Patent ID: 8598760

Claim:
A permanent magnet module ( 101 , 201 , 301 ) for a rotor of a permanent magnet electrical machine, the permanent magnet module extending over at most 180 degrees in a tangential direction (φ) of the rotor and comprising: a stack of ferromagnetic steel sheets ( 104 , 204 , 304 ) comprising at least one groove in a direction perpendicular to the ferromagnetic steel sheets, at least one permanent magnet ( 105 , 205 , 305 a - 305 h ) located in the at least one groove and arranged to produce magnetic flux that penetrates a surface ( 106 , 206 ) of the stack of ferromagnetic steel sheets, the surface of the stack of ferromagnetic steel sheets having a shape suitable for forming a pre-determined magnetic flux density distribution into an air-gap of the permanent magnet electrical machine, and a supporting structure ( 114 , 214 , 215 ) arranged to mechanically support the stack of ferromagnetic steel sheets, characterized in that the permanent magnet module further comprises at least one base-plate ( 102 , 202 , 302 ) made of solid ferromagnetic steel, each base-plate being located at an opening ( 116 , 216 , 316 ) of one of the at least one groove and constituting together with the at least one groove an aperture in which the at least one permanent magnet is located.