Fast 3-dimensional interactive computation of stray field and losses in asymmetric transformers

Contemporary power transformers are very important components of power systems from the points of view of both reliability and energy saving. Their complicated three-dimensional (3-D) structure, leakage-field region with solid nonlinear steel elements and screen/shunt system should be modelled, calculated and designed using 3-D fast, interactive programs. After examination of many known methods it was concluded that only the 3-D reluctance-network method (RNM-3D) fulfils the needs of designers, namely simple. Fast, low cost, easy to use and understand, and giving effective integral-field, power and hotspot output data. Following a short discussion of the principles of such a dedicated 3-D package for power transformers, the satisfactory industrial verification of the method is carried out on six medium and large transformers from 31.5 to 315 MVA