What shape is the core of the most commonly used transformer design?

The core shape of the most commonly used transformer design is typically shell-type. This design is favored because it allows for a more efficient magnetic circuit and minimizes the amount of energy lost to leakage flux. The shell-type transformer features a core that surrounds the winding, providing a closed magnetic path, which enhances the coupling between the primary and secondary coils.

This design not only improves the efficiency of the transformer but also contributes to a more compact design, which is especially beneficial for installation in various settings. In addition, shell-type transformers have better mechanical stability and are less susceptible to noise and vibrations compared to other designs.

On the other hand, disc shapes, cylindrical shapes, and square shapes may have specific applications or advantages in particular contexts, but they are not as widely utilized as the shell-type core in standard transformer designs. The shell-type design's widespread adoption is a testament to its balance between performance, efficiency, and practicality in transformer technology.