Lecture02

Lecture02 - Page 1 Fundamentals of Power Systems Lecture 2...

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Unformatted text preview: Page 1 Fundamentals of Power Systems Lecture 2 1 Electric Power z single-phase (1~) systems ¡ One source ¡ Two energy-carrying wires ¡ Pulsating instantaneous power (2f) z three-phase (3~) systems ¡ Three sources, 120° phase shifted Fundamentals of Power Systems Lecture 2 2 I P V I V I cos I Single Phase Power ¡ ¢ ¡ ¢ ¡ ¢ ¡ ¢ ¡ ¢ ¡ ¢ cos cos m m p t v t i t p t V t I t Z Z I £ £ ¤ Definition: t v, i, p Lagging, for I > 0 I Z = |Z| ¥ I V V V I Z Z V I Z I I I ¥ ¥ ¥ ¤ ¥ ¤ Page 2 Fundamentals of Power Systems Lecture 2 3 Instantaneous and Average Power ¡ ¢ ¡ ¢ > @ E D E D E D £ £ ¤ ¥ cos cos cos cos 2 1 trigonometric identity: ¡ ¢ ¡ ¢ > @ I Z I ¤ £ t I V t p m m 2 cos cos 2 the instantaneous power equation: ¡ ¢ I Z ¤ t 2 cos the average of over a cycle is zero the average power over one cycle: ¡ ¢ I cos 2 1 m m I V P Fundamentals of Power Systems Lecture 2 4 Average Power from RMS Values The average power in terms of rms : ¡ ¢ I cos rms rms I V P 2 1 1 ( )d 2 T rms m V v t t V T ³ for ¡ ¢ ¡ ¢ sin m v t V t Z Root mean square (rms) of an arbitrarily (periodic) AC waveform delivers the same power to a resistor as the corresponding DC quantity. Notation convention (this lecture, not in general): Voltage and currents given in rms if not stated otherwise. e.g. 208 V ¦-30° means V m = § 2·208 = 294 V pk Page 3 Fundamentals of Power Systems Lecture 2 5 Power Factor ¡ ¢ I cos rms rms I V P power factor I I sin I I V I cos I I I sin I I V I cos I Lagging Power Factor Leading Power Factor...
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This note was uploaded on 02/01/2012 for the course EEL 3216 taught by Professor Brooks during the Spring '08 term at FSU.

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Lecture02 - Page 1 Fundamentals of Power Systems Lecture 2...

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