AC and DC Motors Library

This comprehensive Activ® interactive multimedia training program consists of four individual lessons that train participants to understand, maintain, and test AC and DC motors.

Audience: This program is excellent for the training of electricians and electronic technicians as well as for the multi-craft training needs of process and manufacturing facilities.

AC Motor Theory


Prerequisites: This lesson is designed for participants familiar with AC/DC theory, electrical safety, electrical print reading, electrical connections, electrical control equipment, and the proper use of electrical test instruments.

Description:This lesson shows and explains how to measure winding insulation resistance and winding resistance. The lesson also describes the major components of AC motors and explains the theory behind permanent magnet motors, three-phase motors, and induction motors.

Objectives:

  • Identify the components and principles of operation for the major types of AC motors
  • Measure winding insulation resistance
  • Measure winding resistance in AC motors
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AC Motor Maintenance


Prerequisites: This lesson is designed for participants familiar with AC/DC theory, electrical safety, electrical print reading, electrical connections, electrical control equipment, AC motor components, AC motor theory, and the proper use of electrical test instruments.

Description: This lesson shows and explains how to overhaul AC induction motors. Procedures for disassembling, inspecting, cleaning, and reassembling endbells, rotors, and bearings are presented in detail. The lesson also covers procedures for inspecting and cleaning the stator as well as windings and testing the motor once it has been reassembled.

Objectives:

  • Remove endbells, rotor, and bearings from an AC motor
  • Inspect and clean endbells and rotors
  • Reinstall bearings
  • Reassemble an AC motor as well as perform operational tests on it
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DC Motor Theory


Prerequisites: This lesson is designed for participants familiar with basic electrical principles, electrical safety, electrical print reading, electrical control equipment, Ohm’s Law and Three Phase Motors.

Description: This lesson introduces participants to the application of direct current motors and their components. This lesson covers general characteristics of a DC motor, DC motor components, their functions and the design of the brush assembly. This lesson explains concepts such as flux interaction, commutation, the effect of multiple windings, armature’ reaction, compensation and CEMF, and how each of these factors effects motor operation.

Objectives:

  • Know the general requirements of a DC motor and what requirements they meet
  • Be able to identify the basic components and explain the functions of a DC motor
  • Identify the components of the brush assembly and explain its function
  • Explain the effect of armature current on the main flux field and how this results in motor action
  • Explain the process of commutation and how this maintains direct current in a DC motor
  • Describe how the number of windings and commutator segments effects torque and mechanical power
  • Explain how armature reaction shifts the neutral plane, how it affects motor operation, and what measures will correct the reaction
  • Know the requirements for induced voltage in a motor, and explain Counter EMF
  • Explain the designs of a series wound, shunt wound, compound wound, and permanent magnet wound motor and how each of them work
  • Learn about reduced voltage starters and what determines the direction of the rotation of a motor
  • Learn how a reverse contractor works
  • Know how a tapped resistor and field rheostat work
  • Know how a drive control system works
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DC Motor Maintenance


Prerequisites: This lesson is designed for participants familiar with basic electrical principles, electrical safety, electrical print reading, electrical control equipment, and preferably with AC and DC motor theory and AC motor maintenance.

Description: This lesson describes some of the basic concepts of DC motors; explains how DC motors differ from AC motors; describes the components of a DC motor and their functions. This lesson also covers DC motor maintenance, including commutator inspection and maintenance as well as brush maintenance; explains various types of commutator problems and how to remedy diem; describes how to select, install, and seat brushes.

Objectives:

  • Maintain a DC Motor, including identifying components of a DC motor commutator and their functions
  • Describe the color of the commutator and explain the function of the oxide film
  • Identify wear patterns and the causes of arcing, high mica, uneven segments and thrown solder, and know how to correct them
  • Explain how to prepare a commutator for reconditioning, how to undercut the mica of a commutator, and how to clean and check the commutator after maintenance
  • Describe how to inspect, select, install and seat brushes
  • Describe the procedures for cleaning and inspecting the brush holders
  • Explain how to adjust spring pressure
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