UEE301 DIRECT CURRENT MACHINES AND TRANSFORMERS
Single phase Transformers: Introduction, Basic principle, Types of transformer, Construction of singlephase transformer, Transformer windings, Terminals and leads, Bushings, Tapping, Cooling of transformer, Transformer oil, Conservator and breather, Buchhloz realy, Transformer tank, EMF equation of a transformer, Stepup and stepdown transformer, Transformer on noload and on load, Magnetic leakage, Transformer with resistance and reactance, Equivalent resistance and reactance, Equivalent circuit, Open circuit , Short circuit test, Separation of core losses, Total approximate voltage drop of a transformer, Exact voltage drop, Per unit resistance, Leakage reactance and impedance voltage drop, Voltage regulation of a transformer, Losses in a transformer, Efficiency of a transformer, Condition for maximum efficiency, All day efficiency, Polarity test of a singlephase transformer, Sumpner’s test, Parallel operation of singlephase transformers, Load sharing of two transformer, Auto transformer.
Threephase Transformer: Advantages of three phase transformer, Principle of operation, Construction of three phase transformers, connections, Open delta or VV connection, Scott connection or TT connection, Threephase to twophase conversion, Threephase to sixphase conversion, Threewinding transformer, Parallel operation of transformers, Rating of transformers.
Special purpose Transformers: Instrument transformers (CT and PT), Earthing transformer, Pulse transformer, High frequency transformer, Converter transformer.
General concepts of Rotating Electrical Machines: Electromagnetic torque, Reluctance torque, Constructional features of rotating electrical machines, Classifications of rotating electrical machines, Construction of DC machines, Principle of DC generator, Principle of DC motor, Lap winding, Wave winding, Electrical and mechanical degrees. DC Generators: Classification of DC generator, Brush drop, EMF equation, Derivation of generated emf, Losses in DC generator, Power stages, Condition for maximum efficiency, Armature reaction, Demagnetising and crossmagnetising conductors, Demagnetising ampereturns per pole, Crossmagnetising ampereturns per pole, Compensating windings, Commutation, Value of reactance voltage, Methods of improving commutation, Equalizer rings, Characteristic of DC generators, Voltage build up of shunt generators, Conditions for buildup of shunt generator, Voltage regulation, Parallel operation of DC generators, Applications of DC generators.
DC Motors: Voltage equation, Back emf, Condition for maximum mechanical power, Armature torque of a motor, Relation of speed with back emf and flux, Characteristic of DC motors, Speed control of DC motors, WardLeonard control (Voltage control), Necessity of starter for starting of DC motor, Three point starter, Four point starter, DC shunt motor starter design, Electric breakings of DC shunt and series motors, Testing of DC machines: Brake test, Swinburne’s test, Hopkinson’s test or back to back test, Retardation test or Running test, Field’s test. Uses of DC motors. Laboratory Work
DC Machines: Characteristics of generators and motors, Speed control, Efficiency, DC generators in parallel; Transformers: Open and short circuit tests, Parallel operation, Harmonics in no-load current, Three-phase connections, 3phase to 2phase and 6phase conversions.
1. Bimbhra, P.S., Electrical Machinery, Khanna Publishers (2008) 2nd ed. 2. Mukherjee, P.K. and Chakravorty, S., Electrical Machines, Dhanpat Rai (2004) 2nd ed. 3. Nagrath, I.J. and Kothari, D.P., Electric Machines, Tata McGraw Hill (2004) 3rd ed.
Bimbhra, P.S., Generalized Theory of Electrical Machines, Khanna Publishers (2007) 5th ed. 2.
Toro, Vincert, Electromechanical Devices for Energy Conversion, Prentice Hall of India (2004) 2nd ed....
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