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SYLLABUS

UNIT-I

Single phase transformers Single phase transformers - Constructional details - Hysteresis and eddy current losses - E.M.F equation - Operation on no load and on load - Phasor diagrams. Equivalent circuit - Losses and efficiency - Regulation. All-day efficiency - Effect of variations of frequency and supply voltage on iron losses.

UNIT-II

Testing of Transformers, Three-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. Three phase transformers – Connections-Y/Y, Y/∆, ∆/Y, ∆/∆ and open ∆, Third harmonics in phase voltages – Three winding transformers, Tertiary windings – Scott connection.

UNIT-III

Three-Phase induction motors Polyphase induction motors – Constructional details of cage and wound rotor machines – Production of a rotating magnetic field – Principle of operation – Slip – Rotor E.M.F and rotor frequency – Rotor reactance, Rotor current and power factor at standstill and under running conditions – Rotor power input, Rotor copper loss and mechanical power developed and their inter relationship.

UNIT-IV

3-Phase induction motor characteristics Torque equation – Expressions for maximum torque and starting torque – Torque slip characteristic – Load characteristics – Equivalent circuit – Phasor diagram – Crawling and cogging – Circle diagram – No-load and blocked rotor tests – Predetermination of performance.

UNIT-V

Starting and speed control of induction motors Starting methods and starting current and torque calculations, Speed control – Change of frequency; Pole changing and methods of cosequent poles; Cascade connection, Injection of an E.M.F.