Relay - electrical and electronic apparatus for opening and closing various portions of electrical circuits for a given change in the electrical or non-electrical input actions.
Electromagnetic relays are - an electromechanical device that closes and / or opens the mechanical electrical contacts in the feed to the relay coil of an electric current, which generates a magnetic field which causes movement of the ferromagnetic armature relays associated with mechanical contacts and subsequent movement commutes contacts the external circuit.
Often, relays are also referred to a variety of devices, NO or NC contacts when you change some, not necessarily the electrical quantities. This, for example, devices that are sensitive to temperature (thermal relay), illumination (light barrier), the sound pressure level (acoustic relay) and others. Also, often relays are called various timers, for example, a timer Indicator car timers on / off various devices and appliances, such as household appliances (timers).
Type relays can be distinguished by the control signal, for execution by the permissible load on the contacts at the time of operation.
Simply put, relays are designed to switch high current loads. In other words, is a switch, and even easier - working principle relays are - a small current (eg signal button) include a chain with a large current. Currently, the electronics and electrical relays are mainly used to control large currents.
Relay is very widely used in home appliance, especially for automatic switching on and off motors (puskozaschitnoy relays ), as well as in electrical circuits cars. For example, puskozaschitnoy relays are necessarily have in refrigerator, and washing machines. In these devices, relays are is much more reliable electronics because it is resistant to the inrush current when the motor starts and, particularly, to a strong surge when it is turned off.