JAWAHARLAL NEHRU TECHNOLOGICAL UNIVERSITY HYDERABAD

Prerequisite

Basic Electrical Engineering

Course Objectives:

• To study and understand different types of DC generators, Motors and Transformers, their construction, operation and applications.
• To analyze performance aspects of various testing methods.

Course Outcomes

At the end of this course, students will demonstrate the ability to

• Identify different parts of a DC machine & understand its operation
• Carry out different testing methods to predetermine the efficiency of DC machines
• Understand different excitation and starting methods of DC machines
• Control the voltage and speed of a DC machines
• Analyze single phase and three phase transformers circuits.

UNIT - I

D.C. Generators: Principle of operation – Action of commutator – constructional features – armature windings – lap and wave windings – simplex and multiplex windings – use of laminated armature – E. M.F Equation. Armature reaction – Cross magnetizing and de-magnetizing AT/pole – compensating winding – commutation – reactance voltage – methods of improving commutation. Methods of Excitation – separately excited and self-excited generators – build-up of E.M.F - critical field resistance and critical speed - causes for failure to self-excite and remedial measures. Load characteristics of shunt, series and compound generators

UNIT - II

D.C Motors: Principle of operation – Back E.M.F. - Torque equation – characteristics and application of shunt, series and compound motors – Armature reaction and commutation. Speed control of D.C. Motors - Armature voltage and field flux control methods. Motor starters (3-point and 4-point starters) Testing of D.C. machines - Losses – Constant & Variable losses – calculation of efficiency – condition for maximum efficiency.

UNIT - III

Testing of DC Machines: Methods of Testing – direct, indirect, and regenerative testing – Brake test – Swinburne’s test – Hopkinson’s test – Field’s test - separation of stray losses in a d.c. motor test.

UNIT - IV

Single Phase Transformers: Types - constructional details-minimization of hysteresis and eddy current losses- EMF equation - operation on no load and on load - phasor diagrams Equivalent circuit - losses and efficiency – regulation - All day efficiency - effect of variations of frequency & supply voltage on iron losses.

UNIT - V

Testing of Transformers and Poly-Phase Transformers: OC and SC tests - Sumpner’s test - predetermination of efficiency and regulation-separation of losses test-parallel operation with equal and unequal voltage ratios - auto transformers-equivalent circuit - comparison with two winding transformers. Poly-phase transformers – Poly-phase connections - Y/Y, Y/, /Y, / and open

R18 B.TECH EEE

TEXT BOOKS:

• 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.

REFERENCE BOOKS:

• 1. M. G. Say, “Performance and design of AC machines”, CBS Publishers, 2002.
• 2. P. S. Bimbhra, “Electrical Machinery”, Khanna Publishers, 2011.
• 3. I. J. Nagrath and D. P. Kothari, “Electric Machines”, McGraw Hill Education, 2010. R18 B.TECH EEE