In undertaking the preparation of rules for standards for rotating electrical
equipment for railway cars and locomotives under the Rules of Procedure of the American Standards Association, it has been necessary to cover a much wider field than was included in the AIEE Standards for Railway Motors which were published in 1925, approved as American Standards in 1928 and form the basis of this standard. In the first place, the scope of the rules has been changed to include all rotating electrical machinery forming a part of the power equipment of electrically-propelled railway cars and locomotives (including trolley, gasoline-electric and oil-electric coaches). In the second place, it has been found desirable to add new rules covering principally, rating, commutation, and over speed tests. In the third place, the old rules must be brought up-to-date as modern methods of ventilating electrical machinery have changed the situation in many respects. It is therefore felt necessary that some explanatory notes should be added to the rules in order to give the users of the rules a clearer understanding of the reasons for them.