Electrical Machines - II Year - II Sem Lectures

Electrical Machines - II Year - II Sem Lectures

CONTENTS

• Unit-I: Polyphase Induction Motors
• Unit-II: Induction Motors Testing, Starting & Speed Control Methods
• Unit-III: Synchronous Machines
• Unit-IV: Parallel Operation of Synchronous Machines & Synchronous Motors
• Unit-V: Single Phase & Special Purpose Motors

SYLLABUS

• Course Objectives:

  1. Understand construction and operation of polyphase induction motors.
  2. Analyze synchronous generators/motors for electrical power generation.
  3. Explore parallel operation of alternators.
  4. Learn speed control methods for polyphase induction motors.
  5. Study different types of single-phase induction motors and their applications.

• Course Outcomes:

  1. Speed-torque characteristics of 3-phase induction motors.
  2. Starting and speed control of 3-phase induction motors.
  3. Performance characteristics of synchronous machines.
  4. Characteristics of single-phase motors.
  5. Practical applications of above concepts.

UNIT-I: POLYPHASE INDUCTION MOTORS

• Key Concepts:
  • Construction (cage vs wound rotor).
  • Rotating magnetic field production.
  • Operation principles: rotor emf, reactance, current, and power factor.
  • Power input, copper losses, mechanical power, torque equations.
  • Characteristics: torque-slip, speed characteristics.
  • Equivalent circuit, phasor diagram.

UNIT-II: INDUCTION MOTORS: TESTING, STARTING & SPEED CONTROL METHODS

• Key Concepts:
  • Efficiency determination.
  • No-load vs blocked rotor tests.
  • Speed control methods (voltage, frequency, poles).
  • Induction generator principles.

UNIT-III: SYNCHRONOUS MACHINES

• Key Concepts:
  • Features of round rotor and salient pole machines.
  • Armature windings: types and equations.
  • Armature reaction, reactance, impedance and phasor diagrams.
  • Voltage regulation methods:
  • Synchronous impedance method.
  • MMF method.
  • Zero Power Factor method.

UNIT-IV: PARALLEL OPERATION OF SYNCHRONOUS MACHINES

• Key Concepts:
  • Synchronization with infinite bus bars.
  • Operating principles of synchronous generators and motors.
  • Load sharing, excitation impact, and mechanical power input effects.

UNIT-V: SINGLE PHASE & SPECIAL PURPOSE MOTORS

• Key Concepts:

  • Types: induction, reluctance, hysteresis, stepper, brushless DC motors.
  • Single-phase induction motor operation and limitations.
  • Starting methods (split-phase, capacitor-start, etc.).

• Important Formulas & Relations:

  • Synchronous speed: $N_s = \frac{120f}{P}$
  • Electromotive force per phase: $E_{ph} = 4.44 K_c K_d f au T_{ph}$
  • Torque equations and characteristics.

Illustrative Problems & Important Questions (Summary)

• Solved problems relevant to each unit.
• Questions to cover theoretical understanding and practical applications.