Single phase Transformers:
Operation of 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. Choice between 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. Labeling 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.
Auto transformers and Tap changing transformers:
Introduction to 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.
Course Outcomes:
At the end of the course the student will be able to:
•Understand the construction and operation of 1-phase, 3-Phase transformers and Autotransformer.
•Analyze the performance of transformers by polarity test, Sumpner’s Test, phase conversion, 3-phase connection, and parallel operation.
•Understand the construction and working of AC and DC Generators.
•Analyze the performance of the AC Generators on infinite bus and parallel operation.
•Determine the regulation of AC Generator by Slip test, EMF, MMF, and ZPF Methods.
Question paper pattern:
• The question paper will have ten questions.
• Each full question is for 20 marks.
• There will be 2 full questions (with a maximum of three sub questions in one full question) from each module.
• Each full question with sub questions will cover the contents under a module.
• Students will have to answer 5 full questions, selecting one full question from each module.
Text Books
1 Electric Machines D. P. Kothari, et al McGraw Hill 4 th Edition, 2011
2 Principals of Electrical Machines V.K Mehta, Rohit Mehta S Chand 2 nd edition, 2009
Reference Books
1 Electric Machines MulukuntlaS.Sarma,at el Cengage 1 st Edition, 2009
2 Electrical Machines, Drives and Power systems Theodore Wildi Pearson 6 th Edition, 2014
3 Electric Machines Ashfaq Hussain Dhanpat Rai & Co 2nd Edition, 2013