The structure and working principle of electromagnetic relay is similar to that of contactor, which is mainly composed of electromagnetic mechanism and contacts. There are also two types of electromagnetic relays, DC and AC.
The suction value and release value of the relay can be adjusted within a certain range according to the protection requirements. Now the DC electromagnetic relay shown is used as an example to illustrate.

(1) Turn the adjusting nut to adjust the tightness of the reaction spring to adjust the operating current (voltage). The greater the spring reaction force, the greater the action current (voltage), and vice versa.
(2) Change the thickness of the non-magnetic spacer. The thicker the non-magnetic gasket, the larger the air gap and reluctance of the magnetic circuit after the armature is pulled in, and the larger the release current (voltage), and vice versa, the smaller the attraction value is.　　

(3) Adjust the screw to change the size of the initial air gap. When the reaction spring force and the thickness of the non-magnetic spacer are constant, the larger the initial air gap, the larger the attraction current (voltage), and vice versa, the smaller the release value is.