In typical pole-mounted transformers, the windings are surrounded by which coolant?

In typical pole-mounted transformers, the windings are surrounded by which coolant?

• A. Air
• B. Oil
• C. Water
• D. Fiberglass

Answer: (B)

The windings in typical pole-mounted transformers are surrounded by transformer oil because it acts as both a coolant and an insulating dielectric. Immersing the windings in mineral oil allows heat generated in operation to be carried away to external radiators, keeping temperatures down, while providing a strong dielectric medium between conductors to prevent arcing. Air wouldn’t remove heat or provide sufficient insulation for this size and service; water isn’t used due to dielectric breakdown, corrosion risk, and practical handling; fiberglass is only an insulating material, not a circulating coolant. So oil is the practical, effective coolant around the windings.

The windings in typical pole-mounted transformers are surrounded by transformer oil because it acts as both a coolant and an insulating dielectric. Immersing the windings in mineral oil allows heat generated in operation to be carried away to external radiators, keeping temperatures down, while providing a strong dielectric medium between conductors to prevent arcing. Air wouldn’t remove heat or provide sufficient insulation for this size and service; water isn’t used due to dielectric breakdown, corrosion risk, and practical handling; fiberglass is only an insulating material, not a circulating coolant. So oil is the practical, effective coolant around the windings.