Electromechanical Relays and Their Working Principle

In the realm of electronics, an electromechanical relay is a type of switch capable of utilizing the properties of electromagnetism to control circuits. Depending on their type and how they are implemented within a device, such parts may be used to manage a single circuit with a low-power signal or to control several circuits with a single signal. As a versatile electronic component, relays may be found in a number of simple and complex circuits for numerous applications.

Relays are often employed in circuits for varying reasons, sometimes replacing a switch and other times being specifically designed for a set amperage. Generally, however, relays are most commonly installed within a device for the means of switching between high and low currents within the same circuit. Despite this, relays may also be capable of actuating multiple circuits at a time, thus allowing one component to be capable of activating other effects.

For the construction of a simple electromagnetic relay, the device will consist of a solenoid that is wrapped with a coil of wire, an iron yoke, a movable iron armature, and sets of contacts. When a current is induced to the electromagnetic relay during standard circuit operation, the solenoid and wire will produce a magnetic field. Through the principle of electromagnetic attraction, the relay armature is moved by the magnetic field and will either open or close the contact connections. As electricity ceases to flow through the relay, the armature will return to its resting position and the contacts will either open or close again. With this standard method of operation, an electromagnetic circuit relay can act similarly to a switch.

As an electromechanical component, the relay relies on a number of electronic and mechanical parts that aid in its functionality. Contacts may be considered one of the most important parts of the relay, and they should be chosen based on the frequency of interruption, common current values, and voltages of the application. The armature and related components are attached to a spring, and this allows for the assembly to return back to its resting position when the magnetic field drops. As the electromagnet is composed of a soft iron, the coil current typically remains at a value of 5A and the coil voltage may reach up to 220V.

With the variety of roles that a relay can serve for an electrical circuit, they can be beneficial even in the instance that an application does not specifically require their use. With their capabilities, a relay can be used in lieu of high-amperage wiring and switches, all of which can take up precious space and cost significantly more than a relay. Additionally, the compact design of a relay can allow the design of the device’s housing to be smaller and lighter, even permitting the addition of other needed parts or accessories.

Like any electrical component, relays are prone to failure due to certain operating conditions or when they meet the end of their standard service lives. With the use of a tool known as a multimeter, detecting a faulty relay can be done with ease. To do this, the multimeter should be used to measure voltage at the point where relays are attached. To ensure that it is indeed the relay that is the issue, one should also measure any surrounding fuse, circuit breaker, battery, or other power source that may affect the flow of a current. If the relay is indeed faulty, then it may be replaced as soon as needed with a matching component.


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February 12, 2021
November 19, 2020

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