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What is the relation between peak current and effective current of an AC power system generated by commercial power companies in the US?


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March 22, 2014 3:29PM

The situation is basically the same in the U.S. and anywhere else. Power is provided as an AC current; if you graph this current versus time, it basically has the shape of a sine wave.

Effective power is calculate as RMS - meaning root-mean-square. That is, the current at any moment is squared, the average is taken (using an integral), and the square root of the result is calculated.

In the case of a sine wave, RMS (i.e., effective) voltage, or current, is less than the peak voltage, or current, by a factor (square root of 2). As an example, if your home gets its electrical energy at a nominal voltage of 220 volts, that refers to RMS voltage; the peak voltage in this case is about 311 volts. Note that different countries and regions have different nominal voltages, so the above is just an example. However, the factor (square root of 2) should apply equally in other places.