An Electromechanical Relay (EMR) is a crucial component in electrical and electronic systems, offering the ability to control circuits by opening or closing contacts using an electromagnet. Despite the emergence of solid-state relays in recent years, electromechanical relays remain indispensable in a wide array of applications due to their reliability, versatility, and relatively low cost. This article delves into the structure, working principle, types, and applications of electromechanical relays, highlighting their importance in the modern world of automation and electrical engineering.

Structure and Working Principle An electromechanical relay consists of several key components： the coil, armature, contacts, spring, and housing. The coil is the central component of the relay, through which electrical current flows to generate a magnetic field. This magnetic field then interacts with the armature, a movable part connected to the relay’s contacts. When the coil is energized, the armature is attracted to it, causing the contacts to switch states. The relay contacts can be of two types： Normally Open (NO) and Normally Closed (NC). In a NO contact, the circuit is open when the relay is not energized, and it closes when the coil is energized. Conversely, in a NC contact, the circuit is closed when the relay is de-energized and opens when the coil is energized. These simple operations enable the relay to control a wide range of electrical circuits, often with a low control voltage, to switch much higher voltages or currents.