VOLTAGE RATIO IN SYNCHRONOUS CONVERTERS 235 



field. The total harmonics were 21.6 per cent in the 180 E.M.F., 

 and only 7.2 per cent in the 120 E.M.F., which are considerably 

 less than is possible with a three-part pole. Moreover, it is quite 

 possible that a more careful design of the pole faces might result in 

 a farther reduction in the harmonics of the tap E.M.F.'s. Fractional 

 pitch winding and fractional slot connections, would reduce them 

 still slightly farther. 



