Transformer design with 60o degree cutting angle of T-joint is more efficient than the core with cutting angle of T-joint 45o, 23o and 90o. This design (i.e. 60o) was not yet assembled by any transformer manufacturing company in this area. The flux distribution in the core is more uniform compared to other T-joint. The no-load loss of the 60o also showed lowest compared to other T-joint.