Electrical – Measure leakage inductance of flyback transformer with multiple secondary windings


I have a transformer consisting of one primary winding and 3 secondary windings. Now I want to measure the leakage inductance at the primary side, so I need to short the secondary windings. Most of the literature I have read, there is only one secondary winding so it's pretty straightforward how to short the secondary side. But now, I have 3 windings at the secondary side, I am considering of 3 possible ways to measure the leakage inductance at the primary side:
1. Short 3 and 4, 5 and 6, 7 and 8
2. Short each winding one by one while leaving other windings open, e.g 3 and 4 shorted, 5 and 6 open, 7 and 8 open, etc.
3. Short 4 and 5, 6 and 7, 8 and 3.

Assume that my short circuit is perfect, what is the best method to measure? Thank you.

Best Answer

what is the best method to measure?

  • Short the primary and test each secondary separately. The measured inductance (for each of the three tests) is the leakage inductance referred to the secondary.

  • You could short each secondary and measure inductance at the primary but then you'd need to divide by the turns ratio squared to be able to place it in a model on the secondary side.

It all depends on what you are trying to achieve.

Regards actual measuring devices, you could use a meter that measures current and do some calculations to determine impedance and remove any DC resistance artefacts from the answers leaving you with inductance. Or, you could use an LCR meter operating at a frequency that is appropriate for the transformer type.