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

Contemporary power transformers are very important components of power syst ems from the points of view of both reliability and energy saving. Their co mplicated three-dimensional (3-D) structure, leakage-field region with soli d nonlinear steel elements and screen/shunt system should be modelled, calc ulated and designed using 3-D fast, interactive programs. After examination of many known methods it was concluded that only the 3-D reluctance-networ k method (RNM-3D) fulfils the needs of designers, namely simple, fast, low cost, easy to use and understand, and giving effective integral-field, powe r and hotspot output data. Following a short discussion of the principles o f such a dedicated 3-D package for power transformers, the satisfactory ind ustrial verification of the method is carried out on six medium and large t ransformers from 31.5 to 315MVA.