Electrical Frequency

The following article is from The Great Soviet Encyclopedia (1979). It might be outdated or ideologically biased.

Frequency, Electrical


the time parameter of a periodically (cyclically) varying electric current, expressed by the ratio of the number of complete cycles of current variation to unit of time; the quantity is the inverse of the period of current variation. It is measured in hertz (Hz). For a sinusoidal alternating current the concept of angular frequency is used, which is related to the electrical frequency by the formula ω = 2πf (where ω is the angular frequency and f is the electrical frequency).

In many countries of the world, including the USSR, the frequency of the current generated by electric power stations and commercially distributed to industry is 50 Hz; in the USA it is 60 Hz. Railroads in many countries use current with a frequency of 16⅔ Hz (for electric traction) as well as frequencies of 25 and 75 Hz (for automatic block signaling, for example, on track circuits). In aviation, the current used has a frequency of 400 Hz (for independent power-supply systems). In certain industrial and agricultural equipment the operating frequency is raised to 200–400 Hz.

The Great Soviet Encyclopedia, 3rd Edition (1970-1979). © 2010 The Gale Group, Inc. All rights reserved.
References in periodicals archive ?
The converter used for the compensation, if there is difference occurs between the mechanical and electrical frequency, which is done by injecting a rotor current with a variable frequency.
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[n.sub.sync]: Synchronous speed of motor P: Number of poles [[omega].sub.ref] Reference speed [[omega].sub.r]: Rotor speed [[omega].sub.s]: Slip speed [[omega].sub.e]: Inverter command frequency [V.sub.abc]: Inverter output voltage [V.sub.abc*]: Inverter command voltage [f.sup.*]: Command frequency to inverter [V.sub.dc]: DC bus voltage of inverter f: Electrical frequency PI: Proportional integral controller e: Error signal [m.sub.a]: Modulation index [m.sub.f]: Frequency modulation ratio [f.sub.c]: Carrier frequency [f.sub.h]: Frequencies at which harmonics occur [f.sub.1]: Fundamental frequency.
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