Rockwell Automation 1404-M4_M5_M6_M8 Powermonitor 3000 User Manual, PRIOR to Firmware rev. 3.0 - Manual (Page 158)

Publication 1404-UM001D-EN-E - October 2004
8-8 Advanced Features
Crest Factor
This is another quantity that is sometimes used to describe the amount
of distortion present in a waveform. It can also be used to express the
dynamic range of a measurement device. Crest Factor is the ratio of
the peak to the RMS.
A pure sinusoid Crest Factor equals .
TIF
Another method of measuring signal distortion is the Telephone
Influence Factor, sometimes called the Telephone Interference Factor.
This measurement is used to estimate the effect that the power line
harmonics have on nearby analog telephone conductors. This method
weighs each of the harmonics based on the physiological and
audiological characteristics of the human ear. The harmonics are
additionally weighted to reflect the relationship of harmonic
frequency and degree of coupling to the phone lines. These weights
are called single frequency TIF weights. The 1404-M6 uses the most
recent TIF weights (updated in 1960). The single frequency factors are
used to compute the total TIF. The user multiplies the TIF numbers by
the RMS magnitude of the power lines voltage or current to obtain an
index for estimating the amount of interfering energy that is coupled
to the telephone system. The formula for total TIF is:
K-Factor
K-Factor measures additional heating in a power transformer due to
the harmonics in the power signal. These harmonics cause additional
heating due to increased core losses that occur at higher frequencies.
The increased losses are related to the square of the harmonic
frequency. Therefore, a slight harmonic content can significantly
Crest Factor Peak Value RMS Value
⁄
=
2
TIF
∞
Σ
i 1 =
w
i
X
i
( )
2
∞
Σ
i 1 =
X
i
( )
2
--------------------------- =
Where:
• X
i
= single frequency RMS current or
voltage at harmonic i.
• w
i
= single frequency TIF weighting
factor at harmonic i.