Excitation Curve Measurement For An Unwound Iron Core - Omicron CT SB2 User Manual

CT Analyzer User Manual
Note: Exact measurement results are only possible if the primary wire is positioned exactly in the center
of the core.
CT Analyzer does not consider leakage inductances. The leakage inductances are neglected instead.
This way, 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.
3.5.2

Excitation curve measurement for an unwound iron core

Applicable for Advanced CT Test mode only.
Using 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. Please note that this measurement cannot be performed
from the CT Analyzer Suite software.
Proceed as follows to perform the measurement (refer to Figure 3-7 and Figure 3-8). Observe the
general safety rules in section 3.1 on page 23 and the safety instructions given in chapter 1 "Safety
instructions" on page 9.
1. Apply the "auxiliary winding" cable to the unwound core.
2. Connect the CT Analyzer OUTPUT sockets and input SEC to the cable as shown in Figure 3-7. For
cores that require high currents to reach the knee point, several cables can be cascaded to increase
the number of turns, see Figure 3-8.
3. Connect CT Analyzer to a computer as described in section 3.3 on page 26.
4. On the computer, browse for the Excel template "EXL-0007 Measurement of Iron Core ENU.xlt".
This template is installed together with CT Analyzer Suite to the \RemoteEFL\Templates\ folder of
the CT Analyzer Suite installation path. For the default installation path on a 64 bit operating system,
the full path is C:\Program Files\OMICRON\CT Analyzer\RemoteEFL\Templates\, for example.
5. Open the template "EXL-0007 Measurement of Iron Core ENU.xlt" with Microsoft Excel, for example,
by double-clicking the template.
6. Enter the iron parameters to the corresponding worksheet of the template.
7. Start the measurement by clicking the Start Test button in the worksheet
Figure 3-7: Excitation curve measurement using one "auxiliary winding" cable
32
23 turns auxiliary
winding
Iron core without winding
OMICRON