These special Ultra Low Power Electro-Hydraulic Actuators and designed for linear choke valve control with modulating duty generally in remote locations where mains power is unavailable. Operating from a solar array.
- no standard mains power supply (solar power only)
- minimum power consumption of 30 watts
- thrust required to operate choke valve: 2500kgf
- installation in an explosion-proof enclosure (Zone 1 EExd)
When most electric motors are switched on a surge of power is required to initiate them. The potential risk is that such a surge could potentially trip the power supply and hence disrupt the actuator operation. The project therefore required an actuator that would consume as little power as possible. It also required an EExd rated 24vdc electric motor with a power consumption of less than 50 watts.
Since hydraulic actuators and systems are generally about 80% efficient a hydraulic actuator was selected due to its higher efficiency over pneumatic and electric actuators.
Modifications to standard pump: It was found that all standard pumps investigated could not provide the flow or reduced friction required. Modifications to a standard pump met the requirements.
Solenoid valve: Most hydraulic systems use solenoid valves to select the direction of the linear actuator for extend or retract motion. Since solenoids consume power they were designed out of the actuator.
Electric motor: After some detailed searching the a manufacturer of
electric motors was found who, through their own development and some modifications, produced a motor that was both fit for purpose and at an acceptable price point. To overcome the in-rush problem on the electric motor, a current limiter was fitted which gave the motor a “soft start” and protected the system from tripping out. The prototype was thoroughly bench-tested with power consumption data being analysed against hydraulic pressure.