PURPOSE: To increase an electric resistance in a circumferential direction between the closed slots of a rotor core and reduce a cross current loss produced in the rotor core by a method wherein linear recesses extended in the radial direction of the rotor are provided between the closed slots.
CONSTITUTION: A rotor core 6 is composed of a plurality of laminated iron plates on which linear recesses 8 are formed. The linear recesses 8 are not piercing parts of the rotor core plates and, when the iron plates are cast, rotor closed slots 2 are only spaces through which molten iron flows out. Thus, a cage rotor having the linear recesses 8 is made by a casting apparatus. An electrical resistance between the respective closed slots 2 is increased by the linear recess 8, so that a cross current 9 is reduced. Therefore, a cross current loss produced in the rotor core 6 can be reduced and the efficiency of the motor can be maintained and, further, vibration, noise and abnormal torque can be suppressed.
OHARAGI HARUO
IDE KAZUMASA
MIKAMI HIROYUKI
TAKAHASHI MIYOSHI
