A relay is an electrical control device. It is an electrical appliance that causes the controlled quantity to undergo a predetermined step change in the electrical output circuit when the change in the input quantity (excitation quantity) meets the specified requirements. It has an interactive relationship between the control system (also called the input loop) and the controlled system (also called the output loop). Usually used in automated control circuits, it is actually an "automatic switch" that uses a small current to control the operation of a large current. Therefore, it plays the role of automatic adjustment, safety protection, and conversion circuit in the circuit.
In the 18th century, scientists also believed that electricity and magnetism were two unrelated physical phenomena. After the Danish physicist Oster discovered the magnetic effect of electric current in 1820, the British physicist Faraday discovered the phenomenon of electromagnetic induction in 1831. These discoveries confirmed that electrical and magnetic energy can be transformed into each other, which laid the foundation for the birth of later electric motors and generators; human beings have entered the electrical age because of these inventions.Single-Phase Relays Suppliers
In the 1830s, the American physicist Joseph Henry used electromagnetic induction to invent the relay while studying circuit control. The earliest relay is an electromagnetic relay, which uses the phenomenon of the magnetic force generated and disappeared by the electromagnet when the power is turned on and off to control the opening and closing of another circuit of high voltage and high current. Its appearance makes the circuit remote control and protection work It proceeded smoothly. The relay is a great invention in the history of human science and technology. It is not only the foundation of electrical engineering, but also an important foundation of electronic technology and microelectronics technology.