1.Understanding, Calculating, and Measuring Total Harmonic Distortion (THD).
Amplitudes of Harmonics of Distorted Sine Wave
Harmonic Amplitude
1 3.08V
3 0.308V
5 0.159V
7 0.090V
9 0.0487V
11 0.0253V
13 0.0164V
15 0.010V
How to generate a table like using voltage and frequency? what is the equation used for this table?
From the mathematical point of view:
1.
The list means, that the wave shape equals
U(t) = 3.08 sin( w t + p1 ) + 0.308 sin(3 w t + p3) + 0.159 sin(5 w + p5 ) + . . .
where w is the basic angular frequency (=2 \pi f), p1, p3, p5 , . . . are some initial phases of the sines;
2.
Lack of coefficients at even frequences means that the distorsions (i.e. those with higher frequencies 2w, 4w, . . . ) do not appear, probably due to a particular way of generating it.
3.
Formal formulas of the coefficients follow from Fourier integral formulas, see e.g.
http://www.thefouriertransform.com/series/coefficients.php
4.
Comparison to the central line of the table between formula (19) and (20) allows to guess, that the above obtained coefficients came from square wave (sometimes called also rectangular wave)
5.
Technically, using filters, we dimnish the size of higher frequencies leaving the fundtamental w almost unchanged; the result is alsmost a pure sine wave:)
6.
The wave without (not distorted by) higher frequences is needed for supplying with electrical energy the synchronous motors, see e.g.
https://www.testandmeasurementtips.com/basics-of-synchronous-motors/
7.
Therefore the coefficients of the higher frequencies are used a measure the degree of distortion. Usually this is the power of the not-appreciated terms proportional to the sum of all squares of ai/a1 with i=2,3,4, . . .
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