JAWAHARLAL NEHRU TECHNOLOGICAL UNIVERSITY HYDERABAD

Prerequisites

Electrical Circuit Analysis-1 & Electrical Circuit Analysis-2

Course Objectives:

• To study and understand different types of DC machines a n d t hei r performance evaluation through various testing methods.
• To understand the operation of single and ploy-phase Transformers
• To analyze the performance of transformers through various testing methods.

Course Outcomes

After learning the contents of this paper the student must be able to

• Identify different parts of a DC machines & understand their operation.
• Carry out different excitation, starting, speed control methods and testing of DC machines.
• Analyze single & three phase transformers and their performance through testing.

Course Objectives Program Outcomes

PO1 PO2 PO3 PO4 PO5 PO6 PO7 PO8 PO9 PO10 PO11 PO12 To study and 3 2 3 1 1 1 3 1 2 1 2 3 understand different types of DC machines a n d t h e i r p erformance evaluation through various testing methods. To understand the 3 3 3 2 2 1 3 1 2 2 2 3 operation of single and ploy-phase Transformers

To analyse the 3 2 3 2 2 2 3 1 2 1 3 3 performance of transformers through various testing methods

Course Outcomes Program Outcomes

PO1 PO2 PO3 PO4 PO5 PO6 PO7 PO8 PO9 PO10 PO11 PO12 Identify different parts 2 2 2 3 3 2 1 1 3 3 3 3 of a DC machines & understand their operation Carry out different 2 1 3 1 2 3 3 1 3 2 2 3 excitation, starting, speed control methods and testing of DC machines Analyse single & 1 1 2 1 1 3 3 1 3 3 3 3 three phase transformers and their performance through testing

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-excited and remedial measures. Load characteristics and applications 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 and Applications. 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: Open Circuit and Short Circuit 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/Δ, Δ/Y, Δ/Δ and open Δ, Scott connection and Applications.

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.

REFERENCE BOOKS:

• 1. Prithwiraj Purkait, Indrayudh Bandyopadhyay, “Electrical Machines”, Oxford, 2017.
• 2. M. G. Say, “Performance and design of AC machines”, CBS Publishers, 2002.
• 3. A. E. Fitzgerald and C. Kingsley, "Electric Machinery”, New York, McGraw Hill Education, 2013.
• 4. A. E. Clayton and N. N. Hancock, “Performance and design of DC machines”, CBS Publishers, 2004.