What Are Relays and Their Most Common Types?

Relays are a type of electrically operated switch, and they provide input terminals and operating contact terminals for their functionality. Depending on the relay, they may be implemented within a device in order to control a circuit with a low-power signal or several circuits with a single signal. In their infancy, relays served as signal repeaters for long-distance telegraph circuits as well as telephone exchanges. As more advancements were made to such electrical switch components, their applications widened to include a number of electronic systems and appliances for motor control, circuit protection, safety-critical logic procedures, and more. While a number of relays exist to facilitate numerous needs, the three primary types that are most often used include the electromechanical, solid-state, and reed relay.

Electromechanical relays are common types that feature an electromagnetic coil and a mechanical movable contact. For the operation of the electromechanical relay, the coil is induced with current, and a resulting magnetic field causes the movable contact or armature to be drawn in. When energy is lost, the magnetic field drops and a spring serves as a mechanical method of retracting the contact to its resting position. While electromechanical relays are capable of undertaking large amounts of AC and DC currents depending on their design, such relay types are slower in their switching speed.

Solid-state relays are a type of switch that is devoid of any moving components, and this allows them to exhibit long and reliable service lives. In order for the solid-state relay to provide its functionality, it relies on a component that detects a control signal and responds by having power switched to the load circuit with a solid-state switching component as well as enables the control signal to actuate the switch. Solid-state relays are also capable of releasing an output power that is much lower than what is required for its control, thus it has a larger power gain as compared to other types. Furthermore, such relays are also often the smallest type, and they have very quick switching speeds. As such, solid-state relays can often be found in devices such as computers.

Reed relays feature an electromagnet that controls one or more reed switches, and contacts are encased within a narrow glass tube for their protection from corrosion. The glass tube is also filled with inert gas, and the reeds are two metal blades. When current is supplied to the relay’s coil, the blades become attracted to one another and then establish a closed path. As reed relay types are devoid of a moving armature, they are protected from contact wear out. Additionally, such relays are also quick in their switching speed and only need a small amount of voltage from the control circuit for their operations.

Beyond the major types of relays, there are also many others that may be used for various applications such as electromagnetic relay, coaxial relay, time delay relay, and overload protection relay components. With each type, various parts and operational characteristics may be present to facilitate specific types of applications, and thus the choice between each will often be based upon a variety of factors. Regardless of what relays you may need for your operations, the experts at NSN Sourcing can help you procure all the relay components and other electronic parts that you need quickly and easily.

NSN Sourcing is a leading online distributor of aircraft parts, and we offer customers competitive pricing and rapid lead-times on over 2 billion new, used, and obsolete items that we offer. As we only source parts from trusted manufacturers and rigorously test and inspect everything prior to shipment, customers can rest assured that they are receiving the highest quality items possible. If you would like to receive a competitive quote on items that you are interested in, we invite you to fill out and submit an Instant RFQ form as provided on our website and a member of our staff will reach out to you in 15 minutes or less with a personalized solution.


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