AskDefine | Define RPM

Dictionary Definition

rpm n : rate of revolution of a motor; "the engine was doing 6000 revs" [syn: revolutions per minute, rev]

User Contributed Dictionary

English

RPM
  1. Revolutions Per Minute

Extensive Definition

Revolutions per minute (abbreviated rpm, RPM, r/min, or r·min−1) is a unit of frequency: the number of full rotations completed in one minute around a fixed axis. It is most commonly used as a measure of rotational speed or angular velocity of some mechanical component.
Standards organizations generally recommend the symbol r/min, which is more consistent with the general use of unit symbols. This is not enforced as an international standard; in French, for example, tr/mn (tours par minute) is commonly used.
The corresponding International System of Units (SI) unit would be the hertz and we have:
3600 r/min = 60 revolutions per second = 60 Hz
In the SI one often uses the unit for angular velocity which is radians per second (rad·s−1):
1 r/min = 2π rad·min−1 = 2π/60 rad·s−1 ≈ 0.10471976 rad·s−1
To convert revolutions per minute to revolutions per second (hertz), simply divide by 60.

Examples

  • On some kinds of disc or tape-like recording media, the rotational speed of the medium under the read head is a standard given in r/min. Gramophone (phonograph) records, for example, typically rotate steadily at 16, 33⅓, 45 or 78 r/min (⁴⁄₁₅, ⁵⁄₉, ³⁄₄, or 1.3 Hz).
  • Modern dental drills can rotate at up to 500,000 r/min (8 kHz).
  • The "second" hand of a conventional analogue clock rotates at 1 r/min.
  • Audio CD players read their discs at a constant 150 kB/s and thus must vary the disc's rotational speed from around 500 r/min (actually 8 Hz), when reading at the innermost edge, to 200 r/min (actually 3.5 Hz) at the outer edge. CD-ROM drives’ maximum rotational speeds are rated in multiples of this figure, even though they do not hold to constant read speeds when reading from most disc formats.
  • DVD players also usually read discs at a constant linear rate. The disc's rotational speed varies from 1530 r/min (actually 25.5 Hz), when reading at the innermost edge, and 630 r/min (actually 10.5 Hz) at the outer edge.
  • A Zippe-type centrifuge for enriching uranium spins at 90,000 r/min (1,500 Hz) or faster.
  • Gas turbine engines rotate at tens of thousands of r/min. JetCat model aircraft turbines are capable of over 100,000 r/min (1,700 Hz) with the fastest reaching 165,000 r/min (2,750 Hz).
  • An electromechanical battery (EMB) works at 60,000–200,000 r/min (1–3 kHz) range using a passively magnetic levitated flywheel in vacuum. The choice of the flywheel material is not the most dense, but the one that pulverises the most safely, at surface speeds about 7 times the speed of sound.
  • A turbocharger can reach 290,000 r/min (4,800 Hz), while 80,000–200,000 r/min (1–3 kHz) is common.

See also

References

RPM in Catalan: Revolució per minut
RPM in Czech: Otáčky za minutu
RPM in German: Rpm (Maßeinheit)
RPM in Spanish: Revoluciones por minuto
RPM in French: Tour par minute
RPM in Indonesian: Rotasi per menit
RPM in Italian: Giri al minuto
RPM in Latvian: Apgriezieni minūtē
RPM in Hungarian: Percenkénti fordulatszám
RPM in Macedonian: Вртежи во минута
RPM in Dutch: Omwentelingen per minuut
RPM in Japanese: Rpm (単位)
RPM in Norwegian: Omdreiningstall
RPM in Portuguese: Rotações por minuto
RPM in Romanian: Rotaţii pe minut
RPM in Finnish: Kierrosnopeus
RPM in Thai: รอบต่อนาที
RPM in Chinese: 每分鐘轉速

Synonyms, Antonyms and Related Words

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