Introduction To The Principle Of Electromagnetic Relay

The electromagnetic relay is mainly based on the electromagnetic principle. When a current passes through the coil, the coil generates a magnetic field, and the armature is attracted. The armature drives the reed through the action of the lever, and then it can be closed. When there is no current in the coil, the magnetic field of the coil disappears, and the armature resets under the action of the spring force, causing the contacts to open.
There is generally only one coil in an electromagnetic relay and one set of contacts or multiple sets of contacts. Contacts are divided into normally open contacts and normally closed contacts. The so-called normally open contact refers to the contact that is in the off position when the coil is not energized. Normally closed contacts are contacts that are in the on position when the coil is not energized.