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Power Quality Analyzer Model 3945-B
91
Calculation of Harmonic Bins
Harmonic bins are calculated by FFT with 16 bit resolution (1024 samples on
4 cycles) without windowing (IEC 1000-4-7). From real and imaginary compo-
nents, each bin ratio is calculated on each phase Vharm[3][51], Uharm[3][51]
and Aharm[3][51] in proportion to the fundamental value and the phase angles
Vph[3][51], Uph[3][51] and Aph[3][51] between each bin and the fundamental.
Thiscalculationisaccomplishedusingthefollowingprinciple:
cos
sin
=
+×=
+×=
+=+=
∑
∑
∑
=
=
=
1024
0
0
1024
0
1024
0
22
1024
1
512512
1
512512
1
s
s
s
ksk
s
ksk
kkkkk
Fc
s
k
Fa
s
k
Fb
bajabc
ϕ
π
ϕ
π
100mod
1
×=
c
c
k
k
=
k
k
k
b
a
arctanϕ
module in %:
with
angle in degree:
ck: amplitudeofthecomponentwithafrequencyof
1
4
f
k
f
k
=
Fs: sampledsignal
co: DCcomponent
k: ordinalnumber(spectralbin)