US Patent 8026648 Electric machine

An electric machine, especially a brushless DC motor. Said electric machine comprises a rotor and a stator which is provided with current-carrying coils. Said rotor, in the circumferential direction, is provided with a plurality of permanent magnets that are embedded in respective magnet retainers between the peripheral surface and the shaft of the rotor in such a manner that the permanent magnets, in the radial direction, are completely encircled by the peripheral surface of the rotor. In the area of the magnet retainer, recesses extend laterally in the circumferential direction of the rotor and axially within the rotor.