Electrical Machines

TransformersConstruction, Polarity test, Sumpner's test, All day efficiency.Autotransformer Volt-amp relation, Efficiency, Advantages and disadvantages and applications, Three-phase transformers : Connections, Three-phase bank of single phase transformers, Scott connections, Instrument transformers.D.C. MachinesD.C. Machine : Construction, emf and torque equations. Armature reaction, Commutation, Performance characteristics of motors and generators, Starting of motors, Speed control, Losses and efficiency.Three Phase Induction MotorConstruction, Rotating magnetic field and Principle of operation, Equivalent circuit, Torque production, Torque-slip characteristics, Speed control, Starting of squirrel cage and Slip ring induction motors.Three Phase Synchronous MachinesAlternator : Construction, EMF equation and effects of pitch and distribution factors, Phasor diagram, Armature reaction, Voltage regulation and its determination by synchronous impedance method, Methods of synchronization.Synchronous Motor : Principle of operation and starting torque and mechanical power developed, Effect of excitation on line current, (V-curves).Fractional H.P. MotorsSingle phase induction motor : Construction, Revolving field theory and principle of operation, equivalent circuit and starting methods. Two-phase servo-motor, Stepper motor, and their applications.Industrial ApplicationsConcept of braking in dc and ac motors, Two quadrant and four quadrant operation of dc and three phase induction motors, Industrial applications of dc and ac motors.