The working principle and characteristics of electromagnetic relay: electromagnetic relay is usually composed of electromagnet, armature, spring, contact and so on. Its working circuit is composed of two parts: low voltage control circuit and high voltage operation circuit. Electromagnetic relays can also realize remote control and automatic control. As long as the coil ends with a voltage and current will flow through the coil in a, resulting in electromagnetic effects, the armature will attract the electromagnetic force to overcome the spring to return to the core rally absorption, thereby driving the armature static and dynamic contact (normally open).
When the coil is out of power, the electromagnetic attraction will disappear, and the armature will return to its original position by the counterforce of the spring, so that the movable contact is released from the original static contact (normally closed contact). Thus, the pull in and release are achieved so as to achieve the purpose of turn-on and cut off in the circuit. For the relay "normally open and normally closed contacts", it can be to distinguish between: the relay coil is not energized in off the static state of contact, known as the "normally open contact"; in a static contact state called "normally closed contact".