Design features of auxiliary electrical machines for rolling stock

The paper is a review of some of the principal design features and the insulation methods relating to rotating auxiliary electrical machines used on both electric locomotives and multiple-unit stock. Items considered are (a) supply-motor generators (b) Carno convertors (c) exciter-motor generators (d) auxiliary motors. The trend towards alternators with rectifiers instead of d.c. generators is discussed, and the constructional details of modern alternators are given, together with reasons for their preference, particularly when fluorescent lighting is used. The effects of voltage surges and short circuits due to supply disturbances, and the values of starting resistances are considered.