09-08-2012, 10:27 AM
Definitions and Measurement of Power Factor
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Abstract:
The methodology of measurement of cos(φ) was developed long time ago, but it is
usable only for sinusoidal voltages and currents. Nowadays the customer loads use power
supplies built with semiconductors, switching power supplies, power controlling systems,
etc. These loads cause non-sinusoidal current in power lines, energy quality and EMC
problems. The method of Power Factor measurement is described in this article, which is a
good KPI in these cases.
Intoduction
An AC system of Active power (P), Reactive power (Q), and Apparent power (S)
plays a major role in electric power technology. The terms of Active power,
Reactive power, and Apparent power are applied to steady-state alternating
current circuits in which the voltages and currents are non-sinusoidal. Today it is
characteristic in most parts of the applications that the current and voltage are nonsinusoidal.
Conclusions
The quality of electrical energy is not only a technical, but an economical
question, too. Before permeation of semiconductors, the topmost quality
measurement of consumers was the cos(φ), and it was easy to measure in
sinusoidal case.
Nowadays almost every electronic loads contain power supplies, power
controlling systems or semiconductors. In this case the shape of the current is not
sinusoidal, therefore the simple cos(φ) can not be a key performance indicator,
moreover, it is difficult to be assigned.
In non-sinusoidal current or voltage cases a good consumer load key performance
indicator is the Power Factor, but assigning the PF is an even more complicated
task.