Rotary converters, with special reference to railway electrification

Railway electrification in this country will require converting machinery capable of operating from high-tension alternating-current systems with frequencies of 25 to 50 periods per second and delivering direct current at 1,500 volts. For this class of service the rotary converter possesses many desirable characteristics, viz. ease and quickness of starting, high efficiency, high overload capacity, high power factor (especially on full load and overloads), freedom from limitation of high-tension a.c. voltage, reasonable flexibility of control of the d.c. voltage, reasonable freedom from harmonics in the alternating-current supply, and from undulations and ripples in the d.c. voltage delivered. The limiting conditions in design and operation of such equipments are discussed, more particularly the effect of frequency on the generation of direct current at 1500 volts, the effects of short-circuits and flash-overs, and the deviation of the d. c. voltage from a uniform value.