Rated Speed
Rated speed is the speed at which the manufacturer states the engine can continuously produce its declared power, and it is the reference for the nameplate values. Power, fuel consumption and life data are valid at this speed. On constant-speed generator engines the common values are 1500 and 3000 rpm.
Rated speed is not an arbitrary upper limit but the point at which the engine's cooling, lubrication and combustion balance is designed. Running continuously above this speed increases fuel consumption, noise and wear; running markedly below it brings the problems of staying at low load.
- Constant-speed applications (generators) hold the engine at rated speed; since speed determines frequency, there is no choice.
- Variable-speed applications (irrigation pumps, drilling mud pumps, construction machinery) select the speed according to the needs of the job; here rated speed is a ceiling, not a target.
When installing an electronic throttle kit, the upper limit must be set so as not to exceed the engine's rated speed. On the GS740-3P the taught upper limit defines the furthest position the actuator can go to; limiting that to the speed the engine permits is the responsibility of the installer.
Context in which this term is used: Electronic speed and throttle control on diesel engines