| 摘要 |
A squirrel-cage induction motor for frequency convertor operation has a rotor with a plurality of axially extending rotor slots (41) with rotor conductors (4). Those parts (413) of the rotor slots which are facing the rotor surface (11) have a bent shape. Between each rotor conductor and the rotor surface (11) the rotor core has a narrow slit (42). The dimensions and the shape of the core portion (7) located between the rotor slot and the rotor surface are chosen such that the flux -caused by the leakage field of the rotor- in those parts of the rotor core located nearest the slit provides such a flux density that the rotor core operates at or near the knee of the magnetization curve when the load of the motor is equal to the rated load. Preferably, the shape of the core portions (7) is such that, at rated current of the motor, the RMS value of the flux density -caused by the leakage field of the rotor conductors- in that part of the core portions (7) where the flux density is highest lies between 1.5 T and 1.9 T. |
