Fundamental Electrical Power Concepts Instantaneous Power Average Power

Fundamental Electrical Power Concepts Instantaneous Power: Average Power: RMS (effective value):

AC Power Concepts • Source voltage waveform is assumed to be an undistorted sinusoid with zero phase angle. • Current waveforms may contain harmonic distortion components, which increases the RMS value of the current waveform, and hence the apparent power (but not real power).

Current Distortion A distorted current waveform can be decomposed into a set of orthogonal waveforms, (e. g. by Fourier analysis). The RMS value of the composite waveform (I) may be computed as the root-sum-squared of the RMS values of all of the orthogonal components {Ih}. o The DC component I 0 is usually (but not always) equal to zero. o The fundamental component, I 1 is the only component that contributes to real power. o All the other components contribute to the RMS harmonic distortion current, Id :

Total Harmonic Distortion (THD) is defined as the ratio of the RMS harmonic distortion current Id to the RMS value of the fundamental component I 1 : thus… (assuming zero DC)

Apparent Power Apparent power, S, is defined as the product of RMS voltage V, and RMS current I :

Real Power The real power contribution of the fundamental component of the current waveform is given by : Where F is the phase angle between the voltage and fundamental current component. Displacement Power Factor cos F is defined as the “displacement power factor” (DPF).

Power Factor We now can express real power in terms of apparent power S, DPF and THD : Power Factor is defined as the ratio of real power to apparent power:

Complex Power (Assumes current and voltage waveforms are undistorted sinusoids)

Magnetics Concepts

Inductors and Transformers