Fan assembly including an optimised motor

A scroll-free plug fan for medium-low speed ventilation, comprising:

• a blade group controllable to rotate about an axis (X-X), comprising a radial-flow or mixed-flow impeller;
• a motor group operatively connected to the blade group to rotationally drive the blade group up to a maximum design speed, wherein the maximum design speed is preferably equal to about 3600 rpm, wherein the motor group comprises:
• i) a static drive shaft extending along the axis (X-X), and
• ii) a three-phase permanent magnet synchronous motor comprising:
• an inner stator supported by the static drive shaft and having twelve stator slots;
• and
• an outer rotor connected to the blade group rotating about the static drive shaft,
• wherein the outer rotor comprises a rotor pack having an axial length between 35 and 90 millimeters and consisting of a plurality of thin annular rotor laminations axially stacked, the stacking of rotor laminations defining fourteen rotor slots, wherein the outer rotor further comprises permanent magnets made of rare earths, each housed in a rotor slot, wherein each of the permanent magnets comprises lateral sides inclined with respect to the axis (X-X) by a skew angle (α) between 3 and 9 degrees, and wherein the rotor laminations are mutually rotated about the axis (X-X) so that the rotor slots extend with respect to the axis (X-X) at an angle substantially equal to the skew angle (α).