The neutralized series conduction motor on A-C. and D-C. circuits

IT was discovered, in the early eighties, that an ordinary d-c. series conduction motor with a laminated magnetic circuit would operate on alternating current. In those days d-c. series motors usually had few armature and many field ampere-turns and were not neutralized, with the result that, when operated on alternating current, their power factor was very low. Some of the difficulties of the situation were probably first pointed out by G. Kapp, in 1888 or thereabouts. In 1890 Eickemeyer addressed himself to the single-phase series motor and made a commercial machine of it by neutralizing the armature reaction and showing that, contrary to the then prevailing d-c. practise, the armature ampere-turns should be greatly in excess, in fact a multiple of, the motor field producing ampereturns. He also pointed out that these machines were better suited for operation on low than on high periodicities and that they should be built with small air gaps. Beginning about the year 1893, A. G. Helios of Cologne, Germany, built a large number of neutralized single-phase series motors for general stationary work. Ganz & Co. of Budapest, Hungary, also made many single-phase series motors, beginning about 1889, but do not appear to have employed neutralizing windings. The machines built by these European firms were mostly small, seldom exceeding 20 B. h. p. The reason why the single-phase series motor was first used commercially in Europe, is probably to be found in the fact that in the early 90's the periodicities mostly employed in this country were about twice as high as those in vogue in Europe. The advent of the commutatorless polyphase motor had no doubt much to do with the almost complete abandonment of the single-phase series motor somewhere along the year 1896.