## Coil with core, wrong magnetic field strength?

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Bavragor
Posts: 32
Joined: 07 Nov 2013, 14:10
Antispam: Yes

### Coil with core, wrong magnetic field strength?

Hi Forum,

I hope this is the right forum.
I tried to simulate a simple cylindric coil with a core sourrounded by a sphere(see Dropboxlink) with:

sphere with a radius of 300mm,
coil with a length of 60mm and a radius of 10mm
core with a length of 100mm and a radius of 8mm
profile of a winding pi*(1.5mm)^2
current density 1e6A/m^2
N=15
(generated with Salome)

When I use air as the material for the core the magnetic field strength is calculated as expected (see Dropboxlink). With a current of ~7.1A and 15 windings it should be a magnetic field strength ~1700A/m. When I use instead of air a material with a linear relative permeability of 1000 the magnetic field strength is weaken to ~45A/m(I used Paraview for postprocessing). But H should be independent from the material? -->H should be also ~1700A/m? Is there some wrong/missing BC?

https://www.dropbox.com/sh/wga12gk8asel ... V9hha?dl=0

The sif file:

Code: Select all

``````Header
CHECK KEYWORDS Warn
Mesh DB "." "."
Include Path ""
Results Directory ""
End

Simulation
Max Output Level = 10
Coordinate System = Cartesian
Coordinate Mapping(3) = 1 2 3
Steady State Max Iterations = 1
Output Intervals = 1
Timestepping Method = BDF
BDF Order = 1
Solver Input File = coil_15.sif
Post File = coil_15.ep
Coordinate Scaling = 1e-3
End

Constants
Gravity(4) = 0 -1 0 9.82
Stefan Boltzmann = 5.67e-08
Permittivity of Vacuum = 8.8542e-12
Boltzmann Constant = 1.3807e-23
Unit Charge = 1.602e-19
End

Body 1
Target Bodies(1) = 1
Name = "Body 1"
Equation = 2
Material = 3
End

Body 2
Target Bodies(1) = 2
Name = "Body 2"
Equation = 2
Material = 1
End

Body 3
Target Bodies(1) = 3
Name = "Body 3"
Equation = 1
Material = 2
Body Force = 1
End

Solver 2
Equation = MgDyn
Variable = AV
Fix Input Current Density = True
Procedure = "MagnetoDynamics" "WhitneyAVSolver"
Exec Solver = Always
Stabilize = True
Bubbles = False
Lumped Mass Matrix = False
Optimize Bandwidth = True
Steady State Convergence Tolerance = 1.0e-5
Nonlinear System Convergence Tolerance = 1.0e-7
Nonlinear System Max Iterations = 40
Nonlinear System Newton After Iterations = 3
Nonlinear System Newton After Tolerance = 1.0e-3
Nonlinear System Relaxation Factor = 1
Linear System Solver = Iterative
Linear System Iterative Method = CG
Linear System Max Iterations = 5000
Linear System Convergence Tolerance = 1.0e-10
BiCGstabl polynomial degree = 2
Linear System Preconditioning = Diagonal
Linear System ILUT Tolerance = 1.0e-3
Linear System Abort Not Converged = False
Linear System Residual Output = 1
Linear System Precondition Recompute = 1
End

Solver 3
Equation = MgDynPost
Calculate Magnetic Field Strength = True
Potential Variable = AV
Procedure = "MagnetoDynamics" "MagnetoDynamicsCalcFields"
Calculate Electric Field = True
Exec Solver = Always
Stabilize = True
Bubbles = False
Lumped Mass Matrix = False
Optimize Bandwidth = True
Steady State Convergence Tolerance = 1.0e-5
Nonlinear System Convergence Tolerance = 1.0e-7
Nonlinear System Max Iterations = 40
Nonlinear System Newton After Iterations = 3
Nonlinear System Newton After Tolerance = 1.0e-3
Nonlinear System Relaxation Factor = 1
Linear System Solver = Iterative
Linear System Iterative Method = CG
Linear System Max Iterations = 5000
Linear System Convergence Tolerance = 1.0e-10
BiCGstabl polynomial degree = 2
Linear System Preconditioning = Diagonal
Linear System ILUT Tolerance = 1.0e-3
Linear System Abort Not Converged = False
Linear System Residual Output = 1
Linear System Precondition Recompute = 1
End

Solver 1
Equation = Static Current Conduction
Calculate Volume Current = True
Variable = Potential
Procedure = "StatCurrentSolve" "StatCurrentSolver"
Exec Solver = Before Simulation
Stabilize = True
Bubbles = False
Lumped Mass Matrix = False
Optimize Bandwidth = True
Steady State Convergence Tolerance = 1.0e-5
Nonlinear System Convergence Tolerance = 1.0e-7
Nonlinear System Max Iterations = 40
Nonlinear System Newton After Iterations = 3
Nonlinear System Newton After Tolerance = 1.0e-3
Nonlinear System Relaxation Factor = 1
Linear System Solver = Iterative
Linear System Iterative Method = CG
Linear System Max Iterations = 5000
Linear System Convergence Tolerance = 1.0e-10
BiCGstabl polynomial degree = 2
Linear System Preconditioning = Diagonal
Linear System ILUT Tolerance = 1.0e-3
Linear System Abort Not Converged = False
Linear System Residual Output = 1
Linear System Precondition Recompute = 1
End

Solver 4
Equation = Result Output
Procedure = "ResultOutputSolve" "ResultOutputSolver"
Output Format = Vtu
Output File Name = coil_15
Exec Solver = Always
End

Equation 1
Name = "Wire"
Active Solvers(4) = 2 3 1 4
End

Equation 2
Name = "Core+Air"
Active Solvers(3) = 2 3 4
End

Material 1
Name = "Air (room temperature)"
Electric Conductivity = 0
Porosity Model = Always saturated
Relative Permittivity = 1.00059
Density = 1.205
Relative Permeability = 1
End

Material 2
Name = "Copper (generic)"
Electric Conductivity = 59.59e6
Porosity Model = Always saturated
Density = 8960.0
Relative Permeability = 1
End

Material 3
Name = "Steel (carbon - generic)"
Electric Conductivity = 1.449e6
Porosity Model = Always saturated
Density = 7850.0
Relative Permeability = 1000
End

Body Force 1
Name = "BodyForce 1"
Current Density 1 = Equals Volume Current 1
Current Density 3 = Equals Volume Current 3
Current Density 2 = Equals Volume Current 2
End

Boundary Condition 1
Target Boundaries(1) = 4
Name = "Ground"
AV = 0
Potential = 0
AV {e} = 0
End

Boundary Condition 2
Target Boundaries(1) = 6
Name = "Current Density"
Current Density = 1e6
AV = 0
AV {e} = 0
End

Boundary Condition 3
Target Boundaries(1) = 5
Name = "Border"
AV {e} = 0
End``````
pavel
Posts: 34
Joined: 17 Apr 2014, 17:08
Antispam: Yes

### Re: Coil with core, wrong magnetic field strength?

Hi,
Have you tried to increase Steady State Max Iterations ?
Bavragor
Posts: 32
Joined: 07 Nov 2013, 14:10
Antispam: Yes

### Re: Coil with core, wrong magnetic field strength?

Yes, I tried it but it does not change anything.
Bavragor
Posts: 32
Joined: 07 Nov 2013, 14:10
Antispam: Yes

### Re: Coil with core, wrong magnetic field strength?

To get a better overview of the problem:
coil.png
Overview of the model