At its core, a relay power supply utilizes electromagnetic switches known as relays to control the flow of electricity. The fundamental operation involves an electromagnetic coil that gets energized when a voltage is applied, creating a magnetic field. This magnetic field then attracts a movable armature, which in turn opens or closes the relay contacts. This simple mechanism allows a small control signal to switch larger currents, making relay power supplies versatile in managing electrical loads.

    Relays are categorized mainly into two types： electromechanical relays (EMR) and solid-state relays (SSR). Electromechanical relays are constructed with mechanical parts and are suitable for low-frequency operations. On the other hand, solid-state relays utilize semiconductor devices to switch loads, which allows them to operate at higher frequencies and with greater durability, as they have no moving parts that can wear out.