Abridgment of control systems for oil- and gasoline-electric locomotives and cars

A review is given of the development of self-propelled railway vehicles which utilize electrical transmission, paying particular attention to the ways and means of regulating the torque demand on the internal combustion engine which serves as the source of power, and the supply of power to the auxiliaries. Two general designs are discussed and classified as “differential field control” and “torque control.” In differentiating between these two systems, two types of differential field control are outlined, giving their major advantages and limitations. The principle of torque control depending upon constant engine speed is discussed, with enumeration of its advantages over previous schemes, permitting as it does the absorption of the entire engine output for any throttle opening and engine speed selected. The differential field control comprises the minimum amount of apparatus consistent with operation of the car or locomotive and its auxiliaries. In connection with this type of control, however, it should be noted that battery charging and air compressor operation cannot be obtained at both operating and idling speeds of the engine. Torque control equipment functions to vary automatically the generator voltage inversely as the current in such a way that the full available power of the engine is utilized; it ads directly on the generator field and has proved its superiority over methods of regulation involving the exciter field. The availability of the auxiliary generator for compressor operation and battery charging when the engine is running under load represents a marked advance in design. The main generator supplies these auxiliaries during idling. The torque control system meets the requirement of any type of engine.