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Coil with core, wrong magnetic field strength?

Posted: 18 Mar 2016, 15:15
by Bavragor
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
  Simulation Type = Steady state
  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

Re: Coil with core, wrong magnetic field strength?

Posted: 18 Mar 2016, 16:59
by pavel
Hi,
Have you tried to increase Steady State Max Iterations ?

Re: Coil with core, wrong magnetic field strength?

Posted: 20 Mar 2016, 13:12
by Bavragor
Yes, I tried it but it does not change anything.

Re: Coil with core, wrong magnetic field strength?

Posted: 21 Mar 2016, 12:17
by Bavragor
To get a better overview of the problem:
coil.png
Overview of the model
(99.56 KiB) Not downloaded yet
fieldstrength.png
magnetic field strength in a cut through the middle of the coil
(106.02 KiB) Not downloaded yet

I changed the Steady State Max Iterations, the solver and the preconditioner, but the result doesn't change. Any other ideas what I do wrong? Or is my assumption that H should be nearly the same as in the model without a core?