Optimization of Magnetic Shunts Towards Efficient and Economical Power Transformers Design

Abstract

The focus of European and international markets and standards in the last few years is to achieve highly efficient power transformer designs, depending on the application sector (generation, transmission or distribution). The efficiency is directly related to total losses and in turn the heat emission. Losses in the power transformer are the summation of load and no-load losses. The load losses, which generally dominate the total losses, consist of ohmic and stray losses. However, reduction of ohmic losses is limited by the conductivity and design of the winding conductors. The stray losses are generated inside and outside the windings. Losses outside the windings (leads, tank and clamping structure) can be reduced through control of the leakage flux and the trade-off between different electromagnetic materials, such as magnetic shunts. In the current study, we present intensive investigations and optimizations of the application of magnetic shunts to control the leakage flux in power transformers to achieve lower stray losses. Eventually, design rules for the tank and yoke shunts are developed. The developed design tools are applied on case study transformers with different ratings and short-circuit impedances. Results show significant reduction in load losses. Economically, the newly developed design rules can be used to reduce the emitted heat, which will provide the opportunity to optimize the final power transformer design with a potential saving in materials, and therefore the total cost, in addition to meet market requirements.