Electric actuators are mostly used with valves and are used in automated control systems. There are many types of electric actuators, and their modes of operation vary. For example, quarter-turn electric actuators output angular torque, while linear stroke electric actuators output displacement thrust. The type of electric actuator used in a system should be selected according to the operational requirements of the valve. Valves themselves come in various types, and their applications and working principles differ, but generally, a valve controls opening and closing by rotating the valve disc or lifting the valve plate. 

The choice of electric actuator is based on the valve's opening and closing method. 

 1. Electric Rotary Actuator Electric rotary actuators are used with rotary valves. The output shaft of a rotary electric actuator rotates less than one full turn, i.e., 360 degrees. For example, the rotation angles of butterfly valves, ball valves, and plug valves are usually less than 90 degrees. A 90-degree rotary electric actuator can achieve the valve's opening and closing process. According to the installation interface method, quarter-turn electric actuators are divided into direct-coupled electric actuators and base-crank electric actuators. The output shaft of a direct-coupled electric actuator is directly connected to the valve stem, while a base-crank actuator is connected to the valve stem through a crank.

 2. Multi-turn Electric Actuator A multi-turn electric actuator is also an electric actuator that outputs angular torque. Unlike a quarter-turn actuator, its output shaft can rotate more than 360 degrees. Multi-turn electric actuators are suitable for rotary valves whose opening and closing can be completed by multiple turns, such as gate valves and globe valves. 

 3. Linear Stroke Electric Actuator The output of a linear stroke electric actuator is displacement thrust, suitable for valves such as single-seat control valves and double-seat control valves, used for controlling the lift of the disc.