EM-II-class notes

ELECTRICAL MACHINES II NOTES

Einstein College of Engineering

UNIT I

SYNCHRONOUS GENERATOR

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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





Fig. Stretched out synchronous generator

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





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



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