The choice of electric traction-motor equipment by the method of similar speed/time curves

The author describes a method of determining rapidly what the characteristics and ratings of an electric traction motor must be for satisfactory operation under any particular service conditions which may be specified. The method involves the construction in advance of a set of general curves applicable to a particular class of service. The assumptions made in order to bring these curves into accord with observed practice in railway, tramway, and trolley-bus service, are fully described, and the construction of one set of curves is followed through in detail, the necessary calculations being also tabulated. Four sets of curves are shown, and the method of using them is explained; several typical examples are worked out to demonstrate the type of information which can quickly be obtained by the use of the curves.