Inductance in FEMM 4.2, series/parallel connection of coils

[flowwolf]

Dear Forumers,

I have an axisymetric magnetics problem in FEMM 4.2. I'm analyzing a loudspeaker motor (permanent magnet included) with many coils.
I would like to get the inductance for the coils connected in series and in parallel.

Let's say that I have 2 coils, coil A (n=N1) and B (n=N2) with circuits A (I=1A) and B (I=1A). The inductance of the two coils are L1, L2, respectively.

Inductance for the individual circuits is calculated according to 3.2 of http://www.femm.info/wiki/woofer

Can I calculate the total inductance, L, the following way:
For series connection, is L equal to L1 + L2 ?
For parallel connection, is L equal to 1/(1/L1 + 1/L2) ?

Maybe this seems to be a simple question, but for multiple coils the mutual inductance needs to be taken into account.
It seems that femm does this, furthermore, for series connection the result seems to be equal to of a single coil (n=N1+N2) with one circuit.

If yes, can the same formulas be used for calculating the blocked inductance? http://www.femm.info/wiki/BlockedImpedance

Any help would by appreciated.
Akos

 

[mmwave]

Dear Akos,

Thank you for reaching out to the forum for help with your axisymmetric magnetics problem in FEMM 4.2. It seems like you are on the right track with your calculations for the inductance of the coils connected in series and parallel.

For series connection, the total inductance, L, would indeed be equal to the sum of the individual inductances, L1 and L2. This is because the current flowing through both coils is the same, and the magnetic flux from both coils adds up to produce a larger inductance.

For parallel connection, the total inductance, L, can be calculated using the formula you mentioned: 1/(1/L1 + 1/L2). This is because the voltage across both coils is the same, and the magnetic flux from each coil splits to produce a smaller inductance.

However, as you mentioned, for multiple coils the mutual inductance needs to be taken into account. This can affect the total inductance in both series and parallel connections. FEMM does have the capability to calculate mutual inductance, so it is important to include this in your calculations.

As for calculating the blocked inductance, the same formulas can be used as long as the mutual inductance is taken into account. The blocked inductance is essentially the inductance when no current is flowing through the coil, so the mutual inductance would not have any effect in this case.

I hope this helps and good luck with your analysis.