Course Number: 728.1
The Three-Phase Systems textbook covers three-phase motor principles for induction, synchronous, and multi-speed dual-voltage motors. Gives recommended maintenance practices for large AC motors. Covers principles of three-phase motor starters, part winding, reversing, jogging, alternator principles and operation. Describes three-phase power distribution.
This textbook has been recently updated
to include topics lists, objectives, & key terms for every chapter.
Recommended Contact Hours – 15
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Table of Contents
Chapter 1: Principles of Three-Phase Motors
Topics: Induction motors; Squirrel-cage rotors; Pole-phase relationships; Torque, rotor speed, slip, frequency, resistance, reactance, and power factor
- Describe a squirrel-cage rotor.
- List the factors that determine the strength of the magnetic field in an induction motor.
- Discuss pole-phase relationships.
- Demonstrate how to reverse the rotation direction of the magnetic field.
- Discuss the relationship between rotor speed and frequency.
Chapter 2: Induction Motors
Topics: Squirrel-cage motors; Stator and rotor construction; Air gap; Operating features; Wound-rotor motors; Brushes and slip rings; Maintenance
- List the main parts of the stator.
- List operating characteristics of a wound-rotor motor.
- Demonstrate how to check rotor windings for short circuits.
- State the definition of a standard motor.
Chapter 3: Synchronous Motors
Topics: Motor fields, characteristics, and applications; Pull-in torque; Slipping pole; Power factor; Brushless motors; Motor efficiency and care
- List factors that contribute to the torque of an industrial synchronous motor during starting.
- Explain the effects of an amortisseur winding in a synchronous motor.
- State the definition of pull-in torque.
- State the reason why using synchronous motors can increase a low power factor in a plant.
- List the characteristics of brushless synchronous motors.
Chapter 4: Multispeed Motors
Topics: Consequent-pole, constant-horsepower, constant-torque, variable-torque, and dual-voltage motors and connections
- Discuss the operating characteristics of multispeed induction motors.
- Select the best motor for driving equipment that requires the same torque at both high and low speeds.
- State the definition of a variable-torque motor.
- Explain the difference between a constant-horsepower motor and a constant-torque motor.
Chapter 5: Maintaining Three-Phase Motors
Topics: Cleaning; Care of stator and rotor windings; Air gap; Overload and single-phase operation; Motor shaft currents; Bearings; Maintenance schedule
- List the steps in measuring the resistance of the insulation on motor windings.
- Explain how to raise the temperature of a motor winding.
- List the steps in lubricating motor bearings.
- List the conditions that must exist before you can lubricate bearings.
Chapter 6: Motor Starters
Topics: Limitations; Full-voltage and across-the-line starting; Reducing starting current; Primary- and secondary-resistance starters; Maintenance
- Explain how a motor starter works.
- Explain the difference between open transition and closed transition.
- Name the common kinds of reduced-voltage starters.
- List the steps in inspecting motor starters.
Chapter 7: Three-Phase Motor Controllers
Topics: Multiple start-stop controls; Across-the-line reversing starters; Plugging control; Jogging; Controlling surge and backspin
- Explain how to select the best motor starter for a particular application.
- Explain the difference between low-voltage release and low-voltage protection.
- Describe the plugging process.
- Explain how to prevent backspin.
Chapter 8: Alternators
Topics: Characteristics, ratings, and windings; Three-phase alternators; Air gap; Slip rings; Exciters; Voltage regulation; Load characteristics and effects
- Discuss the operating characteristics of alternators.
- List the characteristics that must be considered when you work on alternator windings.
- Name the causes of change in potential difference between terminals as the load changes.
- Demonstrate how to calculate three-phase power in an alternator.
Chapter 9: Auxiliary Generator Systems
Topics: Requirements; Control equipment; Transfer systems; Safety switches; Engine protection; Prime movers and output control; Maintenance
- Explain how an automatic auxiliary generator works.
- List the methods of overcoming voltage-drop problems when starting loads.
- List the parts of a hydraulic starting system.
- State the definition of a prime mover.
- List the four guidelines to follow when troubleshooting or performing routine maintenance on generators.
Chapter 10: Power Distribution Systems
Topics: Distribution voltages; Heat loss; System grounding; Overcurrent protection; Ground relays; Tripping; Network protection
- State the reasons why 240-volt systems are not as widely used as are 480-volt systems.
- Explain the difference between system grounding and equipment grounding.
- List the benefits of system grounding.
- Explain how an overcurrent relay works.
- Name common circuit-opening devices.
Add Chapters to Your Custom Book
- Chapter 1: Principles of Three-Phase Motors
- Chapter 2: Induction Motors
- Chapter 3: Synchronous Motors
- Chapter 4: Multispeed Motors
- Chapter 5: Maintaining Three-Phase Motors
- Chapter 6: Motor Starters
- Chapter 7: Three-Phase Motor Controllers
- Chapter 8: Alternators
- Chapter 9: Auxiliary Generator Systems
- Chapter 10: Power Distribution Systems
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