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1–6 EPM 5300 SERIES ADVANCED POWER METERS – INSTRUCTION MANUAL
WAVEFORM AND HARMONICS CHAPTER 1: AC POWER MEASUREMENT
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:
DISTORTED WAVEFORM:
TOTAL HARMONIC DISTORTION (THD):
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.
FIGURE 1–5: % THD GRAPH
t)( sin •A ⋅ω
L +t)•sin(•A+t)•sin(•A+t)•sin(•A+t) •sin( •A
332211
ωωωω
100
Signal lFundamenta the of RMS
Signal DistortionHarmonic Total of RMS
=THD of % ×