The operation of a proportional solenoid valve is based on the principle of electromagnetism. The valve consists of a solenoid coil and a moveable plunger or armature. When an electrical current is applied to the solenoid coil, it generates a magnetic field that attracts or repels the armature, thereby controlling the opening or closing of the valve.

Unlike on/off solenoid valves that have two positions (open or closed), proportional solenoid valves offer intermediate positions that allow for continuous adjustment of the flow or pressure. The amount of current applied to the solenoid coil determines the position of the armature and, consequently, the flow rate through the valve. This current can be controlled using electronic control systems, such as a proportional controller or a programmable logic controller (PLC).