CHAPTER ONE
Like most rotating machines, a synchronous machine can also operate as both a generator and a motor. In large sizes (several hundred or thousand kilowatts) synchronous motors are used for pumps in generating stations, and in small sizes (fractional horsepower) they are used in electric clocks, timers, turntables, and so forth where constant speed is desired. Most industrial drives run at a variable speed. In industry synchronous motors are used mainly where constant speeds are desired.