On the Definition of Power in an Electrical System

Summary form only given. The definitions of power, and related quantities such as apparent power and reactive power, in sinusoidal and non-sinusoidal situations are reviewed. These definitions are compared with the physical mechanisms for the transfer of power in an electrical circuit by means of the Poynting Vector. Real power flows into and out of resistors; inductors and capacitors are used to provide new definitions for the fundamental power quantities. These definitions do not rely upon the statistical RMS and Fourier concepts normally used. New power equations are developed, defining real, reactive and apparent power. These definitions are more exact and easier to use than definitions based upon harmonic analysis.