Diverse actuator applications in power plant

ABB actuators avoid this effect by defining a small area in front of the end position.
As soon as the actuator reaches this area, single board computer behaves as if it were set to 'Drive to end position'. The three-phase asynchronous motor with cage rotor guarantees safe and reliable operation. The use of a frequency converter allows the torque and stroke time of the intelligent actuator to be varied. This means that both single board computers can be adapted to the actuating element or process independently of each other. The motor is constantly under voltage, and increases or reduces the torque gently and in proportion to the control deviation. The actuator is always switched on, meaning that no technology restrictions are placed on the control loop, even at the maximum permissible ambient temperature.

refer to: http://www.power-eng.com/articles/print/volume-117/issue-8/features/opportunities-to-improve-efficiency.html