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}. The DC component I0 is usually (but not always) equal to zero. The fundamental component, I1 is the only component that contributes to real power. All the other components contribute to the RMS harmonic distortion current, Id :

Total Harmonic Distortion Total Harmonic Distortion (THD) is defined as the ratio of the RMS harmonic distortion current Id to the RMS value of the fundamental component I1 : thus… (assuming zero DC)

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

Displacement Power Factor 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:

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

Magnetics Concepts

Inductors and Transformers