A 1000 kVA ONAN cooled transformer has a load of 500 kVA throughout the day except for a period of 4 hours. What is the permissible overload for a duration of four hours. Assume the permissible load kVA as a fraction of rated kVA is 1.24.

• A. 2480 kVA
• B. 1240 kVA
• C. 620 kVA
• D. 930 kVA

Answer: (B)

Permissible overload = Full load kVA*factor for permissible load
= 1000*1.24
= 1240 kVA