19
CFi
The ratio of the absolute value of the sampling point with the
largest absolute value to the effective value of the current in a
sampling period
THD
u
/THD
i
The calculation of voltage and current total harmonics provides
two calculation standards, namely the IEC standard and the CSA
standard. For details, please see the notes below the table.
Energy
Here T is the integration time set by
the user
Freq
Result of zero crossing detectio
n
The calculation of total harmonics is based on the difference between the International Electro
technical Commission (IEC standard) and the Canadian Standards Association (CSA standard).
There are two corresponding calculation methods (optional on the harmonic settings page), as
follows:
IEC Standard: Calculate the ratio (%) of the root mean square of the effective value of the 2nd to
50th harmonic components to the effective value of the fundamental wave (that is, the first
harmonic). The calculation formula is as follows:
----
Total harmonic calculation
-----
k Sub-harmonic percentage calculation
CSA standard: Calculate the ratio (%) of the root mean square of the effective value of the 2nd to
50th harmonic components to the root mean square of the 1st to 50th effective values. The
calculation formula is as follows:
----
Total harmonic calculation
-----
k Sub-harmonic percentage calculation
Explanation of the meaning of the characters used in the above two formulas:
C 1: the effective value of the fundamental wave (that is, the first harmonic) of U (voltage) or I
(current);
C k: effective value of k sub-harmonic of U (voltage) or I (current);
k: harmonic order index, 2 ~ 50
N: maximum harmonic coefficient, that is, 50.
C k%: Calculation result of the percentage component of the k sub-harmonic of voltage or
current.
