[[File:Rating plate on the Dalchonzie power station generator - geograph.org.uk - 735379.jpg|thumb|right|The rating plate of a generator at the Dalchonzie power station with continuous maximum rating (CMR) of 4 megawatts]]
A '''rating plate''' on a machine carries information about its operational limits. The plate frequently contains the names of the machine and its manufacturer, so the rating plate is often called a name plate (hence the term "nameplate capacity" for a generator), although many devices carry separate nameplates and rating plates.<ref name="National Electric Light Association 1924 p. 1185">{{cite book | author=National Electric Light Association | title=Handbook for Electrical Metermen | publisher=Franklin printing Company | series=Nineteenth Century Collections Online (NCCO): Science, Technology, and Medicine: 1780-1925 | year=1924 | chapter-url=https://books.google.com/books?id=rh1SAQAAMAAJ&pg=PA1185 | chapter = Rating Plate|access-date=2023-07-15 | page=1185}}</ref>
For an electric machine, the power rating is the number on its rating plate and corresponds to a maximum electric load it can carry. There is a distinction between the ''continuous rating'' (for generators, '''continuous maximum rating''' or '''CMR'''<ref name="Stuart 2013 p. 18">{{cite book | last=Stuart | first=S. | title=Electrical (Generator and Electrical Plant): Modern Power Station Practice | publisher=Elsevier Science | year=2013 | isbn=978-1-4831-5751-1 | chapter-url=https://books.google.com/books?id=gqM3BQAAQBAJ&pg=PA18 | access-date=2023-07-15 | page=18 | chapter = The Rating of Generators}}</ref>), at which the machine can be operational without a time limit and short-term rating that can only be used for a specified amount of time.<ref name="British Standards Institution 1917 p. 18">{{cite book | author=British Standards Institution | title=British Standardisation Rules for Electrical Machinery (excluding Motors of Traction Purposes) Rev. September, 1917 | publisher=committee | series=British Standardisation Rules for Electrical Machinery (excluding Motors of Traction Purposes) Rev. September, 1917 | year=1917 | chapter-url=https://books.google.com/books?id=LXNtDgXCABIC&pg=PA18 | access-date=2023-07-15 | page=18 | chapter=Definitions}}</ref>
== Generators == A typical electrical generator rating plate contains the following parameters:{{sfn | Reddy | 2021 | pp=81-84}} * ''power rating'' is specified in terms of apparent power (KVA or MVA), since the exact power factor will be determined by the external factors;{{sfn | Reddy | 2021 | p=81}} * ''power factor'' (PF) is the nominal power factor for other ratings; usually PF = 0.8;{{sfn | Reddy | 2021 | p=81}} * ''insulation class'' (B, F, H) for the primary coil. Typical value is F, although older generators might use class B;{{sfn | Reddy | 2021 | p=81}} * ''type of enclosure'' (IP code);{{sfn | Reddy | 2021 | p=83}} * '''rated voltage''' can be either line to line ("line voltage") or phase to neutral ("phase voltage");{{sfn | Reddy | 2021 | p=83}} * '''rated current''' is derived from the rated power and voltage: <math>{ratedCurrent} = \frac {apparentPower} {lineVoltage}</math>;{{sfn | Reddy | 2021 | p=83}} * ''line frequency'' (50 Hz or 60 Hz) and rotational speed of the prime mover in RPM;{{sfn | Reddy | 2021 | p=83}} * ''connection'' (star or delta).
== See also == * Per-unit system
==References== {{Reflist}}
==Sources== * {{cite book | last=Reddy | first=B.K. | title=Electrical Equipment: A Field Guide | publisher=Wiley | year=2021 | isbn=978-1-119-77168-5 | chapter = Rating Plates | chapter-url=https://books.google.com/books?id=OIA_EAAAQBAJ&pg=PA80 | access-date=2023-10-14}}
Category:Electric power systems components
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