FEMM leakage inductance calculation

Hey

I am new to FEMM, but have a real life problem. I have a transformer, which has 4 layer primary with about 50 turns on each layer (the winding used the entire width of the E core bobbin), and a single layer secondary with 10 turns.

Now, I want to know the leakage inductance with 2 cases:

1: Secondary winding uses the entire width 2: Secondary winding uses 65% of the width, and the copper has the same diameter, so it occupies almost 2 layers (margin tape used on the secondary)

I estimate about 40% increase in leakage inductance from some rule of thumb formulas

I could just rewind the bobbin and measure it, but would like a simulation to quantify changes done

So, as for FEMM, are there any way to get started quickly? Perhaps standard transformer models I can modify? (I think FEMM seems like a big learning curve from the get-go)

Thanks

Klaus

Reply to
Klaus Kragelund
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If it's an E-core and not a pot core, you may not want to use FEMM anyway.

FEMM is restricted to 2-dimensional analysis: you can do cylindrically symmetrical analysis (pot core), or 2-D rectangularly symmetrical analysis (E-core with infinite thickness). But an E-core (at least one of finite thickness) would need a 3-D solver, which FEMM is not.

Of course, you could do the infinite-thickness solution and hope that your answer means something -- but there's no guarantee.

(I used FEMM for real for the first time about a month ago, simulating an inductive power transfer coil. In that case the circularly symmetrical mode was pretty close to my square flat coils on PCB with square flat ferrite over them; I was very pleased to see that the model matched my prototypes).

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Tim Wescott 
Wescott Design Services 
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Reply to
Tim Wescott

That's really nice that you got it to correlate

I'll measure it, and keep dreaming about a tool that can calculate it :-)

Cheers

Klaus

Reply to
Klaus Kragelund

Pro FEM tools probably can -- you just have to pay for the privilege of using them.

I know that mechanical FEM tools work, in general, like circuit simulators

-- they give useful results, but only if you ask the right questions in the right way. Just throwing designs at them and asking for results may get you answers that range from spot on, go through wildly inaccurate, and straight up to total nonsense. I can't imagine that magnetic FEM is any different.

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Tim Wescott 
Wescott Design Services 
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Reply to
Tim Wescott

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