Cf: Crest Factor - AEMC 725 User Manual

CF: Crest Factor

Crest Factor measurements are possible for A AC and V AC by depress-
ing the yellow Shift push button twice.
The crest factor is the ratio of the Peak value of the sinusoidal waveform
to its RMS value.
Crest Factor (CF) =
For a perfect sine wave the crest factor would be 1.414. This relates to the
Peak amplitude of a particular waveform. Typical crest factor ratings are
from 2.0 to 6.0. When harmonics are present crest factors may be less
than (CF of a square wave = 1) or greater than 1.414.
Crest Factor is the ratio of the Peak value of a waveform to its RMS value.
A perfect sine wave has a crest factor of 1.414. In distorted waveforms, the
crest factor is typically greater than 1.414 and gives an indication of the
harmonic content.
The CF may also be used to determine the CBEMA (Computer & Business
Equipment Manufacturers Association) Derating Factor. The CBEMA
Derating Factor is used for evaluating the survivability of existing conven-
tional transformers in service and servicing single-phase nonlinear loads
such as PCs, computer terminals or other office equipment. For further
use of the CBEMA derating factor contact the CBEMA directly. Note that
there is no direct or useful relationship between the CBEMA Derating
Factor, the %THD and Transformer K Factor (IEEE C57.110-1986).
Crest Factor: CF = Peak/ RMS
CBEMA Derating Factor = 1.414 x RMS/Peak = 1.414/CF
i (t)
I peak
I rms
32
Peak value
RMS value
CF = 1.414
i (t) I peak
I rms
0
CF = 2.5
Clamp-On Harmonic Probe Model
t