Electrical Machines-I syllabus

Single phase Transformer: Concept of ideal transformer. Useful and leakage flux, its effects. Resistance, leakage reactance and leakage impedance of transformer windings & their effects on voltage regulation and efficiency. Exact and approximate equivalent circuits referred to L.V. and H. V. side of the transformer. Phasor diagrams for no-load and on- load conditions. Efficiency and condition for maximum efficiency. Concept of all day efficiency. Auto transformers and their applications.

Single phase Transformer: Polarity test. Parallel operation of single-phase transformers, conditions of parallel operations and load sharing. Three Phase Transformers: Standard connections of three phase transformers and their suitability for various applications, voltage Phasor diagrams and vector groups. Descriptive treatment of Parallel operation of three phase transformers Scott connection and V-V connections. Three winding (tertiary windings) transformers.

Part A: Types of DC motors, significance of back E.M.F torque equation, working at no-load and on-load. Losses, power flow diagram and efficiency. Starting of DC motors and types of starters, characteristics and speed control of DC shunt and series motor. Emerging Applications of DC Machines (Descriptive treatment only) Part B: Armature reaction and commutation: Concept of magnetizing, demagnetizing & cross magnetizing armature reaction, compensating winding, concept of commutation, value of reactance voltage, methods of improving commutation, resistance commutation, EMF commutation, interpole or compoles. (Descriptive treatment only)

Construction and types of induction motor, working principle, concept of rotating magnetic field, slip, frequency of rotor emf and rotor currents, mmf produced by rotor currents, its speed w.r.t. rotor and stator mmf. Production of torque, torque equation, torque-slip characteristics, effect of rotor resistance on torque-slip characteristics, condition for maximum torque. Relation between starting torque, full load torque and maximum torque. Losses in three phase induction motor, power- flow diagram, relation between rotor input power, rotor copper loss & gross mechanical power developed, efficiency.

Induction motor as a generalized transformer; phasor diagram. Exact & approximate equivalent circuit. No load and blocked rotor tests to determine the equivalent circuit parameters and plotting the circle diagram. Necessity & types of starters for 3-phase induction motors.