What are the principle characteristics of electromagnetic relays
Electromagnetic relay is an electronic control device. It has a control system (also called an input loop) and a controlled system (also called an output loop). It is usually used in automatic control circuits. It actually uses a smaller current and a lower current. It is a kind of "automatic switch" to control a larger current and a higher voltage. Therefore, it plays the role of automatic adjustment, safety protection, and conversion circuit in the circuit.
(1) Structure: The main components of the electromagnetic relay are electromagnet A, armature B, spring C, moving contact D, static contact E. (as shown in the figure)
(2) The working circuit can be divided into two parts: low-voltage control circuit and high-voltage working circuit. The low-voltage control circuit includes electromagnetic relay coil (electromagnet A), low-voltage power supply E1, switch S; high-voltage working circuit includes high-voltage power supply E2, motor M, electromagnetic The contact D and E parts of the relay.
(3) Working principle-close the switch S in the low-voltage control circuit, the current passes through the coil of the electromagnet A to generate a magnetic field, thereby generating a gravitational force on the armature B, making the moving and static contacts D and E contact, the working circuit is closed, and the motor works ; When the low-voltage switch S is disconnected, the current in the coil disappears, and the armature B disengages the moving and static contacts D and E under the action of the spring C, the working circuit is disconnected, and the motor stops working.
As long as a certain voltage is applied to the two ends of the coil, a certain current will flow through the coil, which will produce electromagnetic effects. Under the action of electromagnetic force, the armature will overcome the pulling force of the return spring and attract to the core, thereby driving the armature. The moving contact and the static contact (normally open contact) are pulled together. When the coil is de-energized, the electromagnetic attraction will disappear, and the armature will return to its original position under the reaction force of the spring, releasing the moving contact and the original static contact (normally closed contact). This pulls in and releases, so as to achieve the purpose of conducting and cutting off in the circuit. The "normally open and normally closed" contacts of the relay can be distinguished as follows: the static contact that is in the off state when the relay coil is not energized is called "normally open contact"; the static contact that is in the on state is called It is a "normally closed contact".