The nine-ring rotary convertor

The design and operating features of rotary convertors are considered and compared with respect to the number of slip-rings. Particular attention is given to the armature reaction and analysis of the magnetomotive force wave-forms, with their effects upon commutating conditions. The d.c. voltage wave-form is also examined. These investigations show that, in general, the 9-ring rotary convertor is superior to both the 6- and 12-ring machines. Voltage regulation and starting are considered. Methods of obtaining symmetrical 9-phase voltage systems from 3-phase supply mains by means of suitable transformer connections are described and examined.