Electrical Control Relays Key Terms

Get acquainted with electrical control relay terminology

By Howard Robertson

An electrical control relay (also called electrical relay) is an important component of an industrial electrical circuit. These relays perform various functions to protect the electrical components in an industrial circuit.

Whether you want to buy electrical control relays or you want to be a supplier, you will need to understand various technical terms. This guide will explain key terms relating to electrical control relays, such as AC, DC, volts, time delay relays and thermal overload relays.

AC (Alternating Current) or DC (Direct Current)

AC is an electric current, in which the direction of flow is reversed at frequent intervals. In one cycle, an alternating current flows from zero to a positive maximum and then to negative maximum, before it again returns to zero. Unlike AC, DC is an electric current, in which the electron flow is unidirectional. DC might be constant or varying. Before selecting an electrical relay, you must have an idea about the characteristics of AC or DC flowing through the electrical circuit.
Try: You can read through the definitions for AC and DC at Energy Classroom, an informative Web site by Xcel Energy. In addition, Baldor Electric Company provides a glossary of technical terms, such as AC and DC.

Volts

Generally, specifications for electrical relays are expressed in terms of volts. It is the unit to measure electric potential between two points. One volt is defined as the potential (or electromotive force or EMF) required to produce a current of one ampere through a resistance of one ohm.
Try: For more information about this unit, read through the glossary at Tyco Electronics, a supplier of industrial electronic products.

Amperes

An ampere is another unit for specifying current rating for electrical relays. You must evaluate the current range for your applications and select the electrical relay accordingly.
Try: To understand the basics of this term, read through information at Maxim Integrated Products. Responsible Energy Corporation also provides a brief description about this term.

Time delay relays

Time delay relays are useful for applications that require time delay. If you require different time relays for each instance, you must use a time delay relay that has selectable time ranges. If the time delay is constant for your application, you can use a single time relay.
Try: All About Circuits, an online information resource, provides a description about time delay relays.

Protective relays

These relays provide a variety of protection and control functions. These instruments are very important for electrical transmission lines and power generation equipment, as the protective relays prevent accidents and damage to equipment and personnel.
Try: To learn more about electrical control relays, read through the description at GlobalSpec, a technical information resource.

Thermal overload relays

Sometimes, due to faulty components, an electrical instrument draws more current than its rating. This might result in overheating and subsequent burning of the instrument. Thermal overload relays or overload relays avoid overheating of electrical equipment.
Try: www.electronics-manufacturers.com offers information about thermal overload relays.