Frequency Stability
Frequency stability is the frequency at the generator output staying within a narrow band around the target value despite load changes. Because frequency arises directly from speed, this is in reality a matter of speed stability. The only way to achieve it is control that measures engine speed and feeds it back.
Stability is assessed through two different behaviours: the deviation in steady state, and the transient deviation on a load change together with the recovery time. On an engine with a mechanical governor, a steady-state deviation already exists because of droop, and typically a difference on the order of 1.5–3 Hz occurs from no load to full load. On an electronic governor running isochronously this difference disappears.
- The way to improve frequency is not to drive the throttle lever more precisely; it is to change the quantity being measured.
- Applying the load change in steps noticeably reduces the transient deviation.
A clear position on the product side: the standard GS740 kit and the GS740-3P do not measure speed and do not provide frequency stability; what these kits provide is repeatable holding of throttle lever position. In an installation requiring frequency precision, the optional active-feedback speed stabilisation module declared for the GS740, or the engine's own electronic governor, is required.
Context in which this term is used: Why is constant speed important on a generator?