Jul.29.2025
The solenoid valve (also known as an electromagnetic valve) is an industrial device that uses electromagnetics to regulate fluids in automation. It is within the actuator category and is not restricted to hydraulic or pneumatic applications. It is used in industrial control systems to change the direction, flow, speed, and other characteristics of the medium.
Solenoid valves may regulate many circuits, ensuring accuracy and versatility. There are several varieties of electromagnetic valves, each having a distinct function at different positions within control systems. The most frequent types are check valves, safety valves, directional control valves, and speed control valves.
Common types of solenoid valves include two-position three-way, two-position five-way, and three-position five-way.
1. Two-position three-way solenoid valves can be normally closed or normally open. Normally closed means that the air passage is closed when the coil is not energized, while normally open means that the air passage is open when the coil is not energized.
- Normally closed two-position three-way solenoid valve principle: When the coil is energized, the air passage is open; once the coil is de-energized, the air passage is closed, resembling a "momentary" action.
- Normally open two-position three-way single electric control solenoid valve principle: When the coil is energized, the air passage is closed; once the coil is de-energized, the air passage is open, resembling a "momentary" action.
Single electric control has only one electromagnetic head. When energized, the electromagnetic valve switches position, and when de-energized, the valve resets due to the action of the spring.
Double electric control has two electromagnetic heads, and they cannot be energized simultaneously for safety reasons.
2. Two-position five-way double electric control solenoid valve principle: Energizing the positive action coil connects the positive action air passage (positive action exhaust port has air). Even if the positive action coil is de-energized, the positive action air passage remains connected until the reverse action coil is energized.
Energizing the reverse action coil connects the reverse action air passage (reverse action exhaust port has air). Even if the reverse action coil is de-energized, the reverse action air passage remains connected until the positive action coil is energized. This is akin to "self-locking."
3. Double electric control two-position electromagnetic valves have 2 electromagnetic heads; only one can be energized. When energized, the electromagnetic valve switches position, and when de-energized, the valve maintains its position. The other side's electromagnetic head must be energized for the valve to return to its original position.
4. Three-position five-way, as the name suggests, has three working positions and five ports.
Three-position five-way electromagnetic valve "Y" is center exhaust type; "P" is center pressure type; center sealed type omits labeling.
The three positions refer to the three positions of the valve core. Three-position electromagnetic valves all have two coils, referred to as A and B coils. When neither A nor B is energized, the valve core is in one position. When A is energized, the valve core moves to the second position. When A is de-energized and B is energized, the valve core's position is the third position. So, there are three positions in total.
Please note that three-position five-way electromagnetic valves have three types, depending on the valve core's state when neither A nor B is energized: center sealed, center open, and center closed.
- Center exhaust: When neither A nor B is energized, both A and B exhaust ports are connected to the atmosphere.
- Center pressure: When neither A nor B is energized, both A and B exhaust ports are connected to the intake port.
- Center sealed: When neither A nor B is energized, both A and B exhaust ports maintain the state when de-energized.
