VOLTECH AT3600 USER MANUAL TRANSFORMER TESTS
TESTS AND TEST CONDITIONS VPN 98 - 024 PAGE 7.1.15.
1.9. LL OR LLO- LEAKAGE INDUCTANCE
WHERE USED
Leakage inductance is important in many applications. One example is flyback
designs for high frequency switched mode power supplies, where the leakage
inductance must be less than a specified critical value for proper operation.
MEASUREMENT CONDITIONS
Leakage inductance is tested by measuring the inductance of a 'primary' winding
when one or more 'secondary' windings are shorted out. In performing the calculation
at the end of the test to extract the inductance value from the measured winding
impedance, the tester uses a series equivalent circuit.
In making the measurement, the tester automatically compensates for the impedance
of the wiring, the connections and the relays in the shorting path.
Leakage inductance can be measured using a test current in the range 20µA to
100mA at a frequency of 20Hz to 1MHz.
You may choose a suitable test current and frequency based on the expected value of
the leakage inductance using the following table:
Leakage Inductance range
Preferred test signal
Frequency Current
100nH
1uH
10uH
100uH
1mH
10mH
100mH
1H
→
→
→
→
→
→
→
→
1uH
10uH
100uH
1mH
10mH
100mH
1H
10H
300kHz
100kHz
30kHz
10kHz
1kHz
100Hz
100Hz
50Hz
50mA
20mA
10mA
5mA
5mA
5mA
1mA
500µA
The Test Conditions for Leakage Inductance Measurement
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