General-purpose relays (GPRs) are crucial components in various electrical and electronic systems, serving as essential switching devices. Their widespread use across multiple industries is a testament to their versatility, reliability, and effectiveness in controlling electrical circuits. This article aims to provide a comprehensive understanding of general-purpose relays, including their construction, working principles, applications, advantages, and limitations.

Construction of General-Purpose Relays A general-purpose relay consists of several key components that enable it to function effectively. These components include： Coil： The coil is the heart of the relay and acts as the control element. When an electric current flows through the coil, it generates a magnetic field. This magnetic field is crucial for the relay’s operation. Armature： The armature is a movable iron lever that, when energized by the magnetic field generated from the coil, moves to mechanically operate the contacts. Contacts： The contacts are conductive metal pieces that open or close to control the flow of current in the circuit. Depending on the design, there are two types of contacts： normally open (NO) and normally closed (NC). NO contacts allow current flow when the relay is energized, while NC contacts allow current flow when the relay is not energized.