Dry-type transformer insulation is designed based on an ambient temperature of which degree Celsius?

The correct answer is based on the standard operational conditions for dry-type transformers, which are typically designed to function effectively under an ambient temperature of 40°C. This temperature consideration is crucial for assessing the insulation materials used in these transformers. The insulation system must withstand the thermal conditions without degrading over time, ensuring longevity and reliability.

Designing transformers to operate at 40°C allows for sufficient margin in various environments, accommodating factors such as potential temperature spikes during operation. When transformers are installed in hotter environments or near heat-generating equipment, this design standard helps to avoid overheating and reduces the risk of insulation failure, which could lead to transformer malfunction or electrical fires.

In contrast, the other temperature options (20°C, 25°C, and 30°C) do not align with the industry standards for dry-type transformer operation, which typically expect higher ambient conditions to ensure the transformer can handle real-world operating scenarios effectively.