteristics of DC motors, losses and efficiency in DC machine, condition for maximum efficiency. -applications of DC motors.

Testing of DC Machines: Brake test, Swinburne’s test, Hopkinson's test, Field test, Retardation test, Separation of core losses -

Single Phase Transformers: Construction and principle of operation, equivalent circuit, phasor diagrams, testing - polarity test, open circuit and short circuit tests, voltage regulation, losses and efficiency, all day efficiency, back-to- back test, separation of core losses, parallel operation of single-phase transformers, applications of single-phase transformer.

Auto Transformer and Three Phase Transformer: Construction and working of auto transformer, comparison with two winding transformers, applications of autotransformer. Three Phase Transformer - Construction, types of connections and their comparative features, Scott connection, applications of Scott connection.

Tasks:

T1. Analyze series and parallel magnetic circuits.

T2:Observe effect of: Flux variation, Number of turns, Frequency in Faraday’s Law of Induced EMF

T3:Explain energy conversion mechanism with examples. T4 Compare: Lap winding & Wave winding

T5:Study the effect on terminal voltage due to armature reaction.

T6:Draw the Phasor diagram for Transformer for any one type of load.

Weightage: Continuous Assessment: 40%, End Semester Examinations: 60%.

Assessment Methodology: Assignments (20%), Solution to application-oriented problems using software (20%), Review of GATE questions (20%), Internal

Examinations (40%).

References:

1. Kothari, D. P., & Nagrath, I. L. (2021). Electric machines (5th ed., fully revised). Tata McGraw Hill Publishing Company Ltd.

2. Bimbhra, P. S. (2021). Electrical machinery (2nd ed.). Khanna Publishers.

3. Fitzgerald, A. E., & Kingsley, C. (2017). Electric machinery (6th ed.). McGraw Hill Education.

4. Clayton, A. E., & Hancock, N. N. (2018). Performance and design of DC machines. CBS Publishers.

5. Say, M. G. (2008). Performance and design of AC machines (1st ed.). CBS Publishers.