# Electrical Machines - II

#### Features Includes:

• 92 - 3D/2D Animation
• 700 Pages of Content
• 60 Lecture Hours
• 34 Solved Problems
• 80 Quiz
• Suitable for All Technical University Syllabus

#### Course Description

This course comprises the Principle of single phase transformer, Three phase transformer, Various transformer connections and various methods of testing. In addition to that specical purpose transformer like Potenital and current transformers are also included.

#### OBJECTIVES:

• To study the working principle of single phase transformers and it types.
• To estimate the various losses taking place in transformer and to study the different testing methods to arrive at their performance.
• To learn about three phase transformer and its connections.
• To study the various special purpose transformer.
###### UNIT I - SINGLE PHASE TRANSFORMER

Principle of single phase transformers - Necessity of transformer, Transformer and its principle, Step-up and step-down transformer. Construction of single phase transformer - Types of transformer, Essential parts of a transformer, Construction of transformer, Winding, Types of transformers according to the magnetic core, Difference between core type and shell type transformer. Ideal transformer - Ideal transformer, Elementary theory of ideal transformer. EMF equation - E.M.F. equation of transformer, Problem based on E.M.F equation of transformer. Transformer ratio - Voltage transformation ratio, Problems & Exercises based on voltage transformer ratio. Working of transformer on No load - Transformer on No load, Importance in the study of transformer, Problems & Exercises based on transformer on no load. Working of transformer on load - Transformer On load, Problems & Exercises based on transformer on load. Real or Practical transformer - Parameters referred to HV/LV windings, Magnetic leakage, Transformer with resistance and leakage reactance, Problems & Exercises based on transformer leakage reactance. Equivalent circuit - Equivalent circuit, Per unit system, Problems & Exercises based on equivalent circuit of transformer. Losses in a transformer - Losses in a transformer, Problem based on losses in transformer. Efficiency - Transformer efficiency - Condition for maximum efficiency, Problem based on efficiency in transformer. Voltage regulation - Regulation of transformer, Problem based on voltage regulation of transformer, Applications of transformer.

###### UNIT II - TESTING OF TRANSFORMER

Testing of transformer - Open circuit or no load test, Short circuit (or) impedance test, Problem based on testing of transformer, Winding resistance test, Polarity Test, Sumpner's or back to back test. Parallel Operation of Transformers - Parallel transformers on No-load, Division of load between transformers in parallel. Cause and effects of harmonics - Harmonics on transformer, Harmonics on three-phase bank of single-phase transformers. Current inrush in transformers - Inrush current. Noise in transformers - Causes of transformer noise, Noise reduction techniques.

###### UNIT III - THREE PHASE TRANSFORMER

Auto transformer - Special purpose transformer, Saving of copper, Welding transformer. Three phase transformers - Introduction, Construction of 3-phase transformer, Advantages of three phase transformer over single phase transformer, Functions of Transformer Accessories, Buchholz relay. Transformer connections - Three phase transformer connections, Connections of primary and secondary windings of 3-phase transformers, Types of 3-phase transformer winding connections, Delta/Delta Connection, Wye/Delta Connection, Delta/Wye Connection, Open delta or V-V connection, Conditions for parallel operation of three phase transformers. Parallel operation of three phase transformer - Parallel operation of transformers, Parallel transformers on No-load, Division of load between transformers in parallel. Phase conversion - Three - phase to two - phase conversion and vice – versa, Three/One-phase Conversion. Three phase Auto transformers - Three phase Auto transformers. Tertiary winding Transformers - Three winding transformers, rating of tertiary winding, Harmonics on transformer, Harmonics on three-phase bank of single-phase transformers.

###### UNIT IV - SPECIAL PURPOSE TRANSFORMER

Instrument transformer - Necessity of instrument transformers, Types of instrument transformers, Current transformers, Ring type current transformer, Precautions in using C.T, Potential transformer. Power measurement with the help of instrument transformer - Single phase power measurement, Three phase power measurement. Tap changing transformers - On load tap changing - Necessity of tap changer, OFF - Load tap changing, ON-Load tap changing.