PURPOSE: To improve starting characteristic, by fitting threephase windings in two steps, and by connecting the respective other side final-ends of the second three-phase windings to one point to form a neutral point.
CONSTITUTION: A squirrel-cage three-phase induction motor is provided with first three-phase windings Va∼Wa and second three-phase windings Vb∼Wb, and first∼second U phase (same also in case of another phase) windings Ua, Ub are respectively wound up in the two steps of the same slot. The winding start ends U1∼W1 of the first three-phase windings are formed, and the final ends of the other ends of the second windings Ub∼Wb are connected to one point to form a neutral point 2. Besides, the U2 of a U phase winding, the U2 of a W phase winding, and the W2 of the W phase winding are provided with single phase input terminals A, B, and a phase-shifting capacitor 3 is connected to a space between the terminals V2, W2. Then, the second three- phase windings Ub∼Wb are set to be exciting windings and all poles are wound up, and so even harmonics are not generated, and accordingly, smooth and strong acceleration is obtained.
HANAI TAKASHI