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By Prof. L.Umanand, Principal Research Scientist, Power Electronics Group, CEDT, IISC Bangalore.
ELECTRICAL MACHINES – II SYLLABUS :
As an extension of Electrical machines I course this subject facilitates to study of the performance of
Transformers and Induction motors which are the major part of industrial drives and agricultural pump
Single Phase Transformers – Construction & Operation
Single phase transformers-types - constructional details-minimization of hystersis and eddy current
losses-emf equation - operation on no load and on load - phasor diagrams
Single Phase Transformers - Performance
Equivalent circuit - losses and efficiency-regulation. All day efficiency - effect of variations of frequency &
supply voltage on iron losses.
Testing of Single Phase Transformer and Autotransformer
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.
Polyphase transformers - Polyphase connections - Y/Y, Y/D, D/Y, D/D and open D, Third harmonics in
phase voltages-three winding transformers-tertiary windings-determination of Zp, Zs and Zt transients in
switching - off load and on load tap changing; Scott connection.
Polyphase Induction Motors
Polyphase induction motors-construction details of cage and wound rotor machines-production of a
rotating magnetic field - principle of operation - rotor emf and rotor frequency - rotor reactance, rotor
current and pf at standstill and during operation.
Characteristics of Induction Motors
Rotor power input, rotor copper loss and mechanical power developed and their inter relation-torque
equation-deduction from torque equation - expressions for maximum torque and starting torque - torque
slip characteristic - double cage and deep bar rotors - equivalent circuit - phasor diagram - crawling and
Circle Diagram of Induction Motors
Circle diagram-no load and blocked rotor tests-predetermination of performance-methods of starting and
starting current and torque calculations
Speed Control Methods
Speed control-change of frequency; change of poles and methods of consequent poles; cascade
connection. injection of an emf into rotor circuit (qualitative treatment only)-induction generator-principle of
1. Electric machinery - A.E. Fitzgerald, C.Kingsley and S.Umans, Mc Graw Hill
Companies, 5th edition
2. Electrical machines-PS Bhimbra, Khanna Publishers.
1. Performance and Design of AC Machines by MG.Say, BPB Publishers
2. Theory of Alternating Current Machinery- by Langsdorf, Tata McGraw-Hill Companies, 2nd
3. Electric Machines –by I.J.Nagrath & D.P.Kothari,Tata Mc Graw Hill, 7th Edition.2005
4. Electromechanics-II (transformers and induction motors) S. Kamakashaiah Hitech publishers.