May 2008
Intermediate to advanced
340 pages
9h 41m
English
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1.4 PHASORS
Power system calculations in the steady-state situation are considerably simplified by introducing the phasor. A phasor is an arrow in the complex plane that has a one-to-one relation with a sinusoidal signal as can be seen from Figure 1.16. When the sine/cosine in Figure 1.16 has a frequency of 50 Hz, a radius with a length 
times the length of the phasor rotates counterclockwise in the complex plane with a frequency of 50 Hz.
Consider the following general sinusoidal voltage and current expressions:
Figure 1.16 Relation between a counterclockwise rotating radius and a sinusoidal signal.
In order to express these quantities as phasors, we apply Euler's identity:
and the sinusoidal voltage and current can be written as:
Re the operator that takes the real part of a complex quantity
V the voltage phasor
I the current phasor
The phasor represents a sinusoidal signal: the length of the phasor equals the effective or RMS value of the signal and the angle of the phasor matches ...
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