We present a comparative approach to three of the main computational numerical analysis software programs used for transformer design: ANSYS, FEMM, and COMSOL.
These software programs can be separated into two categories: ANSYS and COMSOL, which are commercial, paid software that solve multiphysics and three-dimensional (3D) problems, and FEMM, which is open-source, free software (with some reservations regarding commercial use) that solves single-physics and two-dimensional (2D) problems. Some of the main characteristics of these tools will be discussed below.
The ANSYS commercial package offers highly stable and well-established tools for solving engineering problems. These software programs feature simplified interfaces and allow for the easy creation of geometric models within the software itself. Many automatic parameters (without requiring direct user intervention) are applied to generate the mesh and boundary conditions, facilitating the acquisition of results. However, this feature, while helpful in converging complex problems, limits some more specific analyses that are sometimes necessary. The ANSYS platform (WORKBENCH) was structured to address the main needs of multiphysics couplings by combining the analysis modules for each physics component, which were initially built separately.
COMSOL, in turn, is a tool built with the need for multiphysics coupling in mind, generating great flexibility when dealing with coupled and interdependent problems. It’s possible to work with the analysis of physics in a highly integrated way within COMSOL, although these coupling configurations are not trivial and require a fairly in-depth technical knowledge of the problem involved and numerical methods to achieve convergence. There’s no such thing as a free lunch! The excellent flexibility of the COMSOL platform demands a more in-depth technical knowledge to obtain satisfactory results. For this reason, COMSOL is often more commonly used by researchers, experienced designers, and developers of technically complex solutions, while ANSYS is considered a tool better suited to the demands of industry, where there isn’t always enough qualified technical personnel available to adequately handle the COMSOL software.
And lastly, FEMM, which is an extremely powerful tool considering its available resources. A curious fact about the software: imagine a free and open-source tool (except for some commercial conditions outlined in the terms of use), with an installer of less than 8 Megabytes, that solves complex problems involving power transformers and other electrical equipment costing tens of millions of reais? This is the FEMM software. If it’s possible to model the problem using appropriate conditions in FEMM, the results obtained are equivalent to those obtained using the commercial software ANSYS and COMSOL. Obviously, FEMM has fewer geometry and meshing features, but it is a tool that solves the electromagnetic and thermal problems it sets out to solve very well in 2D geometry using planar and axisymmetric symmetry conditions.
Furthermore, it’s worth noting that comparing FEMM software to giants like ANSYS and COMSOL is often considered invalid and meaningless, mainly due to the greater number of features available in paid commercial software. However, with the evolution of the TRINSE team’s technical experience in transformer projects, it has been realized that fantastic results can be obtained using the FEMM tool. In general, by understanding the electromagnetic behavior of the transformer, it is possible to solve more than 90% of numerical analysis needs using FEMM through the use of appropriate strategies for determining boundary and symmetry conditions using 2D geometries.
Obviously, the most complete tools offer fundamental resources for more complex problems. Many typical cases and problems in transformers cannot be solved with 2D geometry symmetries (planar and axisymmetric), so in these cases it is necessary to use software that works with 3D geometries. In these cases, too, the preference for using ANSYS or COMSOL tools will depend on the user’s experience and familiarity with such software. In general, considering the universe of numerical simulations for transformer design, including webinars, discussion forums, and available training, it is possible to conclude that, basically, the same results will be obtained with any numerical analysis tool, provided that its parameterization definitions of the input variables are adequately met.
Ultimately, it’s worth highlighting that more important than knowing the capabilities of a numerical analysis tool is understanding the physical behavior being modeled with these tools. This brings to mind Lewis Carroll’s quote that always pops up in LinkedIn feeds:
“If you don’t know where you’re going, any road will take you there!”
Which we can transform, considering the world of numerical analysis in transformers, into the following phrase:
“For those who don’t know what they’re calculating, any result will do!”