06EE46 - Transformers And Induction Machines (2006 - 2007) |
PART – A |
UNIT – I Basic Concepts |
Concept of coupled circuits. Dot convention. Writing
network equilibrium equations in coupled circuits (problems on coupled
circuits excluded). Principle of transformer action for voltage transformation.
Constructional details of shell type and core type single-phase and threephase
transformers. Description of the following types of transformers —
power transformer, distribution transformer, constant voltage transformer,
constant current transformer, variable frequency transformers, autotransformers |
UNIT – II Single-phase Transformers |
Concept of ideal transformer. Equation for
E.M.F. induced in the two windings. Voltage transformation ratio. Ideal transformer on no-load and loaded condition with corresponding phasor
diagrams. Concept of M.M.F. balance in the magnetic circuit of an ideal
transformer. Current transformation ratio. Concept of referring impedance
connected on one side of ideal transformer to the other side. Practical
transformer – how it deviates from the ideal transformer. Development of
exact equivalent circuit of a practical transformer – visualization of a
practical transformer as an ideal transformer combined with imperfections of
electric and magnetic circuits. Approximate equivalent circuit of a practical
transformer. |
UNIT – III |
Phasor diagram of a practical transformer for both no-load and loaded
conditions. Losses, power and all-day efficiency, regulation. Testing of
transformers — O.C. test, S.C. test and predetermination of efficiency and
regulation. Sumpner’s test. Parallel operation — need, conditions to be
satisfied for parallel operation. Load sharing. |
UNIT - VI Three-phase Transformers |
All types of three-phase transformer
connections including open delta. Choice of connection. Bank of singlephase
transformers for three-phase operation. Phase conversion using
transformers. Scott connection for three-phase to two-phase conversion.
Labeling of three-phase transformer terminals, phase shift between primary
and secondary and vector groups. Conditions for proper operation of threephase
transformers in parallel. |
PART – B |
UNIT – V |
(a) Three-winding Transformers |
Advantages and disadvantages of threewinding
transformers. Equivalent circuit.
|
(b) Basic Concepts of Induction Machines |
Concept of rotating magnetic
field. Operating principle, construction, classification and types — singlephase,
three-phase, squirrel-cage, slip-ring, double-cage types
|
UNIT – VI Three-phase Induction Motor |
Phasor diagram of induction motor on noload
and loaded conditions. Visualization of a three-phase induction motor as
a generalized transformer with a rotating secondary and obtaining its
equivalent circuit. Different kinds of power losses in an induction motor.
Efficiency. Performance evaluation — output power, torque, efficiency,
current and power factor. |
UNIT – VII |
Torque-slip characteristics covering motoring, generating and braking
regions of operation. Induction generator. No-load and blocked rotor tests.
Circle diagram and therefrom performance evaluation of the motor. Cogging
and crawling. Equivalent circuit and performance of double-cage and deepbar
motors.
|
UNIT – VIII |
(a) Starting and Control of Three-phase Induction Motor |
Need for
starter. DOL, Y-Delta and auto-transformer starting. Rotor resistance starting.
Electronic starters (any one type). Speed control — voltage, frequency, and
rotor resistance variations.
|
(b) Single-phase Induction Motor |
Double revolving field theory and
principle of operation. Types of single-phase induction motors: split-phase,
capacitor start, shaded pole motors.
|
REFERENCE |
TEXT BOOKS: |
1. “Power System Engineering”, A. Chakrabarti, M. L. Soni, and P.V. Gupta, Dhanpat Rai and Co., New Delhi.
2. “Elements of Power System Design”, M. V. Deshpande, A. H.Wheeler and Co.
|
Reference Books |
1. “Electric Power Generation, Transmission and Distribution”, S. M. Singh, P.H.I., New Delhi.
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