A regenerative braking system for d.c. railway traction

The d.c. motor at present provides most electric railway motive power, and, since the earliest days of electric traction, a great deal of effort has been expended in devising methods of regenerative braking suitable for d.c. systems. The system described here uses a series motor and features an automatic change from weak- to full-field operation. With this method, which was used for the first time in multiple-unit trainsets owned by London Transport and Danish State Railways, continuous blending of rheostatic and regenerative braking can be incorporated at low cost, and every opportunity can be taken to return energy to the supply