Magnetic Properties of Simultaneously Excited Amorphous and Silicon Steel Hybrid Cores for Higher Efficiency Distribution Transformers

We measured and calculated the distributions of the magnetic flux density and iron loss in a hybrid-configured core consisting of an amorphous wound core combined with a grain-oriented (GO) silicon steel stacked core with the goal of enabling the use of amorphous cores with lower iron loss in larger capacity distribution transformers. Excitation tests revealed that the GO core prevented over-saturation of the amorphous core. The hybrid configuration enabled the design to have an approximately 10% higher magnetic flux density than configurations with only an amorphous core. We then assembled a prototype 5 MVA single-phase hybrid-core transformer designed on the basis of our investigation results. Operation tests on the prototype demonstrated that its efficiency was higher than that of conventional silicon steel core transformers and its size was less than that of transformers with only amorphous cores.