The composition of the power relay and its control function 1

Since the power relay plays such an important role in production, how it is composed and how it has people is the driving force for creating the history of the world.” Through long-term production struggles and scientific experiments, the working people make use of various physical The phenomenon has created various power relays with different structures and functions, and has made great contributions in the struggle of mankind to conquer nature. A long time ago, people made electromagnetic power relays based on the phenomenon of electromagnetic induction to meet the needs of communication. After continuous reform and innovation, it has developed rapidly and has become the most numerous and widely used type of contemporary power relays. The typical structure of this type of power relay is shown in Figure 1-1a, which is mainly composed of iron core, coil , dynamic and static contacts, armature, return spring, etc. Its action principle is not complicated. As long as a certain voltage is applied to both ends of its coil, a certain current will flow in the coil, and a certain magnetic flux will be generated in the iron core. It is magnetized and magnetic, and the moving iron core (that is, the armature) will overcome the pulling force of the return spring and attract to the static iron core under the action of electromagnetic attraction, thereby driving the moving contact and the static contact to close or separate. After the coil is powered off, the electromagnetic attraction disappears. The armature and the moving contact will return to their original positions under the action of the return spring, and the moving and static contacts will also return to their original state.

In use, if the power relay coil is connected to a certain input circuit in a certain way to receive a certain signal, and its contacts are connected to a certain output circuit as an output signal, the button can be used to control the controlled object. various control functions. For example, if connected in the way shown in Figure 1-2, power relay J can energize the coil and close the input circuit to pick up the normally open contact of the circuit according to the will of the person (through the power relay button), so that the power relay shown in Figure 1-2 can be used as a The manual control is connected with the alarm circuit (the display and display lights and the electric bell are the controlled objects), and the display and alarm signals are issued. If connected in the way of Figure 1-3, the power relay can automatically alarm and display that the water level exceeds the specified height. Because as the water level of the water tank rises, the float 4 also rises. After reaching a certain height, A pushes the metal contact block K to make two points 1 and 2 connected, and the power relay J acts, so that the display and alarm circuits are connected and a signal is sent.