stem_material

This crate provides a Material definition for simulation of electromagnetic devices – especially electric motors – built on top of the var_quantity crate. It is used to define motor components within stem - a Simulation Toolbox for Electric Motors. See the stem book for an introduction to the framework.

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Modeling soft magnetism

The following models for soft magnetism can both be used stand-alone and as part of a Material.

Ferromagnetic permeability

The FerromagneticPermeability struct offers a spline-based way to model the ferromagnetic behaviour of a material from measured datapoints. It is particularily optimized for usage with iterative solvers and slightly modifies the resulting curve to achieve numerical stability and fast convergence. Additionally, it can also take the iron fill factor of lamination sheets into account.

The struct models both µr = f(H) and µr = f(B), meaning that either the magnetic field strength H or the magnetic flux density B can be used to calculate the relative permeability.

The following image shows the (modified) spline derived from raw data both for an iron fill factor of 100 % and of 95 % (the other 5 % are modeled as air with a relative permeability of 1).

Jordan model for iron losse

The JordanModel type provides a simple and fast model for calculating hysteresis and eddy current losses based on the equation p = kh * f * B² + kec * (f * B)². The accompanying module offers ergonomic ways to obtain the the loss coefficients kh and kec using least-square fitting.

Due to the model only having two parameters, its modeling accuracy is limited. The following image shows the raw loss data for different frequencies and the interpolated curves created by the according JordanModel. It can be clearly seen that the model precision is very good for small frequencies, but degrades for higher frequencies.

Serialization and deserialization

The serde integration is gated behind the serde feature flag.

Most of the types (except errors) in this crate implement serialization and deserialization. See the docstrings of the individual types for details.

Documentation

The doc images are created by a second crate located within its repository (docs/create_doc_images) which uses this crate and the awesome plotters crate. The images shown in this documentation can be created with cargo run from within docs/create_doc_images.