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alternating current

An electric current that varies periodically in value and direction, first flowing in one direction in the circuit and then flowing in the opposite direction; each complete repetition is called a cycle, and the number of repetitions per second is called the frequency; usually expressed in Hertz (Hz).
McGraw-Hill Dictionary of Architecture and Construction. Copyright © 2003 by McGraw-Hill Companies, Inc.
References in periodicals archive ?
An advantage over a-c motor is claimed in the waveform used by the brushless d-c motor.
Also, brushless d-c motors are not subject to thermal problems at very low speeds, which Lee singles out as a drawback of a-c drives.
Lee claims that the high power factor of brushless d-c drives - 0.95 to 0.98 -is better than both brush-type d-c and most a-c inverter drives.
Lee disputes competitors' claims that a-c drives have high power factor.
In a-c drives with no input inductor - and many do not have the same wave shape.