Simple Analytical Method for Magnetic Flux Density in Amorphous and Silicon Steel Hybrid-Core for Three-Phase 30 MVA Higher-Efficiency Distribution Transformer

To provide a 30 MVA transformer with a lower-loss and higher-mechanical-strength core, we devised a hybrid configuration consisting of amorphous and grain-oriented silicon steel (GO) cores. We investigated the magnetic flux density (B) distribution in the hybrid-core and found that reluctance network analysis (RNA) was useful by comparing it with a prototype hybrid-core transformer (HBT). We also found that the HBT could operate at a 10% higher B than a transformer with an amorphous wound core only, and the standby power was reduced by 62% compared with that of a GO core transformer.