Electrical Machines I (DC Machines & Transformers)
Single-phase and three-phase transformers, DC generators, DC motors, and efficiency tests.
Syllabus Units (4)
- Unit 1
Single-Phase Transformers
Working principle, EMF equation, exact and approximate equivalent circuits referred to primary/secondary, phasor diagrams under lagging/unity/leading loads, losses, voltage regulation, condition for maximum efficiency, and Open-Circuit & Short-Circuit tests.
Read note - Unit 2
Three-Phase Transformers & Auto-Transformers
Three-phase bank connections (Y-Y, Δ-Δ, Y-Δ, Δ-Y), vector groups and clock hour phase displacement, tertiary windings, Open-Delta (V-V) connection and capacity derating, Scott connection for 3Φ-to-2Φ transformation, and auto-transformer operating principles, copper savings, and power throughput boost.
Read note - Unit 3
DC Generators: Principles, Armature Reaction & Characteristics
Constructional architecture (yoke, poles, commutator, brushes), simplex lap vs wave armature windings, EMF equation, armature reaction demagnetizing and cross-magnetizing effects, MNA shift, commutation and interpoles, OCC magnetization curve, critical field resistance (Rc) and critical speed (Nc) for voltage build-up, and external load characteristics of shunt, series, and compound generators.
Read note - Unit 4
DC Motors, Speed Control & Testing
Working principle, Lorentz force, back EMF as natural speed governor, gross and shaft torque derivations, torque-speed characteristics of shunt, series, and compound motors, starter architectures (3-point and 4-point), speed control methods (armature rheostat, flux weakening, Ward-Leonard drive), and testing methods (Swinburne no-load test and Hopkinson regenerative back-to-back test).
Read note