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Home / Technical Notes / Magnetic analysis / Inductance Calculation
Inductance Calculation
The inductance calculation in the magnetic analysis is as follows.
Inductance Calculation Conditions
The obtainable outputs are listed in the table below.
|
Analysis Type |
Condition |
Self Inductance Mutual Inductance Coupling Coefficient |
Leakage Inductance |
|
Static Analysis |
--- |
Yes |
Yes |
|
Harmonic Analysis |
Select [Inductance Calculation] on the Magnetic Analysis tab of the analysis condition. |
Yes |
Yes |
|
Transient Analysis |
Select [Inductance Calculation] on the Magnetic Analysis tab of the analysis condition. |
Yes |
No |
Inductance Calculation Type
There are apparent inductance and differential inductance.
See [Inductance Calculation Type] for details.
Inductance Value in Nonlinear Harmonic Analysis
In harmonic analysis using magnetic materials with nonlinear permeability, the inductance value is approximately calculated from the peak amplitude of the current.
The calculation procedures are shown below.
1. Perform the nonlinear static analysis with the peak amplitude of the current to obtain the distribution of working points on the B-H curve.
2. Using the given distribution of operating points on the B-H curve, calculate B/H at each point as permeability to obtain the permeability distribution.
3. With the given permeability distribution, the linear harmonic analysis is performed to calculate the apparent inductance.
Inductance Value in Transient Analysis
Depending on ON/OFF of the external circuit coupling, calculation is performed as follows
-
If External Circuit Coupling is ON
Calculation is performed with FEM coils on the external circuit. External Circuit Conversion is taken into account. -
If External Circuit Coupling is OFF
Calculation is performed with coils in the analysis model. External Circuit Conversion is not taken into account.
By using an external circuit, the serial inductance of multiple coils can be calculated.
The skin effect or induced current is not taken into account in the transient analysis.
It is taken into account in the harmonic analysis.
Expressions for Impedance Z in Harmonic Analysis
Rc: resistance of the inductor
Ri: resistance of iron loss, or sum of losses of induced current and hysteresis
L: inductance of the inductor
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Impedance Z is calculated under the condition that the current is applied only to the inductor which is to be analyzed.
Therefore, if the model has two or more inductors that the currents are applied to,
Z is calculated with the ports of the inductors other than the analyzed one being open and only the induced currents going through those inductors.
-
With the bulk coil whose number of turns is set to 2 or larger and the induced current existing, R isn't calculated accurately.
Notation and Expressions for Leakage Inductance
Given two coils, coil 1 and coil 2,
the leakage inductance of coil 1 with respect to coil 2 is denoted as 'Le1-2.'
Le1-2 is calculated with the defining equation below.
K1-2: Coupling coefficient between coil1 and coil 2, L1: Self inductance of coil 1
The equation above is based on the definition used by the academic association. Note that it differs from the leakage inductance Lsc defined by the industrial association.
Lsc and Le can be interchanged according to the equation below.
