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Operation
Methods of Measurement/Formulas 3
3-21
K-Factor formula:
∑
=
=
==
50
1
22
h
h
h
f
t
hI
P
P
K
where
t
P total eddy current loss
f
P eddy current loss at fundamental frequency
h
I relative harmonic current component at order h (relative to fundamental)
h harmonic order
Factor K formula:
∑
=
+=
⎟
⎟
⎠
⎞
⎜
⎜
⎝
⎛
⎟
⎟
⎠
⎞
⎜
⎜
⎝
⎛
⎟
⎠
⎞
⎜
⎝
⎛
+
+=
50
2,1
2
1
2
1
1
1
n
nn
n
q
I
I
n
I
I
e
e
K
where
e eddy current loss at the fundamental frequency divided by the loss due to a dc current
equal to the RMS value of the sinusoidal current (constant factor to be entered by the
user – see dialog below)
q exponential constant that is dependent on the type of winding and frequency. Typical
values are 1.7 for transformers with round or rectangular cross section conductors in both
windings and 1.5 for those with foil low voltage windings (to be entered by the user – see
dialog below)
I
rms value of the sinusoidal current including all harmonics
n
I magnitude of the harmonic current of order n
1
I magnitude of the fundamental current component
h harmonic order
3_1.bmp
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