Electrical Machines -1

JAWAHARLAL NEHRU TECHNOLOGICAL UNIVERSITY KAKINADA

II Year B.Tech EEE I-Sem

ELECTRICAL MACHINES - I

Objective :

Electrical machines course is one of the important courses of the Electrical discipline. In this

course the different types of DC generators and motors which are widely used in industry

are covered and their performance aspects will be studied.

UNIT – I Electromechanical Energy Conversion

Electromechanical Energy conversion – forces and torque in magnetic field systems – energy

balance- energy and force in a singly excited magnetic field system, determination of

magnetic force - co-energy – multi excited magnetic field systems.

UNIT – II D.C. Generators – Construction & Operation

D.C. Generators – Principle of operation – Constructional Features-E.M.F Equation- Action

of commutator – armature windings – lap and wave windings – simplex and multiplex

windings –Methods of Excitation-Types of DC generator: separately excited and self excited

generators

UNIT – III Armature Reaction in D.C. Generator

Armature reaction – Cross magnetizing and de-magnetizing AT/pole –commutation Process –

reactance voltage – methods of improving commutation – Compensating windings –

Interpoles.

UNIT – IV Characteristics of D.C Generators

O.C.C– build-up of E.M.F - critical field resistance and critical speed - causes for failure to

self excite and remedial measures—Internal & External characteristics of shunt, series and

Compound generator-Applications, Losses and Efficiency.

UNIT – V Parallel Operation

Need for parallel operation - Parallel operation of DC Shunt and Compound generators – use

of equalizer bar and cross connection of field windings – load sharing.

UNIT – VI D.C. Motors

D.C Motors – Principle of operation – Back E.M.F. - Torque equation –characteristics of

shunt, series and compound motors – Armature reaction and commutation, Losses and

Efficiency.

UNIT – VII Speed Control of D.C. Motors

Speed control of d.c. Motors: Armature voltage and field flux control methods. Ward-

Leonard system. Principle of 3 point and 4 point starters – protective devices—Application

of DC Motors.

UNIT – VIII Testing of D.C. Machines

Testing of d.c. machines: methods of testing-:Brake test, Indirect testing: Swinburne’s

method-- Regenerative or Hopkinson’s method-- Field’s test for series machines—

Retardation test-- separation of losses

TEXT BOOKS:

1.Electrical Machines – P.S. Bimbra., Khanna Publishers

REFERENCE BOOKS:

1.Electrical Machines by R.K.Rajput, Lakshmi publications,5th edition

2.Electrical Machines by D P.Kothari, I .J .Nagarth,Mc GrawHill Publications, 4th edition

3.Electrical Machines by J.B.Guptha. S.K.Kataria & Sons