Abstract: An electric motor has a rotor (36) and a stator (28) having a lamination stack formed with slots (126). The slots have a predetermined slot pitch (?s), and a multi-phase stator winding is arranged in them. The rotor (36) has salient poles having pole shoes (136) and a magnetic return path (130). Between the return path (130) and each pole shoe (136), a recess (138, 140) is formed for receiving a permanent magnet (38). On each side of such a permanent magnet (38), a region (146a, 146b) of poor magnetic conductivity is arranged, in order to make the flux distribution in the air gap more sinusoidal. Measuring in a circumferential direction, the width (?) of a pole shoe (136) decreases with increasing distance from an interface (138) between said return path and said permanent magnet (38), and, at a place of lowest width, the pole shoe has an angular extent (?c) which has, with respect to the slot pitch (?s) between said stator slots (126), the following relationship: ?c=n*?s*(1?0.02) . . . n*?s*(1?0.

Abstract: A low-ripple multi-phase internal rotor motor has a slotted stator (28) separated by an air gap (39) from a central rotor (36). The rotor has a plurality of permanent magnets (214), preferably neodymium-boron, arranged in pockets (204) formed in a lamination stack (37), thereby defining a plurality of poles (206) separated by respective gaps (210). In a preferred embodiment, the motor is three-phase, with four rotor poles and six stator poles. As a result, when the first and third rotor poles are so aligned, with respect to their opposing stator poles, as to generate a reluctance torque, the second and fourth rotor poles are aligned to generate oppositely phased reluctance torques, so that these torques cancel each other, and essentially no net reluctance torque is exerted on the rotor. In order to magnetically separate the rotor magnets from each other, a hollow space (224, 238) is formed at the interpolar-gap-adjacent end face (216, 218) of each rotor magnet.

Abstract: An electric motor has a rotor (36) and a stator (28) having a lamination stack formed with slots (126). The slots have a predetermined slot pitch (?S), and a multi-phase stator winding is arranged in them. The rotor (36) has salient poles having pole shoes (136) and a magnetic return path (130). Between the return path (130) and each pole shoe (136), a recess (138, 140) is formed for receiving a permanent magnet (38). On each side of such a permanent magnet (38), a region (146a, 146b) of poor magnetic conductivity is arranged, in order to make the flux distribution in the air gap more sinusoidal. Measuring in a circumferential direction, the width (?) of a pole shoe (136) decreases with increasing distance from an interface (138) between said return path and said permanent magnet (38), and, at a place of lowest width, the pole shoe has an angular extent (?C)which has, with respect to the slot pitch (?S) between said stator slots (126), the following relationship: ?C=n*?S*(1?0.02) . . . n*?S*(1?0.

Abstract: A low-ripple multi-phase internal rotor motor has a slotted stator (28) separated by an air gap (39) from a central rotor (36). The rotor has a plurality of permanent magnets (214), preferably neodymium-boron, arranged in pockets (204) formed in a lamination stack (37), thereby defining a plurality of poles (206) separated by respective gaps (210). In a preferred embodiment, the motor is three-phase, with four rotor poles and six stator poles. As a result, when the first and third rotor poles are so aligned, with respect to their opposing stator poles, as to generate a reluctance torque, the second and fourth rotor poles are aligned to generate oppositely phased reluctance torques, so that these torques cancel each other, and essentially no net reluctance torque is exerted on the rotor. In order to magnetically separate the rotor magnets from each other, a hollow space (224, 238) is formed at the interpolar-gap-adjacent end face (216, 218) of each rotor magnet.