Coupled thermo-magnetic simulation of a foil-winding transformer connected to a nonlinear load

Foil-winding power transformers contain compact sets of flat conductors having a large aspect ratio. Modeling the eddy currents in the individual foils is therefore difficult and requires completely meshed conductors, especially when the influence of the thermal field on the local conductivity is considered. Coupled 2D magnetic and thermal models of a 30 kVA transformer having 50 secondary foils are presented. In the thermal model, thin layer elements or equivalent anisotropic materials are used to model the insulation material between the conductors. The coupled problem is solved for the steady-state and transient case. A novel method will be introduced to solve the transient coupled problem using time steps, much larger than the magnetic subproblem's time constants.