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. A
control circuit (147) provides electronic commutation and current control, based on rotor position signals generated with the aid of a control
magnet (110) on the rotor shaft (40).