Evaluation of No-Load Losses in the Single-Sheet, Double-Sheet, and Triple-Sheet Step Lap Joints of the Transformer Core

Power transformers are crucial pieces of equipment in power grids, and the working of transformers directly impacts the safety of the power system. Transformer-increased losses due to core design can increase the transformer’s operational cost. With the development of numerical methods and the growth of finite element analysis techniques, tremendous progress has been made in applying the finite element method in the design of the transformer, which provides new ideas for designing and optimizing the transformer design. This paper analyzes the no-load losses of step lap cores based on finite element analysis and summarizes the impact of flux density distribution on single-sheet step lap joints (SSSL), double-sheet step lap joints (DSSL), and triple-sheet step lap joints (TSSL). Three different step lap joints of power transformers are examined at different magnetic flux densities and give guidelines to select the optimal step joints to achieve low losses and cost-effective design.