CHAPTER 1: AC POWER MEASUREMENT
4
EPM 5000 series Advanced Power Meters GE Multilin
1.4: Waveform and Harmonics
Ideal power distribution has sinusoidal waveforms on voltages and currents. In real-life applications,
where inverters, computers, and motor controls are used, distorted waveforms are generated. These
distortions consist of harmonics of the fundamental frequency.
SINUSOIDAL WAVEFORM:
t)( sin •A
ω
DISTORTED WAVEFORM:
L +t)•sin(•A+t)•sin(•A+t)•sin(•A+t) •sin( •A
332211
ω
ω
TOTAL HARMONIC DISTORTION (THD):
100
Signal lFundamenta the of RMS
Signal DistortionHarmonic Total of RMS
=THD of % ×
HARMONIC DISTORTION: A destructive force in power distribution systems. It creates safety problems,
shortens the life span of distribution transformers, and interferes with the operation of electronic devices.
The Futura+ monitors the harmonic distortion to the 31st harmonic. A waveform capture of distorted
waveform is also available.
% THD GRAPH
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