TRANSFORMER TESTS VOLTECH AT3600 USER MANUAL
PAGE 7.1.16. VPN 98 - 024 TESTS AND TEST CONDITIONS
NOTE: Because leakage inductance is measured with a secondary winding shorted
out, be careful to choose a test signal that will not cause excessive currents to flow.
This is particularly significant in transformers where the turns ratio is very high and
the shorted winding has only a few turns.
If, for example, the primary winding has 300 turns, and the secondary 3 turns, a
test current of 10mA flowing through the leakage inductance on the primary
side will give rise to a current of 1 Amp flowing in the shorted secondary
winding.
In order to protect transformer windings, the test current when measuring leakage
inductance is limited in the table to 50mA maximum.
In addition, the problem of self-resonant frequency listed under the primary
inductance test also applies when measuring leakage inductance, so always use the
lower of the available band of frequencies.
User Offset (LLO test only)
This is used to offset the result returned by the AT by a user defined amount.
i.e.
Result returned = Measured result + User offset
Normally a user offset would not be required. However for small values of leakage
inductance (<1µH) when there are a number of additional low terminals, it is not
always possible during fixture compensation for the tester to remove all of the
parasitic errors of the test fixture. In this case, the user offset may be required to fully
remove the errors. The LLO test provides this additional feature.
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