The theory and practice of regenerative braking of d.c. locomotives, with particular reference to multiple-unit operation

After briefly dealing with train braking in general, the electrical characteristics of the regenerative brake are developed. The stabilizing line is introduced, giving the relationship between the armature current and the field current (regulation curve) to give stable regenerative braking into a receptive contact wire. Regenerative braking circuits employed in traction systems are indicated. By means of the stabilizing line theory their characteristics can be deduced, thus enabling their suitability to be judged. The requirements for good load-sharing in multiple-unit operation are dealt with and a method is described based on the theory outlined in the earlier part, which enables the matching of different locomotives of multiple-unit groups even when their excitation circuits differ. Results of service tests carried out on the 3 000-volt electrification in Natal, during which loads up to 1 600 tons were handled exclusively by the multiple-unit regenerative brake with regenerated outputs up to 5 000 kW, are briefly shown in a number of figures.