Passenger cars of the railway transport are being constantly improved, thus becoming ever more comfortable for public conveyance. These cars are fitted with air conditioners, installations for heating and forced ventilation, heaters, refrigerators, lighting, radio and TV sets, communication equipment, etc. All the listed fittings need continuous and secure electricity supply from a primary independent source. The paper considers the possibilities of meeting requirements for particular power supply systems – first of all for undercar generators. At operation of such a high-power generator under rugged conditions it should be highly reliable, possessing a reasonable mass and high efficiency. The existing designs of these generators still do not meet the listed requirements in full measure. To improve the efficiency of the undercar generator it is proposed to integrate its excitation winding into the armature one, thus reducing the copper consumption, losses and mass, while – which is the most important – considerably raising reliability of the generator and its availability factor.