DC Machines & Transformers

DC MACHINES

DC Generator:

                      Laws of magnetic circuit  Principle of operation, Constructional details, Armature Windings, EMF equation, Methods of Excitation, Separate, shunt, series and compound excitations.

No load characteristics  Armature reaction, Commutation, Interpoles, Compensating windings, Load characteristics of various types of DC Generators.  

DC MOTORS:

                      Principle of operation  Torque equation, Electrical and Mechanical characteristics of DC shunt, series and compound motors. Starters  Speed control  Armature and field control  Braking.

Losses and efficiency  Swinburnes test  Separation of losses, Hopkinsons test.                         

DC MACHINE

TRANSFORMERS

transformer:

          Principle of operation  Constructional features, Classification of Transformers, EMF equation, Transformation ratio, Transformer on no-load and load, Phasor diagrams.          

Equivalent circuit - Voltage regulation, Regulation curve, Losses, Efficiency, All day efficiency                                    

Phasing out, polarity and voltage ratio tests  Open circuit and short circuit tests, Sumpners test. Separation of losses  Parallel operation                                  
Auto-Transformer  Principle of operation  Saving of copper  Phasor diagram  Equivalent circuit  Three phase Transformer connections  Instrument Transformers.  

Transformer