Patent ID: 7091643

Claim:
An electric motor which comprises: a stator ( 28 ) having a polyphase stator winding; a rotor ( 36 ; 36 ′; 36 ″). separated from the stator ( 28 ) by an air gap ( 39 ); said rotor having, on its side facing away from the air gap, a yoke made of magnetically conductive material, and having, on its side facing the air gap ( 39 , a plurality of salient poles with pole shoes ( 260 A, 260 B, 260 C, 260 D; 292 A, 292 B, 292 C, 292 D) service to generate, in operation, sinusoidal induced voltages (Uind) in the polyphase stator winding; a respective recess ( 266 A, 266 B, 266 C, 266 D) being provided between the magnetic yoke ( 200 ) and each pole shoe ( 260 A, 260 B, 260 C, 260 D; 292 A, 292 B, 292 C, 292 D), in which recess at least one permanent magnet ( 262 A, 262 B, 262 C, 262 D; 290 A, 290 B, 290 C, 290 D) is arranged, said permanent magnet having two poles, one pole thereof facing the adjacent pole shoe and defining a pole shoe boundary, and the other pole thereof facing the yoke and defining a yoke boundary, said recess being adjoined, approximately in the circumferential direction and on each circumferential side thereof, by a respective low magnetic conductivity region; such a low magnetic conductivity region being bounded, on its side facing toward the air gap ( 39 ), by a retaining segment ( 270 ′ 270 ″) made of ferromagnetic material and serving to mechanically connect the cole shoe ( 260 A, 260 B, 260 C, 260 D; 292 A, 292 B, 292 C, 292 D to the magnetic yoke; and at least one flow path element ( 274 ′, 274 ″, 290 ; 292 ; 296 A) made of ferromagnetic material and extending from a source region ( 264 A; 298 A) of the at least one permanent magnet 262 A, 262 B, 262 C, 262 D; 290 A, 290 B, 290 C, 290 D) which source region is closer to the pole shoe boundary of the magnet than to the yoke boundary thereof, and through the low magnetic conductivity region adjacent to the source region, to a target region ( 270 ′″) of the retaining segment ( 270 ″, 270 ″) adjacent to said respective low magnetic conductivity region, in order to conduct, towards said target region ( 270 ′″), an additional magnetic flux from the respective permanent magnet ( 262 A, 262 B, 262 C, 262 D).