Coupled thermo-magnetic simulation of a foil-winding transformer connectedto a non-linear load

Foil-winding power transformers contain compact sets of flat conductors hav ing a large aspect ratio. Modeling the eddy currents in the individual foil s is therefore difficult and requires completely meshed conductors, especia lly when the influence of the thermal held on the local conductivity is con sidered. Coupled 2D magnetic and thermal models of a 30 kVA transfomer havi ng 50 secondary foils are presented. In the thermal model, thin layer eleme nts or equivalent anisotropic materials are used to model the insulation ma terial between the conductors. The coupled problem is solved for the steady -state and transient case. A novel method will be introduced to solve the t ransient coupled problem using time steps, much larger than the magnetic su bproblem's time constants.