Print this page Relays and Contactors
Joseph E. Fleckenstein, P.E.
Course Outline
This course treats the subject of relays and contactors. Various types of relays are used in control and protection circuits. Control relays are used to allow or prevent specific operations depending on a defined permissive function. Time delay relays allow functions to occur before or after a chosen time delay. Protective relays are important to prevent damage or malfunctions to major electrical gear as generators, transformers and motors. The course explains these relays and more. Contactors are similar to relays in functionality and the similarities to relays are explained. The course outlines the correct methods to be followed in selecting relays and contactors for a specific application.
This course includes a multiple-choice quiz at the end, which is designed to enhance the understanding of the course materials.
Learning Objective
Upon completing the course, the student will:
- Understand the purpose and operation of control relays;
- Understand the purpose and operation of machine tool relays;
- Understand the purpose and operation of time delay relays;
- Understand the purpose and operation of electromechanical relays;
- Understand the purpose and operation of reed relays;
- Understand the purpose and operation of solid state relays;
- Understand the purpose and operation of protective relays;
- Understand the purpose and operation of contactors;
- Understand the types of enclosures commonly used to house relays and contactors;
- Understand the various types of terminations commonly available on relays and contactors; and
- Become familiar with the correct procedures involved in the selection of relays and contactors for reliability and prolonged life.
Intended Audience
This course is intended primarily for electrical engineers who either design or correct control circuits that use relays or contactors. The material of the course would also be of value to electricians or contractors involved in the design or maintenance of control or protective circuits.
Benefit for Attendee
Attendees will learn the types and features of relays that are available for use in control and protective circuits. The course also explains the differences between relays and contactors.
Course Introduction
Relays and contactors are used extensively in the electrical industry. An engineer or electrician who must use or apply these devices properly would be well advised to understand the functioning and limitations of these devices. Otherwise misapplications may result and, in the extreme, equipment damage and failures could be the result.
Course Content
The course content is contained in the following PDF file:
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Course Summary
Relays are widely used in the circuits that control and protect numerous types of electrical gear. In order to select a relay for a specific application an engineer should be familiar with the capabilities as well as the limitations of those relays that are available in the marketplace. An improper selection can lead to premature failure and in some instances a loss of adequate protection. Contactors are intended for applications that generally involve higher currents. A familiarity with the common terms can be helpful.
Quiz
Once you finish studying the above course content, you need to take a quiz to obtain the PDH credits.
DISCLAIMER: The materials contained in the online course are not intended as a representation or warranty on the part of PDH Center or any other person/organization named herein. The materials are for general information only. They are not a substitute for competent professional advice. Application of this information to a specific project should be reviewed by a registered architect and/or professional engineer/surveyor. Anyone making use of the information set forth herein does so at their own risk and assumes any and all resulting liability arising therefrom.
