AC Generators and Motors

The AC Generators and Motors online PDH course is a part of the Electrical Engineering category of courses. This online course introduces AC Generators and Motors and provides details on type of generators and motors, calculation of power, speed and frequency.

Most of the electrical power used is alternating current. As a result, the ac generator is the most important means of producing electrical power. AC generators, generally called alternators, vary greatly in size depending upon the load to which they supply power. For example, the alternators in use at hydroelectric plants, such as Hoover Dam, are tremendous in size, generating thousands of kilowatts at very high voltage levels. Another example is the alternator in a typical automobile, which is very small by comparison. It weighs only a few pounds and produces between 100 and 200 watts of power, usually at a potential of 12 volts.

Since ac generators are so widely used, majority of the motors used operate on ac. There are other advantages in the use of ac motors besides the wide availability of ac power. In general, ac motors cost less than dc motors.

Some types of ac motors do not use brushes and commutators. This eliminates many problems of maintenance and wear. It also eliminates the problem of dangerous sparking. An ac motor is particularly well suited for constant-speed applications. This is because its speed is determined by the frequency of the ac voltage applied to the motor terminals. The dc motor is better suited than an ac motor for some uses, such as those that require variable speeds.

An ac motor can also be made with variable speed characteristics but only within certain limits. Industry builds ac motors in different sizes, shapes, and ratings for many different types of jobs. These motors are designed for use with either polyphase or single-phase power systems.

This course is based on Chapters 3 and 4 of Module 5 titled “Alternating Current Generators” and “Alternating Current Motors” of the Naval Education and Training Materials (NAVEDTRA 14177), Electricity and Electronic Training Series.

This course is intended for use by electrical engineers, facility managers, construction professionals, students and others interested in learning about the AC Generators and Motors.

Learning Objectives:

Upon completion of this course, you will be able to:

• Describe the principle of magnetic induction as it applies to ac generators
• Describe the differences between the two basic types of ac generators
• List the advantages and disadvantages of the two types of ac generators
• Describe exciter generators within alternators; discuss construction and purpose
• Compare the types of rotors used in ac generators, and the applications of each type to different prime movers
• Explain the factors that determine the maximum power output of an ac generator, and the effect of these factors in rating generators
• Explain the operation of multiphase ac generators and compare with single-phase
• Describe the relationships between the individual output and resultant vectorial sum voltages in multiphase generators
• Explain, using diagrams, the different methods of connecting three-phase alternators and transformers
• List the factors that determine the frequency and voltage of the alternator output
• Explain the terms voltage control and voltage regulation in ac generators, and list the factors that affect each quantity
• Describe the purpose and procedure of parallel generator operation
• List three basic types of ac motors and describe the characteristics of each type
• Describe the characteristics of a series motor that enable it to be used as a universal motor
• Explain the relationships of the individual phases of multiphase voltages as they produce rotating magnetic fields in ac motors
• Describe the placement of stator windings in two-phase, ac motors using rotating fields
• List the similarities and differences between the stator windings of two-phase and three-phase ac motors
• State the primary application of synchronous motors, and explain the characteristics that make them suitable for that application
• Describe the features that make the ac induction motor the most widely used of electric motors
• Describe the difference between the rotating field of multiphase motors and the “apparent” rotating field of single-phase motors
• Explain the operation of split-phase windings in single-phase ac induction motors
• Describe the effects of shaded poles in single-phase, ac induction motors