What is a proportional valve?
A proportional valve is a hydraulic valve whose opening changes in proportion to an electrical signal. Unlike an on/off valve, it adjusts flow or pressure steplessly.
What does a proportional valve do?
It steplessly controls the speed, direction or pressure of a cylinder or hydraulic motor, so motion can be adjusted rather than starting and stopping abruptly.
Working principle
- The driver card applies a current to the proportional solenoid according to the command.
- The solenoid produces a force proportional to the current.
- This force moves the spool against a spring, and the spool position sets the valve opening.
- In some valves, the spool position is measured with a position sensor and controlled in a closed loop.
What does a proportional valve driver card do?
A driver card turns the command signal into coil current. Because coil resistance changes with temperature, the current is usually controlled in a closed loop. The first value to check when choosing a card is the valve’s coil current, which the card’s current range must cover.
Where is it used?
- Construction machinery and mobile hydraulics
- Presses and injection moulding machines
- Industrial automation and production lines
- Test setups that need speed and pressure adjustment
On/off, proportional and servo valves compared
| On/off valve | Proportional valve | Servo valve | |
|---|---|---|---|
| Operation | Only fully open or closed | Also works in between | Works in between, usually in a closed loop |
| Flow or pressure adjustment | No stepless adjustment | Stepless | Stepless and precise |
| Dynamics | — | Usually lower than a servo valve | Generally higher |
| Oil contamination | — | Generally less sensitive | More sensitive |
Frequently asked questions
What is the difference between a proportional valve and an on/off valve?
An on/off valve works only fully open or closed. A proportional valve also works in between, adjusting flow or pressure steplessly.
What is the difference between a proportional valve and a servo valve?
Proportional valves are simpler and generally less sensitive to oil contamination. Servo valves generally offer higher dynamics and precision.
To drive proportional valves
MotorTech HSV drives proportional valves with coil currents up to 400 mA under current control.
Proportional valve driver card