Squirrel-Cage Induction-Motor Core Losses

An experimental method is presented for segregating the various no-load losses of a squirrel-cage induction motor. It is shown that for insulated rotor bars the losses consist principally of stator fundamental-frequency losses, rotor surface losses and eddy-current losses in the rotor bars due to radial and tangential slot-leakage fluxes in the rotor slots caused by reluctance pulsations in the air-gap between stator and rotor teeth. The pulsation losses vary about as the square of the air-gaP induction and about as the 1.2 power of the frequency. The surface losses for the particular slots described are from ?? to ?? of the total pulsation losses. The pulsation losses are approximately the same whether or not the rotor bars are connected by end rings, and are approximately equal to the stator fundamental-frequency losses.