I'm studying LTSpice, and I'm playing in transformer simulation. I want to modelize a real world power line transformer in a reasonable way: I mean I don't need an exact simulation of some specific model, but something reasonably closed to the reality. Let suppose we want to simulate a 12 – 220 v transormer, with some empyrical attempts I ended with this model:
Thats produce the followint simulation ( note I drive from the 12 v side )
Note the 50 Henry inductance on the 220v side: it seems a monster to me, is this value reasonable? Note also the coupling factor is 1, I really suspect this won't happen in reality, which value should I use?
Even for the 12 v Side: how is the correct way in determining the correct value ?
Best Answer
Yes, that's correct. All other things being equal, inductance is proportional to the square of the number of turns in an inductor. Your inductance ratio is 50/.15 = 333.3, so the turns ratio is the square root of that, or 18.26. This makes your output voltage 18.26 × 12V = 219V.
Depending on their size, real transformers would have values about 1/10 to 1/100 of what you used, but for modeling purposes, it isn't all that critical.
The other transformer parameters are very dependent on the physical design of the transformer, and different designs are used to optimize certain parameters for particular applications. Coupling coefficient might be sacrificed for high isolation, fine wire might be used to get a lower magnetizing current, at the expense of increased series resistance, etc.