I have just measured my power transformer with a LCR metre, a scope and a signal generator. The transformer is rated 625VAC, with 1 x 240V primary and 2 separate 45V secondaries.

When shorting the primary to measure the leakage inductance, on one secondary the reading was 28.8uH, on the other secondary it was 44.6uH. Is that normal? Is there anything wrong? Should they be identical?

When shorting the secondary windings to measure the leakage inductance from the primary side, the reading was 1.06mH. This is much higher. Should leakage inductance be the same when measuring from either the primary or secondary side? I must be somehow wrong, as the leakage inductance is unlikely that high.

One secondary winding gives a stable 0.15R reading, and the other jumps around between 0.14R to 0.15R. Does it mean there is some inbalance? The primary has 2.09R.

When I entered these numbers into PSU2, it works out that the transformer can deliver 10A on each of the secondary, with a Source Resistance = 0.225R.

I also connected the signal generator with a 1k resistor in series on the secondaries and measured the voltage developed across the coils and found the resonant frequency to be 910kHz for both secondary windings. So when I return to work tomorrow with a much better calculator I can easily work out the leakage capacitance very easily.

So if I am going to model this with LTSpice, should I model the transformer to be an ideal voltage source in series with the parallel of H=28.8uH (44.8uH for the other), R=0.15 (or 0.225R?) and C=? (to be worked out)? Please see an illustration in the attached picture.

Thanks.

When shorting the primary to measure the leakage inductance, on one secondary the reading was 28.8uH, on the other secondary it was 44.6uH. Is that normal? Is there anything wrong? Should they be identical?

When shorting the secondary windings to measure the leakage inductance from the primary side, the reading was 1.06mH. This is much higher. Should leakage inductance be the same when measuring from either the primary or secondary side? I must be somehow wrong, as the leakage inductance is unlikely that high.

One secondary winding gives a stable 0.15R reading, and the other jumps around between 0.14R to 0.15R. Does it mean there is some inbalance? The primary has 2.09R.

When I entered these numbers into PSU2, it works out that the transformer can deliver 10A on each of the secondary, with a Source Resistance = 0.225R.

I also connected the signal generator with a 1k resistor in series on the secondaries and measured the voltage developed across the coils and found the resonant frequency to be 910kHz for both secondary windings. So when I return to work tomorrow with a much better calculator I can easily work out the leakage capacitance very easily.

So if I am going to model this with LTSpice, should I model the transformer to be an ideal voltage source in series with the parallel of H=28.8uH (44.8uH for the other), R=0.15 (or 0.225R?) and C=? (to be worked out)? Please see an illustration in the attached picture.

Thanks.

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