Question

What is the flow rate of the circulating oil in an air cooler with natural air cooling?

(a) 12.5 litre per minute per KW of losses

(b) 12 litre per minute per KW of losses

(c) 14 litre per minute per KW of losses

(d) 13 litre per minute per KW of losses

This question was addressed to me in an internship interview.

My question is based upon Methods of Cooling of Transformers topic in division Design of Transformers of Design of Electrical Machines

Answer 1

Correct option is (b) 12 litre per minute per KW of losses

Best explanation: When natural air cooling is used, the flow rate is 12 litres per minute per KW of losses. Even when the air blast cooling is used, the transformer output increases roughly to the same extent.