AC Machines Lecture Notes

ELECTRICAL MACHINES II NOTES

UNIT I SYNCHRONOUS GENERATOR

Einstein College of Engineering


Introduction









Direction of induced e.m.f

Fig. Fleming's right hand rule for direction of induced EMF



Generated EMF in a Synchronous Generator



Frequency of an A.C. Synchronous Generator

Constructional Details of Rotor



Figure 14: Synchronous machines with stator slots and armature windings omitted (a)Two pole cylindrical rotor,(b) Four-pole cylindrical rotor, (c) Developed view of two pole cylindrical rotor field structure, (d) Salient pole and field coil



Fig. Cylindrical rotor mmf wave and its fundamental of a synchronous machine

Excitation Systems for Synchronous Machines

Brushless Excitation System



Fig. Conventional excitation systems for synchronous machines



Fig. Brush less excitation system

The Action of the Synchronous Machine

Armature Reaction



l Figure 18: Stretched out synchronous generator

Figure 19: Stretched out synchronous motor



Fig. Stretched out synchronous generator


ELECTRICAL MACHINES II NOTES Fig. Stretched out synchronous generator

Theory of Salient-pole machines:(Blonde’s Two-reaction Theory)


ELECTRICAL MACHINES II NOTES Experimental Determination of xd and xq

Losses and Efficiency

S



Parallel Operation of two Generators



Figure 35: Parallel operation



UNIT 3 THREE PHASE INDUCTION MOTOR



Introduction

The Rotating Magnetic Field





Principles of Torque Production









Construction











Equivalent Circuit









Determination of Circuit Parameters



The no-load test



Blocked-rotor Test



UNIT 4 STARTING AND SPEED CONTROL OF THREE PHASE INDUCTION MOTOR



Speed control of Induction Machines

Speed control by changing applied voltage



Rotor resistance control



Cascade control





Pole changing schemes





Stator frequency control








AC Machines Lecture Notes

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