Name of the Subject:
Subject Code:
Contact Hours: 3L + 1T
ELECTRICAL MACHINES I
EENUGPC04
Credit: 4
Course Objectives:
1. To explore the basic principles of transformer and dc machines and analyze comprehensively their
steady –state behaviors.
2. To examine characteristic of static and dynamic DC Machine, Transformer, 3-Ph Induction motor.
3. To classify and outline the operation and construction of D.C. and A.C. machines.
4. To solve machines related problems which finds application in modern industries, homes and offices.
Course Outcome:
After the completion of this course, the students will be able to:
1. Be familiar with D.C. and A.C. machines, their operating and control characteristics,
2. Understand basic measurement of Power losses, Efficiency and Characteristic of DC Machine,
Transformer, 3-Ph Induction motor.
3. Compare the performance characteristics of different machines.
4. Categorize different phenomena occurring in DC machines and AC three phase motors.
5. Identify possible applications of different machines.
Uni
t
No.
1
2
3
4
5
6
Topics
Single Phase Transformer: Construction of core and shell type transformers;
Classifications of transformers; Basic principle of operation; EMF equation; Equivalent
circuit and phasor diagrams; Voltage regulation; Losses and Efficiency; Parallel operation of
transformers; Tests: Polarity test, Open- circuit test, Short Circuit test. Autotransformer:
Autotransformer: Principle of operation, phasor diagram. Comparison of weight, copper
loss, equivalent reactance with 2 winding transformers.
D.C. Machine – Construction & Operation: D.C. Generators: Principle of operation,
Action of commutator, constructional features, armature windings, lap and wave windings,
use of laminated armature, E. M.F Equation.
Armature reaction in D.C. Machine: Armature reaction, Cross magnetizing and demagnetizing AT/pole, interpoles, compensating winding, reactance voltage, methods of
improving commutation.
DC Generators: Methods of Excitation– separately excited and self-excited generators,
build-up of E.M.F, critical field resistance and critical speed, causes for failure to self-excite
and remedial measures. Load characteristics of shunt, series and compound generators,
parallel operation.
D.C. Motors: D.C Motors – Principle of operation, Back E.M.F. Torque equation.
Characteristics and application of shunt, series and compound motors. Principle of 3 point
and 4 point starters.
Speed control of d.c. Motors: Armature voltage and field flux control methods. WardLeonard system.
Testing of D.C. Machines: Testing of d.c. machines: Losses – Constant & Variable losses,
calculation of efficiency, condition of maximum efficiency.
Allotte
d
Hours
8
5
4
3
5
4
Methods of Testing – direct, indirect and regenerative testing – brake test – Swinburne’s test
–Hopkinson’s test.
3-ph Induction Machines: Construction; Principle of operation and rotating magnetic
field, concept of slip, rotor frequency, rotor e.m.f.; Derivation of per phase equivalent
circuit, measurement of parameters and performance calculation Circuit model and phasor
diagram.
Operating characteristics of 3-ph Induction Motor: Effects of varying V and f on
motor performance, Torque –slip characteristics and its analysis.
Different methods of speed control- voltage control, frequency control, and slip power
control, resistance and reactance variation, variation of no of poles. Methods of starting and
testing of squirrel cage and slip ring motors. High torque cage motors –Deep bar and
double cage.
7
8
Text Books:
1.
2.
3.
4.
A. E. Fritzgerald, C. Kingsley and S. Umans, “Electric Machinary”, Mc Graw-Hill Companies.
P.S. Bimbra, “Electrical Machines”, Khanna Publishers.
I.J. Nagrath& D.P. Kothari, “Electric Machines” Tata McGraw Hill- Publishers.
P. K Mukherjee & S Chakravorti, “Electrical Machines”, Dhanpat Rai.
Reference Books:
1. S.K. Bhattacharya, “Electrical Machines”, MH.
2. P.S. Bimbhra, “Generalized Theory of Electrical Machines”, Khanna Publishers.
3. Clayton & Hancock, “Performance and Design of D.C Machines”, BPB Publishers
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7