This standard describes certain electrical and mechanical characteristics and takes into consideration certain safety features of 60-Hz, two-winding, ventilated dry-type transformers with self-cooled ratings 1 to 500 kVA, single-phase, and 15 to 500 kVA, three-phase, inclusive; high-voltage 601 to 34 500 volts, and low-voltage 120 to 600 volts, inclusive; generally used for step-down purposes. (Forced-air-cooled ratings for certain sizes are listed in Part II.)

This standard is intended to set forth characteristics relating to performance, limited electrical and mechanical interchangeability, and safety of the equipment described, and to assist in the proper selection of such equipment.