29
Setup and Connection
Figure 2-6 Using a copper foil formed to a ring as primary wire
Note: Exact measurement results are only possible if the primary wire is
positioned exactly in the center of the core.
The CT Analyzer does not consider leakage inductances. The leakage
inductances are neglected instead. This way, the CT Analyzer is able to reach a
measurement error of approx. 0.1% for class PR and class TPY CTs and
approx. 0.8% for class TPZ CTs.
2.5.2 Excitation Curve Measurement for an Unwound Iron Core
Using the CT Analyzer it is possible to measure the magnetic properties of an
empty, unwound iron core. For this purpose, it is necessary to apply an "auxiliary
winding" of at least 20 turns to the core.
For this purpose, OMICRON offers a special cable with 23 turns (VEHK0658)
and a special Microsoft Excel template for the required calculations.
Proceed as follows to perform the measurement (refer to Figure 2-7 and Figure
2-8). Observe the general safety rules in section 2.1 on page 21.
1. Apply the "auxiliary winding" cable to the unwound core.
2. Connect the "Output" sockets and input "Sec" of the CT Analyzer to the cable
as shown in Figure 2-7. For cores that require high currents to reach the knee
point, several cables can be cascaded to increase the number of turns, see
Figure 2-8.
3. Start the CTA Remote Excel File Loader with the special Excel template
mentioned above.
4. Enter the iron parameters to the template.
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