Voltech AT360, User Manual

Page: 318 / 470

T
ESTS AND
T
EST
C
ONDITIONS
P
AGE
7-20 V
OLTECH
AT
I
U
SER
M
ANUAL
Test Conditions
To measure inductance, the tester applies an AC voltage across the selected
windings and measures the voltage across and the current through the
winding. Using harmonic analysis, the measured voltage is divided by the
current to obtain the complex impedance from which the inductance is
extracted.
Generally, it is not necessary to measure the inductance at the normal
operating conditions of the transformer, which could involve, for example,
hundreds of volts. This is because the core material can normally be assumed
to behave linearly in the operating region, and the inductance measured at a
low level represents the inductance that will appear in use.
Also, it can usually be assumed that the inductance value does not vary
significantly with frequency. Therefore, although high frequencies are
available with the tester, measurement frequencies above a few hundred
kilohertz should be used with caution. This is because the errors caused by
the stray inductance and capacitance of your fixture may become much more
significant at these frequencies. Compensation can be used to eliminate these
errors.
Choosing the Test Signal
Wherever possible, the table below should be used for all inductance tests.
The inductance range should be chosen based on minimum value of
inductance expected.