Factors Affecting the Design of D-C. Motors for Locomotives

The designer of motors for locomotive service is confronted with at least two limitations; space and weight. For large locomotives, the second limitation may not be of prime importance, but the first must be constantly in the mind of the designer. The paper gives a comparison between different types of motor mounting as regards the amount of power which may be developed in the available space with direct current motors. The comparisons are largely qualitative but within reasonable limits are also quantitative. The available space between wheels or locomotive side frames is divided into two parts. One of these parts is made up of units which are assumed to be constant within the range considered, while the other part is made up of variables. Expressions for the variables are derived, generally in terms of armature diameter, and constants and variables are then combined into a complete expression for motor output. The voltage applied to motor commutator, voltage-to-ground, number of poles, peripheral speed and track gage, as well as type of motor mounting are considered in the comparison.