Finding Transformer Leakage Impedance from S/C, O/C and Winding resistance tests

Question

I've recently done an experiment on a 415/100 V transformer. Performing the S/C test on the HV side and the Open Circuit test on the LV side and finding winding resistance from applied DC voltage and current.

Therefore I now have results from the experiment and have solved Magnetizing reactance, core loss Resistance, Copper/winding resistance and Leakage reactance equivalent values, depending on which side I transfer the equivalent values to according to my turns ratio (a).

The issue I'm having is that I cannot find a way to split the equivalent leakage reactance into its 2 components (LV winding and HV winding).

Equivalent winding resistances are split into their 2 values from the measured applied DC voltage and current Test.

I was beginning to think that if I had measured the voltage across the S/C side in the S/C test (although it would be small, it would still exist) I would have had enough unknowns to solve for Xl LV side; but because I did not measure that voltage assuming 0 volts, I cannot.

Any ideas? I'm stumped.

Answer 1

You can split the overall leakage inductance into two parts proportional to the turns ratio squared. For instance, you know that if the transformer was 1:1 the leakage inductance would be shared equally between primary and secondary .

You also know that if the turns ratio was (say) 10:1 and you measured a 1 mH total leakage (referred to the primary) you could attribute all of this 1 mH to the secondary by dividing it by \$(10:1)^2\$. In other words 10 uH on the secondary is equivalent to 1 mH on the primary.

So, whatever your combined leakage is referred to the primary (let's assume it to be 1 mH), split it into two halves and keep 0.5 mH at the primary and transfer 5 uH to the secondary.