VFSTR University
III Year B.Tech. EEE
I - Semester
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EE313 A.C. MACHINES – II
Course Description & Objectives:
To understand the construction of Synchronous generators & motors and
special machines. Develop the ability to use Synchronous generators and
motors for various practical applications.
Course Outcomes:
l Identify the different features of synchronous & special machines.
l Examine the real problem happening in power plants with governor
variation.
l Determine and compare voltage regulation of alternators by different
methods.
l Plot V and inverted V curves for synchronous generator and motors for
different power factors and loadings and Plot the power circles of
Synchronous motor.
UNIT I - Construction & Characteristics of Alternators :
Constructional features of Alternators : Types of alternators–revolving field
type- rotating armature type – salient pole and non-salient pole field structure.
Speed and frequency – cooling.
Armature windings: Single layer – double layer – full and fractional pitch
windings – pitch factor, distribution factor, winding factor – expression for
induced emf – Harmonics and their reduction.
Load characteristics: Voltage regulation – causes – effective resistance –
leakage reactance – armature reaction – synchronous reactance – open
circuit and short circuit tests – phasor diagrams.
UNIT II - Voltage Regulation and SC Characteristics :
Methods of predicting regulation : EMF and MMF methods – ZPF
characteristic – Potier reactance – ASA method
Regulation of Salient pole generator : Slip test – direct and quadrature axes
synchronous reactance – phasor diagrams – regulation.
Armature current oscillograms on sudden short circuit – determination of
subtransient and transient reactances, (Xd”, Xd’).
Electrical & Electronics Engineering
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VFSTR University
UNIT III - Parallel Operation :
Parallel operation-methods of synchronization-circulating current – effect of
change in excitation – effect of change in prime mover torque – influence of
governors on load division between parallel units – Hunting of Alternators –
synchronizing power.
UNIT IV - Analysis of Synchronous motors:
Synchronous motor : Principle of operation – phasor diagram– effects of
changes of load and excitation on the phasor diagrams V - and inverted Vcurves at constant power output - Hunting – damping – starting methods.
Mathematical analysis – Expression for power developed various conditions
of maxima – stiffness of coupling – phasor diagrams of salient pole motor –
expression for power developed-applications.
Graphical Analysis: Excitation circles – Power circles – construction –
maximum and minimum conditions.
UNIT V - Special Machines :
Single phase induction motor: Constructional details – starting arrangements
– performance curves and applications - equivalent circuit based on double
revolving field theory determination of parameters.
A.C. Series motor – Characteristics – phasor diagram – compensated motorcommutation – interpoles – universal motors - applications.
Special Motors : Permanent magnet motors – stepper motors.
TEXT BOOKS:
1. P.S. Bimbhra, “Electrical Machinery”, 7th ed., Khanna publishers, 2007.
2. I.J. Nagrath and D.P. Kothari “Electrical Machines”, 3rd ed., Tata McGraw
Hill, 2006.
REFERENCE BOOKS:
1. Alexander S.Langsdorf , “Theory of alternating current machinery”, 2 nd
ed., Tata MC Graw Hill, 2005.
2. M.G. Say, “Performance and design of alternating current machines” 3rd
ed., CBS, 2002.
3. Charles I Hubert, “Electric Machines (Theory, operation, applications,
adjustment and control)” 2nd ed., Pearson, 2009.
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Electrical & Electronics Engineering