Voltech AT3600 - Page 310

TRANSFORMER TESTS VOLTECH AT3600 USER MANUAL
PAGE 7.1.30. VPN 98 - 024 TESTS AND TEST CONDITIONS
The following table suggests suitable test conditions for different values of expected
average inductance:
Average Inductance
(Geometric Mean)
Preferred test signal
Frequency Voltage
100nH
1uH
10uH
100uH
1mH
10mH
100mH
1H
10H
100H
1kH
→
→
→
→
→
→
→
→
→
→
→
1uH
10uH
100uH
1mH
10mH
100mH
1H
10H
100H
1KH
10KH
300KHz
100KHz
30KHz
10KHz
1KHz
100Hz
100Hz
50Hz
50Hz
50Hz
20Hz
10mV
30mV
50mV
100mV
100mV
100mV
300mV
1V
5V
5V
5V
Test Conditions for Inductance Match Measurement
Wherever possible, this table should be used for all inductance tests. The inductance
range should be chosen based on minimum value of inductance expected.
When choosing the test conditions, the following potential problems should be
considered:
A) CURRENT LEVELS
The upper voltage limits should be chosen to give a maximum current level of
about 100mArms. for the lowest inductance expected. In some cases, this
current may cause core saturation, and a lower voltage should be used. The
minimum voltage level must be chosen so that the test current does not become
so low that it cannot be sensibly measured. The lower voltage limits in the
table above always give test currents higher than 3µA rms.
B) SELF-RESONANT FREQUENCY
At lower frequencies, the capacitance of the windings can normally be ignored
because its impedance is much higher than that of the inductance. However, at
very high frequencies, this is not so, the capacitance dominates and inductance
cannot be measured. The self-resonant frequency of the transformer is the
change-over point between these two regions.