In this paper a comparison of mechanical failure criteria for transformer design is presented. The von Mises, Tresca and maximum mechanical stress are the evaluated criteria. The comparison is based on the electromechanical stresses in the conductive material of the windings and in the advantages and disadvantages of each criteria. The safety and the final cost of the equipment are also analysed. According to the results, the maximum mechanical stress criterion is the most conservative, resulting in a safer design, with the use of a larger amount of conductive material, which is the copper, and a higher cost involved. The von Mises criterion is the most realistic one, because it is a combination of all principal stresses. Its use can result in a lower-cost design due to there being no need for oversizing the windings. The Tresca criterion represents a two of the principal stresses and requires a lower computational effort.

Index Terms Transformer, von Mises Stress, Maximum Mechanical Stress, Tresca Stress, Mechanical Failure Criterion.