Stray Loss Evaluation of Power Transformers Using Simplified Air-Core Model With Tank and Frame

This article reports stray loss generated in tanks, frames, and shields of a power transformer, and the shielding effect is qualitatively discussed for its design optimization. First, simplified transformer models composed of an air-core coil, a tank/frame, and a magnetic shield are newly proposed to reproduce stray loss generated in practical oil-filled power transformers. Then, accurate methods of measuring the stray loss in the proposed models were examined. The accuracy of the stray loss estimation based on a finite-element method was verified by comparing it with the measurement results.