(a) Sensitivity:
Sensitivity in an engine governor refers to the responsiveness of the governor to changes in engine speed. A highly sensitive governor reacts quickly to even small speed variations, adjusting fuel delivery promptly to maintain speed stability. However, excessive sensitivity can lead to hunting, so achieving the optimal balance is crucial.
(b) Hunting:
Hunting describes an undesirable oscillation in engine speed caused by an overly sensitive governor. The governor overreacts to minor speed deviations, leading to adjustments in fuel supply that overshoot the correction needed. This creates a feedback loop where corrections become too large, causing speed to swing back and forth around the desired value.
(c) Speed Droop:
Speed droop is a fundamental characteristic of most engine governors. It defines the relationship between engine speed and load: as the load on the engine increases, the governor allows the engine speed to decrease slightly. This intentional “droop” ensures stable load sharing between multiple engines operating in parallel on a common bus. Without droop, load changes would cause large speed variations and unstable operation.
(d) Stability:
Stability in an engine governor refers to the system’s ability to maintain the desired engine speed despite external disturbances or load changes. A stable governor minimizes speed fluctuations and quickly returns to the setpoint after any transient event. Various factors, including governor sensitivity, droop settings, and control algorithms, contribute to achieving stable governor performance.
(e) Isochronous Governing:
Isochronous governing, also known as constant-speed governing, aims to maintain engine speed exactly at the setpoint regardless of load variations. Unlike governors with droop, an isochronous governor completely compensates for load changes by adjusting fuel delivery to keep the speed constant. This is desirable for applications requiring precise and constant speed, such as generators supplying critical equipment. However, isochronous governors may require more complex control algorithms and can be less tolerant of disturbances compared to droop governors.