EE25402 DC Machines and Transformers – Semester IV – EEE – R-2025

Subject Code & Name: EE25402 – DC Machines and Transformers

Regulation: R-2025

Semester: IV (Fourth Semester)

Branch: B.E. Electrical and Electronics Engineering (EEE)

Credits / L-T-P: 3 Credits | L-T-P: 3-0-0

Course Objectives

• 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.

Full Unit-wise Syllabus

Unit I – 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

Unit II – 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. Parallel operation of DC Generators, equalizing connections - applications of DC Generators.

Unit III – 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.

Unit IV – Testing of DC Machines

Brake test, Swinburne’s test, Hopkinson's test, Field test, Retardation test, Separation of core losses -

Unit V – 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.

Unit VI – 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.

Course Outcomes (COs)

• CO1: Explain principles of electromechanical energy conversion and magnetic circuits.
• CO2: Analyze the performance and characteristics of DC generators under various operating conditions.
• CO3: Evaluate the operation, control, and testing methods of DC motors.
• CO4: Analyze single-phase, auto, and three-phase transformers including testing, performance, and applications.

Assessment Pattern (Quick Note)

• Weightage: Continuous Assessment 40% | End Semester Examinations 60%
• Internal methodology: Assignments (20%), Solution to application-oriented problems using software (20%), Review of GATE questions (20%), Internal Examinations (40%)

Source: Official Anna University – B.E. Electrical and Electronics Engineering R-2025 Syllabus
Last Updated: October 2026