# Inductance in FEMM 4.2, series/parallel connection of coils

• flowwolf
In summary, FEMM 4.2 is a software used for electromagnetic simulation, which includes the option to model and analyze inductance of coils. The program allows for the connection of coils in series or parallel, which can be useful for studying the effects of different configurations on inductance values. FEMM 4.2 also offers the ability to calculate and visualize the magnetic flux density and current distribution within the coils, providing a comprehensive analysis of inductance behavior.
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

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.

## 1. What is inductance in FEMM 4.2?

Inductance in FEMM 4.2 refers to the measurement of the ability of a coil or circuit to store energy in the form of a magnetic field. It is a key parameter in the analysis and design of electromagnetic systems.

## 2. How is inductance calculated in FEMM 4.2?

The inductance of a coil or circuit can be calculated in FEMM 4.2 using the finite element method, which involves solving a set of mathematical equations that describe the behavior of the electromagnetic system. FEMM 4.2 has built-in tools and functions to help with the calculation of inductance.

## 3. What is the significance of series/parallel connection of coils in FEMM 4.2?

The series/parallel connection of coils in FEMM 4.2 allows for the analysis of complex circuits and systems that consist of multiple coils. It helps to understand the behavior of the system as a whole and how the inductance of individual coils affects the overall inductance of the system.

## 4. Can FEMM 4.2 simulate the effects of series/parallel connection of coils?

Yes, FEMM 4.2 has the capability to simulate the effects of series/parallel connection of coils. It uses the finite element method to solve the mathematical equations and accurately predict the behavior of the system. This allows for the optimization of inductance and design of efficient electromagnetic systems.

## 5. Are there any limitations to using FEMM 4.2 for inductance analysis?

FEMM 4.2 is a powerful tool for inductance analysis, but like any software, it has its limitations. It is important to understand the assumptions and limitations of the finite element method and to validate the results with experimental data. Additionally, the accuracy of the simulation may be affected by factors such as mesh density, boundary conditions, and material properties.

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