Flux distribution and core loss calculation for single phase and five limb three phase transformer core designs

This paper presents results of an analytical core loss calculation method developed for single phase and five limb three phase core types. Shown are calculation results of flux distributions, flux density waveshapes, spatial flux density curves and loss distributions in cores other than the 3 phase-3 limb core. The analytical results show that the flux distribution is essentially uniform in the single-phase 2 limb and 3 limb cores. The flux waveforms are also shown to be essentially sinusoidal in different regions of the core. However, for the single-phase 4 limb core and the three-phase 5 limb core, the flux distribution is nonuniform and flux waves are very distorted. The calculated values of core losses were, generally, in excellent agreement with tested core losses of actual commercial transformers. The results on the very large 4 and 5 limb cores show that the production complexity of these cores cause a slightly higher tested core loss which needs to be included in the development of the core loss calculation for these cores.