This document discusses analytical methods for determining voltage regulation in a salient pole alternator. It presents three phasor diagrams to analyze voltage regulation at lagging and leading power factors. In the first case at lagging power factor, the armature current lags both the induced EMF and terminal voltage. In the second case at leading power factor, the armature current leads the terminal voltage but lags the induced EMF. In the third case, the armature current leads both the induced EMF and terminal voltage. Equations are given relating armature current, induced EMF, terminal voltage, and power factor in each case.

1. Electrical Machines-II
6th Semester, EE and EEE
By
Dr. Binod Kumar Sahu
Associate Professor, Electrical Engg.
Siksha ‘O’ Anusandhan, Deemed to be University,
Bhubaneswar, Odisha, India
Lecture-12

2. 2
Learning Outcomes: - (Previous Lecture_11)
 To analyse the armature reaction in salient pole alternator.
 To analyse the phasor diagram of salient pole alternator.
 To determine the voltage regulation of a salient pole alternator.

3. 3
Learning Outcomes: - (Today’s Lecture_12)
 To analyse the phasor diagram of salient pole alternator.
 To determine the voltage regulation of a salient pole alternator using
analytical method.

4. 4
Analytical method of determination of voltage regulation
(Analytical Method): -
At lagging power factor: -
E
V
IaR
a
jIdXd
jIqXq
E/
Id
Iq



Vcos

IaR
a
Vsin

jIaX
q
Vcos q aI R d dI X
O
A
B
C
D
jIdXq
 d d qI X X

F
G

5. 5
   
cos q a d dE V I R I X  
 From the right angle triangle, OBD,
sin
tan
cos
a q
a a
V I XBD BC CD
OB OA AB V I R




  
 
, sin , cosd a q aWhere I I and I I  

6. 6
At leading power factor: -
 Case I : When armature current Ia leads the terminal voltage (V) but lags the induced
emf (E).
E
V
jIdXd
jIqXq
E/
Id
Iq



Vcos
IaRa
VsinjIaXq
Vcos q aI R d dI X
Ia IaRa
A
O
B
C
D

7. 7
   
cos q a d dE V I R I X  
 From the right angle triangle, OBC,
sin
tan
cos
a q
a a
I X VBC DC DB
OB OA AB V I R




  
 
, sin , cosd a q aWhere I I and I I  

8. 8
At leading power factor: -
 Case I : When armature current Ia leads the terminal voltage (V) as well as the
induced emf (E).
E
V
jIdXd
jIqXq
E/
Id
Iq

 Vcos
Vsin
Vcos q aI R
Ia
IaRa
jIaX
q
IaRa
O
A
B
D
C

9. 9
   
cos q a d dE V I R I X  
 From the right angle triangle, OBC,
sin
tan
cos
a q
a a
V I XBC BD CD
OB OA AB V I R




  
 
, sin , cosd a q aWhere I I and I I  

10. 10
Thank you