Transient Electromagnetic-Thermal FE-Model of a SPICE-Coupled Transformer Including Eddy Currents with COMSOL Multiphysics 4.2

H. Neubert[1], R. Disselnkötter[2], and T. Bödrich[1]
[1]Technische Universität Dresden, Institute of Electromechanical and Electronic Design, Dresden, Germany
[2]ABB AG, Forschungszentrum Deutschland, Ladenburg, Germany

Current transformers are used to measure currents in power grid systems. They are characterized by strong interactions between external electrical sources and loads respectively and the magnetic subsystem. Self-heating due to losses has to be considered because of the temperature-dependent material behaviour.

The paper presents a transient 3D FEA transformer model which includes a H(|B|) formulation of the ferromagnetic material behavior based on rational approximation functions, SPICE coupling at the primary and the secondary side, eddy currents computation using a global equation and distributed time-average computation of the losses. This model is bi-directionally coupled to a thermal model. Due to the different time scales of both models, the problem is solved by iteration of each stationary solution of both models.