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Shaft horsepower (shp) is the power delivered to a propeller shaft, a turbine shaft, or to an output shaft of an automotive transmission. [32] Shaft horsepower is a common rating for turboshaft and turboprop engines, industrial turbines, and some marine applications. Equivalent shaft horsepower (eshp) is sometimes used to rate turboprop engines ...
where rotational speed is in revolutions per minute (rpm, rev/min). Some people (e.g., American automotive engineers) use horsepower (mechanical) for power, foot-pounds (lbf⋅ft) for torque and rpm for rotational speed. This results in the formula changing to:
Engine power is the power that an engine can put out. It can be expressed in power units, most commonly kilowatt, pferdestärke (metric horsepower), or horsepower.In terms of internal combustion engines, the engine power usually describes the rated power, which is a power output that the engine can maintain over a long period of time according to a certain testing method, for example ISO 1585.
The torque on shaft is 0.0053 N⋅m at 2 A because of the assumed radius of the rotor (exactly 1 m). Assuming a different radius would change the linear K v {\displaystyle K_{\text{v}}} but would not change the final torque result.
In this case, unless external limitations are applied, the maximum torque is achieved at low RPM. For example, the AC motor found in the Tesla Roadster (2008) produces near constant maximum torque from 0 to about 6000 RPM, while maximum power occurs at about 10000 RPM, long after torque begins to drop off. The Roadster's redline is 14000 RPM.
Speed has dropped out of the equation, and the only variables are the torque and displacement volume. Since the range of maximum brake mean effective pressures for good engine designs is well established, we now have a displacement-independent measure of the torque-producing capacity of an engine design – a specific torque of sorts.
With a governor set to 8% accuracy, the rated power is 21.33 kW (29 bhp; 29 PS) at 3000 min −1, the highest torque is 69.63 N⋅m (51 lbf⋅ft) at 2000 min −1. [4] For other applications, the power and torque output may vary, e.g. On the Beetle produced 41 PS (40 bhp; 30 kW) at 3900 rpm and 88 N⋅m (65 lbf⋅ft) of torque at 2400 rpm.
The useful power of an engine with shaft power output can be calculated using a dynamometer to measure torque and rotational speed, with maximum power reached when torque multiplied by rotational speed is a maximum. For jet engines the useful power is equal to the flight speed of the aircraft multiplied by the force, known as net thrust ...