What surrounds the windings in typical 75 kVA dry-type distribution transformers?

In a typical 75 kVA dry-type distribution transformer, the windings are surrounded by air. This is a fundamental design choice for dry-type transformers, where the insulation system relies on air to dissipate heat generated during operation. Unlike liquid-filled transformers, which generally utilize oil for cooling and insulation, dry-type transformers do not contain any oil or liquid medium. Instead, they utilize natural air convection to facilitate heat dissipation, making them suitable for various applications, particularly in environments where fire safety is a concern.

Air surrounding the windings also serves as the primary insulator for the electrical components, ensuring that there is adequate space between the conductors to prevent any dielectric breakdown. In addition, dry-type transformers are often constructed with materials that enhance air insulation, allowing for more compact designs without the risk associated with liquid-filled units.

This makes the transformer lighter and easier to install in a variety of settings, emphasizing the advantages of using air as a cooling and insulating medium.