The inductance of a transformer winding when a bias current is flowing 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 are 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 ‘LSB Inductance with Bias (Series cct)’ or ‘LPB Inductance with Bias (Parallel cct)’ from the Available Tests window, a dialogue box will be displayed.

or:

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 Chapter 7 - ‘Test Conditions’, which lists recommended test conditions for different values of inductance.)
Note also that the Measure button may be used here as outlined in section 3.9, with the combinations of test parameter specification shown in the following table:

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 more stable readings (for tighter limits) at the expense of an increased test time, and 'Short' will test at the maximum speed, but may give a slightly noisier reading.
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 the 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 percentage values.
><		Enter minimum and maximum values.
>		Enter just a minimum value.
<		Enter just a maximum value.
Note that the Measure button may be used here as outlined in section 3.9.

Select OK. The test specification will then be displayed in the program window.

Prev Next