Servo Motor / Actuator
A Servo Motor (or Actuator) is a precision electric motor used in modulating burners to position air dampers and fuel valves. It ensures the correct air-fuel ratio is maintained across the entire firing range with high positioning accuracy (often ±0.1°).
Function in Combustion Control
In modern burners (especially those with Electronic Ratio Control), servo motors are the "muscles" that move the mechanical components.
- Air Control: Adjusts the air damper opening to increase or decrease combustion air, typically requiring high torque (e.g., 3 Nm to 40 Nm) to overcome draft pressure.
- Fuel Control: Adjusts the butterfly valve or fuel regulator to match the fuel input to the air.
- Positioning: They receive signals (e.g., 4-20mA, 0-10V, or digital bus like CAN or Modbus) from the Burner Controller and move to exact angles (e.g., 45.5° with ±0.1° accuracy). Running times from 0° to 90° typically range from 3 to 60 seconds depending on the model.
Features
- Feedback Potentiometer: Provides position feedback (e.g., 1000 Ω) to the controller to verify the valve is exactly where it should be.
- High Torque: Capable of moving heavy dampers against furnace draft pressure (models range from small 1.2 Nm actuators to heavy-duty 40+ Nm units).
- Fail-Safe: Some actuators have spring-return mechanisms (closing in <1 second) to safely shut valves upon power loss.