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Three-phase transformer with four-wire output for 208Y/120 volt service: one wire for neutral, others for A, B and C phases Three-phase electric power (abbreviated 3ϕ [ 1 ] ) is a common type of alternating current (AC) used in electricity generation , transmission , and distribution . [ 2 ]
The service factor is typically in the 1.15-1.4 range, with the figure being lower for higher-power motors. For every hour of operation at the service-factor-adjusted power rating, a motor loses two to three hours of life at nominal power, i.e. its service life is reduced to less than half for continued operation at this level.
The other end of the three secondary windings and the neutral are brought down the service drop to the service panel. 230 V loads are connected between any of the three-phase wires and the neutral. Because the phases are 120 degrees from each other, the voltage between any two phases is sqrt(3) * 230V = 400V, compared to the 2 * 120V = 240V in ...
The slash rating, under the United States National Electrical Code, is given to circuit interrupt hardware and specifies a maximum line-to-ground voltage rating in combination with a maximum line-to-line voltage rating.
As an example, the 5-15R is the common 125 V two-pole, three-wire receptacle rated for 15 A. The L5-15R, while sharing the same electrical rating, is a locking design that is not physically compatible with the straight-blade 5-15 design. The 5-30R has the same two-pole, three-wire configuration and 125 V rating, but is rated for 30 A.
Series II current ratings are 20, 30, 60, 100, 200, 300, 350, 500 and 600 amps. The voltage ratings go up to 1000 V AC. These have been replacing the American-style for some time and are much more likely to be found in food processing, data centers, healthcare, entertainment, and other industries.
In some cases both edges are graduated differently in order to allow comparison between two systems of measurement. A few gauges are made with holes into which the wire has to be thrust. All gauges are hardened and ground to dimensions. In some applications wire sizes are specified as the cross sectional area of the wire, usually in mm 2.
Each type specifies characteristics of an enclosure, but not, for example, a specific enclosure size. Note that higher numbers do not include the lower-numbered tests. For example, types 3, 4 and 6 are intended for outdoor use, but type 5 is not. A NEMA enclosure rating does not mean that it also meets the same UL enclosure rating. [2]