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# Transformers in LTspice IV

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#### Docc

##### Junior Member level 1
Hi
I'm a bit confused on how to set leakage inductance.
Do I change the mutual coupling coefficient?
If I have a primary inductance of 100u and 5u leak, do I set it to 0.95 for 5%?

Yes, for a 1:1 transformer.

What if it's not 1:1?
say, 6:1? How do I calculate that?
Example Coilcraft FA2443, 200u primary, 5.9u leak and 6:1 to two secondaries.
So secondary inductance should be 5.55u
I have that set up with a mutual coupling coefficient of 0.97

I have that set up with a mutual coupling coefficient of 0.97
Right. But you see a different leakage inductance at the secondary.

Yes, and thats where I'm stuck.
How do I define a spice directive for both primary and secondary leakage?

I don't understand the problem. SPICE is simply reproducing the behaviour of the real component. So if you want to understand
the relation of coupling coefficient, mutual and leakage inductance, consult an electrical engineering text book, or get paper
and pencil and figure it out.

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