電磁閥一般用于液壓系統，來關閉和開通油路。實際上，根據流過介質的溫度（進口高溫電磁閥），壓力（進口高壓電磁閥）等情況，比如管道有壓力和自流狀態無壓力。電磁閥的工作原理是不同的 。比如在自流狀態下需要零壓啟動的，就是通電后，線圈整個把閘體吸起來。而有壓力狀態的電磁閥，則是線圈通電后吸出插在閘體上的一個銷子，用流體自身的壓力把閘體頂起 來。這兩種方式的不同之處是，自流狀態的電磁閥，因為線圈要吸起整個閘體，所以體積較大而帶壓狀態的電磁閥，只需要吸起銷子，所以體積可以做的比較小。
The structure and working principle of the brief solenoid valve The solenoid valve coil, magnet, and ejector. When the coil is connected to electricity, they generate a magnetic, mutual attraction with the magnet, the magnet will pull the mandrel. Turn off the power supply, magnet and plunger on reset, so that the solenoid valve complete for the power process. This is the working principle of the solenoid valve. The solenoid valve is generally used in hydraulic systems, closing and opening of the oil. In fact, according to the temperature, pressure flow through the media, such as pipeline pressure and gravity state pressure. Solenoid valve working principle is different. For example, in gravity state zero pressure started, is energized, the coil throughout the gate body sucked up. Pressure on the state of the solenoid valve coil is energized, sucked out of a pin inserted in the gate body, top of the gate body with the pressure of the fluid itself. These two modes of difference is that the gravity state of the solenoid valve coil you want to pick up the entire gate body, so the larger solenoid valve with a pressure state, only need to pick up the pin, so the volume can be done relatively smaller.