Multiphysics modeling with open source software

University of Latvia

November, 2018

In this project, a simple transformer with discrete windings is modelled. Simulation setup is similar to an induction heating problem - the primary coil carries driving current and induces magnetic field inside a ferromagnetic core. Magnetic field is contained within the core and is directed through the second coil, wherein secondary currents are induced.

This project is part of the EOF-Library training course. EOF-Library is efficient, fully parallelized Elmer FEM and OpenFOAM coupler designed for coupled electromagnetic, fluid and heat transfer simulations.

Given

- A video tutorial for geometry and mesh generation in Salome-platform
- A video tutorial for setting up Elmer FEM
- Mesh in the Elmer FEM format

Problem definition

Frequency | 50 Hz |

Coil properties | Copper |

Core properties | Transformer steel (for basic tasks, use constant permeability) |

Conductivity of core | 0 S/m |

Primary coil | Potential difference 1 V |

Secondary coil | Short-circuited, potentials on outputs 0 V |

Tasks

Basic

- Get simulation running and produce meaningful results.

- Calculate losses in secondary winding, compare with power in primary winding.
- Check convergence for different linear solvers.
- Check Elmer parallelization efficiency (strong scaling test).

Advanced

- Try different numbers of windings / different transformer configurations.
- Try simulating transformer core with realistic BH curve by adding permeability dependence on magnetic field (hint: use the nonlinear solver).
- Attempt to make your own improvements - decrease computational time, while maintaining accuracy; modify parameters and settings to further explore the problem and Elmer FEM functionality.

Hints

- A reference solution in Ansys Maxwell and access to computer with licensed software is available to students registered to the course. Ask tutors for more info.

- To find all Elmer test cases that are using harmonic electromagnetic solver WhitneyAVHarmonicSolver call from Elmer’s source directory:

grep -r -i -n "WhitneyAVHarmonicSolver" fem/tests/

- From our experience BiCGStabl iterative solver with polynomial degree 4 has the best convergence rate for electromagnetics.

Useful links

Elmer

- http://nic.funet.fi/index/elmer/doc/ElmerOverview.pdf
- http://www.nic.funet.fi/index/elmer/doc/ElmerSolverManual.pdf
- http://www.nic.funet.fi/index/elmer/doc/ElmerModelsManual.pdf
- http://www.elmerfem.org/forum/