When is there an offset needed when adding additional low terminals with the leakage inductance test?
As part of a leakage inductance program, secondary high and low terminals are selected, these terminals will be shorted out during the test. As the short-circuit applied via the relay matrix in the tester cannot be perfect, additional measurements will be made to these terminals to compensate.
If there are additional low terminals , these terminals are also shorted out during the test, but they are not used in the compensation measurements.
If only one secondary winding is to be shorted, then there will be no additional low terminals. If several windings are to be shorted, then the Secondary Terminals should be on the winding with the largest number of turns, and Additional Low terminals should be used for the rest.
For low values of leakage inductance a user offset may be required and its value if applicable should be entered. This value will be added to the measured value to give the returned result.
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.