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Revolutions per minute (abbreviated rpm, RPM, rev/min, r/min, or r⋅min −1) is a unit of rotational speed (or rotational frequency) for rotating machines. One revolution per minute is equivalent to 1 / 60 hertz.
Rotational frequency, also known as rotational speed or rate of rotation (symbols ν, lowercase Greek nu, and also n), is the frequency of rotation of an object around an axis. Its SI unit is the reciprocal seconds (s −1 ); other common units of measurement include the hertz (Hz), cycles per second (cps), and revolutions per minute (rpm).
Cutting speed may be defined as the rate at the workpiece surface, irrespective of the machining operation used. A cutting speed for mild steel of 100 ft/min is the same whether it is the speed of the cutter passing over the workpiece, such as in a turning operation, or the speed of the cutter moving past a workpiece, such as in a milling operation.
Specific speed N s, is used to characterize turbomachinery speed. [1] Common commercial and industrial practices use dimensioned versions which are of equal utility. Specific speed is most commonly used in pump applications to define the suction specific speed —a quasi non-dimensional number that categorizes pump impellers as to their type and proportions.
2 Dunkerley’s formula (approximation) 3 See also. ... where the frequency of whirling is the same as the rotational speed. ... (RPM) equivalent as follows: ...
For example, for a four-pole, three-phase motor, = 4 and = = 1,500 RPM (for = 50 Hz) and 1,800 RPM (for = 60 Hz) synchronous speed. The number of magnetic poles, p {\displaystyle p} , is the number of north and south poles per phase.
The mean piston speed is the average speed of the piston in a reciprocating engine. It is a function of stroke and RPM. There is a factor of 2 in the equation to account for one stroke to occur in 1/2 of a crank revolution (or alternatively: two strokes per one crank revolution) and a '60' to convert seconds from minutes in the RPM term.
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: