Transformers and Generators
TRANSFORMERS AND GENERATORS
Single phase Transformers: Operation of the practical transformer under no-load and on-load with phasor diagrams. Open circuit and Short circuit tests, calculation of equivalent circuit parameters and predetermination of efficiency-commercial and all-day efficiency. Voltage regulation and its significance.
Three-phase Transformers: Introduction, Constructional features of three-phase transformers. The choice between the single unit three-phase transformer and a bank of three single-phase transformers. Transformer connection for three-phase operation– star/star, delta/delta, star/delta, zigzag/star and V/V, comparative features. Phase conversion-Scott connection for three-phase to two-phase conversion. Labelling of three-phase transformer terminals, vector groups.
Tests, Parallel Operation of Transformer& Auto Transformer: Polarity test, Sumpner’s test, separation of hysteresis and eddy current losses
Parallel Operation of Transformers: Necessity of Parallel operation, conditions for parallel operation– Single-phase and three-phase. Load sharing in case of similar and dissimilar transformers.
Autotransformers and Tap changing transformers: Introduction to the autotransformer-copper economy, equivalent circuit, no-load and on-load tap changing transformers.
Three-Winding Transformers & Cooling of Transformers: Three-winding transformers. Cooling of transformers.
Direct current Generator: Armature reaction, Commutation and associated problems,
Synchronous Generators: Armature windings, winding factors, e.m.f equation. Harmonics–causes, reduction and elimination. Armature reaction, Synchronous reactance, Equivalent circuit.
Synchronous Generators Analysis: Alternator on load. Excitation control for constant terminal voltage. Voltage regulation. Open circuit and short circuit characteristics, Assessment of reactance-short circuit ratio, synchronous reactance, Voltage regulation by EMF, MMF and ZPF
Synchronous Generators (Salient Pole): Effects of saliency, two-reaction theory, Parallel operation of generators and load sharing. Methods of Synchronization, Synchronizing power, Determination of Xd & Xq – slip test
Performance of Synchronous Generators: Power angle characteristic (salient and non-salient pole), power angle diagram, reluctance power, Capability curve for large turbo generators. Hunting and damper windings.