Polyphase Systems and Component Transformations (EE229)


B.Tech (E&E)




Programme Specific Electives (PSE)

Credits (L-T-P): 

04 (3-1-0)


Balanced Polyphase Circuits: Generation of polyphase voltages, Phase sequence, Three-phase 3-wire and 4-wire systems, wye and delta connections, The n-phase star and mesh, Power calculations in balanced systems, General n-wire balanced systems, Harmonics in Wye- and Delta-systems.

Unbalancd Polyphase Circuits:  Unbalanced loads, The Wye-Wye system with and without neutral connections,  Neutral shift, the Wye-delta system,  Phase-sequence effects, Methods of checking voltage phase sequence, The three-wattmeter/Two-wattmeter methods of measuring three-phase power, the use of (n-1) wattmeters for measuring n-wire power, Power-factor in unbalanced three-phase systems, Extensions to non-sinusoidal behaviour.

Introduction to Symmetrical components: A brief historical review, Application of the method, Fundamental principles, Symmetrical component systems, resolution of three vectors into symmetrical components, Independence of sequences in symmetrical systems, sequence impedances.

Calculation of Unbalanced faults: Sequence networks, Connection of networks to represent faults, Outline of short-circuit calculations, Treatment of transformer connections, Measurement of sequence voltages and currents.  Measurement of sequence power quantities,  Flow of power due to unbalance.

Multiphase systems:  Resolution of multiphase systems into symmetrical components, 2-phase and 4-phase systems, Irregular systems, General treatment of polyphase circuits, Impedances of symmetrical polyphase systems, Harmonics.


1. C.F. Wagner, R.D. Evans, Symmetrical Components, McGraw-Hill, 1933.
2. J.L. Blackburn , Symmetrical Components for Power System Engineering, Marcel-Dekker ,1993.
3. Edith Clarke, Circuit Analysis of AC Power Systems – Volumes I and II, John Wiley and Sons, 1950.


Electrical and Electronics Engineering