A multi-turn electric actuator is an automation device that converts electrical energy into angular displacement (multi-turn rotation); it is primarily used to drive valves (such as ball valves, butterfly valves, and plug valves) for fully open/closed operation or intermediate position regulation.
Mechanical Structure
1. Power Unit
Electric motor (typically a three-phase asynchronous motor): Provides rotational power.
2. Transmission Mechanism
Reduction unit: Uses gear sets, worm gears, or harmonic drives to reduce speed and increase output torque, meeting the torque requirements for opening and closing the valve.
Output shaft: Connects directly to the valve stem to transmit torque, driving the stem through multi-turn rotation (e.g., 90°, 180°, or multiple full rotations).
3. Feedback System
Encoder: Incremental or absolute encoder; outputs pulse signals or analog signals to provide real-time feedback on valve position (angle or travel), enabling closed-loop control.
Limit switches: Hard limit protection (e.g., mechanical stops or electromagnetic sensors).
Working Principle (Closed-loop Control)
1. Signal input: Receives 4-20mA DC, 0-10V DC, or digital signals (e.g., Modbus).
2. Controller processing: Compares the target position with the feedback signal and generates PWM or sine-wave drive signals.
3. Motor drive: Controls motor direction and speed via a driver (e.g., H-bridge circuit).
4. Position adjustment: The actuator drives the valve to the set position, while the feedback signal corrects errors in real time.
