Relay (English Name: relay) is an electrical control device, which is an electrical device in the electrical output circuit that makes a predetermined step change in the electrical output circuit when the input (excitation) changes to the specified requirements. It has the interaction relation between the control system (also called input circuit) and the controlled system (also called output loop). Usually used in automation control circuits, it is actually a small current to control the operation of large current of an automatic switch". Therefore, the circuit plays an automatic adjustment, security protection, conversion circuit and so on.
There are three basic forms of the relay's contacts:
1, movable (Chang Kai) (type H) coil is not energized, the two contact is disconnected, after power, the two contacts closed. The phonetic prefix "H" is used to express the word.
2, moving and breaking (Chang Bi) (type D) coil is not energized, the two contact is closed, after power, the two contact will be disconnected. With the hyphenation of phonetic prefix "D" said.
3, conversion type (Z type) this is the contact type. The contact group has three contacts, the middle is the movable contact, and the upper and lower each static contact. The coil is not energized, the movable contact and a static contact disconnect and another closed coil is energized, the movable contacts on the move, the original broken into closed, the original closed into a disconnected state, to achieve the purpose of conversion. Such a contact group is called a change-over contact. Use the phonetic prefix "Z" to indicate the word "turn".