Stray inductance of mutual inductors in SPICE

I know: K goes up, Lstray goes down. But what is the precise mathematical relationship between the two and the inductors?

Thanks: robert

Reply to
Robert Latest
Loading thread data ...

Try the Wikipedia explanation at

formatting link
starting about 2/3 of the way down the page at the part titled "mutual inductance." In short, two inductors which share some magnetic field have mutual inductance, M. Remember that in an isolated ideal inductor,

V = L * di/dt

(It may also be useful to recall that Faraday's Law says that there is an electric potential around any closed loop which is proportional to the rate of change of magnetic field enclosed by that loop...)

But when you add mutual inductance M between L1 and L2, where i1 is the current in L1 and i2 the current in L2,

V(L1) = L1 * di1/dt + M * di2/dt.

Then the coupling coefficient k is given by

k = M/sqrt(L1*L2).

Clearly, if k=1, 100% of the magnetic field of L1 is shared by the turns of L2, and vice-versa; and if k=0, none of the magnetic field of either inductor is shared by the turns of the other. This gives some clues about how to maximize k. Can you deduce that k is the fraction of the magnetic field which is shared?

Cheers, Tom

Reply to
Tom Bruhns

ElectronDepot website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.