CT Analyzer User Manual
28
2.5 Connection for Special Applications
2.5.1 Measurement on a Gapped Core
For gapped cores, the position of the primary wire inside the core has a large
influence on the ratio measurement results.
Therefore, in order to obtain correct measurement results, it is very important to
arrange the primary wire during measurement to the same position inside the
core as it is during real operation. Depending on the position of the primary wire
inside the core, the measured ratio can differ by up to 20%.
The figure below shows how the ratio error can differ depending on the position
of the primary wire inside the core.
Figure 2-5 Ratio error depending on the position of the primary wire inside
the gapped core
As shown in Figure 2-5, the measured ratio error may differ considerably
depending on the position of the primary wire. Best measurement results are
obtained if the primary wire is positioned exactly in the center of the core. As an
alternative, a copper foil formed to a ring and placed to the inner side of the core
can be used as shown in Figure 2-6.
Air gap
Position 2
Ratio error measured: +5%
Position 1
Ratio error measured: +0.5%
Position 3
Ratio error measured: -15%
Primary wire
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