Class 13 DCGenerator types

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```					  Types of D.C. Generators

According to the way in which their fields
are excited, generators are classified into :
i) Separately excited D.C. Generator
ii) Self- excited D.C. Generator

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i)   Separately excited D.C. Generators are those whose field
magnets are energized from an independent source of D.C. Current

If                              I
Brush
+
L
Eg           O   V
A
Field Winding                         D

-
Brush

R

V  E g  IR a  Brush Drops
Ra = Armature Resistance

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ii) Self excited D.C. Generators are those whose field
magnets are energized by the currents produced by the generators
themselves.

There are 3 types of self-excited D.C. Generators named according to
the manner in which their field coils are connected to the armature.

These are :

•   Shunt wound D.C. Generator
•   Series wound D.C. Generator
•   Compound wound D.C. Generator

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i)   Shunt wound D.C. Generator

Ish                  I
+
Ia
Ra       L
Shunt Field                                   O   V
Eg                A
Rsh                                      D

-

Rsh – Shunt Field Resistance
Ra - Armature Resistance
I a  I  I sh
V  E g  I a R a  Brush Drops
V  I sh R sh
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ii) Series wound D.C. Generator

Ia=Ise=I   Rse

Series Field
+
L
O   V
Eg
A
D

V  E g  I a ( R a  R se )  Brush Drops

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iii) Compound wound D.C. Generator

I

Series Field

Ish
L   V
Ia       O
A
D
Shunt Field                  Eg

Short Shunt

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Ish                I

Series Field

Ia
Shunt Field                           L   V
O
Eg             A
D

Long Shunt

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Ex.1 A D.C. Shunt Generator delivers 450A at 230V and the
resistance of the shunt field and armature are 50Ω and 0.03 Ω
respectively. Calculate the generated EMF.

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Ex.2 An 8 - pole D.C. Shunt Generator with 778 wave
wound armature conductors running at 500 rpm supplies
a load of 12.5Ω resistance at terminal voltage of 250V.
The armature resistance is 0.24Ω and the field resistance is 250Ω .
Find the armature current, the generated EMF and the flux per pole.

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