D.C. Generators

UNIT – II

Chapter – 3

D.C. Generators

Syllabus

Principle of operation, constructional details, armature windings and its types, EMF equation, wave shape of induced emf, armature reaction, demagnetizing and cross magnetizing Ampere turns, compensating winding, commutation, methods of improving commutation, interpoles, OCC and load characteristics of different types of DC Generators. Parallel operation of DC Generators, equalizing connections- applications of DC Generators.

Contents

3.1 Introduction... 3-3

3.2 Principle of Operation of a D.C. Generator . . .3-3

Dec.-16, May-10, 15, Marks 8

3.3 Constructional Features of a D.C. Machine ... 3-5

May-09, Dec.-16, Marks 8

3.4 Types of Armature Winding. 3-8

3.5 Winding Pitches. . . .3- 11

3.6 E.M.F. Equation of D.C. Generator. . . . .3-12

Dec.-03, 06, 07, 08, 10, 14, 19, May-10, 15, 16, 19, Marks 8

3.7 Introduction to Armature Reaction. ...3 - 14

3.8 Concept of Armature Reaction ..........3-15

Dec.-05, 09, 15, May-10, 16, Marks 16

3.9 Demagnetising and Cross Magnetising Conductors. ..3-17

Dec.-06, 17, 19, May-07, 17, Marks 8

3.10 Effects of Armature Reaction . . . .3 - 19

Dec.-05, 06, 09, May-17, Marks 4

3.11 Reduction of Effects of Armature Reaction. . 3 - 20

Dec.-05, 09, 16, 17, Marks 12

3.12 Action of Commutator.. 3-21

3.13 Practical Commutation....3-23

Dec.-07, 09, 12, 15, 16, 17, May-03, 10, Marks 10

3.14 Methods of Improving Commutation......3- 26

May-03, 05, 06, Dec.-09, 12, 13, 17, 19, Marks 8

3.15 Symbolic Representation of D.C. Generator. . 3-28

3.16 Methods of Excitation. ...3 - 28

May-05

3.17 Separately Excited Generator............3-29

Dec.-17, 18, May-04, 05, 08, Marks 8

3.18 Self Excited Generator.3-31

3.19 Shunt Generator...3-31

May-04, 05, 07, 09, 14, 15, 17, Dec.-04, 08, 18, Marks 16

3.20 Series Generator......3-34

Dec. 18, Marks 15

3.21 Compound Generator....3 35

May-04, 05, 13, 15, Dec.-06, 07, 10, 11, 19, Marks 16

3.22 Voltage Building in Self Excited Generator..3-40

3.23 Characteristics of D.C. Generators . . . . . .3-41

3.24 Characteristics of Separately Excited D.C. Generators....3-42

3.25 Load Characteristics of D.C. Shunt Generator ......3 - 43

May-07, 10, Dec.-03, 09, 10, 11, Marks 8

3.26 Load Characteristics of D.C. Series Generator............ 3 - 44

May-10, Dec.-03, 09

3.27 Load Characteristics of D.C. Compound Generator.......3-45

May-07, 12, 15, Dec.-03, 09, 10, 15, Marks 8

3.28 Applications of Various Types of Generators..........3-46

Dec.-07

3.29 Critical Field Resistance in D.C. Shunt Generator.........3-46

Dec.-05, Marks 16

3.30 Necessity of Parallel Operation of Generators ..............3 - 51

3.31 Two Marks Questions with Answers .... 3-58