Electromagnetic relays are the earliest and most widely used relays in relays. Electromagnetic relays are generally composed of iron core, electromagnetic coil, armature, return spring, contacts, bearings and pins.
The working principle of the electromagnetic relay is not complicated, and it mainly works by using the principle of electromagnetic induction. When the coil is energized, the coil generates a magnetic field, and the core in the middle of the coil is magnetized to generate a magnetic force, so that the armature is attracted to the core under the action of electromagnetic attraction. At this time, the armature drives the strut to push the leaf spring away, so that two often The closed contact is broken. When the current of the relay coil is disconnected, the core loses its magnetic force, and the armature returns to the initial state under the action of the leaf spring, and the contact is closed again.
The form of the contact is generally divided into three types: one is a static contact that is in an on state when the relay coil is not energized, and is called a normally closed contact. It is represented by the letter H; the second is a static touch in an open state. The point, called the normally open contact, is indicated by the letter D; the other is a moving contact and a static contact normally closed, while at the same time being normally open with a static contact, forming an open and closed switching contact form. . It is indicated by the letter I. The normally closed contact is disconnected from the closed state when the coil is energized, so it is also called the dynamic break contact, and the normally open contact is called the dynamic contact changeover contact. There are two cases, that is, the conversion after the first break and the break. Contact and break-before-make conversion contacts Figure 7-2 shows the circuit in the form of contacts. In a relay, there may be one or several (group) normally open points, normally closed contacts and corresponding switching contact forms.