Thanks to the stable output and large torques, electric drives are often used to automate quarter turn valves. There are also no pressure losses as with pneumatic actuators, making long distances easy to bridge.
The electric actuator generally consist of a handwheel, a gearbox, a servomotor and peripheral electronics including adjustable limit switches.
When an electric currents is sent through the coil of the electric motor, a magnetic field is generated which makes the rotor, coupled to the gearbox, rotate. This rotor is in turn coupled to the control shaft of the valve. The speed at which the valve is operated depends on the gear ratio.
The electric motor needs a high starting torque to overcome the valve's release moment. The handwheel serves as an emergency control and can be disengaged as soon as the electric drive is engaged. The end-of-run switches switch off the servo motor when a certain torque setting value is exceeded.