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NEMA contact ratings are how much current at a rated voltage a relay or other pilot device can switch. The current rating of smaller NEMA contactors or their auxiliaries are defined by NEMA ICS 5: Industrial Control and Systems, Control Circuit and Pilot Devices [1] standard. The nomenclature is a letter followed by a three-digit number, the ...
Design depends on specified conditions of pressure and time; submersible in water or oil; used in quarries, mines, and manholes. 7 Certified and labelled for use in areas with specific hazardous conditions: for indoor use in Class I, Groups A, B, C, and D environments as defined in NFPA standards such as the NEC.
A non-grounded device may be two-pole, two-wire; three-pole, three-wire; etc. [citation needed] The numerals following the hyphen is the current rating of the device in amperes. This number is followed by the letter 'R' to indicate a receptacle (socket) or 'P' to indicate a plug (prongs).
Contact force or pressure increases the size of the a-spot which decreases the constriction resistance and the electrical contact resistance. [11] When the size of contacting asperities becomes larger than the mean free path of electrons, Holm-type contacts become the dominant transport mechanism, resulting in a relatively low contact ...
A wire or cable has a voltage (to neutral) rating and a maximum conductor surface temperature rating. The amount of current a cable or wire can safely carry depends on the installation conditions. The international standard wire sizes are given in the IEC 60228 standard of the International Electrotechnical Commission.
The standard includes preferred current ratings and wire gauges for both International (deemed Series I) and North American (deemed Series II) applications. Series I preferred current ratings (in amps) are: 16, 32, 63, 125, 250, 400, 630 and 800, with wire gauges specified as mm 2 .
For AC-operated devices (e.g. coaxial cable, loudspeakers), there may even be two power ratings, a maximum (peak) power rating and an average power rating. [ 5 ] [ 6 ] For such devices, the peak power rating usually specifies the low frequency or pulse energy, while the average power rating limits high-frequency operation. [ 5 ]
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 [ 2 ] ), at which the machine can be operational without a time limit and short-term rating that can only be ...