Patent ID: 8740584

Claim:
An induction motor comprising: a stator having a stator iron core produced by laminating a predetermined number of electromagnetic steel plates which have been punched out into a predetermined form, a plurality of stator slots formed along an inner circumferential edge of the stator iron core, and windings inserted into the stator slots; and a rotor placed inside of the stator via a gap, the rotor including: a rotor iron core produced by laminating a predetermined number of electromagnetic steel plates which have been punched out into a predetermined form; a plurality of double squirrel-cage rotor slots formed along an outer circumferential edge of the rotor and filled with conductive material; and three air hole parts provided around a rotating shaft hole of the rotor iron core to which a rotating shaft is fitted and having an opening which is open to the rotating shaft hole, wherein an inner diameter part of at least one of end rings which short circuit both edges of the conductive material filled into the double squirrel-cage rotor slots is placed adjacent to the air hole parts, and wherein the three air hole parts are placed with an almost equal interval, so that 2α+β<180 degrees, where an angle formed by both edges of one of the air hole parts and a center of the rotor shaft is α, and an angle formed by two edges of a closer side of two adjacent air hole parts and the center of the rotor shaft is β.