relæerne

Relæerne is the Danish term for relays, devices used to control an electrical circuit by a separate signal. They provide electrical isolation between control and power circuits and enable switching of high currents with a relatively small control input.

An electromechanical relay consists of a coil, an armature, and a set of contacts. When the coil is energized, the magnetic field draws the armature, closing or opening the contacts. Relays commonly have normally open (NO) or normally closed (NC) configurations.

Solid-state relays substitute semiconductors for moving parts, offering faster switching, longer life, and immunity to mechanical wear. They require appropriate drive circuitry and can introduce a small voltage drop and heat generation.

Relæerne have a long history in telecommunication and industrial control, expanding from early telegraph systems to contemporary automation, automotive electronics, and power distribution. They are still used where electrical isolation, signal amplification, or remote control is needed.

In practice, engineers choose relæerne type—electromechanical or solid-state—based on switching speed, load current, isolation needs, and duty cycle. Relay logic, though largely superseded by solid-state control, remains a foundational concept in control engineering.