3.6.5 LSBX – Inductance with External Bias (Series Circuit)
The inductance of a transformer winding while an external bias current is flowing through it may be tested using series or parallel equivalent circuit models. Initially the DC bias current is set up and allowed to stabilize. An AC voltage is applied across the selected winding; the voltage across, and current through, the winding is then measured using harmonic analysis. The measured voltage is divided by the current to obtain a complex impedance and the inductance is calculated.
On selecting 'LSBX Inductance with External Bias (Series Circuit)' or 'LPBX Inductance with External Bias (Parallel Circuit) from the 'Available Tests' window, a dialogue box will be displayed.
Fig.11
To program the test:
- Enter the signal, frequency and bias current required for the test.
Note that the signal is normally entered as a voltage by selecting the 'mV' or 'V' button; but you may optionally enter it as a current by selecting the 'mA' button. (If in doubt refer to the 'Test Conditions' chapter of your AT user manual.
Note also that the measure button may be used here, as outlined in your AT user manual, with the combinations of test parameter specification shown in the following table:
| |
Option 1 |
Option 2 |
Option 3 |
Option 4 |
Signal |
Specified voltage |
Specified current |
Auto |
Auto |
Frequency |
Specified |
Specified |
Specified |
Auto |
Bias |
Specified |
Specified |
Specified |
Specified |
- Select (mouse click the button) the integration time you require. 'Medium' is the default setting. 'Long' will give you more stable readings (for tighter limits) at the expense of test time, and 'Short' will test at the maximum speed, but may give slightly noisier readings.
- Enter the terminal names between which the inductance will be measured. By pulling down the menu along side the fill-in box, you may select the high and low terminals for each test.
- Select (mouse click the button) the type of limits you require, and enter the values.
% Enter a nominal value and then the limits as negative and positive values.
>< Enter minimum and maximum values.
> Enter just a minimum value.
< Enter just a maximum value.
- Select OK. The test specification will then be displayed in the program window.