Issue No. / Date: 01/26.07.2019
Revn. No. / Date:00
Roll No : ………………………………
Name : ……….……………………………..
CEMP/ISO/UG/EEE/657
COLLEGE OF ENGINEERING AND MANAGEMENT PUNNAPRA
Under CAPE Government of Kerala
DEPARTMENT OF ELECTRICAL AND ELECTRONICS ENGINEERING
B Tech Degree 4th Semester ELECTRICAL AND ELECTRONICS ENGINEERING
First Series Examination September 2021
EET 202 DC MACHINES AND TRANSFORMERS
Time : 1 Hr
Q. No
1
2
3.
4.
Question
Part A
(Answer all questions)
Derive the emf equation of dc generator
With the help of speed armature current characteristics ,explain why the series
motors should not be started with out any load
Compare the electrical and mechanical characteristics of a dc shunt motor with
those of a DC series motor.mention their applications also
Point out the necessity of equalizer rings in a lap wound dc machine.why this is
not applicable in wave wound machines
Max Marks : 25
Mark CO BL
2.5
CO1 L2
2.5
CO3 L3
2.5
CO2 L2
2.5
CO2 L1
(4+3.
5)
CO1 L2
Part B: Answer Anyone Question (1 X 7.5 Marks)
5
A) In a 120 V compound generator,the resistance of the armature,shunt and
series windings are 0.06Ω, 25Ω and 0.04Ω respectively.The load current is
100A at 120 V.Find the induced emf and armature current when the machine is
connected as 1)Long shunt 2)short shunt
B)What is mean by armature reaction? What are its effects on main field flux.
Write any two methods for compensating the effects of armature reaction in DC
generators
OR
6
The magnetisation characteristics for a 4-pole, 110V, 1000 r.p.m d.c shunt
generator is as follows
Field
0
0.5
1
1.5
2
2.5
3
Current
O.C
5
50
85
102
112
126
120
Volatge
(v)
7.5
CO2 L3
(4+3.
B) Find the useful flux per pole on no-load of 250 V, 6 pole shunt motor having
5)
a wave connected armature winding with 110 turns. The armature resistance is
0.2Ω. The armature current is 13.3 A at the no load speed of 908 r.p.m
CO3 L2
The armature is lap connected with 144 conductors. Field resistance is 45Ω.
Determine the a). Residual flux per pole b). The critical Field resistance
Part C: Answer Anyone Question (1X 7.5 Marks)
A) Derive the condition for maximum power output in a dc motor
7
OR
8
A) A dc shunt generator has a full load output of 9.5 kw at 220V. The armature
and shunt field winding resistances are 0.4 ohm and 150 ohm respectively.The
sum of mechanical and iron losses is 800w.calculate the power required at the
driving shaft at full load condition
7.5
COURSE OUTCOMES (CO)
CO1: To enable the students to understand the concept of dc machines
CO 2:To enable the students to identify various types of dc generators,their
characteristics and applications
CO2: To enable the students to understand the various types of dc
motors,working,characteristics and applications
BL- BLOOM’S TAXONOMY LEVELS
1- Remembering
2-Understanding
3-Applying
Verified by HOD
CO2 L3