- Describe, with the aid of a sketch, the operation of a diesel generator speed and load sensing electronic governor, labelling the MAIN components.(10)
Operation of a Diesel Generator Electronic Governor
An electronic governor automatically controls the fuel rack/actuator position to maintain generator speed (and therefore frequency) while sharing load proportionally with other generators in parallel.
1. Main Components
- Speed Sensing Unit (Magnetic Pickup / MPU):
- A magnetic or electronic pickup measures engine speed by detecting teeth on the flywheel.
- Produces an electrical signal proportional to engine speed (frequency).
- Electronic Control Unit (ECU) / Governor Controller:
- Compares the actual speed signal with the reference speed setting.
- Uses a PID control algorithm to calculate the required correction.
- Also processes load sharing signals when operating in parallel.
- Load Sensing / Droop Circuit:
- Introduces a controlled reduction in fuel at higher loads (droop characteristic).
- Allows stable load sharing between generators without oscillation.
- Actuator / Servo Motor:
- An electro-hydraulic or electric actuator connected to the fuel control rack of the diesel engine.
- Adjusts fuel supply in response to ECU signals to increase or decrease speed and load.
- Power Supply & Protection Circuits:
- Ensures stable voltage to the governor electronics.
- Includes surge protection, fault monitoring, and alarms.
2. Principle of Operation
- Speed Control (Isolated Operation):
- The pickup sends actual speed → ECU compares with set point.
- If speed falls (increased load), ECU sends a signal to actuator → more fuel injected → speed restored.
- If speed rises (load decreases), ECU reduces fuel.
- Load Sharing (Parallel Operation):
- The load sensing circuit applies droop so that as load increases, engine speed reference slightly decreases.
- Ensures that each generator shares load proportionally according to its governor setting.
- Electronic governors may also include load sharing lines for isochronous load control.
- Steady State:
- ECU continuously balances fuel input to maintain desired engine speed (frequency) and stable load distribution.
Summary
- The electronic governor integrates speed sensing, load sharing, and actuator control.
- Its main role is to maintain constant frequency and ensure safe, stable load sharing between generators.
- Components: speed sensor, ECU, droop/load sharing circuit, actuator, and power supply.