A new alternating-current general-purpose motor

The desirability of motors possessing the good characistics of induction motors and being capable of operating with leading power factor is pointed out. A new machine is described which operates as self-excited synchronous motor under normal operating conditions. During the starting period and excess overloads, it has the characteristics of an induction motor with wound secondary. The machine has excellent starting and synchronizing torque with a small current draw. The electrical and mechanical phenomena, during the starting and synchronizing periods, are discussed. The size of the machine is nearly equal to that of a slip-ring induction motor of equal rating, and the full-load efficiency is approximately equal to that of a corresponding induction motor. It is shown that the overall efficiency of a plant, consisting of squirrel-cage motors and this new type of motor, is usually higher than that of an equivalent plant using induction motors only, correcting the power factor by idle running correcting devices.