No-Load Speed
No-load speed is the steady speed measured when the throttle setting is at the working position and no load is on the engine. It is the upper reference point of the droop calculation and, on engines with mechanical governors, it is a few percent above the full-load speed. It should not be confused with idle speed.
The difference is this: idle is the minimum speed with the throttle lever at its lowest position. No-load speed is the speed the engine settles at with the throttle lever at the working position and no load present. This is the value measured before the generator is switched in.
- When adjusting, the no-load speed is set first, then load is applied and the drop is observed. On a 4-pole alternator, 1500 rpm at full load is targeted for 50 Hz; the no-load value comes out somewhat above that.
- The difference between no load and full load directly gives the engine's droop characteristic.
In practice this measurement is an acceptance test: if after installing a GS740 or GS740-3P you set the upper limit according to the no-load reading only, you will end up below your target speed when load is applied. For that reason the setting must always be verified under real load.
Context in which this term is used: Electronic speed and throttle control on diesel engines