Resumo:
The Classical Phasor Theory goes back to the pioneer work of Charles Proteus Steinmetz
in the study of alternating current electrical circuits. According to Steinmetz, a classical
or static phasor is a complex number that represents a sinusoidal function whose amplitude,
phase and angular frequency are constants and it transforms ordinary differential
equations with constant coefficients, which are models for alternating current electrical
circuits, in linear systems with complex coefficients. When either amplitude, phase or
angular frequency is no longer constant, the phasor theory must be adapted in such a
way to preserve the classical results. In this new theory, which deals with a large class
of functions rather than only sinusoidal functions, the phasor is called dynamic or timevariable
phasor. Following this line, the main objective of this work is to present three new
theories about dynamic phasors built from integral transforms, namely, the short-term
Fourier transform, the generalized Laplace transform and the Hilbert transform. More
precisely, the dynamic phasors arise through injective linear operators between suitable
vector spaces and they have similar properties to those of the dynamic phasors usually
found in the literature.