电磁式继电器的结构、工作原理与特性（The structure, working principle and characteristics of electromagnetic relay）.doc

电磁式继电器的结构、工作原理与特性（The structure, working principle and characteristics of electromagnetic relay） The structure, working principle and characteristics of electromagnetic relay The relay is used to switch on or off the control circuit according to the change of an input signal to realize automatic control and protection of the automatic device of the electric device. There are many kinds of relays, which are divided into voltage relay, current relay, time relay, temperature relay, speed relay, pressure relay and so on according to the nature of input signal; According to the principle of operation can be divided into: electromagnetic relays, induction relays, electric relays, thermal relays and electronic relays; According to the form of output can be divided into: contact and non-contact two categories, according to the use can be divided into: control and protection relays. 1. electromagnetic relay structure and working principle Electromagnetic relay is the earliest and most widely used type. The structure and working principle of the contactor are approximately the same. The electromagnetic relay is composed of electromagnetic system, contact system and release spring. The principle of electromagnetic relay is shown in Figure L. Because the relay is used to control the circuit, the current flowing through the contacts is relatively small (less than 5A in general), so the arc extinguishing device is not needed. The common electromagnetic relays include voltage relay, intermediate relay and current relay. 2. electromagnetic relay characteristics The main characteristic of relay is the input output characteristic, also called relay characteristic. When the relay input X is increased from zero to X2, the relay output Y is zero. When the input amount X is increased to X2, the relay is pulled in and the output is Y1; if X continues to increase, the Y remains unchanged. When the X is reduced to X1, the relay is released, and the output is changed from Y1 to zero. If X co