How do electric actuators work and when are they preferred?

Electric actuators use electric motor to drive valve through gear train, converting rotary motor motion to linear (globe) or rotary (ball/butterfly) valve motion. Types: multi-turn (linear valves), quarter-turn (rotary valves), and linear (direct linear motion). Advantages over pneumatic: no air supply needed, precise positioning, high thrust capability, and easy status feedback. Disadvantages: slower response, less suitable for hazardous areas (unless explosion-proof), and no inherent fail-safe (requires battery backup or spring return). Preferred for remote locations, large valves, and where instrument air unavailable.