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.

This standard describes certain electrical and mechanical characteristics and takes into consideration certain safety features of 60-Hz, two-winding, threephase, ventilated dry-type transformers with selfcooled ratings 501 kVA and larger, generally used for step-down purposes. Forced-air-cooled ratings for certain sizes are listed in Part II.

Specific rating combinations are described in the range from 750/1000 to 7500/10 O00 kVA inclusive, with high-voltage 2400 to 34 500 volts inclusive and low-voltage 208Y/120 to 4160 volts inclusive.

This standard does not apply to other types of transformers such as specialty, ventilated dry-type 500 kVA and smaller, sealed dry-type, pad-mounted dry-type, liquid immersed, instrument, regulating, furnace, mine, and rectifier transformers. Transformers with high voltage 600 volts or less are excluded.

When this standard is used on a mandatory basis, the word “shall” indicates mandatory requirements, and the words “should” and “may” refer to matters that are recommended and permissive, respectively, but not mandatory.

NOTE: The Foreword of this standard describes the circumstances under which the document may be used on a mandatory basis.

Part I of this standard describes electrical and mechanical requirements. Part II describes other requirements or alternatives which may be specified for some applications.