Relationship Between Transformer Turns and Layers

[metalman89]

Hello,

I'm working on designing a HF flyback transformer for an AC to DC power supply and I have a question about the relationship between the winding turns and layers on the transformer. If we take a transformer with 200 primary turns would there be a difference in how these turns are distributed per layer? For example, what if I just used all 200 turns in one layer as opposed to 10 turns per layer and a total of 20 layers (same total number of windings in both cases). Does the second example behave the same way as the first even though the outer windings are now a further distance away from the core?

 

[IRstuff]

flux density ought to be different

TTFN
I can do absolutely anything. I'm an expert!
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[Comcokid]

Depending upon the frequency the transformer is going to operate at these things can make a great deal of difference. There are a lot of parasitic effects at work inside a transformer. Transformers are somewhat a compromise between the parasitic capacitance between the primary and secondary, and the leakage inductance - both are undesirable to different degrees, and if you wind to reduce one, you increase the other.

Winding further out from the core tend to have higher leakage inductance. Leakage inductance arises from the magnetic field not fully enclosing all of the winding turns. There are other issues with the location of turns close to the core or to other winding layers that are called proximity effects where the current flows more on one side of the wire than the other.

Books are written on the subject, and seminars are taught. However the fine refinements of the transformer can be left for later in development stages of a project. Many of the construction details can be determined by the transformer supplier. The main issue early on is to select a core based upon power, flux, and wire size, determine your turns ratio and wire size, and get the rest of your circuit functioning.