The working principle of an electric actuator is the conversion of electrical energy into mechanical motion through an electromagnetic motor and a mechanical transmission system
Core Mechanism
- Electrical Activation: An input signal (digital on/off or analog 4-20mA) triggers the control unit to supply power to the internal motor.
- Motor Rotation: Current flowing through the motor's wire coils creates a magnetic field. This field interacts with magnets in the motor to rotate a shaft at high speed with relatively low torque.
- Torque Amplification: A gearbox (e.g., spur, worm, or planetary gears) reduces the motor's high speed while significantly increasing the torque to provide the force necessary to move heavy loads.
- Motion Conversion:
- Rotary Actuators: The geared output directly turns a shaft, typically for 90° (quarter-turn) or 360° (multi-turn) valve operations.
- Linear Actuators: The rotational motion is converted into straight-line motion using a lead screw or ball screw. As the screw spins, a nut moves along its length, extending or retracting a rod or piston.
Control and Safety Features
- Limit Switches: These cut power to the motor when the actuator reaches its fully extended or retracted position, preventing mechanical damage.
- Feedback Sensors: Components like potentiometers or encoders provide real-time data on the actuator's exact position to a PLC (Programmable Logic Controller) for precise modulating control.
- Fail-Safe Mechanisms: In the event of power loss, systems such as battery backups or spring-return mechanisms return the actuator to a safe "default" position.
- Brakes: Often mounted on the motor, these lock the rotor in position when not in use to prevent external forces (like fluid pressure in a pipe) from back-driving the mechanism.